Insufficient Coronary Flow and Myocardial Failure as a Complicating Factor in Late Hemorrhagic Shock

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Abstract
Left main coronary flow was continuously recorded during hemorrhagic hypotension in the open chested dog along with pressures recorded in the femoral and pulmonary arteries and right and left auricles. After varying periods of hypotension, 1st the left and then the right ventricles exhibit evidence of myocardial failure. This shows itself as a rise in auricular pressure (more marked on the left), a grossly observable cardiac dilatation, and a decrease in the vigor and rapidity of arterial systole. If no intervention is made, ventricular fibrillation or arrest occurs. The elevated left auricular pressure and gross cardiac dilatation can be promptly reversed by augmenting left main coronary flow, even while maintaining the same degree of hypotension and without increasing blood vol. Preliminary observations with one of the sympathomimetic amines (Aramine) suggest that an augmentation of coronary flow and lowering of left auricle pressure similar to that seen with mechanical coronary perfusion can be achieved with that agent. An elevation of 1st left and then right auricle pressure was also observed in control dogs without a cannula present in the left main coronary artery. This suggests that the procedure by means of which coronary flow was measured cannot alone account for the phenomena observed. From these data and the previous work of others reviewed here, it appears that myocardial failure plays a significant role in hemorrhagic shock and that under these circumstances this failure results from an insufficient coronary flow.