Pulmonary blood volume ratio response to exercise; a noninvasive determination of exercise-induced changes in pulmonary capillary wedge pressure.

To determine if changes in pulmonary capillary wedge pressure could be determined from the pulmonary blood volume (PBV) ratio response on exercise-gated blood pool images, 42 patients had simultaneous exercise-gated blood pool imaging and hemodynamic monitoring during cardiac catheterization. Nine patients were normal and 33 patients had cardiac disease. Changes in the PBV ratio were determined from the 500 left anterior oblique end-diastolic frames by placing a region of interest over the left lung. The ratio of exercise/rest counts (PBV ratio) was calculated. The exercise-induced change in mean pulmonary capillary wedge pressure correlated with the PBV ratio (r = 0.72, p < 0.001). Patients were grouped into those with a definite (> 3-mm Hg) exercise-induced decrease, no change or an increase in mean pulmonary capillary wedge pressure in response to exercise. The PBV ratio was 0.929 ± 0.076 (mean SD) for the 10 patients with a decrease in wedge pressure, 1.027 ± 0.065 for the eight patients with no change in wedge pressure (p < 0.05), and 1.214 ± 0.131 for the 24 patients with an increase in wedge pressure (p < 0.05). Heart rate and blood pressure response to exercise did not differ for the three groups. The nine normal subjects had no increase in mean pulmonary capillary wedge pressure with exercise and a normal PBV ratio (mean PBV ratio = 0.92 + 0.06). Thirteen of the patients with coronary artery disease, 14 with chronic aortic or mitral regurgitation, three with cardiomyopathy (two congestive and one hypertrophic), and one with aortic stenosis and regurgitation had an exercise-induced increase in mean pulmonary capillary wedge pressure and an abnormal PBV ratio. The two patients with mitral stenosis had normal PBV ratios despite exercise-induced increases in mean pulmonary capillary wedge pressure. We conclude that determination of the PBV ratio from exercise-gated cardiac blood pool images c be used as a noninvasive means of estimating exercise-induced changes in left ventricular filling pressure.