Myocardial ultrastructure in patients with chronic aortic valve disease.

Light and electron microscopic observations were made on left ventricular myocardium removed at operation from 16 patients with chronic aortic valve disease. In all 16 patients most cardiac muscle cells were hypertrophid, and surrounded by small amounts of fibrous tissue. In two of the six patients with pure aortic regurgitation and in four of the five patients with combined aortic stenosis and regurgitation, cardiac muscle cells with evidence of degeneration were present in addition to hypertrophied, nondegenerated cells. Degenerated cardiac muscle cells were not observed in the six patients with predominant aortic stenosis. Cardiac muscle cells with mild degeneration showed focal myofibrillar lysis, with preferential loss of thick myofilaments, and focal proliferation of tubules of sarcoplasmic reticulum. More severely degenerated muscle cells showed a marked decrease in the numbers of myofibrils and T tubules and proliferation of sarcoplasmic reticulum or mitochondria, or both. Severly degenerated cells usually were present in areas of marked fibrosis, often were atrophic, had thickened basement membranes and had lost their intercellular connections. These findings suggest that degenerated cardiac muscle cells have poor contractile function and may be responsible for impaired cardiac performance in some patients with chronic aortic valve disease.