Cardiovascular limitations in chronic pulmonary disease.

Chronic lung disease has significant impact on cardiovascular function. Much of this effect is because of increased right ventricular afterload caused by increased pulmonary vascular resistance resulting from structural changes in the pulmonary circulation, and because of hypoxic pulmonary vasoconstriction. In the case of chronic obstructive diseases, there may be additional increases in afterload resulting from dynamic hyperinflation. These processes can lead to structural changes in the heart (cor pulmonale), including right ventricular dilatation and hypertrophy, to maintain right ventricular output. In most ambulatory patients with chronic obstructive disease, it appears that cardiac output may be maintained at levels that are similar to normal both at rest and during exercise, with no consistent improvement in maximal exercise function afforded by interventions that increase blood flow. In contrast, diseases characterized by fibrosis or infiltration of the lung parenchyma may be associated with a disproportionate increase in pulmonary vascular resistance and more pronounced cardiovascular impairment, particularly with exercise.