Venodilatory

In contrast, l-arginine-derived endogenous nitrates do not develop tolerance. 15 Exogenous nitrates are endothelium-independent vasodilators in that they are not dependent on intact functioning endothelial layer for their conversion to NO and vasodilator properties. 16 In fact, the action of exogenous nitrates is particularly augmented in blood vessels with a low basal production of NO, such as atherosclerotic coronary arteries; therefore, nitrates play an important role in such patients. 15 Nitroglycerin alleviates anginal symptoms by decreasing myocardial oxygen consumption as a function of: 1) reducing preload, systolic wall stress, and afterload; 2) restoring flow imbalances; dilating coronary arteries (pre-stenotic, stenotic, and post-stenotic segments); 3) increasing subendocardial myocardial perfusion by lowering left ventricular diastolic pressure; 4) preventing coronary artery vasospasm; and 5) acting as a physiologic substitute for EDRF in endothelial dysfunction. 14, 17 Due to the potent venodilatory effects on capacitance vessels, nitrates reduce left ventricular filling pressures and preload, which may be a very useful therapeutic adjunct clinically, in patients with heart failure. 17 Nitrates produce vasodilation, with predominant venous effects on large capacitance vessels.