Although nitroglycerin can indirectly decrease heart rate by reducing preload and afterload and thus cardiac workload, this is not the most direct effect.

In fact, nitroglycerin decreases systemic vascular resistance by causing vasodilation.

While nitroglycerin does decrease cardiac preload by venous dilation that reduces venous return to the heart, this decrease in preload is not related to the dietary changes.

Therapy with nitroglycerin and dietary modification aim to decrease, not increase, myocardial oxygen consumption by reducing cardiac workload and cellular metabolic demands.