Changes in infarction arrhythmias resulting from changes in arterial pressure

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Abstract
In dogs with ventricular arrhythmias 1 or 2 days after the anterior descending artery was occluded, arterial pressure was varied by withdrawal and reinfusion of blood and by constriction and release of the aorta. Following bilateral vagotomy and excision of sympathetic ganglia, T1-T4, the most frequent effect of pressure reduction (hemorrhage) was to increase ventricular ectopic frequency. Restoration of blood reversed this effect. In hearts with nerves intact, the main effect was similar except that reflex sinus acceleration producedbrief (20-60sec) sinus dominance at the beginning of the low-pressure period. Ventricular tachycardia soon superseded the sinus rhythm as ectopic autorhythmicity intensified. Fewer trials in both groups showed reduction or no change in ectopic frequency. Aortic constriction most often increased ectopic activity, but exceptionally, reduction or no change occurred. Hypothetical explanatory factors are: decreased perfusion of the infarct border tissue intensifies excitatory gradients; these effects are reversed by improving border perfusion; increase of arterial pressure (stretch) directly induces excitatory effects.