Why does nitrate drug decrease preload of heart?

Nitrate drugs decrease preload by dilating venous blood vessels, which reduces the volume of blood returning to the heart. This venodilation lowers the pressure and volume in the venous system, leading to decreased left ventricular filling. As a result, the heart experiences less stretch and workload during diastole, ultimately reducing the overall preload. This effect helps alleviate symptoms in conditions like heart failure and angina by decreasing cardiac demand.