The JT-area indicates dispersion of repolarization in dogs with atrioventricular block

Heterogeneity in cardiac repolarization (DeltaAPD) is known to be arrhythmic. In the dog model of chronic complete AV-block and acquired long QT syndrome, an increase in DeltaMAPD (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 DeltaMAPD with the planimetric total area of the T-wave on the surface ECG ( (J)integral (T), mV.ms). Methods: The relationship between DeltaMAPD 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 DeltaMAPD (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.ms(#)). Ischemia increased both DeltaMAPD (30+/-25 ms to 90+/-40 ms(#)) and JT-area (60+/-55 mV.ms to 75+/-50 mV.ms(#)). Both levcromakalim and reperfusion reversed these conditions. Dronedarone had no effect on DeltaMAPD or on JT-area while a faster frequency reduced both DeltaMAPD and JT-area. Conclusion: 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.