The pressure-flow response of the pulmonary circulation in patients with heart failure and pulmonary vascular disease.

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Abstract
Although it is well known that the pulmonary circulation is altered in patients with pulmonary arterial or venous hypertension, the resultant hemodynamic behavior has not been systematically studied. We undertook to do so in a group of patients with pulmonary hypertension of diverse etiology. We measured pulmonary arterial (PAP) and occlusive wedge pressures and cardiac output at rest (i.e., standing) and during progressive upright treadmill exercise in 51 patients. Forty-two had chronic, stable, cardiac failure secondary to ischemic, myopathic or valvular heart disease and were grouped according to whether their mean PAP was less than (normotensive) or greater than (hypertensive) 19 mm Hg, and nine had pulmonary vascular disease of diverse etiology and were considered separately. In the majority of patients, we found that irrespective of whether the hypertension was arterial or venous in origin or etiology: the mean PAP-flow relationship was linear; pulmonary capillary wedge pressure was greater than or equal to the average closure pressure of the pulmonary vascular bed and could therefore be used as the downstream pressure in calculating pulmonary vascular resistance; and pulmonary vascular resistance declined with exercise. Notable exceptions to the third observation were patients with valvular heart disease or a resting pulmonary vascular resistance greater than 800 dyne-sec-cm-5.