Heart disease (HD) can stress the alveolar blood-gas barrier, resulting in parenchymal inflammation and remodeling. Patients with HD may therefore display any of the symptoms commonly attributed to primary pulmonary disease, although tissue documentation of corresponding changes through surgical lung biopsy (SLB) is rarely done. Intent on exploring the basis of HD-related alveolar-capillary barrier dysfunction, a retrospective analysis of SLB histopathology was conducted in patients with clinically diagnosed HD, diffuse pulmonary infiltrates, and no evidence of primary pulmonary disease. Patients eligible for the study had a clinical diagnosis of heart disease, acute or chronic, and presented with diffuse infiltrates on chest X-ray. All qualified subjects (N = 23) who underwent diagnostic SLB between January 1982 and December 2005 were subsequently examined. Specific biopsy parameters investigated included demonstrable edema, siderophage influx, hemorrhage, venous and lymphatic ectasia, vascular sclerosis, capillary congestion, and fibroblast proliferation. Based on observed alveolar-capillary barrier (ACB) alterations, three main morphologic groups emerged: one group (6 patients) with alveolar edema; a second group (11 patients) characterized by pulmonary congestion; and a final group (6 patients) showing microscopic foci of acute ACB lung injury. Alveolar-capillary stress due to acute high-pressure or volume overload often manifests as diffuse pulmonary infiltrates with variable but generally predictable histopathology. In patients with biopsy-proven alveolar edema, pulmonary congestion, or acute microscopic lung injury, the clinician must be alert for the possibility of primary heart disease, particularly if the patient is elderly or when a history of myocardial, valvular, or coronary vascular disease exists.