Which agent is preferred for the initial treatment of heart failure?

Choice A reason: This is not an adverse effect of ACE inhibitors. Insomnia is a common side effect of stimulant medications, such as caffeine or amphetamine, which increase the activity of the central nervous system and cause difficulty falling or staying asleep.

Choice B reason: This is not an adverse effect of ACE inhibitors. Bradycardia is a slow heart rate, usually below 60 beats per minute. ACE inhibitors do not cause bradycardia, but rather lower the blood pressure by blocking the formation of angiotensin II, a potent vasoconstrictor.

Choice C reason: This is not an adverse effect of ACE inhibitors. Chest pain is a sign of angina or myocardial infarction, which are caused by reduced blood flow to the heart muscle. ACE inhibitors can actually prevent or treat these conditions by improving the blood flow and reducing the workload of the heart.

Choice D reason: This is an adverse effect of ACE inhibitors. Hyperkalemia is a high level of potassium in the blood, which can cause cardiac arrhythmias and muscle weakness. ACE inhibitors can cause hyperkalemia by reducing the secretion of aldosterone, a hormone that regulates the sodium and potassium balance in the body.

Choice A reason: Cardiac output has not fallen below normal levels. Cardiac output is the amount of blood pumped by the heart per minute. It is affected by the heart rate and the stroke volume. Angina pectoris does not directly affect the cardiac output, but it can reduce the stroke volume due to impaired ventricular filling.

Choice B reason: The vagus nerve is not stimulated. The vagus nerve is a cranial nerve that innervates the heart and other organs. It is part of the parasympathetic nervous system, which slows down the heart rate and lowers the blood pressure. Angina pectoris does not activate the vagus nerve, but it can trigger the sympathetic nervous system, which increases the heart rate and blood pressure.

Choice C reason: Myocardial stretch has not exceeded the upper limits. Myocardial stretch is the degree of tension or load on the cardiac muscle fibers. It is determined by the end-diastolic volume, which is the amount of blood in the ventricle at the end of relaxation. Angina pectoris does not cause excessive myocardial stretch, but it can impair the myocardial contractility due to ischemia.

Choice D reason: The myocardial oxygen supply has fallen below demand. This is the main cause of angina pectoris. It occurs when the coronary arteries, which supply blood and oxygen to the heart muscle, are narrowed or blocked by atherosclerosis or spasm. This creates an imbalance between the oxygen demand of the heart, which increases during exertion, and the oxygen supply, which is reduced by the obstruction.