Experiments were performed on 20 anesthetized @entity235 to determine the effects of premature stimulation of the His bundle on epicardial conduction and late potentials recorded on the body surface. Fifteen @entity235 underwent occlusion of the left anterior descending coronary for 2 hr followed by reperfusion, and five that did not undergo operation served as controls. Animals were studied 2 to 52 weeks after the induction of @entity1188 , and four animals with @entity1188 and four control animals exhibited no sustained @entity943 in response to programmed ventricular extrastimulation. Five @entity235 with @entity1188 and one control @entity235 had @entity2224 while the six remaining @entity235 had inducible sustained @entity1165 . All animals with @entity1165 had late potentials in the terminal portion of the signal-averaged body surface QRS complexes during sinus rhythm and QRS durations in the animals were 64 msec or greater. The voltage in the last 20 msec of the QRS complex was 13.5 microV or less and the duration of late activity below 30 microV was 18.2 msec or more. These values did not overlap values in animals with no inducible @entity943 . @entity2224 was a nonspecific end point in these experiments and values overlapped those in animals with no @entity943 and those with @entity1165 . All animals with @entity1188 and late potentials associated with their QRS complexes also had delayed and prolonged epicardial electrograms that extended into the time of the late potentials recorded from 45 standard sites in the infarcted regions. A single premature beat evoked by His bundle pacing (coupling interval of 192 to 270 msec) had no significant effect on late potentials or their relationship to epicardial activation in the area of @entity1188 . However, changes in the durations of electrograms in response to premature beats were different in animals with @entity1188 and @entity1165 than in those with @entity2224 . In animals with @entity1165 , electrograms at 15 of 210 sites increased in duration by more than 10 msec while those at 61 of 210 sites decreased in duration. In animals with @entity2224 , electrograms at 40 of 207 sites were of increased duration while those at 26 of 207 decreased. The decreases in duration were usually due to components of fractionated electrograms "dropping out" and likely represent local conduction block near the recording electrode.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of premature stimulation of the His bundle on epicardial activation and body surface late potentials in XXXX susceptible to sustained @entity1165 .

@entity1165 :: ('MESH:D017180', 'Disease') :: ['ventricular tachycardia'] @entity235 :: ('9615', 'Species') :: ['dog', 'dogs'] @entity1188 :: ('MESH:D007238', 'Disease') :: ['infarction', 'infarct'] @entity2224 :: ('MESH:D014693', 'Disease') :: ['ventricular fibrillation', 'Ventricular fibrillation'] @entity943 :: ('MESH:D001145', 'Disease') :: ['arrhythmias']
@entity235 :: (9615,Species) :: ['dogs']
