LETTERSTOTHEEDITOR 665
Corrected
QT
interval
and
corrected
QT
interval
dispersion
is
worthwhile
when
interpreted
with
other
repolarization
measurements
Intervalo
QT
corrigido
e
dispersão
do
intervalo
QT
corrigido
são
válidos
quando
interpretados
com
outras
mensurac
¸ões
de
repolarizac
¸ão
DearEditor:
We read the article entitled ‘‘The effect of esmolol on corrected-QT interval, corrected-QT interval dispersion changes seen during anesthesiainduction in hypertensive patientstakinganangiotensin-convertingenzymeinhibitor’’ by Ceker et al. with interest.1 The authors investigated
the effects of esmolol on the hemodynamic, corrected-QT (QTc) interval and corrected-QT interval dispersion (QTcD)changesduringanesthesiainductioninhypertensive patients.Finally, theyconcludedthatprolonging effectof endotracheal intubation and anesthesia induction on QTc andQTcDcanbepreventedbyesmololadministration.We wouldliketothanktotheauthorsfortheirvaluable contri-bution.
Electricalinhomogeneityofmyocardiummaylead poten-tially life threatening cardiac arrhythmias. There are someinvasive andnon-invasivemethodstodetermine the myocardialinhomogenity.QTdandQTcdarewellknown non-invasiveparametersand canbemeasured onsurfaceECG by manually or on digital platform. Unfortunately repro-ducibility of QTmeasurements islow both in manual and automatic measurements.2,3 Additionally, in manuel
mea-surements,inter-andintraobservervariabilityofQTdisvery high.3Inthisstudy,itisunknownwhetherthemeasurements
were done manuallyor in digital platform. Itwould have beenbetteriftheauthorshadmentionedthemeasurement type.
Transmural dispersion of repolarization (TDR) quanti-fiesmyocardialinhomogeneityinadditiontoQTd.4Isolated
cellsfromdifferentlayersofthemyocardiumrevealedthat myocardiumconsistsof threedifferentmyocytetypes: (i) endocardial,(ii)epicardial,and(iii)midmyocardialMcells.5
Thesemyocytestructureshavevariouselectrophysiological characteristics.Thisheterogeneitymaycausetoelectrical instability andare measurable onsurface ECG. Epicardial repolarization phase ends at the peak of the T-wave, M cellsrepolarizationcontinuesuntiltheendoftheTwave.5
Thus, the distance between the peak and end of the T waveisentitledasTp-einterval,whichreflectsTDR. Previ-ously,wepresentedthatTDRwasincreasedinpatientswith
obstructivesleep apnea and chronic arsenic exposure via drinkingwater.6,7 Ithasbeen also demonstratedthatTDR
isincreasedinST-elevationmyocardialinfarction.5Adding
TDRmeasurementswouldhavebeenbetterfordetermining myocardialinhomogeneity.
We believethat the paperof Ceker etal. willlead to further studies concerning myocardial heterogeneity and instability.However,Tp-eintervalassessmentwouldmake thisstudymoreprecise.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
References
1.CekerZ,TakmazSA,BaltaciB,etal.Theeffectofesmololon corrected-QTinterval,corrected-QTintervaldispersionchanges seen duringanesthesia inductioninhypertensivepatients tak-ing anangiotensin-converting enzyme inhibitor.Br JAnaesth. 2015;65:34---40.
2.StattersDJ, MalikM,WardDE,etal.QT dispersion:problems ofmethodologyandclinicalsignificance.JCardiovasc Electro-physiol.1994;5:672---85.
3.Malik M, Batchvarov VN. Measurement, interpretation and clinical potential of QT dispersion. J Am Coll Cardiol. 2000;36:1749---66.
4.Antzelevitch C.Tpeak-Tend interval as anindex of transmu-ral dispersion of repolarization. Eur J Clin Invest. 2001;31: 555---7.
5.GuptaP,PatelC,PatelH,etal.T(p-e)/QTratioasanindexof arrhythmogenesis.JElectrocardiol.2008;41:567---74.
6.KilicaslanF,TokatliA,OzdagF,etal.Tp-einterval,Tp-e/QTratio, and Tp-e/QTc ratio are prolonged in patients withmoderate andsevereobstructivesleepapnea.PacingClinElectrophysiol. 2012;35:966---72.
7.YildizA,KaracaM,BicerogluS,etal.Effectofchronicarsenic exposurefromdrinkingwatersontheQTintervalandtransmural dispersionofrepolarization.JIntMedRes.2008;36:471---8.
MehmetDogana,∗,OmerYiginera,MehmetTezcanb, IbrahimCetindaglic
aGulhaneMilitaryMedicalAcademy,HaydarpasaTraining
HospitalDepartmentofCardiology,Istanbul,Turkey
bGumussuyuMilitaryHospital,DepartmentofCardiology,
Istanbul,Turkey
cGulhaneMilitaryMedicalAcademy,HaydarpasaTraining
HospitalDepartmentofInternalMedicine,Istanbul,Turkey
∗Correspondingauthor.
E-mail:[email protected](M.Dogan).
