Left and right ventricular function at rest and during bicycle exercise in the supine and sitting positions in normal subjects and patients with coronary artery disease. Assessment by radionuclide ventriculography.

To assess the hemodynamic influence of posture during radionuclide cardiac studies, rest and exercise electrocardiographically gated blood pool cardiac scintigraphy was performed in the supine and sitting positions in 22 normal subjects and in 20 patients with coronary artery disease (CAD). In normal subjects, left ventricular ejection fraction was higher in the sitting position both at rest (67 +/- 6% versus 64 +/- 5%, p less than 0.01) and during exercise (79 +/- 9% versus 76 +/- 6%, p less than 0.05). Left ventricular end-diastolic volume in the sitting position was smaller at rest (by 19 +/- 26%, p less than 0.001), but this variable was similar in both positions during exercise (p greater than 0.05). Left ventricular end-systolic volume was smaller in the sitting position both at rest, by 26 +/- 31 percent, and during exercise, by 14 +/- 20% (p less than 0.001). Left ventricular end-diastolic volume increased from rest to exercise, in the sitting position by 31 +/- 23% (p less than 0.001) and in the supine position by 6 +/- 22% (p greater than 0.05). In patients with CAD, similar left ventricular ejection fractions in both postures were found at rest and during exercise. Left ventricular end-diastolic volume in the sitting posture was smaller at rest by 16 +/- 22% (p less than 0.01) and during exercise by 8 +/- 18% (p less than 0.05). Sitting left ventricular end-systolic volume was smaller by 18 +/- 20% (p less than 0.001) at rest and by 14 +/- 21% (p less than 0.01) during exercise. Left ventricular end-diastolic volume increased from rest to exercise, in the sitting position by 45 +/- 36% (p less than 0.001) and in the supine position by 32 +/- 51% (p less than 0.01). Despite significant hemodynamic differences, the value of rest-exercise radionuclide cardiac studies to detect CAD was similar in the 2 positions.