Mechanism of nitroglycerin effect in valvular aortic stenosis

The hemodynamic effects of nitroglycerin taken sublingually were studied during cardiac catheterization in 10 patients with valvular aortic stenosis. Hemodynamics and cineangiographic left ventricular volumes were determined before administration of nitroglycerin and at peak nitroglycerin effect. Diastolic pressure-time and ejection pressure-time product were used to evaluate left ventricular energy supply and demand. Pressurevolume loops and left ventricular wall tension were calculated. There was a decrease (P < 0.05) in aortic systolic pressure, but heart rate and aortic diastolic pressure did not change significantly. Left ventricular ejection pressure-time declined by more than 20 percent and diastolic pressuretime did not show a significant change. Thus, the ratio of diastolic pressure-time to ejection pressure-time increased from 0.59 ± 0.07 (mean ± standard error) to 0.71 ± 0.09 (P < 0.05). There were significant declines in left ventricular peak systolic and end-diastolic pressures, endsystolic and end-diastolic volumes and peak left ventricular wall tension. Thus, the peripheral unloading effects of nitroglycerin were reflected in the left ventricle despite the fixed aortic valve obstruction. There was no significant change in any measure of left ventricular contractility after administration of nitroglycerin.

It is concluded that sublingual nitroglycerin in aortic valve stenosis: (1) improves indirect indexes of left ventricular energy supply/demand ratio, (2) decreases left ventricular preload and afterload, and (3) does not change left ventricular contractility.