Stenosis

Description: MEDICAL: Cardiac Congenital and Vascular Disorders, Age >17 with CC

^Aortic stenosis (AS) is a narrowing of the aortic valve orifice, which obstructs outflow from the left ventricle during systole. The left ventricle must overcome the increased resistance to ejection by generating a higher-than-normal pressure during systole, which is achieved by stretching and generating a more forceful contraction. The blood is propelled through the narrowed aortic valve at an increased velocity. Aortic valve stenosis accounts for approximately 5% of all congenital heart defects. About 4 in 1000 live births have AS, making this condition a relatively common birth defect.

As the stenosis in the aortic valve progresses, two sequelae occur. One is that cardiac output becomes fixed, making increases even with exertion impossible. The other is left-sided heart failure. Pressure overload of the heart occurs with concentric hypertrophy of the left ventricle. Left ventricular end-diastolic pressure rises, myocardial oxygen demand increases, and left ventricular mass and wall stress are increased. The increase in left ventricular pressure is reflected backward into the left atrium. Because the left atrium is unable to empty adequately, the pulmonary circulation becomes congested. Eventually, right-sided heart failure can develop as well.

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