Compensatory cardiac mechanisms evoked by acute occlusion of the right coronary artery in dogs

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Abstract
The cardiac response to intermittent occlusion of the right coronary artery was examined in anesthetized open‐chest dogs at different levels of blood volume. The reduction in stroke volume averaged 15±2% and was related to the extent of the ischemic area (r=0.72), which comprised 45–70% of the free wall of the right ventricle. Ultrasonic recordings of segment lengths showed end‐diastolic distention and activation of the Frank‐Starling mechanism in the uninjured parts of the free wall. The transseptal end‐diastolic pressure difference was abolished, suggesting movement of the interventricular septum to the left. Nevertheless, the relationship between stroke volume and left ventricular end‐diastolic pressure (left ventricular function curve) as well as the relationship between stroke volume and the end‐diastolic segment length of the left ventricular free wall were unaltered. Comparisons of data obtained at similar stroke volume showed activation of the Frank‐Starling mechanism in the interventricular septum which may compensate for the negative effect of a change in its position.