Acute Dynamic Effects of a Shunt Between a Systemic Artery and the Left Atrium

Abstract

A communication was established between the left subclavian artery and left atrium in dogs to assess the acute dynamic effects of a diastolic input load on the left heart. Sudden diastolic pressure loading, produced by opening the shunt abruptly was followed by acute ventricular dilatation and fibrillation, and pulmonary congestion and edema. Gradual opening of the shunt provided time for cardiac adjustments to the increased ventricular output, and acute failure did not occur. These data suggest that adjustments in myocardial function can take place quickly in response to a markedly enhanced input load. On opening the shunt the aortic pressure fell in consonance with the decreased total peripheral resistance, while the left atrial pressure increased sharply. The pulmonary arterial pressure remained unchanged. Systemic vasoconstriction produced by adrenalin, strophanthin or asphyxia enhanced the flow through the shunt.