The JT-area indicates dispersion of repolarization in dogs with atrioventricular block.
Heterogeneity in cardiac repolarization (Delta APD) is known to be arrhythmic. In the dog model of chronic complete AV-block and acquired long QT syndrome, an increase in Delta MAPD (defined as left ventricular monophasic action potential duration (MAPD) minus right ventricular MAPD) is often associated with changes in T-wave morphology. The purpose of this study was to correlate known changes in Delta MAPD with the planimetric total area of the T-wave on the surface ECG (integral of J-T, mVx ms).


METHODS
The relationship between Delta MAPD and total area of the T-wave (i.e., JT-area) was assessed in four different protocols with different types of dispersion: (1) class III drugs followed by levcromakalim (n= 7), (2) LAD coronary artery occlusion and reperfusion (n = 6), (3) dronedarone i.v., an amiodarone like agent (n = 5) and (4) steady state pacing at cycle lengths of 1000 ms and 500 ms (n = 5).


RESULTS
Class III drugs increased Delta MAPD (55 +/- 40 ms to 120 +/- 50 ms(#), P<0.05), which was correlated (r = 0.74, P < 0.001) with JT-area (50 +/- 40 mV. ms to 95 +/- 35 mV x ms(#)). Ischemia increased both Delta MAPD (30 +/- 25 ms to 90 +/- 40 ms(#)) and JT-area (60 +/- 55 mV x ms to 75 +/- 50 mV x ms(#)). Both levcromakalim and reperfusion reversed these conditions. Dronedarone had no effect on Delta MAPD or on JT-area while a faster frequency reduced both Delta MAPD and JT-area.


CONCLUSIONS
Changes in dispersion of ventricular repolarization are reflected by alterations in JT-area. This non-invasive parameter may therefore be used to indicate changes in heterogeneity in ventricular repolarization.
van Opstal
Jurren M
JM
Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands.
Verduyn
S Cora
SC
Winckels
Stephan K G
SK
Leerssen
Hendrik M
HM
Leunissen
Jet D M
JD
Wellens
Hein J J
HJ
Vos
Marc A
MA
D000200:Action Potentials; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D018780:Body Surface Potential Mapping; D019806:Cromakalim / Q000494:pharmacology; D004195:Disease Models, Animal; D004285:Dogs; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D006327:Heart Block / Q000503:physiopathology*; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D013449:Sulfonamides / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D013449:Sulfonamides; D019806:Cromakalim; C067192:ibutilide