To test the utility of electrocardiographically gated spin echo nuclear magnetic resonance (NMR) imaging in quantitating right and left ventricular volumes and function in patients with primary pulmonary hypertension, right and left ventricular end-diastolic and end-systolic volumes, stroke volumes and ejection fractions were determined in 11 patients with primary pulmonary hypertension and in 10 subjects with normal echocardiographic findings. Ventricular chamber volumes were computed by summing the ventricular chamber volumes of each NMR slice at enddiastole and end-systole. This technique was verified by comparison of results obtained by this method and with the water displacement volumes of eight water-filled latex balloons and ventricular casts of eight excised bovine hearts.
In the patients with primary pulmonary hypertension, right ventricular volume indexes were 121 ± 45 ml/m2at end-diastole and 70.1 ± 41.6 ml/m2at end-systole; both values were significantly greater than values in the normal subjects (67.9 ± 13.4 and 27.9 ± 7.5 ml/m2, respectively). Left ventricular end-diastolic volume index was significantly less in the patients (44.9 ± 9.7 ml/m2) than in the normal subjects (68.9 ± 13.1 ml/m2). There was no significant difference in left ventricular end-systolic volume between the two groups (24.4 ± 8.6 and 27.1 ± 7.8 ml/m2, respectively). Right and left ventricular ejection fractions in the patients with primary pulmonary hypertension (0.43 ± 0.21 and 0.46 ± 0.15, respectively) were significantly less than values in normal subjects (0.59 ± 0.09 and 0.6 ± 0.11, respectively).
The ratio of right to left ventricular stroke volume indexes was 0.97 ± 0.1 in the normal subjects, not significantly different from the expected value of 1. In the patients with primary pulmonary hypertension, this ratio was significantly greater (3.17 ± 2.3), in part reflecting the presence of tricuspid regurgitation in these patients. Intra- and interobserver errors in the computation of ventricular volumes were low but were greater in patients with primary pulmonary hypertension. Nuclear magnetic resonance imaging provides a means of ventricular volume determination in the normal and failing ventricle.
