THE PULMONARY CAPILLARY BED IN MITRAL VALVE DISEASE

Diffusion capacity in heart transplant recipients

Preoperative diffusion capacity per liter alveolar volume (Kco) in cardiac transplant recipients with an intrinsic normal lung is within the normal range. In the first postoperative year, Kco showed a significant mean decrease of 12 percent (p less than 0.004). Lung function (TLC, VC, FEV1) tended to normalize after heart transplantation. Ventilation distribution remained stable before and after heart transplantation. Preoperatively, weak correlations were found between Kco and diastolic pulmonary arterial pressure (dPAP) and mean pulmonary capillary wedge pressure (PCWP). Postoperatively, correlation between Kco and PCWP was weak, and between Kco and dPAP it was not significant at all. These pressures determine the capillary blood volume before and after transplantation. Probably these weak correlations indicate that intrapulmonary factors, not cardiac factors, are of primary importance in the regulation of blood distribution. The percentage of decrease in Kco in the first postoperative year correlated with the change in dPAP and PCWP, but also with the cyclosporine level in the first posttransplant year. No correlation was found between cyclosporine level and pulmonary vascular resistance. It is suggested that higher levels of cyclosporine influence the alveolar capillary membrane, so that Kco decreases. The percentage of decrease in Kco was significantly more outspoken in patients who had rales on auscultation preoperatively. Using multiple regression analysis, we found that the factors most strongly related to the percentage of change in Kco in the first posttransplant year were the preoperative Kco, the cyclosporine level in the first postoperative year, and the change in dPAP in that year.

Pulmonary function abnormalities in chronic severe cardiomyopathy preceding cardiac transplantation

Pulmonary function data, including diffusing capacity, were evaluated in 56 patients with chronic severe cardiomyopathy before heart transplantation. Cardiac catheterization data were used to describe the relationship between cardiac and pulmonary function. Of 56 patients 44 had some abnormality in pulmonary function. The majority, 30 of 56, had a restrictive impairment alone. Of 28 patients in whom diffusing capacity was measured, 64% had a diffusion impairment. There was no association of pulmonary function impairment with type of cardiomyopathy or smoking history. Pulmonary capillary wedge pressure correlated positively with DLCO, but not with FVC or TLC. Cardiac index and ejection fraction did not correlate with diffusing capacity. This precardiac transplantation cardiomyopathy patient group demonstrated frequent pulmonary function abnormalities not previously recognized.

Pulmonary diffusing capacity in disorders of the pulmonary circulation

The pulmonary diffusing capacity for carbon monoxide was measured by single breath (DcoSB) and steady state (DcoSS) techniques in 48 patients with various pulmonary circulatory disorders and the results compared with the type of hemodynamic abnormality. Patients with pure inflow obstruction (primary pulmonary hypertension, recurrent pulmonary emboli) had the lowest Dco (mean DcoSB = 14.3 ml/min/mm Hg [59%], mean DcoSS = 9.0 ml/min/mm Hg [58%]). Patients with inflow and outflow obstruction, (valvular heart disease with increased pulmonary vascular resistance [PVR]), had higher values (mean DcoSB = 16.2 [68%], mean DcoSS = 10.2 [65%]). In patients with pure outflow obstruction (valvular heart disease and normal PVR) Dco was normal (means 23.2 [96%] and 14.4 [87%] respectively). Patients with increased pulmonary blood flow (PBF), (left to right shunts), had the highest Dco (means 31.3 [118%] and 16.4 [106%]). There was a reciprocal relationship between Dco and PVR, a low Dco being characteristic of pulmonary inflow obstruction. Patients with increased PBF had lower Dco values than exercising normal subjects with comparable PBF. In patients with pulmonary circulatory abnormalities and no obstructive or restrictive lung disease, Dco is low when inflow obstruction predominates. Dco inceases with the addition of outflow obstruction and is above normal when there is an increased PBF and low PVR.