USMLE Step 1 Quiz
Practice Cardiovascular Pharmacology in USMLE Step 1 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.
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A 62-year-old man with hypertension and type 2 diabetes mellitus is started on a new medication. Two weeks later, he presents with a persistent, nonproductive cough. His blood pressure is well-controlled at 132/84 mmHg. He has no fever, wheezing, or other signs of infection.
The patient's symptom is most likely a side effect of a drug that acts by which of the following mechanisms?
This quiz focuses on Cardiovascular Pharmacology, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 1.
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A 62-year-old man with hypertension and type 2 diabetes mellitus is started on a new medication. Two weeks later, he presents with a persistent, nonproductive cough. His blood pressure is well-controlled at 132/84 mmHg. He has no fever, wheezing, or other signs of infection.
The patient's symptom is most likely a side effect of a drug that acts by which of the following mechanisms?
Explanation: The patient's persistent dry cough is a classic adverse effect of angiotensin-converting enzyme (ACE) inhibitors (e.g., lisinopril, enalapril). ACE is responsible for the breakdown of bradykinin. Inhibition of ACE leads to an accumulation of bradykinin, which is thought to cause bronchial irritation and cough. Angiotensin II receptor blockers (ARBs) do not affect bradykinin levels and are a suitable alternative for patients who develop an ACE inhibitor-induced cough. Calcium channel blockers can cause peripheral edema and gingival hyperplasia. Loop diuretics inhibit the Na-K-2Cl cotransporter and can cause electrolyte abnormalities.
A 65-year-old man with a history of coronary artery disease presents to the emergency department with severe, substernal chest pain. He is given a sublingual medication, and his pain improves within minutes. His blood pressure decreases from 140/90 mmHg to 125/80 mmHg, and his heart rate increases from 80/min to 95/min.
The therapeutic effect of this medication is primarily mediated by which of the following intracellular changes?
Explanation: The patient was treated with sublingual nitroglycerin for an anginal attack. Nitrates are metabolized to nitric oxide (NO), which stimulates soluble guanylate cyclase to produce cyclic GMP (cGMP). Increased cGMP activates protein kinase G, which leads to the dephosphorylation of myosin light chains in vascular smooth muscle, causing relaxation. This effect is more pronounced on veins than arteries, leading to venodilation, decreased preload, and reduced myocardial oxygen demand. The drop in blood pressure can cause a reflex tachycardia. Increased cAMP is the mechanism of beta-agonists. Decreased calcium is a downstream effect, not the primary mediator.
A 72-year-old woman is being treated for essential hypertension. Her routine laboratory work shows a serum sodium of 136 mEq/L, potassium of 3.2 mEq/L, calcium of 10.8 mg/dL, and glucose of 115 mg/dL. Her uric acid level is also elevated.
Which of the following medications is most likely responsible for these laboratory findings?
Explanation: The constellation of hypokalemia, hypercalcemia, hyperglycemia, and hyperuricemia is characteristic of thiazide diuretics like hydrochlorothiazide. They inhibit the Na-Cl cotransporter in the distal convoluted tubule. In contrast, loop diuretics like furosemide cause hypocalcemia because they inhibit calcium reabsorption in the thick ascending limb. Spironolactone is a potassium-sparing diuretic and would cause hyperkalemia. Lisinopril, an ACE inhibitor, can cause hyperkalemia, particularly in patients with renal insufficiency.
A 68-year-old man with a history of atrial fibrillation is treated with a medication to maintain normal sinus rhythm. A follow-up ECG shows a heart rate of 70/min and a QT interval of 520 ms (normal < 450 ms). The patient is at increased risk for developing torsades de pointes.
The medication responsible for this ECG finding most likely acts by blocking which of the following ion channels?
Explanation: Significant QT prolongation is a hallmark effect of Class III antiarrhythmic drugs (e.g., amiodarone, sotalol, dofetilide, ibutilide). These drugs primarily block the delayed rectifier potassium channels responsible for phase 3 repolarization of the cardiac action potential. This prolongs the action potential duration and, consequently, the QT interval on the ECG, increasing the risk for early afterdepolarizations and torsades de pointes. Sodium channel blockers (Class I) primarily affect the QRS duration. Calcium channel blockers (Class IV) primarily affect the PR interval. Funny current blockers (ivabradine) slow the heart rate without affecting the QT interval.
A 55-year-old man with a history of a prior myocardial infarction is experiencing frequent, symptomatic premature ventricular contractions (PVCs). He is started on a medication that effectively suppresses the PVCs. However, he is warned about an increased risk of sudden cardiac death from this drug class.
The medication most likely belongs to which class of antiarrhythmics?
Explanation: Class IC antiarrhythmics, such as flecainide and propafenone, are potent sodium channel blockers with slow dissociation kinetics. They are very effective at suppressing ventricular ectopy. However, the Cardiac Arrhythmia Suppression Trial (CAST) demonstrated that these drugs increase mortality in patients with underlying structural heart disease, such as a prior myocardial infarction, due to a significant proarrhythmic risk. Therefore, their use is contraindicated in this patient population. Class IB agents (e.g., lidocaine) are safer in the post-MI setting.
A 42-year-old woman with difficult-to-control hypertension is prescribed a new medication. Several months later, she develops joint pain, myalgias, and a malar rash on her face. Laboratory studies are positive for anti-histone antibodies.
Which of the following drugs is most likely responsible for this patient's syndrome?
Explanation: The patient's presentation of arthralgias, myalgias, malar rash, and positive anti-histone antibodies is characteristic of drug-induced lupus erythematosus (DILE). Hydralazine, a direct-acting arterial vasodilator, is one of the most common causes of DILE, along with procainamide. The risk is higher in patients who are slow acetylators. Prazosin is an alpha-1 blocker, clonidine is a central alpha-2 agonist, and minoxidil is another direct vasodilator, but they are not strongly associated with DILE.
A 75-year-old man with benign prostatic hyperplasia and hypertension is started on a new medication to manage both conditions. On the first day of treatment, he feels dizzy and nearly faints upon standing up from his chair. His blood pressure, which was 150/90 mmHg in the clinic, is now 110/70 mmHg while standing.
This adverse effect is most characteristic of a drug with which of the following mechanisms?
Explanation: The patient is experiencing first-dose orthostatic hypotension, a classic side effect of α1-adrenergic blockers such as prazosin, terazosin, and doxazosin. These drugs are used for both hypertension and BPH. By blocking α1 receptors on vascular smooth muscle, they cause both arteriolar and venous dilation. The venodilation leads to peripheral pooling of blood, reducing venous return and causing a sharp drop in blood pressure upon standing. This effect is most pronounced with the first dose.
A 70-year-old man with HFrEF (EF 25%) is managed with an ACE inhibitor, a beta-blocker, and a loop diuretic. Despite this therapy, he remains symptomatic. His physician adds spironolactone.
The primary survival benefit of adding spironolactone in this patient is attributed to preventing which of the following long-term pathologic changes?
Explanation: Spironolactone is a mineralocorticoid receptor antagonist (MRA). In heart failure, aldosterone levels are elevated and contribute to disease progression. While spironolactone is a potassium-sparing diuretic and helps with fluid and electrolyte balance, its major survival benefit in HFrEF comes from blocking the non-epithelial effects of aldosterone on the heart and blood vessels. Aldosterone promotes myocardial fibrosis, inflammation, and adverse ventricular remodeling. By blocking these effects, MRAs improve long-term outcomes in HFrEF.
A 68-year-old man is in the coronary care unit following an acute myocardial infarction. He develops sustained ventricular tachycardia. An intravenous antiarrhythmic agent is administered that selectively binds to and blocks sodium channels in the inactivated state. This drug has a minimal effect on the QRS duration in normal sinus rhythm.
Which of the following drugs was most likely administered?
Explanation: Lidocaine is a Class IB antiarrhythmic agent. Class IB drugs exhibit 'use-dependence,' meaning they have a high affinity for sodium channels in the open or inactivated states, but low affinity for channels in the resting state. Ischemic myocardium is partially depolarized, which means more sodium channels are in the inactivated state. This makes lidocaine particularly effective for arrhythmias arising from ischemic tissue, such as post-MI ventricular tachycardia. Its rapid dissociation kinetics mean it has little effect on the QRS complex at normal heart rates. Flecainide (Class IC) and Procainamide (Class IA) have slower kinetics and widen the QRS.
A 58-year-old woman with a history of hypertension and stable angina is prescribed a medication that causes gingival hyperplasia and peripheral edema. The medication is effective in controlling both her blood pressure and anginal symptoms.
Which of the following is the primary mechanism of action of this medication for treating her hypertension?
Explanation: The patient's side effects, gingival hyperplasia and peripheral edema, are characteristic of dihydropyridine calcium channel blockers (e.g., amlodipine, nifedipine). These drugs act by blocking L-type calcium channels on vascular smooth muscle, leading to arteriolar vasodilation. This reduces systemic vascular resistance and blood pressure. Non-dihydropyridine calcium channel blockers (e.g., verapamil, diltiazem) have a greater effect on the heart, decreasing the SA node firing rate, but are less associated with these specific side effects. Nitrates increase cGMP. Thiazide diuretics inhibit sodium reabsorption in the distal convoluted tubule.
A 62-year-old woman is hospitalized for acute decompensated heart failure with signs of low cardiac output, including cool extremities and poor urine output. An intravenous infusion of dobutamine is initiated. Her cardiac output improves, and her systemic vascular resistance decreases.
Dobutamine exerts these effects primarily through which of the following mechanisms?
Explanation: Dobutamine is a synthetic catecholamine used as an inotropic agent in acute heart failure and cardiogenic shock. Its primary mechanism is agonism at β1-adrenergic receptors, which increases myocardial contractility and heart rate via the Gs-adenylyl cyclase-cAMP pathway. This leads to an increase in cardiac output. Dobutamine also has weak β2-agonist activity, which results in mild vasodilation and a decrease in systemic vascular resistance (afterload reduction). It has negligible α1-agonist effects. Milrinone inhibits phosphodiesterase.
An 80-year-old woman with heart failure and atrial fibrillation is brought to the emergency department due to nausea, vomiting, and visual disturbances described as 'yellow halos around lights.' Her medications include digoxin, furosemide, and an ACE inhibitor. An ECG shows atrial fibrillation with a slow ventricular response and frequent premature ventricular contractions. Her serum potassium is 2.9 mEq/L.
The patient's digoxin toxicity is most likely exacerbated by which of the following factors?
Explanation: The patient is presenting with classic signs of digoxin toxicity (gastrointestinal upset, visual changes, arrhythmias). Digoxin works by inhibiting the Na+/K+-ATPase pump. Potassium and digoxin compete for the same binding site on this pump. Hypokalemia, a common side effect of loop diuretics like furosemide, reduces the competition for binding sites, allowing for increased digoxin binding and leading to enhanced therapeutic and toxic effects. While renal impairment (which can be worsened by ACE inhibitors) also increases the risk of digoxin toxicity by reducing its clearance, the presence of severe hypokalemia is a direct and potent precipitating factor.
A 66-year-old man with type 2 diabetes and heart failure with reduced ejection fraction is started on a new oral medication. The primary mechanism of this drug involves inhibiting a transporter in the proximal convoluted tubule of the kidney. In addition to improving his glycemic control, this medication has been shown to reduce mortality and hospitalizations for heart failure.
Which of the following best describes the primary renal mechanism of action of this drug?
Explanation: The medication described is a sodium-glucose cotransporter 2 (SGLT2) inhibitor (e.g., empagliflozin, dapagliflozin). These drugs have emerged as a key therapy for HFrEF, regardless of diabetes status. They work by blocking the SGLT2 transporter in the proximal convoluted tubule, which prevents the reabsorption of filtered glucose and sodium. This leads to glucosuria and an osmotic diuresis, which reduces intravascular volume and preload, contributing to their cardiovascular benefits.
A 45-year-old man presents to the emergency department with a sudden onset of palpitations and lightheadedness. His heart rate is 180/min, and blood pressure is 110/70 mmHg. An ECG shows a narrow-complex supraventricular tachycardia. A bolus of a short-acting intravenous medication is administered, which transiently causes flushing, chest pain, and a brief period of asystole before the rhythm converts to normal sinus.
The administered drug exerts its therapeutic effect by activating which of the following?
Explanation: This clinical scenario describes the administration of adenosine for acute termination of paroxysmal supraventricular tachycardia (PSVT). Adenosine has a very short half-life (<10 seconds) and causes transient side effects like flushing and chest pain. It acts on A1 purinergic receptors in the AV node, which are coupled to an inhibitory G protein (Gi). Activation of this pathway opens potassium channels, causing hyperpolarization of the cell membrane and slowing conduction through the AV node, which terminates the reentrant circuit. Acetylcholine acts on M2 receptors (C), but this is not adenosine's mechanism.
A 64-year-old woman with atrial fibrillation and hypertension is prescribed a medication for rate control. She later complains of constipation and her ECG shows a first-degree AV block.
The medication responsible for these findings primarily exerts its effects by blocking which of the following?
Explanation: The combination of rate control in atrial fibrillation, first-degree AV block, and constipation points to a non-dihydropyridine calcium channel blocker, such as verapamil or diltiazem (with verapamil being more known for causing constipation). These drugs block L-type calcium channels in cardiac tissue (slowing AV conduction) and in smooth muscle (causing vasodilation and decreased gut motility). Beta-blockers (A) can cause AV block but do not typically cause constipation. Anticholinergics (C) cause constipation but would cause tachycardia. Digoxin (D) can cause AV block but is more associated with nausea/vomiting than constipation.
A 67-year-old man with stable chronic heart failure with reduced ejection fraction (HFrEF) is being managed with an ACE inhibitor and a diuretic. His physician decides to add a new medication known to improve long-term survival in HFrEF. Shortly after starting the new drug at a low dose, the patient reports increased fatigue and shortness of breath.
The added medication most likely has which of the following mechanisms of action?
Explanation: Beta-blockers (e.g., carvedilol, metoprolol succinate, bisoprolol) are a cornerstone of HFrEF therapy and improve long-term survival. However, due to their negative inotropic and chronotropic effects, they can cause a transient worsening of heart failure symptoms upon initiation. This is why they are started at a very low dose and titrated slowly. The other agents listed do not typically cause an initial worsening of symptoms. Direct vasodilators (hydralazine/isosorbide dinitrate) reduce preload and afterload. Digoxin is a positive inotrope. Aldosterone antagonists like spironolactone primarily prevent myocardial fibrosis.
A 50-year-old man is treated for recurrent, symptomatic atrial fibrillation. He is prescribed a medication that has both beta-blocking activity and the ability to prolong the cardiac action potential duration. His ECG shows bradycardia and a prolonged QT interval.
The drug prescribed has properties of which two Vaughan Williams antiarrhythmic classes?
Explanation: The drug described is sotalol. Sotalol is a unique antiarrhythmic agent that has properties of both Class II (beta-blockade) and Class III (potassium channel blockade). The beta-blocking (Class II) activity is responsible for the bradycardia. The potassium channel blocking (Class III) activity prolongs repolarization and the action potential duration, which manifests as QT prolongation on the ECG. This dual action makes it useful for treating both supraventricular and ventricular arrhythmias. No other option correctly combines these two specific effects.
A 60-year-old woman with symptomatic heart failure with a reduced ejection fraction of 30% is being treated with carvedilol and spironolactone. Her physician decides to switch her from lisinopril to a combination drug containing sacubitril and valsartan.
The sacubitril component of this medication improves cardiac function primarily by increasing the levels of which of the following substances?
Explanation: Sacubitril is a neprilysin inhibitor. Neprilysin is an endopeptidase that degrades several endogenous vasoactive peptides, including natriuretic peptides (ANP, BNP), bradykinin, and angiotensin II. By inhibiting neprilysin, sacubitril increases the levels of natriuretic peptides. ANP and BNP promote vasodilation, natriuresis, and diuresis, which counteracts the maladaptive neurohormonal activation in heart failure. Because neprilysin inhibition also increases angiotensin II, it must be co-administered with an angiotensin receptor blocker (ARB) like valsartan.
A 59-year-old woman with hypertension develops a dry cough after starting lisinopril. Her physician switches her to an alternative medication that also blocks the renin-angiotensin-aldosterone system but does so by a different mechanism that does not cause cough.
The new medication most likely works by which of the following mechanisms?
Explanation: The patient was switched from an ACE inhibitor (lisinopril) to an angiotensin II receptor blocker (ARB) like losartan or valsartan. ACE inhibitors (mechanism A) block the enzyme that converts angiotensin I to angiotensin II but also block the breakdown of bradykinin, leading to cough. ARBs directly and selectively block the AT1 receptor, preventing the actions of angiotensin II without affecting bradykinin metabolism. Therefore, they do not cause cough. Beta-blockers can inhibit renin release (B). Spironolactone antagonizes the aldosterone receptor (D).
A 55-year-old man is in the intensive care unit with acute decompensated heart failure and cardiogenic shock. His blood pressure is 85/60 mmHg and cardiac index is 1.5 L/min/m^2. He is started on a continuous infusion of a drug that increases cardiac contractility and causes significant vasodilation. The drug works independently of adrenergic receptors.
Which of the following is the mechanism of action of the administered drug?
Explanation: The drug described is a phosphodiesterase-3 (PDE3) inhibitor, such as milrinone. These drugs are inodilators. By inhibiting the breakdown of cAMP, they increase intracellular cAMP levels in both cardiac myocytes (increasing contractility, or inotropy) and vascular smooth muscle (causing vasodilation, which reduces afterload). This combination is useful in cardiogenic shock. Dobutamine (B) is a β1-agonist. Levosimendan (C) is a calcium sensitizer. Digoxin (D) inhibits the Na+/K+-ATPase pump and is not used as an infusion for acute shock.