Measurement of systemic cardiac output at rest and exercise in patients with atrial septal defect

Abstract

The problem of accurate measurement of systemic cardiac output at rest and during exercise in patients with atrial septal defect was studied by three interrelated approaches. 1. (1) The optimal method of approximation of mixed venous blood oxygen saturation from the oxygen saturation of superior and inferior vena caval samples was evaluated by comparisons with pulmonary arterial samples in patients without intracardiac shunts. Optimal formulas derived by regression analysis were as follows: Mixed venous blood at rest = (3 SVC + 1 IVC) 4 Mixed venous blood during exercise = (1 SVC + 2 IVC) 3 2. (2) Arterial dye-dilution curves after left ventricular injection were established as a reliable method for determination of cardiac output by comparison with standard Fick determinations in patients without intracardiac shunts. 3. (3) Fick cardiac output values using the derived formulas were compared with dye-dilution values following left ventricular injection in patients with atrial septal defect. A close correlation was noted. It is concluded that systemic cardiac output may be measured with reasonable accuracy both at rest and during exercise in patients with atrial septal defect by either the Fick or the dye-dilution method.