A 63-year-old man comes to the emergency department with substernal chest pain and diaphoresis. The pain started one hour ago and was not relieved with antacids. His medical problems include asthma, for which he uses inhaled fluticasone, and peptic ulcer disease, for which he takes omeprazole. Blood pressure is 160/100 mm Hg and pulse is 90/min. A bruit is heard over the right carotid artery, and a mild systolic murmur is present at the cardiac apex. Sublingual nitroglycerin and aspirin are administered and within minutes the patient reports resolution of pain. Which of the following most likely accounts for the improvement in his symptoms?

Question

A 63-year-old man comes to the emergency department with substernal chest pain and diaphoresis.  The pain started one hour ago and was not relieved with antacids.  His medical problems include asthma, for which he uses inhaled fluticasone, and peptic ulcer disease, for which he takes omeprazole.  Blood pressure is 160/100 mm Hg and pulse is 90/min.  A bruit is heard over the right carotid artery, and a mild systolic murmur is present at the cardiac apex.  Sublingual nitroglycerin and aspirin are administered and within minutes the patient reports resolution of pain.  Which of the following most likely accounts for the improvement in his symptoms?

Quizplus · Accepted Answer

Nitrates are excellent antianginal drugs and are used frequently to relieve chest pain in patients with stable angina pectoris and acute coronary syndrome. Nitrates are primarily vasodilators and dilate veins, arterioles, and coronary arteries by relaxing vascular smooth muscle cells. Although nitrates act as venodilators and coronary vasodilators, their primary anti-ischemic effects are due to systemic vasodilation rather than coronary vasodilation. Systemic venodilation lowers preload and left ventricular end-diastolic volume and reduces myocardial oxygen demand by reducing wall stress. Nitrates also cause arterial and arteriolar vasodilation, although to a lesser degree, and can decrease systemic vascular resistance and blood pressure. The fall in systemic blood pressure reduces wall stress, which leads to further decrease in myocardial oxygen demand. (Choice A) Nitrates do not have a direct effect on heart rate. However, a fall in blood pressure with nitrates can induce reflex tachycardia with an increase in myocardial oxygen demand and worsening angina. This can best be prevented by concomitant use of beta blockers. (Choice B) Nitrates have no direct effect on cardiac chronotropy or inotropy (contractility) and left ventricular ejection fraction. They can indirectly cause reflex tachycardia in patients with a significant fall in blood pressure. (Choices D and F) Systemic venodilation caused by nitrates leads to a decrease, not an increase, in preload. Systemic arterial dilation also causes a decrease in afterload, which occurs to a much lesser degree than a decrease in preload. In contrast, an increase in preload and/or afterload will cause an increase in wall stress with increased myocardial oxygen demand and worsening angina. (Choice E) Nitrates have no direct effect on left ventricular compliance. Educational objective: The primary anti-ischemic and antianginal effects of nitrates are due to systemic vasodilation rather than coronary vasodilation. Systemic venodilation lowers preload and left ventricular end-diastolic volume, reducing wall stress and myocardial oxygen demand.

A 63-Year-Old Man Comes to the Emergency Department with Substernal