Estimation of pulmonary hypertension by perfusion lung scintigraphy: gravitational effect of postural changes between the lateral decubitus positions.

To estimate pulmonary hypertension in patients with various heart diseases, we devised a new method using perfusion lung scintigraphy with technetium-99m-labelled macroaggregated albumin. In this method, changes in the distribution of pulmonary perfusion caused by gravitational effects, namely, changes in the total count ratios of the right lung against the left lung between right and left lateral decubitus positions (rt/lt), were assessed in 62 patients and in 10 normal subjects. The rt/lt ratios were calculated as indices of the above changes. They correlated significantly with mean pulmonary arterial pressure (mPAP) (gamma = -0.62, P less than 0.001), pulmonary capillary wedge pressure (gamma = -0.63, P less than 0.001) and pulmonary arteriolar resistance (gamma = 0.50, P less than 0.001) in all subjects. In 17 patients with valvular heart diseases, the ratio correlated significantly with mPAP (gamma = -0.84, P less than 0.001). In 10 patients with various heart diseases, the U/S ratio, i.e. the index of changes in the count ratios of the upper field against the lower field for the right lung following postural change from the upright to the supine position, was also obtained as well as the rt/lt ratio. The latter evidenced a better correlation with mPAP (gamma = -0.90, P less than 0.001) than the former (gamma = -0.64, P less than 0.05). We conclude that this method is valuable as a noninvasive approach for the estimation of pulmonary hypertension.