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

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 <0.01) and during exercise (79 ± 9% versus 76 ± 6%, p <0.05). Left ventricular end-diastolic volume in the sitting position was smaller at rest (by 19 ± 26%, p <0.001), but this variable was similar in both positions during exercise (p >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 <0.001). Left ventricular end-diastolic volume increased from rest to exercise, in the sitting position by 31 ± 23% (p <0.001) and in the supine position by 6 ± 22% (p >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 <0.01) and during exercise by 8 ± 18% (p <0.05). Sitting left ventricular end-systolic volume was smaller by 18 ± 20% (p <0.001) at rest and by 14 ± 21% (p <0.01) during exercise. Left ventricular end-diastolic volume increased from rest to exercise, in the sitting position by 45 ± 36% (p <0.001) and in the supine position by 32 ± 51% (p <0.01). Despite significant hemodynamic differences, the value of rest-exercise radionuclide cardiac studies to detect CAD was similar in the 2 positions.