Ventricular dysrhythmias after congenital heart surgery: a canine model

To examine the possible mechanisms of ventricular dysrhythmias in the presence of right ventricular hypertension and following ventriculotomy, we instrumented 6-month-old puppies. There were four groups: 1) six animals served as controls (instrumentation only); 2) six animals underwent ventriculotomy only; 3) six animals underwent pulmonary artery banding with a pneumatic vessel occluder to produce right ventricular hypertension; 4) six animals had both ventriculotomy and right ventricular hypertension. Each week for 8 wk, 24-h electrocardiograms and electrophysiologic studies were performed with the animals awake and unsedated. We attempted to induce ventricular dysrhythmias with premature extrastimuli, rapid pacing, isoproterenol, and vagal stimulation. The following "chronic" data were obtained in week 8 (p value for overall analysis of variance; values are mean +/- SD): heart rate - 126 +/- 16 beats/min (no significant difference between groups; all animals); right ventricular systolic pressure: control 26 +/- 6 mm Hg, ventriculotomy 30 +/- 3, right ventricular hypertension 65 +/- 5, ventriculotomy and right ventricular hypertension 75 +/- 18 (p less than 0.001); right ventricular end diastolic: control 4 +/- 1 mm Hg, ventriculotomy 4 +/- 3, right ventricular hypertension 11 +/- 5, ventriculotomy and right ventricular hypertension 16 +/- 7 (p less than 0.001); QRS duration: control 22 +/- 5 ms, ventriculotomy 33 +/- 7, right ventricular hypertension 44 +/- 6, ventriculotomy and right ventricular hypertension 49 +/- 4 (p less than 0.01); right ventricular apex-base interval with ventricular pacing: control 20 +/- 3 ms, ventriculotomy 34 +/- 9, right ventricular hypertension 30 +/- 5, ventriculotomy and right ventricular hypertension 31 +/- 6 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)