S e rg ioA . C . G a rz o n , A d a lb e rto M . L o rg a , J o s e C a rlo s N ic o la u
E l e c t r o c a r d i o g r a p h y
in
C h a g a s ' h e a r t d i s e a s e
Instituto
de Mo1estias Cardiovasculares
Sao Jose do Rio Preto • Sao Paulo, Brazil
C o n v e n tio n a l E C G s till p la y s a n im p o rta n t ro le in th e o v e ra ll k n o w le d g e o f C h a g a s ' c a rd io p a th y , b e c a u s e o f its im p o rta n c e in lo n g itu d in a l a n d e p id e m io lo g ic a l s tu d ie s , its d ia g n o s tic v a lu e , a n d its u tility in p ro g n o s tic e v a lu a tio n . T h e a u th o rs d is c u s s th e s e a s p e c ts , a s w e ll a s th e u s e o f E C G in th e a c u te p h a s e a n d th e s ig n ific a n c e o f a n o rm a l E C G in C h a g a s ' d is e a s e . C o rre la tio n s w e re
m a d e b e tw e e n E C G a n d h e m o d y n a m ic /a n g io g ra p h ic v a ria b le s a m o n g 1 0 1 0 p a tie n ts w ith p o s itiv e la b o ra to ry te s ts fo r C h a g a s ' d is e a s e : a ) in th e g ro u p w ith n o rm a l E C G th e re w e re n o s ig n ific a n t d iffe re n c e s b e tw e e n s y m p to m a tic a n d n o n -s y m p to m a tic p a tie n ts w ith re g a rd to e je c tio n fra c tio n a n d a n g io g ra p h ic a b n o rm a litie s ; b ) s lig h t a b n o rm a litie s o n th e E C G c o rre s p o n d e d to a n in te rm e d ia te le v e l o f s e v e rity o f th e d is e a s e , th a t is , b e tw e e n n o rm a l E C G a n d E C G w ith s ig n ific a n t a b n o rm a litie s ; c ) fib ro s is o n th e
E C G w a s n o t p re d ic tiv e o f a k in e s ia in th e re la te d a re a o n th e a n g io g ra p h y ; d ) c o m b in e d E C G a b n o rm a litie s g e n e ra lly c o rre la te d w ith g re a te r m y o c a rd ia l c o m p ro m is e c o m p a re d to is o la te d a b n o rm a litie s ; e ) u n d e r m u ltip le re g re s s io n a n a ly s is th e E C G a b n o rm a litie s th a t in d e p e n d e n tly c o rre la te d w ith d e p re s s e d e je c tio n fra c tio n w e re : p re m a tu re v e n tric u la r b e a ts , v e n tric u la r ta c h y c a rd ia , le ft b u n d le b ra n c h b lo c k , a tria l fib rilla tio n , c o m p le te A V b lo c k , a n d a n te rio r a n d in fe rio r fib ro s is . M a le s e x , c a rd ia c
in s u ffic ie n c y a n d c a rd io m e g a ly o n th e th o ra x ra d io g ra p h y w e re a ls o s ig n ific a n tly re la te d .
UNITERMS:
E le c tro c a rd io g ra p h y . C h a g a s ic c a rd io p a th y . A m e ric a n try p a n o s o m ia s is .IN T R O D U C T IO N
T
h e d e v e l o p m e n t o f n o n - i n v a s i v e d i a g n o s t i c m e t h o d s w i t h g r e a t c a p a c i t y t o e v a l u a t e a n a t o m y a n d c a r d i a c f u n c t i o n s - m u l t i p l a n a l e c h o d o p p l e r c a r d i o g r a p h y , s c i n t i g r a p h y a n d r a d i o i s o t o p i c a n g i o g r a p h y - o r t o i d e n t i f y i n l o n g r e g i s t e r s t h e p r e s e n c e o f a r r h y t h m i a s - d y n a m i c e l e c t r o c a r d i o g r a p h y - c a n c r e a t e t h e i m p r e s s i o n t h a t
A d d re s s fo r c o rre s p o n d e n c e : S e rg io A . C . G a rz o n
In s titu to d e M o le s tia s C a rd io v a s c u la re s R u a C a s te lo d 'A g u a , 3 0 3 0
S a o J o s e d o R io P re to -S a o P a u lo - B ra s il- C E P 1 5 0 1 5 -2 1 0
802
c o n v e n t i o n a l e l e c t r o c a r d i o g r a p h y ( E C G ) m i g h t b e a n e x a m o f s e c o n d a r y i m p o r t a n c e f o r c a r r i e r s o f C h a g a s ' d i s e a s e .
T o d a y t h e E C G i s s t i l l o f g r e a t v a l u e d u e t o i t s s i m p l e a t t a i n m e n t , p r a c t i c a l i t y , l o w c o s t a n d i t s h i g h s e n s i t i v i t y i n d e t e c t i n g , q u a n t i f y i n g a n d a c c o m p a n y i n g m o s t m a n i f e s t a t i o n s o f c h a g a s i c c a r d i o p a t h y
I t h a s g r e a t e p i d e m i o l o g i c a l v a l u e a n d i s t h e m e t h o d o f c h o i c e i n l o n g i t u d i n a l p o p u l a t i o n a l s t u d i e s i n e n d e m i c a r e a s ; b e s i d e s t h e a d v a n t a g e s m e n t i o n e d , i t s r e g i s t e r d o e s n o t r e q u i r e g r e a t q u a l i f i c a t i o n o r t r a i n i n g o f t h e o p e r a t o r a n d t h e t r a c i n g s c a n b e a r q u i v e d f o r l a t e r i n t e r p r e t a t i o n . I t i s k n o w n t h a t i n t h e n a t u r a l h i s t o r y o f C h a g a s ' d i s e a s e , t h e p r e c o c i t y a n d p r e v a l e n c e o f e l e c t r o c a r d i o g r a p h i c a l t e r a t i o n s a r e r e l a t e d t o t h e s u r v i v a l c u r v e s . F o r a l l o f t h e s e r e a s o n s i t h a s g r e a t d i a g n o s t i c v a l u e , s i n c e i n m o s t
to w n s w h e r e it is e n d e m ic th e m e d ic a l a tte n d a n c e is p r e c a r io u s a n d th e E C G , if a v a ila b le , c o u ld b e th e o n ly r e s o u r c e in th e id e n tif ic a tio n o f th e c a r d io p a th y , s in c e its a lte r a tio n s p r e c e d e th e a p p e a r a n c e o f s y m p to m s a n d a b n o r m a litie s in th e p h y s ic a l e x a m a n d th o r a x r a d io g r a p h y . I t e v e n h a s p r o g n o s tic v a lu e , s in c e c e r ta in a b n o r m a litie s , in th e m s e lv e s c a n in d ic a te d if f e r e n t e v o lu tio n s .
ELECTROCARDIOGRAM
IN TH!=
ACUTE FORM
T h e a c u te p h a s e o f C h a g a s ' d is e a s e r e f e r s to a g e n e r a liz e d in f e c tio n b y
T. cruzi,
a n d is c h a r a c te r iz e d b y th e f in d in g o f th e p a r a s ite in th e p e r ip h e r a l b lo o d . I t g e n e r a lly ta k e s a b e n ig n c o u r s e , w ith m o r ta lity o f 5 % a n d 1 0 % th r o u g h m y o c a r d itis o r m e n in g o e n c e p h a llitis , m a in ly in th e f ir s t y e a r s o f lif e ( 7 5 % o f th e o b its ) .T h e m y o c a r d itis c a n s h o w v a r ia b le s e v e r ity , o n ly m a n if e s tin g its e lf a s o n ly a ta c h y c a r d ia d is p r o p o r tio n a te to th e f e v e r o r a s s e v " e r e c a r d ia c in s u f f ic ie n c y a n d h y p o te n s io n " . T h e E C G w a s n o r m a l in 6 3 % o f th e n o n -f a ta l c a s e s a n d in 1 4 % o f th e f a ta l c a s e s o f B a m b u i ( 1 5 ) . I t c a n d is p la y tr a n s ito r y a lte r a tio n s o r a b n o r m a l s ta te s e v e n w ith o u t c lin ic a l e v id e n c e o f c a r d itis . T h e m o s t f r e q u e n t f in d in g s a r e n o n - s p e c if ic a n d c o m m o n to a n y m y o c a r d itis : s in u s ta c h y c a r d ia a n d p r im a r y a lte r a tio n o f th e v e n tr ic u la r r e p o la r iz a tio n a n ~ lo w Q R S v o lta g e , le f t v e n tr ic u la r o v e r lo a d a n d f ir s t d e g r e e a tr io v e n tr ic u la r b lo c k . I n m o r e s e v e r e m y o c a r d itis , m o r e a d v a n c e d a tr io v e n tr ic u la r b lo c k s a n d b u n d le - b r a n c h b lo c k c a n a p p e a r . T h e p r e s e n c e o f in a c tiv e a r e a s , S T s e g m e n t c h a n g e s , c o m p le x v e n tr ic u la r a r r h y th m ia a n d a tr ia l f ib r illa tio n in d ic a te a w o r s e p r o g n o s is . T h e b e h a v io r o f th e E C G in th e a c u te p h a s e c o u ld b e in d ic a tiv e o f th e la te p r o g n o s is o f th e d is e a s e . A m o n g p a tie n ts w ith a n o r m a l E C G in th is p h a s e s o n ly 3 0 % e x h ib it a n a lte r e d E C G in th e c h r o n ic p h a s e s ; o n th e o th e r h a n d , a m o n g th o s e s h o w in g s o m e a b n o r m a lity , 6 0 .9 % s h o w a n a lte r e d E C G .
A f te r th e d is a p p e a r a n c e o f th e c lin ic a l m a n if e s ta tio n s in th e a c u te p h a s e th e a lte r a tio n s te n d to d is a p p e a r ; a f te r o n e y e a r 7 5 % o f th e c a s e s s h o w a n o r m a l E C G . S o m e ( 1 0 % - 2 0 % ) a lte r n a te n o r m a l tr a c in g s a n d a b n o r m a l tr a c in g s w ith in te r m itte n t f ir s t d e g r e e a tr io v e n tr ic u la r b lo c k a n d a lte r a tio n o f th e v e n tr ic u la r r e p o la r iz a tio n .
NORMAL ELECTROCARDIOGRAM
IN
CHAGAS DISEASE"
A n o r m a l E C G , o n e o f th e p a r a d ig m s in th e c h a r a c te r iz a tio n o f th e in d e te r m in a te f o r m O f C h a g a s ' d is e a s e , s h o w s a v a r ia b le p r e v a le n c e in d iv e r s e e n d e m ic r e g io n s , r e f le c tin g th e p a th o g e n e s is o f th e d is e a s e : 9 1 .6 % in th e B r a z ilia n s ta te o f R io G r a n d e d o S u I a n d 6 8 % in th e s ta te o f G o ia s . I t is m o r e c o m m o n in th e f ir s t 2 0 y e a r s a f te r th e a c u te f o r m , w ith th e p o s te r io r a p p e a r a n c e o f s o m e ty p e o f e le c tr o c a r d io g r a p h ic a lte r a tio n a t a f r e q u e n c y o f 2 % to 5 % p e r y e a r . T h e s tu d y o f th e in d e te r m in a t~ f o r m , w h ic h w ill b e m o r e th o r o u g h ly d is c u s s e d in a n o th e r c h a p te r , h a s s h o w n th r o u g h th e u s e o f m o r e s e n s itiv e d ia g n o s tic m e th o d s , e ith e r in v a s iv e o r n o n - in v a s iv e , th a t m o s t c h a g a s ic p a tie n ts w ith n o r m a l E C G h a v e s o m e ty p e o f a n a to m ic a l o r f u n c tio n a l a lte r a tio n . G e n e r a lly th e y a r e o f lo w in te n s ity a n d r e p e r c u s s io n , w h ic h w o u ld im p ly a g o o d p r o g n o s is . T h is w a s c o n f ir m e d b y F o r ic h o n ( 7 ) , in B a m b u i, w h o , a c c o m p a n y in g 8 8 5 y o u n g s e r o p o s itiv e p a tie n ts f o r 1 0 y e a r s , v e r if ie d th a t in th e g r o u p w ith n o r m a l E C G , 9 7 .4 % r e m a in e d a liv e w h ile o n ly 6 1 .3 % o f th o s e w h o d is p la y e d s o m e ty p e o f e le c tr o c a r d io g r a p h ic a n o m a ly s u r v iv e d . T h e s u r v iv a l o f s e r o p o s itiv e s w ith a n o r m a l E C G w a s e q u a l to th a t o f s e r o n e g a tiv e s , a n d th e y h a d 9 tim e s m o r e c h a n c e o f s ta y in g a liv e a s th o s e w ith a n a b n o r m a l E C G . C a r r a s c o ( 3 ) r e f e r s to 1 0 0 % s u r v i v a l a f te r 1 2 y e a r s f o r th e g r o u p w ith n o r m a l E C G , e v e n w ith s lig h t v e n tr ic u lo g r a p h ic a lte r a tio n s , a g a in s t 4 2 % o f th e g r o u p w ith a b n o r m a l E C G w ith o u t c a r d ia c in s u f f ic ie n c y . I n o u r e x p e r im e n t ( 8 ) w ith 1 0 9 s e r o p o s itiv e s w ith n o r m a l E C G s u b m itte d to h e m o d y n a m ic s tu d y a n d le f t a n d r ig h t c in e a n g io c a r d io g r a p h y , w e v e r if ie d th a t 9 1 .7 % h a d n o r m a l le f t v e n tr ic u la r e je c tio n f r a c tio n s , b u t 4 3 .1 % s h o w e d a b n o r m a lity o n th e c in e a n g io g r a p h y o f th e le f t v e n tr ic le , s u c h a s a s y n e r g y o f th e a p ic a l w a ll ( 2 6 .6 % ) , o f th e a n te r io r w a ll ( 4 .6 % ) , o r d if f u s e h y p o c o n tr a c ta b ility ( 8 .3 % ) . A s m a lle r p r o p o r tio n o f p a tie n ts ( 1 4 .3 % ) h a d c o n tr a c tile a lte r a tio n o f th e r ig h t v e n tr ic le .
C u r io u s ly , w h e n w e d iv id e th is g r o u p u p in to a s y m p to m a tic in d iv id u a ls ( 7 4 c a s e s ) a n d th o s e w h o s h o w e d s y m p to m s ( 3 5 c a s e s ) , w e c o u ld v e r if y , in th e c o m p a r is o n o f c lin ic a l a n d h e m o d y n a m ic -c in e a n g io g r a p h i-c v a r ia b le s , th a t th e s y m p to m a tic s u b g r o u p , in s p ite o f a g r e a te r a v e r a g e a g e , s h o w e d m o r e c a s e s o f n o r m a l le f t v e n tr ic le ( 7 1 .4 % ) o n th e c in e a n g io g r a p h y a n d a g r e a te r n u m b e r o f n o r m a l le f t v e n tr ic le e je c tio n f r a c tio n s ( 9 7 .1 % ) th a n th e s u b g r o u p o f a s y m p to m a tic in d iv id u a ls ( 8 9 ,2 % ) . H o w e v e r , th o u g h c u r io u s , th e s e n u m b e r s w e r e p o t s ta tis tic a lly s ig n if ic a n t
T a b le 1
C h a ra c te ris tic s o f th e p o p u la tio n w ith C h a g a s ' d is e a s e a n d s u b m itte d to le ft v e n tric le c in e a n g io v e n tric u lo g ra p h y
A s y m p to m a tic S y m p to m a tic T o ta l p
N o . 7 4 3 5 1 0 9
M e n 4 4 (5 9 .5 % ) 1 9 (5 4 .3 % ) 6 3 (5 7 .8 % ) n s
A g e 3 7 .9 :t 9 .1 4 2 .3 :t 8 .3 3 9 .8 :t 9 .1 p < 0 .0 5
N o rm a l L V 3 7 (5 0 % ) 2 5 (7 1 .4 % ) 6 2 (5 7 % ) n s
L V E F N o rm a l 6 6 (8 9 .2 % ) 3 4 (9 7 .1 % ) 1 0 0 (9 1 .7 % ) n s
L V E F D e p re s s e d 8 (1 2 .2 % ) 1 (2 .9 % ) 9 (8 .3 % ) n s
A p ic a l a s y n e rg y 2 2 (2 9 .7 % ) 7 (2 0 .0 % ) 2 9 (2 6 .6 % ) n s
A n te rio r a s y n e rg y 4 (5 .4 % ) 1 (2 .9 % ) 5 (4 .6 % ) n s
N o rm a l L V = n o rm a l le ft v e n tric le ; L V E F N o rm a l= n o rm a lle ft v e n tric u la r e je c tio n fra c tio n ; L V E F D e p re s s e d = d e p re s s e d le ft v e n tric le e je c tio n fra c tio n ; n s = N o s ta tis tic a l s ig n ific a n c e .
(T a b . 1 ). O f th e 3 5 s y m p to m a tic p a tie n ts w ith n o rm a l
E C G ,7 s u ffe re d c e re b ra l o r s y s te m a tic e m b o li a , 5 o f th e m
w ith n o rm a l le ft v e n tric le , a ll w ith n o rm a l e je c tio n
fra c tio n s o f th e le ft v e n tric le , a n d w ith o u t m u ra l th ro m b u s
d e te c te d b y th e c in e a n g io v e n tric u lo g ra p h y o r th e
e c h o c a rd io g ra m .
In a n a n a ly s is o f 1 0 1 0 c h a g a s ic p a tie n ts s u b m itte d
to c in e a n g io v e n tric u lo g ra p h y o r th e s a m e ty p e o f c lin ic a l
a n d h e m o d y n a m ic -c in e a n g io c a rd io g ra p h ic e v a lu a tio n , w e
o b s e rv e d th a t p a tie n ts w ith n o rm a l E C G , w h e n c o m p a re d
to p a tie n ts w ith E C G a b n o rm a litie s s u c h a s v e n tric u la r
e x tra s y s to le s , rig h t b u n d le b ra n c h b lo c k , b lo c k o f th e
a n te ro s u p e rio r d iv is io n o f th e le ft b u n d le b ra n c h a n d
is o la te d a tria l e x tra s y s to le s , h a d a s ig n ific a n tly y o u n g e r
a v e ra g e a g e , fe w e r c a s e s o f d e p re s s e d e je c tio n fra c tio n o f
th e le ft v e n tric le a n d le s s a b n o rm a l c in e a n g io
-v e n tric u lo g ra p h y o f th e le ft v e n tric le (T a b . 2 ).
A n o rm a l E C G in c h a g a s ic p a tie n ts , s y m p to m a tic o r
n o t, e v e n c o in c id in g w ith a n a to m ic a l o r fu n c tio n a l
a lte ra tio n s d e te c te d b y o th e r p re lim in a ry m e th o d s ,
in d ic a te s a fa v o ra b le p ro g n o s is w ith le s s m y o c a rd ia l
d y s fu n c tio n , e v a lu a te d b y th e e je c tio n fra c tio n o f th e le ft
v e n tric le a n d m o re n o rm a l le ft v e n tric le o n th e
c in e a n g io v e n tric u lo g ra p h y , th a n in p a tie n ts w ith is o la te d
E C G a lte ra tio n s , e v e n th o s e m o s t fre q u e n tly fo u n d in
C h a g a s ' d is e a s e .
T a b le 2
Is o la te d fin d in g s o n th e e le c tro c a rd io g ra m o f 1 0 1 0 c h a g a s ic p a tie n ts
N o . o f c a s e s A g e D e p re s s e d L V E F A b n o rm a l L V
N o rm a l 1 0 9 3 9 .3 :t 9 .1 8 .3 % 4 3 %
V E 4 0 4 7 .5 :t 9 .9 * * * 5 0 % * * * 2 0 % * * *
R S S 3 9 4 6 .1 :t 1 3 * * * 2 3 .1 % * 3 0 .8 % * *
L A H S 1 8 4 5 .3 :t 9 .8 * 3 3 .3 % * * 2 7 .8 % *
A S F 5 5 8 .5 :t 1 2 * * * 6 0 % * * 2 0 % n s
*= p < O .0 5 ;* * = p < O .0 1 ;* * * = p < O .0 0 1 (s ta tis tic a l a n a ly s is -e a c h is o la te d a lte ra tio n v e rs u s n o rm a l e le c tro c a rd io g ra m ). N o rm a l= n o rm a l e le c tro c a rd io g ra m ; V E = v e n tric u la r e x tra s y s to le s ; R B B = R ig h t b ra n c h b lo c k ; L A H B = L e ft a n te rio r h e m ib lo c k ; A S F = a n te ro s e p ta l fib ro s is ; n s = n o s ta tis tic a l s ig n ific a n c e .
ID m ~ ~ :w ~ ~ ~ ~ ~ ~ * = ,~ ~ ~ S 'm .:w .sw ~ ~ '> 'lrei= W ~ = m II:= = < @ M m s< ~ ~ m s< _ ~ i< l'% Ji$ _ ~ ~ ,.j,;~ ~ ~ ~ ~ ~ ~ ~
E L E C T R O C A R D IO G R A M
IN T H E C H R O N IC
P H A S E
T h e atten d an ce an d o b serv atio n o f p o p u latio n s in
en d em ic areas w ith . sy stem atic reg istry o f E C G in reg u lar
in terv als o v er y ears an d ev en d ecad es (6 ,1 2 ) allo w s
an aly sis o f th e tim e o f ap p earan ce an d ty p es o f alteratio n s
fo u n d , co rrelatin g th em w ith sero lo g ical ex am s fo r
ch ag asic in fectio n . T h is b ro u g h t u s im p o rtan t k n o w led g e
ab o u t th e n atu ral electro card io g rap h ic h isto ry o f C h ag as'
d isease, w h ich w e su m m arize as fo llo w s:
a) T h e p rev alen ce o fE C G alteratio n s in sero p o sitiv es
can b e as m u ch as 4 tim es m o re freq u en t th an sero n eg ativ es
in th e sam e reg io n . T h is reach es 9 .6 tim es m o re freq u en t
b etw een th e ag es o f 2 5 an d 4 4 , w ith red u ctio n o f th is
d isp ro p o rtio n after th e fifth d ecad e. In o ld er p erso n s (o v er
6 4 ), an d in y o u th s u p to 1 4 y ears o ld , th ere is n o d ifferen ce
b etw een sero p o sitiv es an d sero n eg ativ es (C astro A lv es, B ah ia (1 4 ).
b ) In n atio n al electro card io g rap h ic in q u iry (1 1 ), th e
p rev alen ce o f electro card io g rap h ic alteratio n s w as 3 7 .4 %
in sero p o sitiv es ag ain st 2 2 .6 % in sero n eg ativ es, th is b ein g
v ariab le acco rd in g to th e reg io n stu d ied : 8 .4 % in R io
G ran d e d o S u I an d u p to 3 2 % in G o ias. T h is b eh av io r
reflects reg io n al d ifferen ces in th e p ath o g en esis o f th e
d isease, w h ich is k n o w n to b e m o re sev ere in th e states o f
G o ias, M in as G erais, B ah ia, S ao P au lo an d P aran a, an d
less in th e S o u th ern states an d th e A m azo n reg io n .
c) T h e p rev alen ce o f ab n o rm al E C G is 4 .3 tim es
g reater in sero p o sitiv e m en th an in sero n eg ativ e m en , w h ile
sero p o sitiv e w o m en are o n ly 2 .6 tim es as lik ely to h av e
ab n o rm al E C G as sero n eg ativ e w o m en .
d ) D ias (5 ), an aly zin g th e casew o rk o f B am b u i,
v erified th at E C G alteratio n s lik e in co m p lete rig h t b ran ch
b lo ck , b lo ck o f th e an tero su p erio r d iv isio n o f th e left
b u n d le b ran ch , flatten ed T w av es, an d first d eg ree
atrio v en tricu lar b lo ck , sh o w ed u p earlier, b etw een 1 0 an d
2 0 y ears o ld in th e acu te p h ase an d o ften p reced ed th e
m an ifestatio n o f th e d isease, an d its d etectio n b y p h y sical
ex am in atio n an d th o rax rad io g rap h y .
e) R ig h t b u n d le b ran ch b lo ck an d v en tricu lar
ex trasy sto les o ccu rred later an d o th er ab n o rm alities lik e
in activ e areas, co m p lex arrh y th m ias an d to tal atrio v en tricu lar b lo ck o ccu rred in ev en later p erio d s.
T h is k in d o f ev o lu tio n co u ld b e ex p lain ed b y th e fact
th at th e in itial lesio n s, tran sito ry o r sp ecific, co rresp o n d
w ith an activ e in flam m ato ry p ro cess, n ev erth eless fo cal,
T a b le 3
T h e e le c tr o c a r d io g r a m in c h r o n ic c h a g a s ic c a r d io p a th y . P r e v a le n c e o f th e m o s t c o m m o n a b n o r m a litie s
M a g u ir e e t a l. * D ia s - K lo e tz e l* * C e lm o P o r to * * * G a r z o n - L o r g a * * * *
V E 7 .5 % 1 7 .5 % 2 8 % 4 0 .3 %
R B B 1 3 .3 % 2 4 .8 % 3 1 .5 % 3 3 .3 %
L A H B 2 .9 % 3 2 .7 %
L B B 0 % 0 .8 % 2 .3 % 3 .1 %
S T - T 9 % 4 .9 % 9 .2 % 2 6 .7 %
L V Q R S 7 .6 % 2 .6 % 7 %
A V B 1 s t 1 .2 % 3 % 3 %
A V B 2 n d 0 .3 % 2 % 3 %
A V B 3 r d 0 % 2 .6 % 4 % 5 .6 %
V T 0 % 0 .3 % 8 .2 %
A F 0 % 1 .8 % 2 .3 % 2 .5 %
A S F 2 .5 % 1 0 .3 %
lE A 3 .5 % 2 ,8 % 0 % 2 5 .1 %
V E = v e n tr ic u la r e x tr a s y s to le s ; R B B = r ig h t b r a n c h b lo c k ; L A H B = le ft a n te r io r h e m ib lo c k ; L B B = le ft b r a n c h b lo c k ; S T - T = a lte r a tio n s o f
th e S T -T s e g m e n t; L V Q R S = lo w v o lta g e o f th e Q R S ; A V B 1 s t = fir s t d e g r e e A V b lo c k ; V T = v e n tr ic u la r ta c h y c a r d ia ; A F = a tr ia l
fib r illa tio n ; A S F = a n te r o s e p ta l fib r o s is ; IE A = p r e s e n c e o f in a c tiv e e le c tr ic a l a r e a .
.• = N o n - s e le c te d s a m p le s , 3 4 6 c a s e s , c ity o f C a s tr o A lv e s , B a h ia , B r a z il.
.• .• = N o n - s e le c te d s a m p le s , 3 8 7 c a s e s , B a m b u i, M in a s G e r a is
.• .• .•= S e le c te d s a m p le s fr o m d o c to r o ffic e s , 5 0 3 c a s e s , T r iE ln g u lo M in e ir o
.• .• .• .•= S e le c te d fr o m d ia g n o s tic c e n te r , 1 0 1 0 c a s e s , S a o J o s e d o R io P r e to , S P
T a b le 4
R e s u lts o f le ft v e n tric u lo g ra p h y in g ro u p s w ith p ro g re s s iv e d e g re e s o f e le c tro c a rd io g ra p h ic a lte ra tio n s .
N E C G S A E C G A S E C G
N o . o f c a s e s 1 0 9 1 1 8 3 9 2
M e n 6 3 (5 7 .8 % ) n s 6 2 (5 2 .5 % ) n s 2 3 6 (6 0 .2 % ) A g e 3 9 .8 .:!: 9 .1 * * * 4 5 .1 .:!: 1 1 .1 n s 4 4 .1 .:!:1 1 S Y M P 3 5 (3 2 .1 % )* * * 9 5 (8 0 .5 % ) n s 3 4 4 (8 7 .7 % ) L V n o rm a l 6 2 (5 6 .9 % )* 5 0 (4 2 .4 % )* * * 7 8 (1 9 .9 % ) L V E F n o rm a l 1 0 0 (9 1 .7 % )* * 9 0 (7 6 .3 % )* 2 4 9 (6 3 .5 % ) A p ic a l a s y n e rg y 2 9 (2 6 .6 % ) n s 3 9 (3 3 .1 % )* * 2 2 4 (5 7 .1 % )
N E G G = n o rm a l E G G ; S A E G G = s lig h t o r in itia l E G G a lte ra tio n s ; A S E G G = A b n o rm a l E G G w ith n o rm a l R X a n d w ith 9 u t c a rd ia c in s u ffic ie n c y ; S Y M P = 's y m p to m a tic ; L V = le ft v e n tric le ; L V E F = le ft v e n tric le e je c tio n fra c tio n .
*= p < O .0 5 /* * = p < O .0 1 /* * * = p < O .0 0 1
w h i l e t h e m o r e s e v e r e a n d l a t e r a l t e r a t i o n s c o r r e s p o n d w i t h
p e r m a n e n t l e s i o n s t h r o u g h t h e f o r m a t i o n o f f i b r o s i s a n d
s c a r r i n g .
H o w e v e r , s t u d i e s i n e n d e m i c a r e a s s h o w t h a t
e l e c t r o c a r d i o g r a p h i c a l t e r a t i o n s a r e m o r e f r e q u e n t i n
s e r o p o s i t i v e m e n t h a n w o m e n , t h a t t h e r e i s a p e r i o d o f 1 0
t o 2 0 y e a r s a f t e r i n f e c t i o n w i t h a l o w p r e v a l e n c e o f
a b n o r m a l i t i e s , a n d t h a t t h e i r a p p e a r a n c e i s n o r m a l l y
g r a d u a l , a r o u n d 2 .6 % p e r y e a r i n p e r s o n s w i t h i n i t i a l l y
n o r m a l E C G . T h e f r e q u e n t o c c u r r e n c e o f c o n d u c t i o n
d e f e c t s , e s p e c i a l l y r i g h t b u n d l e b r a n c h b l o c k w i t h o r
w i t h o u t b l o c k o f t h e a n t e r o s u p e r i o r d i v i s i o n o f t h e l e f t
b u n d l e b r a n c h , i s c h a r a c t e r i s t i c i n e n d e m i c a r e a s .
V e n t r i c u l a r e x t r a s y s t o l e s a r e m o r e c o m m o n t h a n a t r i a l o n e s
a n d w e a l s o n o t i c e t ~ a t w a v e a l t e r a t i o n s a r e m o r e p r e v a l e n t
i n y o u n g s e r o p o s i t i v e p a t i e n t s w h e n c o m p a r e d w i t h
s e r o n e g a t i v e p e o p l e o f t h e s a m e a g e . C u r i o u s l y , t h e
i n c i d e n c e o f s i n u s a r r h y t h m i a a m o n g y o u n g s e r o p o s i t i v e s
w a s s i g n i f i c a n t l y l e s s t h a n t h a t o f s e r o n e g a t i v e s , p o s s i b l y
t h r o u g h d a m a g e t o t h e a u t o m a t i c c a r d i a c s y s t e m . S o m e o f
t h e m o r e f r e q u e n t e l e c t r o c a r d i o g r a p h i c a l t e r a t i o n s o f
C h a g a s ' d i s e a s e h a v e a w e l l - d e f i n e d a n a t o m i c a l s u b s t r a t e .
A n a t o m o p a t h o l o g i c a l s t u d i e s d o n e b y A n d r a d e , O l i v e i r a ,
P r a t a , a n d M o t t , s h o w p r e d i l e c t i o n o f t h e d i s e a s e f o r t h e
c o n d u c t i o n s y s t e m , a s o b s e r v e d b y a r e a s o f d e g e n e r a t i o n
a n d f i b r o s i s m a i n l y i n t h e r i g h t h a l f o f t h e H i s b u n d l e , t h e
r i g h t b r a n c h , t h e l e f t a n t e r o s u p e r i o r f a s c i c l e a n d l e s s i n
t h e p o s t e r i o r - i n f e r i o r f a s c i c l e . T h i s f a i r l y r a n d o m
d i s t r i b u t i o n e x p l a i n s t h e h i g h p r e v a l e n c e o f r i g h t b u n d l e
b r a n c h b l o c k , i t s f r e q u e n t a s s o c i a t i o n w i t h b l o c k o f t h e
a n t e r o s u p e r i o r d i v i s i o n o f t h e l e f t b u n d l e b r a n c h a n d t h e
u n c o m m o n p r e s e n c e o f b l o c k o f t h e p o s t e r i o r - i n f e r i o r
d i v i s i o n o f t h e b u n d l e b r a n c h a n d l e f t b r a n c h b l o c k , e x c e p t
w h e n m o r e 'e x t e n s i v e l e s i o n s l e a d t o t o t a l a t r i o v e n t r i c u l a r
b l o c k s o f t h e t r i f a s c i c u l a r t y p e .
V e n t r i c u l a r a r r h y t h m i a s , s o f r e q u e n t l y f o u n d , c o u l d
h a v e t h e i r g e n e s i s : a ) i n l e s i o n s l o c a t e d i n t h e H i s - P u r k i n j e
( i n t r a v e n t r i c u l a r ) r e g i o n , c r e a t i n g f o c a l p o i n t s o f e c t o p i c
a c t i v i t y o r r e - e n t r y m e c h a n i s m s ; b ) f r o m a u t o m a t i c
i m b a l a n c e w i t h g r e a t e r s e n s i t i v i t y t o c i r c u l a t i n g
c a t e c h o l a m i n e s ; c ) i n a r e a s o f t i s s u e l e s i o n t h r o u g h
i n f l a m m a t o r y p r o c e s s ; d ) a d j a c e n t t o a r e a s o f f i b r o s i s a n d
a n e u r y s m a t i c f o r m a t i o n s , m a i n l y i n a p i c a l r e g i o n s o f b o t h
v e n t r i c l e s a n d p o s t e r i o r a n d i n f e r o l a t e r a l w a l l s o f t h e l e f t
v e n t r i c l e .
D IA G N O S T IC IM P O R T A N C E
C o n v e n t i o n a l E C G i s s e n s i t i v e i n t h e d e t e c t i o n o f
c h r o n i c c a r d i o p a t h y a n d E C G a l t e r a t i o n s a l m o s t a l w a y s
p r e c e d e t h e a p p e a r a n c e o f s i g n s a n d s y m p t o m s . I n o u r
e x p e r i e n c e , E C G a l t e r a t i o n s h a v e a l w a y s p r e c e d e d t h e
a p p e a r a n c e o f a b n o r m a l i t i e s o n t h o r a x r a d i o g r a p h y . T h i s
o c c u r s d u e t o t h e p r e f e r e n c e o f t h e d i s e a s e f o r t h e
c o n d u c t i o n s y s t e m a n d e x c i t o c o n d u c t i o n s y s t e m ,
p r o d u c i n g l e s i o n s t h a t m a n i f e s t t h e m s e l v e s e a r l y o n t h e
E C G , a n d th a t c a n . b e th e o n ly e v id e n c e o f c a r d io p a th y u n til c o n tr a c tile d y s f u n c tio n s a n d th e ir c lin ic a l. r e p e r c u s s io n s a p p e a r .
C h a g a s ' d is e a s e c a n c a u s e a n y ty p e o f E C G a lte r a tio n , b u t c la s s ic a lly w e r e c o g n iz e r ig h t b u n d le b r a n c h b lo c k , a s s o c ia te w ith b lo c k o f th e a n te r o s u p e r io r d iv is io n o f th e le f t b u n d le b r a n c h a n d v e n tr ic u la r e x tr a s y s to le s a s ty p ic a l E C G tr a c in g s .
I n th e lite r a tu r e , th e p r e v a le n c e v a r ie s w ith th e p o p u la tio n s tu d ie d . I n T a b le 3 w e s e e , in th e f ir s t tw o c o lu m n s , c a s e w o r k in e n d e m ic r u r a l a r e a s w ith n o n -s e le c te d s a m p le s ; th e la s t tw o c o lu m n s r e f e r to s a m p le s f r o m d o c to r 's o f f ic e s a n d u r b a n d ia g n o s tic c e n te r s in a r e a s o f h ig h in c id e n c e o f th e d is e a s e .
T h e p e r c e n ta g e v a lu e s v a r y w ith th e ty p e o f s e le c tio n , b u t r ig h t b u n d le b r a n c h b lo c k , b lo c k o f th e a n te r o s u p e r io r d iv is io n o f th e le f t b u n d le b r a n c h , v e n tr ic u la r e x tr a s y s to le s a n d a lte r a tio n s in th e T w a v e a r e th e m o s t f r e q u e n t f in d in g s . R ig h t b u n d le b r a n c h b lo c k is th e m o s t c h a r a c te r is tic a lte r a tio n , s in c e it is h ig h ly p r e v a le n t, f a ir ly s p e c if ic a n d o f g r e a t p o s itiv e p r e d ic tiv e v a lu e ; it is r a r e in a s e r o n e g a tiv e p e r s o n u n d e r 5 0 ( 5 .5 % ) , w h ile it o c c u r s in u p to 5 3 % o f th e s e r o p o s itiv e p o p u la tio n ( M a g u ir e [ 5 ] ) . I n c o m p le te r ig h t b u n d le b r a n c h b lo c k , b lo c k o f th e a n te r o s u p e r io r d iv is io n o f th e le f t b u n d le b r a n c h a n d b lo c k o f th e p o s te r o in f e r io r d iv is io n o f th e le f t b u n d le b r a n c h , o c c u r in is o la tio n in s e r o p o s itiv e s a s m u c h a s s e r o n e g a tiv e s , b u t th e ir a s s o c ia tio n is h ig h ly s p e c if ic .
T a b le 5
A n a ly s e s o f th e " fib r o s is ty p e a b n o r m a litie s " te s ts o n th e E C G in o r d e r to d e te c t a lte r a tio n s o f th e s e g m e n ta l c o n tr a c tio n o f th e le ft v e n tr ic le th r o u g h c in e a n g io g r a p h y
. S e g m e n ta l
E C G a lte r a tio n S e n s .% S p e c .% + P V % - P V % O R
A n te r io r A p ic a l
19
89
66
49
1.8
S e p ta l A p ic a l
16
90
63
49
1.6
A n te r o s e p ta l A p ic a l
12
92
65
48
1.7
In fe r io r In fe r io r
11
95
8
96
2.2
A n te r io r A n te r io r
17
85
12
89
1.1
L a te r a l L a te r a l
4
95
2
98
0.8
P o s te r io r D o r s a l
0
100
0
97
0
E C G = e le c tr o c a r d io g r a p h ic a lte r a tio n s u g g e s tiv e o f fib r o s is ; S e n s .= s e n s itiv ity ; S p e c .= s p e c ific ity ; + P V = p o s itiv e p r o g n o s tic v a lu e ; - P V = n e g a tiv e p r o g n o s tic v a lu e ; O R = o d d s r a tio .
O th e r f a ir ly c h a r a c te r is tic a lte r a tio n s b e f o r e th e s e v e n th d e c a d e a r e s e c o n d d e g r e e a tr io v e n tr ic u la r b lo c k ( M o b itz ty p e ( 7 ) ) , a n d to ta l a tr io v e n tr ic u la r b lo c k , w h ic h a r e u n c o m m o n in s e r o n e g a tiv e s . L e f t b r a n c h b lo c k , f r e q u e n tly s e e n in d ila te d c a r d io m y o p a th y , is r a r e in C h a g a s ; d is e a s e , h a v in g a n a v e r a g e p r e v a le n c e 2 8 tim e s s m a lle r th a n th a t o f r ig h t b u n d le b r a n c h b lo c k . I s o la te d v e n tr ic u la r e x tr a s y s to le s a r e f r e q u e n tly f o u n d b u t a r e n o n -s p e c if ic , n o t d if f e r e n tia tin g s e r o p o s itiv e s f r o m s e r o n e g a tiv e s , o c c u r r in g a s m u c h in h e a lth y p e r s o n s a s in d iv e r s e c a r d io p a th ie s . I ts p r e s e n c e in s e r o p o s itiv e s h a s g r e a t p r e d ic tiv e v a lu e f o r r e p e titiv e v e n tr ic u la r a r r h y th m ia s : 8 2 % o f c h a g a s ic p a tie n ts w ith v e n tr ic u la r • e x tr a s y s to le s o n th e c o n v e n tio n a l E C G h a d p a ir s o r v o lle y s
o f e x tr a s y s to le s o n th e H o lte r a g a in s t 2 1 % in n o n - c h a g a s ic in d iv id u a ls ( 1 2 ) . I n e n d e m ic a r e a s th e r e g is te r o f 2 4 h o u r d y n a m ic e le c tr o c a r d io g r a m s h o w s th a t th e a v e r a g e n u m b e r o f v e n tr ic u la r e x tr a s y s to le s is 1 3 7 tim e s h ig h e r in s e r o p o s itiv e s th a n in s e r o n e g a tiv e s , a n d p a ir s a n d v o lle y s a r e m o r e f r e q u e n t a s w e ll.
I s c h e m ic ty p e a lte r a tio n s o c c u r s in 1 0 % o f o u r p a tie n ts a n d c a n b e c o n f u s e d w ith is c h e m ic c a r d io p a th y . I s o la te d a n d d is c r e te a lte r a tio ~ s lik e f ir s t d e g r e e a tr io v e n tr ic u la r b lo c k , lo w Q R S v o lta g e , r a r e v e n tr ic u la r e x tr a s y s to le s , in c o m p le te r ig h t b r a n c h b lo c k a n d lo c a liz e d f la tte n in g o f th e T w a v e c o u ld b e th e f ir s t a n d o n ly s ig n o f C h a g a s ' d is e a s e . T h e a u th o r s ( 8 ) , in o r d e r to v e r if y th e im p o r ta n c e o f th is a b n o r m a lity , s e le c te d a g r o u p o f
Table 6
Electrocardiographic and clinical variables versus the presence of apical lesion of the
left ventricle-simple
and multiple regression analyses
Variable
VE
Is c h e m ia
V T
R S S L A H S L S S
A n te rio r E G G S e p ta l E G G In fe rio r E G G L a te ra l E G G A g e
S y n c o p e
Dependent correlation
p < O .0 0 0 1 p < O .0 0 0 1 p < O .0 0 0 1 p < O .0 0 0 1 p < O .0 0 0 1 p < O .0 0 5 p < O .0 0 0 1 p < O .0 0 1 p < O .0 1 p < O .0 0 2 p < O .0 1 p < O .0 0 1
Independent correlation
p < O .0 0 0 1 p < O .0 0 0 1
n s
n s n s
n s
n s n s n s n s n s p < O .0 4
V E = v e n tric u la r e x tra s y s to le s ; V T = v e n tric u la r ta c h y c a rd ia s ; R B B = rig h t b ra n c h b lo c k ; L A H B = le ft a n te rio r h e m ib lo c k ; L B B = le ft b ra n c h b lo c k ; E C G = e le c tro c a rd io g ra p h ic a lte ra tio n s u g g e s tiv e o f fib ro s is ; Is c h e m ia = is c h e m ic ty p e S T -T a lte ra tio n .
c h a g a s ic p a tie n ts w ith th e s e in itia l a lte ra tio n s a n d
c o m p a re d it w ith a g ro u p w ith n o rm a l E C G a n d a g ro u p
w ith g re a te r E C G a lte ra tio n s , b u t w ith ra d io g ra p h y th a t
in d ic a te d a n o rm a l c a rd ia c a re a a n d n o c a rd ia c
in s u ffic ie n c y (T a b .. 4 ). T h e v a ria b le s a n a ly z e d w e re s e x ,
a g e , d e p re s s e d e je c tio n fra c tio n o f th e le ft v e n tric le ,
a b n o rm a l le ft v e n tric le c in e a n g io v e n tric u lo g ra p h y a n d th e
p re s e n c e o f a p ic a l a s y n e rg y . T h e " s lig h tly a lte re d E C G "
g ro u p p o s itio n e d its e lf in in te rm e d ia te s e v e rity b e tw e e n
th e n o rm a l E C G g ro u p a n d th e o b v io u s ly a b n o rm a l E C G
g ro u p a s fa r a s p re v a le n c e o f d e p re s s e d e je c tio n fra c tio n
o f th e le ft v e n tric le a n d a b n o rm a l le ft v e n tric le
c in e a n g io v e n tric u lo g ra p h y : 2 6 .7 % h a d d e p re s s e d e je c tio n
fra c tio n v e rs u s 7 .6 % in th e n o rm a l E C G g ro u p (p < 0 .0 1 )
a n d 3 6 .5 % in th e a b n o rm a l E C G g ro u p (p < 0 .0 5 ).T h e le ft
v e n tric le c in e a n g io v e n tric u lo g ra p h y w a s a b n o rm a l in
5 7 .6 % v e rs u s 4 6 .1 % in th e n o rm a l E C G g ro u p (p < 0 .0 5 )
a n d 8 0 .0 1 % in th e a b n o rm a l E C G g ro u p (p < 0 .0 0 1 ). T h e
p a tie n ts w ith s lig h tly a lte re d E C G s h o w e d , in re la tio n to
th e n o rm a l E C G g ro u p , a h ig h e r a v e ra g e a g e (p < O .O O1 )
a n d a g re a te r p re v a le n c e o f s y m p to m a tic p a tie n ts
(p < O .O O 1 ), th o u g h th e in c id e n c e o f a p ic a l le s io n w a s n o t
s ig n ific a n t. In re la tio n to th e g ro u p w ith a b n o rm a l E C G ,
th e re w a s n o d iffe re n c e a s to a v e ra g e a g e a n d th e p re s e n c e
o f s y m p to m s , th o u g h th e y h a d fe w e r a p ic a l le s io n s , 3 6 .1 %
v e rs u s 5 7 .1 % (p < 0 .0 1 ). T h e s e d a ta c o in c id e w ith c lin ic a l
e x p e rie n c e th a t s h o w s th a t p a tie n ts w ith s lig h t E C G
808
a lte ra tio n s a re a t ris k o f d e v e lo p in g m o re a c c e n tu a te d
a lte ra tio n s a n d g re a te r p ro g re s s io n o f th e d is e a s e , a n d th e ir
c a s e s s h o u ld b e c a re fu lly a c c o m p a n ie d .
C o n tra c tile a lte ra tio n s o f th e a p ic a l w a ll o f th e le ft
v e n tric le , o r " a p ic a l le s io n " , a re a n a to m ic a l p e c u lia ritie s
o f C h a g a s ' d is e a s e a n d th e ir e le c tro c a rd io g ra p h ic
c o rre s p o n d e n c e h a s b e e n s e a rc h e d fo r. A n te rio r, s e p ta l a n d
a n te ro s e p ta l fib ro s is h a v e a lre a d y b e e n p ro p o s e d a s
e le c tro c a rd io g ra p h ic m a n ife s ta tio n s . C o rre la tio n s d o n e b y
th e a u th o rs s h o w th a t th e s e a lte ra tio n s g e n e ra lly h a v e g o o d
s p e c ific ity , th o u g h v e ry lo w s e n s itiv ity a n d p o s itiv e
p re d ic tiv e v a lu e (+ P V ) (T a b . 5 ). In s ta tis tic a l s tu d ie s o f
u n i- a n d m u ltiv a ria te a n a ly s is , c o n s id e rin g a ll th e E C G
a lte ra tio n s a n d w ith a p ic a l le s io n a s a d e p e n d e n t v a ria b le
(T a b . 6 ), it w a s o b s e rv e d th a t m o s t e le c tro c a rd io g ra p h ic
a lte ra tio n s re la te to a p ic a l le s io n s , th o u g h o n ly v e n tric u la r
e x tra s y s to le s , th e is c h e m ic p a tte rn o f th e S T s e g m e n t a n d
le ft b ra n c h b lo c k re la te w ith it in d e p e n d e n tly .
In is c h e m ic c a rd io p a th y th e re is a g o o d c o rre la tio n
b e tw e e n th e in a c tiv e a re a s o r " fib ro s is " o f c e rta in w a lls
a n d th e c o rre s p o n d e n t a lte ra tio n o f th e s e g m e n ta l
c o n tra c tio n o r th e le ft v e n tric le o n th e
c in e a n g io v e n tric u lo g ra p h y . In o u r e x p e rie n c e , s u c h
c o rre s p o n d e n c e d o e s n o t o c c u r in C h a g a s ' d is e a s e : T a b le
5 s h o w s th a t th e a n te rio r, in fe rio r, p o s te rio r a n d la te ra l
fib ro s is e s h a v e lo w p o s itiv e p re d ic tiv e v a lu e (+ P V ) fo r
c o rre s p o n d in g a s y n e rg ic a re a s o n th e
c in e a n g io v e n tric u lo g ra p h y . T h e su m o fth e se n sitiv ity a n d
sp e c ific ity p e rc e n ta g e s is c lo se to 1 0 0 % , in d ic a tin g a n
a le a to ry re la tio n sh ip b e tw e e n E C G a lte ra tio n a n d lo c a liz e d
c o n tra c tile d y sfu n c tio n o f th e le ft v e n tric le .
P R O G N O S T I C I M P O R T A N C E
A g iv e n E C G a lte ra tio n sh o u ld n o t b e c o n sid e re d in
iso la tio n in th e p ro g n o stic e v a lu a tio n o f a c h a g a sic p a tie n t,
b u t ra th e r to g e th e r w ith th e c lin ic a l c h a rt a n d a n a to m ic a l
a n d fu n c tio n a l d a ta o b ta in e d th ro u g h o th e r c o m p le m e n ta ry
e x a m s. H o w e v e r, c e rta in a lte ra tio n s c a n , n e v e rth e le ss, b e
p ro g n o stic a lly im p o rta n t b e c a u se o f th e ir in h e re n t se v e rity ,
fo r e x a m p le , a v e n tric u la r ta c h y c a rd ia , o r w h e n it
re p re se n ts a g g re ssio n o f sp e c ific c o n d u c tio n tissu e s, su c h
a s a trio v e n tric u la r b lo c k s o r b ra n c h b lo c k s.
A s it h a s b e e n p re v io u sly d isc u sse d (7 ,8 ,1 2 ), it is
k n o w n th a t a n o rm a l E C G in d ic a te s a sig n ific a n tly g re a te r
su rv iv a l ra te a n d th a t c e rta in iso la te d a b n o rm a litie s o f little
im p o rta n c e c a n c o rre sp o n d to g re a te r m y o c a rd ia l
c o m p ro m ise . O th e r iso la te d a lte ra tio n s, b u t m a in ly in
a sso c ia tio n , c a n in d ic a te g re a te r a g g re ssio n b y th e d ise a se
a n d a w o rse p ro g n o sis.
L o n g itu d in a l stu d ie s (4 ,5 ,1 5 ,1 7 ), so m e p e rfo rm e d
d e c a d e s a g o (5 ,1 5 ), in d ic a te to u s w h ic h
e le c tro c a rd io g ra p h ic a lte ra tio n s a re re la te d to g re a te r
m o rta lity , b u t w e sh o u ld re m e m b e r th a t to d a y th e u se o f
m o re e ffe c tiv e d ru g s in th e tre a tm e n t o f a rrh y th m ia s a n d
c a rd ia c in su ffic ie n c y h a v e m o d ifie d th e su rv iv a l c u rv e s.
P o rto (l0 ) a n d D ia s a n d K lo itz e l (6 ), L a ra n ja (l0 ),
a n d B ra sil (2 ) a n d th e ir c o lla b o ra to rs, in th e se lo n g itu d in a l
stu d ie s, c o m p a re d th e e le c tro c a rd io g ra p h ic fin d in g s o f
liv in g p a tie n ts w ith th e fin d in g s o f th e g ro u p o f d e a d
p a tie n ts a n d a g re e d th a t m u ltifo c a l v e n tric u la r e x tra sy sto le ,
to ta l a trio v e n tric u la r b lo c k , le ft b ra n c h b lo c k , a tria l
fib rilla tio n a n d fib ro sis in d ic a te d g re a te r risk o f d e a th .
P o rto (5 ) a n d D ia s (6 ), c o m m e n t th a t c e rta in
a lte ra tio n s lik e rig h t b u n d le b ra n c h b lo c k a n d
m o n o m o rp h ic v e n tric u la r e x tra sy sto le s, w h e n iso la te d , h a d
g o o d p ro g n o sis, h o w e v e r, w h e n a sso c ia te w ith th e m se lv e s,
w ith o th e r b u n d le b lo c k s (h e m ib lo c k o f th e a n te ro su p e rio r
d iv isio n o f th e rig h t b u n d le b ra n c h ), o r d iffe re n t ty p e s o f
fib ro sis, th e re w a s le ss su rv iv a l.
T H E N U M B E R O F A L T E R A T I O N S P E R
T R A C I N G
P o rto (1 5 ), v e rifie d a n a v e ra g e n u m b e r o f 1 .5
a lte ra tio n s p e r tra c in g , a n a v e ra g e th a t, in a g ro u p w ith
fa ta l e v o lu tio n , w a s 1 .8 , a n d n o n -fa ta l,
104.
H e su g g e ste dth a t in a tra c in g w ith o n e a lte ra tio n , th e p ro g n o sis w a s
g o o d , tw o w a s w o rse , a n d in c a se s w ith th re e o r m o re
a b n o rm a litie s p e r tra c in g th e p ro g n o sis w a s b le a k .
D ia s (6 ) fo u n d a n a v e ra g e o f 1 .7 5 , o b se rv in g th a t
th e fa ta l g ro u p h a d a n a v e ra g e o f 2 a lte ra tio n s p e r tra c in g .
In o u r m a te ria l o f 9 0 1 c h a g a sic p a tie n ts w ith
e le c tro c a rd io g ra p h ic a lte ra tio n s, to g e th e r w ith c lin ic a l a n d
ra d io lo g ic a l e v a lu a tio n s, a n d le ft v e n tric le e je c tio n
fra c tio n s m e a su re d b y c in e a n g io v e n tric u lo g ra p h y , w e
v e rifie d a n a v e ra g e o f 3 .0 6 : t 0 .9 a lte ra tio n s p e r tra c in g .
In c a se s w h e re th e le ft v e n tric le e je c tio n fra c tio n w a s
n o rm a l, th e a v e ra g e w a s 2 .5 : t 0 .9 v e rsu s 3 .5 3 : t 1 .0 in
c a se s w ith d e p re sse d e je c tio n fra c tio n s (p < O .O O 1 ). T h e
a v e ra g e n u m b e r p e r tra c in g w a s a lso sig n ific a n tly la rg e r
(p < O .O O l) in th e g ro u p w ith c a rd io m e g a ly o n th e ir th o ra x
ra d io g ra p h y (3 .5 2 : t 0 .9 ) th a n in th e g ro u p w ith n o rm a l
th o ra x ra d io g ra p h y (2 .6 2 : t 0 .8 5 ). T h is su g g e sts th a t
tra c in g s c o m b in in g a g re a te r n u m b e r o f a lte ra tio n s
c o rre sp o n d w ith a lo w e r e je c tio n fra c tio n a n d g re a te r
c a rd io m e g a ly o n th e th o ra x ra d io g ra p h y , in d ic a tin g a w o rse
p ro g n O S IS .
B R A N C H B L O C K S
M a g u ire e t a l. (1 2 ) a n d D ia s e t a l. (6 ) o b se rv e d th a t
iso la te d rig h t b u n d le b ra n c h b lo c k o c c u rre d a s m u c h in th e
fa ta l g ro u p a s in th e n o n -fa ta l g ro u p , b e in g c o m p a tib le w ith
lo n g life . W h e n a sso c ia te d w ith o th e r a lte ra tio n s, p rin c ip a lly
v e n tric u la re x tra sy sto le s a n d fib ro sis, it w a s th re e tim e s m o re
c o m m o n in th e fa ta l g ro u p . W h e n o b se rv e d in y o u n g
p a tie n ts, th e re w a s a g re a te r risk o f p ro g re ssio n o f th e
d ise a se , a n d c a rd ia c in su ffic ie n c y a n d to ta l a trio v e n tric u la r
b lo c k , n e c e ssita tin g m o re fre q u e n t c lin ic a l a tte n tio n . T h e
a sso c ia tio n w ith v e n tric u la r e x tra sy sto le s w a s re la te d to a
g re a te r in c id e n c e o f su d d e n d e a th .
In o u r c a se w o rk (T a b . 7 ), o f th e c a se s w ith iso la te d
rig h t b u n d le b ra n c h b lo c k , 7 7 % h a d n o rm a l e je c tio n
fra c tio n s o f th e le ft v e n tric le ; h o w e v e r, w h e n it w a s
a sso c ia te w ith so m e o th e r a lte ra tio n , it w a s n o rm a l in o n ly
4 5 .2 % (p < O .O O 1 ). If th e a sso c ia tio n w a s w ith v e n tric u la r
e x tra sy sto le s, th e n u m b e r o f n o rm a l e je c tio n fra c tio n s w a s
e v e n le ss (3 6 % ).
T a b le 7
Is o la te d a n d c o m b in e d E C G a lte ra tio n s .
C o m p a ris o n w ith in c id e n c e o f d e p re s s e d le ft v e n tric le e je c tio n fra c tio n
Is o la te d a lte ra tio n s C o m b in e d a lte ra tio n s p
N o . D E F % N o . D E F %
VE
4 0 5 0 4 0 7 6 1 .2 p < 0 .0 5R B B 3 9 2 3 .1 3 3 6 5 4 .8 p < 0 .0 0 1
L A H B 1 8 3 3 .3 3 3 0 5 8 .5 n s
L B B 1 1 8 1 .8 3 1 9 0 .3 n s
"F ib ro s is " 3 3 4 2 .4 2 2 8 6 9 .7 p < 0 .0 1
R B B + L A H B 4 9 2 4 .5 2 1 7 5 9 p < 0 .0 5
N o . = n u m b e r o f p a tie n ts ;' D E F % = % o f c a s e s w ith d e p re s s e d e je c tio n fra c tio n in th e g ro u p ; V E :::;v e n tric u la r e x tra s y s to le s ; R B B = rig h t b ra n c h b lo c k ; "F ib ro s is "= in a c tiv e a re a s ; p = s ig n ific a n c e o f c o m p a ris o n b e tw e e n th e p re v a le n c e o f d e p re s s e d e je c tio n
fra c tio n in th e g ro u p s w ith is o la te d E G G a lte ra tio n s v e rs u s th e g ro u p s w ith c o m b in e d a lte ra tio n s ; n s = n o s ta tis tic a l s ig n ific a n c e .
A s s o c ia tio n w ith b lo c k o f th e a n te r o s u p e r io r d iv is io n
o f th e le f t b u n d le b r a n c h d id n o t c o r r e s p o n d w ith th e w o r s e
p r o g n o s is a n d 7 5 .5 % o f th o s e c a s e s h a d n o r m a l le f t
v e n tr ic le e je c tio n f r a c tio n s . I s o la te d b lo c k o f th e
a n te r o s u p e r io r d iv is io n o f th e le f t b u n d le b r a n c h
c o r r e s p o n d e d to 6 6 .7 % n o r m a l le f t v e n tr ic le s ; if a s s o c ia te
w ith o th e r a lte r a tio n s , th e n 4 1 .5 % ( n o t s ig n if ic a n t) .
I n c h a g a s ic p a tie n ts w ith le f t b r a n c h b lo c k ( 3 1 c a s e s ) ,
th e le f t v e n tr ic le e je c tio n f r a c tio n w a s o n ly n o r m a l in 9 .7 % ,
c o n f ir m in g a p o o r p r o g n o s is .
V E N T R IC U L A R A R R H Y T H M IA S
V e n tr ic u la r e ~ tr a s y s to le is f o u n d m o r e o f te n in th e
E C G o f c h a g a s ic p a tie n ts ; it o c c u r s in 4 0 % o f o u r p a tie n ts ,
in 4 % b e in g th e o n ly a lte r a tio n , a n d it o c c u r s in 5 4 .5 % o f th e c a s e w o r k o f S a n ta n a ( 1 7 ) . W h ile s o m e a u th o r s s u g g e s t
th a t is o la te d v e n tr ic u la r e x tr a s y s to le s d o n o t im p ly a w o r s e
p r o g n o s is , o th e r s p o in t o u t th a t its p r e s e n c e o n th e tr a c in g a lr e a d y in d ic a te s th e h ig h p r e v a le n c e o f c o m p le x , r e p e titiv e
f o r m s a n d o f v e n tr ic u la r ta c h y c a r d ia o n 2 4 h o u r c o n tin u o u s
r e g is te r s .
W e h a v e o b s e r v e d th a t 5 0 % o f o u r p a tie n ts w ith
is o la te d v e n tr ic u la r e x tr a s y s to le s o n c o n v e n tio n a l E C G h a d
d e p r e s s e d e je c tio n f r a c tio n s o f th e le f t v e n tr ic le , a n d in
c a s e s w h e r e v e n tr ic u la r e x tr a s y s to le s c o m b in e d w ith o th e r
a lte r a tio n s th e n th e in c id e n c e r o s e to 6 7 .2 % ( p < 0 .0 5 ) . I f
th e c o m b in a tio n w a s w ith s o m e k in d o f f ib r o s is , th e n it
w a s w o r s e : 8 4 .4 % h a d d e p r e s s e d e je c tio n f r a c tio n s .
B a r r e tto ( 1 ) f o u n d v e n tr ic u la r e x tr a s y s to le s in 1 4 % o f th e
p a tie n ts w ith n o r m a l e je c tio n f r a c tio n a n d in 6 5 % w h e n
th e e je c tio n f r a c tio n . w a s le s s th a n 4 4 % , w ith s im ila r
v e n tr ic u la r ta c h y c a r d ia b e h a v io r o n th e H o lte r e x a m . S a n ta n a e t a l. ( 1 7 ) o b s e r v e d th a t in c a s e s w ith O w n ty p e
4 B v e n tr ic u la r e x tr a s y s to le s , p a tie n ts h a d a 4 8 % c h a n c e
o f s u r v iv a l in 7 y e a r s ,. b u t th a t if th e r e w a s a s s o c ia te
c a r d io m e g a ly th e c h a n c e s o f s u r v iv a l w e r e o n ly 2 9 .5 % .
C o n v e n tio n a l E C G c a n n o t r e c o g n iz e th e tr a n s ito r y
c h a r a c te r o f a v e n tr ic u la r a r r h y th m ia , n o r c a n it a llo w
e v a lu a tio n o f its f r e q u e n c y o r s e v e r ity ; n e v e r th e le s s , w h e n p r e s e n t, th e s e a r r h th m ia s a r e in d ic a to r s o f s e v e r ity . I f
a s s o c ia te d w ith c lin ic a l d a ta , o th e r e le c tr o c a r d io g r a p h ic
a lte r a tio n s o r f u n c tio n a l in d ic a to r s o f g r e a te r m y o c a r d ia l
c o m p r o m is e , th e p r o g n o s is is s ig n if ic a n tly w o r s e . R a s s i
e t a l. ( 1 6 ) v e r if ie d m o r ta lity o f n e a r ly 1 0 0 % in 5 y e a r s in p a tie n ts w ith s u s ta in e d v e n tr ic u la r ta c h y c a r d ia ; L o r g a e t
a l. ( 9 ) a c c o m p a n ie d th e c a s e s o f 4 0 c h a g a s ic p a tie n ts w ith s u s ta in e d v e n tr ic u la r ta c h y c a r d ia o v e r 1 3 y e a r s , c e r tif y in g
t h a t i n t h e g r o u p w i t h n o r m a l e j e c t i o n f r a c t i o n t h e r e w e r e
n o o b i t s , w h i l e o f t h e p a t i e n t s w i t h v e r y d e p r e s s e d e j e c t i o n
f r a c t i o n o n l y 2 0 % s u r v i v e d .
A T R I O V E N T R I C U L A R B L O C K S
S i n c e t h e t i m e w h e n C a r l o s C h a g a s c a l l e d a t t e n t i o n
t o t h e f r e q u e n c y a n d i m p o r t a n c e o f " s l o w p u l s e " , g r e a t
p r o g r e s s h a s b e e n m a d e i n t h e d i a g n o s i s a n d t r e a t m e n t o f
b r a d y a r r h y t h m i a s .
D y s f u n c t i o n s o f t h e s i n u s n o d e a r e b e t t e r i d e n t i f i e d
t h r o u g h e l e c t r o p h y s i o l o g i c s t u d y t h a n w i t h c o n v e n t i o n a l
E C G , b u t t h e y r a r e l y m a n i f e s t t h e m s e l v e s c l i n i c a l l y , a n d
n e e d t o b e i d e n t i f i e d i n s y m p t o m a t i c p a t i e n t s a n d i n
c a n d i d a t e s f o r t h e u s e o f b r a d y c a r d i a l d r u g s .
A t r i o v e n t r i c u l a r b l o c k s , a s h a s a l r e a d y b e e n s e e n ,
a r e r e l a t i v e l y f r e q u e n t ; h o w e v e r , b e s i d e s t h e d e g r e e o f t h e
b l o c k , i t s l o c a t i o n s h o u l d a l s o b e i d e n t i f i e d : w h e t h e r i t i s
i n t h e a t r i o v e n t r i c u l a r n o d e o r i n t h e H i s - P u r k i n j e
( i n t r a v e n t r i c u l a r ) s y s t e m , s i n c e t h e s e d i s p l a y d i v e r s e
e v o l u t i o n s a n d p r o g n o s i s e s . B l o c k s o f t h e H i s - P u r k i n j e
a r e u s u a l l y s y m p t o m a t i c , a p p e a r i n g s u d d e n l y , w i t h l o w e r
f r e q u e n c y , a n d d o n 't r e s p o n d t o v a g a l e x e r c i s e o r v a g a l
i n h i b i t i o n a n d h a v e , a w o r s e p r o g n o s i s t h a n n o d a l b l o c k s .
R a s s i e t a l . ( 1 6 ) , s t u d y i n g a t r i o v e n t r i c u l a r b l o c k s i n
c h a g a s i c p a t i e n t s t h r o u g h e l e c t r o c a r d i o g r a m o f t h e H i s
b u n d l e ( E H B ) , v e r i f i e d t h a t f i r s t a n d s e c o n d d e g r e e t y p e I
a t r i o v e n t r i c u l a r b l o c k w i t h o u t a s s o c i a t e b r a n c h b l o c k , a n d
t o t a l a t r i o v e n t r i c u l a r b l o c k w i t h n a r r o w Q R S g e n e r a l l y a r e
l o c a t e d i n t h e a t r i o v e n t r i c u l a r n o d e . F i r s t d e g r e e
a t r i o v e n t r i c u l a r b l o c k s , t o t a l a t r i o v e n t r i c u l a r b l o c k s w i t h
w i d e Q R S a n d s e c o n d d e g r e e t y p e I I a t r i o v e n t r i c u l a r b l o c k s
m o s t c o m m o n l y c o r r e s p o n d t o l e s i o n s i n t h e H i s - P u r k i n j e
s y s t e m . I n c a s e s o f s e c o n d d e g r e e t y p e I a t r i o v e n t r i c u l a r
b l o c k w i t h w i d e Q R S t h e m o s t f r e q u e n t l o c a t i o n i s i n t h e
a t r i o v e n t r i c u l a r n o d e ( 7 0 % ) , a n d i t i s r a r e t h a t i t e v o l v e s
t o t o t a l a t r i o v e n t r i c u l a r b l o c k ( 2 0 % o f t h e c a s e s ) . T h e
a t r o p i n e t e s t i s u s e f u l i n h e l p i n g i t s l o c a l i z a t i o n .
O u t o f t h e 5 7 c a s e s o f t o t a l a t r i o v e n t r i c u l a r b l o c k
t h a t w e s t u d i e d h e m o d y n a m i c a l l y , 6 6 .6 % h a d d e p r e s s e d
l e f t v e n t r i c l e e j e c t i o n f r a c t i o n . T h i s p a r a m e t e r s e e m s t o
b e i m p o r t a n t i n t h e p r o g n o s t i c a n a l y s i s , s i n c e t h e f o l l o w
-u p o f t o t a l a t r i o v e n t r i c -u l a r b l o c k s t r e a t e d w i t h p a c e m a k e r s
s h o w e d t h a t , i n s p i t e o f t h e r e l i e f o f l o w o u t p u t s y m p t o m s ,
i t d i d n o t s i g n i f i c a n t l y i n c r e a s e s u r v i v a l w h e n t h e
c o n t r a c t i l e s y s t e m w a s s e v e r e l y c o m p r o m i s e d .
S a o P a u lo M e d ic a l J o u r n a l/ R P M 1 1 3 ( 2 ) M a r / A p r 1 9 9 5
I N A C T I V E A R E A S
T h e p r e s e n c e o f " f i b r o s i s " i n t h e E e G h a s a l w a y s
b e e n c o n s i d e r e d a s i g n o f s e v e r i t y a n d i t s a s s o c i a t i o n w i t h
v e n t r i c u l a r a r r h y t h m i a s a n d b r a n c h b l o c k s w o u l d i n d i c a t e
a g r e a t e r m y o c a r d i a l l e s i o n a n d l e s s s u r v i v a l .
I n o u r c a s e s w o r k w e f o u n d " f i b r o s i s " i n 2 2 8 c a s e s
( 2 2 .5 % ) , o c c u r r i n g a s t h e o n l y e l e c t r o c a r d i o g r a p h i c
a l t e r a t i o n i n 3 3 c a s e s ( 6 .3 % ) . W h e n t h e y w e r e a n i s o l a t e d
m a n i f e s t a t i o n , f i b r o s i s e s c o r r e s p o n d e d t o a d e p r e s s e d l e f t
v e n t r i c l e e j e c t i o n f r a c t i o n i n 4 2 .4 % ; w h e n a s s o c i a t e w i t h
o t h e r e l e c t r o c a r d i o g r a p h i c a l t e r a t i o n s t h e r e w e r e 6 9 .7 %
w i t h d e p r e s s e d e j e c t i o n f r a c t i o n ( p < O .O O l ) ( T a b .7 ) .
E C G A L T E R A T I O N S V E R S U S L E F T
V E N T R I C L E E J E C T I O N F R A C T I O N : S I M P L E
A N D M U L T I P L E R E G R E S S I O N A N A L Y S I S
T h e c o m b i n a t i o n o f e l e c t r o c a r d i o g r a p h i c a l t e r a t i o n s
i s q u i t e f r e q u e n t i n t h e t r a c i n g s o f c h a g a s i c p a t i e n t s a n d i s
c o n s i d e r e d a n a g g r a v a t i n g f a c t o r i n t h e p r o g n o s i s . I n o r d e r
t o v e r i f y t h e b e h a v i o r o f t h e s e v a r i a b l e s w i t h r e g a r d t o l e f t
v e n t r i c l e e j e c t i o n f r a c t i o n o b t a i n e d w i t h l i n e a r
c i n e v e n t r i c u l o g r a p h y , t h e a u t h o r s ( 9 ) d i d a u n i - a n d
m u l t i v a r i a t e a n a l y s i s , v e r i f y i n g ( T a b .8 ) t h a t a l m o s t a l l
a b n o r m a l i t i e s w i t h t h e e x c e p t i o n o f t h e a l t e r a t i o n o f t h e
v e n t r i c u l a r r e p o l a r i z a t i o n a n d l o w Q R S v o l t a g e , r e l a t e d
i n d e p e n d e n t l y w i t h d e p r e s s e d l e f t v e n t r i c l e e j e c t i o n
f r a c t i o n . N e v e r t h e l e s s , m u l t i v a r i a t e a n a l y s i s s h o w e d t h a t
t h e e l e c t r o c a r d i o g r a p h i c v a r i a b l e s t h a t r e l a t e d
i n d e p e n d e n t l y w i t h l o w e r l e f t v e n t r i c l e e j e c t i o n f r a c t i o n
w e r e o n l y v e n t r i c u l a r e x t r a s y s t o l e s , v e n t r i c u l a r
t a c h y c a r d i a , l e f t b r a n c h b l o c k , a t r i a l f i b r i l l a t i o n , t o t a l
a t r i o v e n t r i c u l a r b l o c k a n d a n t e r i o r a n d i n f e r i o r i n a c t i v e
a r e a s . R i g h t b u n d l e b r a n c h b l o c k , b l o c k o f t h e
a n t e r o s u p e r i o r d i v i s i o n o f t h e l e f t b u n d l e b r a n c h a n d s e p t a l
a n d a n t e r i o r f i b r o s i s w e r e n o t c o n s i d e r e d s i g n i f i c a n t l y
r e l a t e d t o d e p r e s s e d l e f t v e n t r i c l e e j e c t i o n f r a c t i o n .
\ ,y h e n w e a d d e d t h e c l i n i c a l v a r i a b l e s s u c h a s a g e ,
s e x , s y m p t o m s o f c a r d i a c i n s u f f i c i e n c y a n d c a r d i o m e g a l y
o n t h e t h o r a x r a d i o g r a p h y t o t h e e l e c t r o c a r d i o g r a p h i c
a l t e r a t i o n s , w e v e r i f i e d t h a t t h e s a m e e l e c t r o c a r d i o g r a p h i c
p a r a m e t e r s c o n t i n u e d t o b e s i g n i f i c a n t l y r e l a t e d , b u t w i t h
a s l i g h t a l t e r a t i o n i n t h e p r o b a b i l i t y r a t e . W e n o t i c e d t h a t ,
o f t h e c l i n i c a l v a r i a t i o n s , o n l y a g e d i d n o t i n d e p e n d e n t l y
T a b le 8
C o rre la tio n b e tw e e n E C G a lte ra tio n s , c lin ic a l v a ria tio n s a n d lin e a r v a lu e s o f th e e je c tio n fra c tio n o f th e le ft v e n tric le - s im p le a n d m u ltip le re g re s s io n a n a ly s e s
V a ria b le
VE
A n te rio r "fib ro s is " V T
In fe rio r "fib ro s is " L B B
AF
RBB
L A H B
L a te ra l "fib ro s is " S e p ta l "fib ro s is " M a le
A g e
C a rd io m e g a ly C I
P re v a le n c e
4 0 7
1 5 3
83
52
3 1
25
336
3 3 0
48
1 3 1
6 2 4
1 0 1 0
2 7 1
4 0 4
D e p e n d e n t C o rre la tio n p <
0 .0 0 0 1
0 .0 0 0 1
0 .0 0 1
0 .0 0 0 1
0 .0 0 0 1
0 .0 0 0 1
0 .0 5
0 .0 0 0 1
0 .0 0 0 1
0 .0 0 0 1
0 .0 0 0 1
0 .0 3
0 .0 0 0 1
0 .0 0 0 1
In d e p e n d e n t C o rre la tio n
p <
0 .0 0 0 1
0 .0 2 6
0 .0 1 1
0 .0 0 1
0 .0 0 0 1
0 .0 1 7
n s n s n s n s
0 .0 0 1
n s
0 .0 0 0 1
0 .0 0 1
O b s e rv a tio n : T h e o th e r E C G a lte ra tio n s d id n o t s h o w a n y s ta tis tic a l c o rre la tio n . F ib ro s is = in a c tiv e a re a ; V E = v e n tric u la r e x tra s y s to le s ; V T = v e n tric u la r ta c h y c a rd ia s ; R B B = rig h t b ra n c h b lo c k ; L A H B = le ft a n te rio r h e m ib lo c k ; L B B = le ft b ra n c h b lo c k ;
A F = a tria l fib rilla tio n ; C I= c a rd ia c in s u ffic ie n c y ; c a rd io m e g a ly = in c re a s e d c a rd io th o ra c ic in d e x o n X -ra y ; n s = n o s ta tis tic a l s ig n ific a n c e .
r e la te to th e le f t v e n tr ic le e je c tio n f r a c tio n . M a le s e x ,
c a r d ia c in s u f f ic ie n c y a n d c a r d io m e g a ly r e la te d to a lo w e r
le f t v e n tr ic le e je c tio n f r a c tio n .
C O N C L U S IO N S
C o n v e n tio n a l E C G s till h a s a n im p o r ta n t p la c e
a m o n g p r e lim in a r y m e th o d s f o r th e s tu d y o f C h a g a s '
d is e a s e .
B e c a u s e o f its lo w c o s t, e a s y u s e a n d in te r p r e ta tio n ,
it h a s e p id e m io lo g ic a l v a lu e in e n d e m ic a r e a s w ith o u t
a c c e s s to m o r e s e n s itiv e e x a m s .
I ts d ia g n o s tic im p o r ta n c e c o m e s f r o m k n o w le d g e
a b o u t th e g r e a te r p r e v a le n c e o f c e r ta in a lte r a tio n s . R ig h t
b u n d le b r a n c h b lo c k a s s o c ia te w ith b lo c k o f th e
a n te r o s u p e r io r ju n c tu r e o f th e le f t b u n d le b r a n c h a n d /o r
v e n tr ic u la r e x tr a s y s to le s in y o u n g p e o p le o r a d u lts u p to
th e f if th d e c a d e , f o r e x a m p le , c a n b e h ig h ly s u g g e s tiv e o f
th e d is e a s e .
T h e d e v e lo p m e n t o f d ia g n o s tic m e th o d s th a t a llo w
e v a lu a tio n o f th e a n a to m y a n d c a r d ia c f u n c tio n s a n d th a t
q u a n tif y th e in te n s ity o f a r r h y th m ia s h a s c o n s id e r a b ly
in c r e a s e d o u r k n o w le d g e o f th is c a r d io p a th y . T h e
c o r r e la tio n o f th e s e f in d in g s w ith c e r ta in E C G a lte r a tio n s
h a s m a d e th is s im p le m e th o d v e r y v a lu a b le in th e
p r o g n o s tic e v a lu a tio n o f C h a g a s ' d is e a s e .
M o r e in f o r m a tio n c a n b e e x tr a c te d f r o m E C G
th r o u g h th is m e th o d o lo g y , r e n d e r in g it m o r e u s e f u l a n d
in d e e d in d is p e n s a b le in th e d ia g n o s is , o b s e r v a tio n a n d
f o llo w - u p o f c h a g a s ic c a r d io p a th ic p a tie n ts .
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