Dispersion of ventricular repolarization and arrhythmia: study of two consecutive ventricular premature complexes

The effect of two consecutive ventricular premature stimuli (S1S2) during atrial pacing on dispersion of repolarization and inducibility of ventricular arrhythmias was studied in 16 dogs under control conditions and in four dogs in the presence of an increased dispersion of repolarization during atrial pacing induced by general hypothermia and regional warm blood perfusion via selective cannulation of the distal branch of left anterior decending coronary artery. Dispersion of repolarization was measured as the maximal difference between the ends of six simultaneously recorded monophasic action potentials (MAPs) from anterior ventricular surface, and consisted of MAP duration difference and activation time difference. Dispersion of repolarization during atrial pacing at control was 29 +/- 7 msec (activation time difference 4 +/- 6 msec, MAP duration difference 25 +/- 8 msec), that after S1 at paraseptal the site was 81 +/- 8 msec (activation time difference 73 +/- 12 msec, MAP duration difference 8 +/- 5 msec), and that after S1S2 was 148 +/- 27 msec (activation time difference 103 +/- 21, MAP duration difference 44 +/- 26 msec). Neither S1 nor S1S2 induced ventricular arrhythmia. Hypothermia and regional warm blood reperfusion increased dispersion of repolarization during atrial pacing to 70 +/- 22 msec (activation time difference 9 +/- 3 msec, MAP duration difference 61 +/- 19 msec). During hypothermia and regional warm blood reperfusion, S1 produced a dispersion of repolarization of 149 +/- 29 msec (activation time difference 85 +/- 8 msec, MAP duration difference 64 +/- 23 msec) and did not induce ventricular arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)