Pathophysiology

In 20 percent of patients, the cause of aortic incompetence is acute in nature. Infective endocarditis accounts for the majority of acute cases; aortic dissection at the aortic root causes the remainder. In acute cases, a sudden increase in backflow of blood into the ventricle raises left ventricular end-diastolic pressure, which may cause acute heart failure. Increased ventricular pressure elevates pressure in the left atrium, and pulmonary congestion results. Rheumatic heart disease and congenital disease cause the majority of chronic cases. Syphilis, ankylosing spondylitis, and Reiter syndrome are less frequent causes. An association between the appetite-suppressant drugs (fenfluramine and phentermine or dexfenfluramine) has also been found for aortic incompetence. 2 Chronic disease is more common in males than in females, with a ratio of 3:2. In chronic disease, the ventricle progressively dilates to accommodate the regurgitant blood volume. Wide pulse pressures result from the fall in diastolic pressure, and marked peripheral vasodilation is seen. During exercise and tachycardia, the diastolic filling period shortens, thus decreasing the number of times per minute that regurgitation can occur. Cardiac function is therefore close to normal with exercise early in the course of the disease. In contrast, isometric exercise or stress may precipitate symptoms.

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