An 82-year-old man is brought to the emergency department after a syncopal episode. He has had no chest pain or dyspnea but he has constipation of recent onset. He was hospitalized 2 weeks ago for atrial fibrillation with rapid ventricular response and was discharged home with oral medications after appropriate management. Medical history is also significant for hypertension and severe chronic obstructive pulmonary disease requiring home supplemental oxygen. Blood pressure is 105/60 mm Hg and pulse is 50/min. Examination reveals bilaterally decreased breath sounds, no wheezing, and normal heart sounds. ECG shows new-onset second-degree atrioventricular block. Which of the following drugs is the most likely cause of his current condition?

Question

An 82-year-old man is brought to the emergency department after a syncopal episode.  He has had no chest pain or dyspnea but he has constipation of recent onset.  He was hospitalized 2 weeks ago for atrial fibrillation with rapid ventricular response and was discharged home with oral medications after appropriate management.  Medical history is also significant for hypertension and severe chronic obstructive pulmonary disease requiring home supplemental oxygen.  Blood pressure is 105/60 mm Hg and pulse is 50/min.  Examination reveals bilaterally decreased breath sounds, no wheezing, and normal heart sounds.  ECG shows new-onset second-degree atrioventricular block.  Which of the following drugs is the most likely cause of his current condition?

Quizplus · Accepted Answer

This patient's constipation and new-onset second-degree atrioventricular (AV) block (causing syncope) are likely adverse effects of therapy with a nondihydropyridine calcium channel blocker (CCB) (eg, diltiazem, verapamil). These drugs are frequently used to treat hypertension, angina pectoris, and supraventricular arrhythmias, including atrial fibrillation (as in this patient). Nondihydropyridine CCBs exert their primary action by blocking the L-type calcium channels, thereby decreasing phase 0 depolarization and conduction velocity in the sinoatrial and AV nodes. This leads to slowing of the sinus rate and slowing of conduction through the AV node, which can cause bradycardia and varying degrees of AV block. The drugs also have a negative inotropic effect and are relatively contraindicated in patients with left ventricular systolic dysfunction. Constipation, which is typically more prominent with verapamil than diltiazem, likely occurs due to reduced contraction of colonic smooth muscle. (Choice A) Amlodipine is a dihydropyridine CCB that has a predominant vasodilator effect with minimal negative effect on cardiac conduction and contractility. Major adverse effects include lightheadedness, flushing, and peripheral edema. (Choice C) Hydrochlorothiazide is a thiazide diuretic used for the treatment of hypertension. It has no role in the management of atrial fibrillation. Adverse effects include hypokalemia and hyponatremia. (Choice D) Lidocaine is occasionally used in the management of symptomatic ventricular arrhythmias, usually in the setting of acute myocardial infarction. It is not used to treat atrial arrhythmias. (Choice E) Beta blockers are commonly used for heart rate control in patients with atrial fibrillation and can cause or worsen AV block. However, propranolol is a nonselective beta blocker that impairs bronchodilation and is typically avoided in patients with severe chronic obstructive pulmonary disease. In addition, constipation is not a significant adverse effect of beta blockers. (Choice F) Terazosin is an alpha-1 adrenergic antagonist used in the treatment of benign prostatic hyperplasia and hypertension. Major adverse effects include lightheadedness and orthostatic hypotension. (Choice G) Valsartan is an angiotensin II receptor blocker used in the management of hypertension and heart failure with reduced ejection fraction. Common adverse effects include hypotension and hyperkalemia. Educational objective: Common adverse effects of nondihydropyridine calcium channel blockers (eg, diltiazem, verapamil) include constipation, bradycardia, atrioventricular block (negative chronotropic effect), and worsening of heart failure in patients with left ventricular systolic dysfunction (negative inotropic effect).

An 82-Year-Old Man Is Brought to the Emergency Department After