Maximum cardiac output during incremental exercise by first-pass radionuclide ventriculography.

Abstract

STUDY OBJECTIVE: To validate a noninvasive first-pass radionuclide ventriculographic (FPRV) measurement of maximum cardiac output (Qv) during exercise. DESIGN: Comparison of Qv to that measured by the Fick principle (Qf) at peak exercise. SETTING: Academic cardiopulmonary exercise laboratory. PATIENTS: Seventy-eight consecutive patients without a history of septal defect undergoing clinically indicated maximum incremental cardiopulmonary exercise testing with pulmonary arterial catheterization and FPRV. MEASUREMENTS AND RESULTS: Ventilation and gas exchange were measured breath-by-breath or by a mixing chamber/mass spectrometer system. Arterial and mixed venous O2 content were measured each minute during exercise. When patients without left-to-right ventricular stroke count ratio evidence for left-sided regurgitation were isolated, peak Qv was linearly related to Qf (r=0.75, p=0.0001). To account for a small systematic overestimation (bias) of Qf by Qv, the linear equation for the Qv/Qf relation was derived for patients studied between 1990 and 1993 and applied to those studied subsequently. The resulting corrected peak Qv was tightly related to peak Qf (r=0.90, p<0.001) with confidence intervals for slope and intercept overlapping identity. CONCLUSION: FPRV can reasonably estimate maximum cardiac output during incremental exercise in patients for whom the technique has ruled out left-sided cardiac regurgitant lesions.