The Apex Cardiogram in Left Ventricular Outflow Tract Obstruction

Abstract

The use of the apex cardiogram offers a simple yet valuable aid in the diagnosis of obstruction of the left ventricular outflow tract. Characteristic changes in the ejection component of the apex cardiogram distinguish obstruction due to hypertrophic subaortic stenosis from obstruction due to valvular aortic stenosis. A second systolic wave is inscribed in the mid-ejection period of the apex cardiogram in hypertrophic subaortic stenosis. This wave reflects the development of the obstruction of the outflow tract of the left ventricle by the hypertrophied septum. This obstruction is not apparent in the apex cardiogram at the onset of ejection but becomes manifest as contraction progresses. Although the apex cardiogram in patients with subaortic stenosis may appear normal at rest, isoproterenol may act as a provocative agent inducing the characteristic changes of this condition. In valvular stenosis obstruction is reflected in the apex cardiogram from the very onset of ejection and is manifest throughout the total ejection phase as a sustained gradual sloping plateau.