Abstract

Ventricular function was evaluated in twenty-five adult patients with atrial septal defects, by combined right and left heart catheterization and hemodynamic measurements at rest and during exercise. Systemic cardiac output was measured by the dye dilution method and by the Fick method using superior and inferior vena caval samples to determine mixed venous blood oxygen content according to formulas determined in patients without intracardiac shunts. The resting systemic cardiac output was consistently below the age-related normal value but was associated with a left ventricular end-diastolic pressure (LVEDP) which for the group was significantly below normal. It is concluded that the decreased systemic cardiac output is due to impaired delivery of blood to the left ventricle secondary to the left to right shunt and does not represent an intrinsic abnormality of the left ventricle. Using exercise as a stress, three distinct patterns of ventricular function were found. In young asymptomatic patients, both ventricles functioned normally. In a somewhat older group, right ventricular failure was present but left ventricular function remained normal. In the oldest patients, both right and left ventricular failure were present. Left ventricular failure in the absence of right ventricular failure was not demonstrated in any of these patients. Clinical congestive heart failure was present in patients with evidence of right ventricular failure and normal left ventricular function on exercise, as well as in patients with biventricular failure. The data support the concept that the functional and structural impairment that occurs in response to overload of one ventricle is a generalized myocardial response with involvement of and eventual failure of both ventricles and that this is the usual mechanism for left ventricular failure in patients with atrial septal defects.

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