The Use of Angiotensin in the Assessment of Left Ventricular Function in Fixed Orifice Aortic Stenosis

Abstract

Catheterization of the left heart permits sophisticated assessment of the mechanical problem in aortic stenosis. Selection of patients for surgical repair requires an additional judgment regarding the contractile state of the left ventricle. Angiotensin has recently been used to study the function of the unobstructed left ventricle by imposing controlled pressure loads on both compensated and failing human hearts. The present study was designed to determine whether angiotensin might be of value in characterizing left ventricular function in the presence of aortic stenosis. Accordingly, controlled amounts of the drug were infused during transseptal left heart catheterization in 12 patients in whom fixed obstruction to left ventricular outflow was the sole mechanical fault. Observations were made before and during a series of stepwise increments in systemic systolic pressure. The following information was obtained: cardiac rate, stroke volume, peripheral vascular resistance, left ventricular systolic and end-diastolic pressures, brachial arterial systolic and diastolic pressures, aortic gradient, left ventricular stroke work, systolic ejection period, and aortic valve area. Left ventricular function curves were constructed by relating stroke work to diastolic filling pressure. Rises in brachial systolic pressure exceeded rises in left ventricular systolic, regularly diminishing the gradients. Elevations in systemic arterial pressure consistently elevated left ventricular end-diastolic pressure, indicating that angiotensin can be used to impose a pressure load on the left ventricle despite the interposition of fixed obstruction. In an attempt to gain further information on the mechanical and myocardial factors that coexist in aortic stenosis, three types of observations were made regarding the hemodynamic response of the left ventricle to the graded pressure loads: (1) the directional changes in stroke volume accompanying the increments in ventricular stress, (2) the magnitude of the increase in left ventricular systolic pressure accompanying a given increment in diastolic filling pressure, and (3) the relation between ventricular end-diastolic pressure and stroke work (ventricular function curves). Although the individual responses did not uniformly distinguish mechanical from myocardial influences, when stroke volume, left ventricular end-diastolic pressure, and ventricular function curves were taken together, a clearer impression of the behavior of the left ventricle emerged. Such information may prove useful in view of the practical need to assess ventricular adequacy in aortic stenotic patients considered for corrective surgery.