Effects of Increased Transmural Pressures upon Atrial and Ventricular Rhythms in the Dog Heart-Lung Preparation

Abstract

The effects of increased transmural pressures upon atrial and ventricular rhythms have been studied in the heart-lung preparation of the dog. Increases in right-heart pressure resulted in increased sinus rates when the SA node was intact. When the SA node was crushed and an A-V nodal rhythm revealed, increased right-heart pressure resulted in more rapid A-V nodal rhythms in some preparations while shifts to more rapid pacemakers, adjacent to the SA node, were detected in others. Independent ventricular pacemakers emerged during periods of elevated pressure in every preparation in which the sinus node had been crushed. Left-heart pressure was increased by augmenting the systemic resistance, the minute volume, or both. In A-V dissociated hearts, epinephrine or metaraminol were administered to enable the generation of higher aortic pressures (above 150 mm Hg). During the periods of elevated pressure, new or increased pacemaker activity was seen in the independently beating ventricle. These results and others cited show that atrial dilatation or elevated arterial pressure may participate in the genesis of some cardiac arrhythmias.