The reproducibility of radionuclide angiographic measurements of left ventricular function in normal subjects at rest and during exercise.

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Abstract
The reproducibility of radionuclide measurements of left ventricular ejection fraction, end-diastolic volume, end-systolic volume, stroke volume, pulmonary transit time, pulmonary blood volume and cardiac output was determined in 10 normal subjects. First-pass radionuclide angiocardiograms were performed at rest and during upright, submaximal bicycle exercise on day 1 and day 3. The resting heart rate for the group decreased from 79 .+-. 17 beats/min on day 1 to 71 .+-. 14 beats/min on day 3 (P < 0.01). This biologic variation probably contributed to the small but significant decreases in ejection fraction (62 .+-. 7 to 59 .+-. 7%, P < 0.05) and cardiac output (7.7 .+-. 1.9 to 6.6 .+-. 1.5 l/min, P < 0.02) and the increase in pulmonary transit time (5.8 .+-. 1.6 to 6.2 .+-. 1.3 s, P < 0.05) between day 1 and day 3. The mean variabilities in ejection fraction, cardiac output and pulmonary transit time were 4.0 .+-. 3.8%, 1.24 .+-. 1.23 l/min and 0.65 .+-. 0.64 s, respectively. No significant differences between studies were observed in resting end-diastolic volume, end-systolic volume and stroke volume. The mean variability in end-diastolic volume was 9.9 .+-. 5.1 ml. Heart rate varied less during exercise to the same work load and only pulmonary transit time and blood volume differed significantly between studies. During exercise the mean variabilities in ejection fraction, end-diastolic volume, cardiac output and pulmonary transit time were 3.2 .+-. 2.5%, 9.8 .+-. 6.2 ml, 1.59 .+-. 0.67 l/min and 0.25 .+-. 0.25 s, respectively. Radionuclide measurements of left ventricular function are highly reproducible if obtained under comparable hemodynamic conditions.