[Non-invasive determination of cardiac pump function by respiratory gas exchange measurement during submaximal...

The continuous measurement of respiratory gas exchange under linearly increasing work load allows a relatively exact and reproducible localization of the point of rise of the ventilatory equivalent for oxygen (ASV). On the basis of the values of oxygen consumption (V(O2)(ASV)), oxygen pulse (O2-pulse(asv)) and relative ventilatory equivalent (Vetn. Equivalent(asv)/V(O2(ASV)), measured at the point ASV, it is possible to divide patients with different severity of heart disease into 4 groups of cardiac response to exercise: group I = normal, group II = diminished, group III = definitely limited and group IV = severely limited cardiocirculatory capacity. Simultaneous cardiac output measurements (thermodilution method) as well as the comparison with hemodynamic and angiographic data acquired during separate heart catheterization reveal good correlations between V(O2(ASV) and O2-pulse(asv) on the one hand and exercise values of cardiac output and stroke volume on the other (r = 0.82). Consequently, definite relations exist between the absolute ASV values as well as the group classification (I--IV) based on these and further heart catheterization data such as left bentricular (LV) enddiastolic pressure, LV ejection fraction, contraction pattern of the left ventricle and coronary angiogram respectively. The described method of measuring respiratory gas exchange under submaximal unsteady state bicycle exercise represents a reliable and rapid non-invasive stress test of cardiac pump function without putting too much strain on the heart patient as is frequently the case with the more familiar steady state (maximal) tests.