Cardiovascular Drugs — MCQs

Cardiovascular Drugs Indian Medical PG Practice Questions and MCQs

Question 1031: Which of the following statements about the mechanism of action of digitalis is incorrect?

A. There is rise in intracellular Na+
B. Digitalis action is independent of cardiac innervation (Correct Answer)
C. It has positive inotropic action
D. It binds to the extracellular face of Na+ ATPase enzyme

Explanation: ***Digitalis action is independent of cardiac innervation*** - This statement is **incorrect** because digitalis, while directly affecting cardiac contractility, also has **indirect effects** through the **vagus nerve**, leading to decreased heart rate and atrioventricular conduction. - Its effects can be modulated by the **autonomic nervous system**, indicating it is not entirely independent of cardiac innervation. *There is rise in intracellular Na+* - Digitalis **inhibits the Na+/K+-ATPase pump**, leading to an **accumulation of intracellular sodium (Na+)**. - This increased intracellular Na+ then reduces the activity of the **Na+/Ca2+ exchanger**, causing a rise in intracellular **calcium (Ca2+)** levels. *It has positive inotropic action* - The increased intracellular Ca2+ due to Na+/K+-ATPase pump inhibition leads to more Ca2+ being released from the sarcoplasmic reticulum, enhancing the interaction between actin and myosin. - This results in increased force of myocardial contraction, which is known as a **positive inotropic effect**. *It binds to the extracellular face of Na+ ATPase enzyme* - Digitalis **binds to a specific receptor site on the extracellular face** of the alpha subunit of the **Na+/K+-ATPase enzyme**. - This binding leads to a conformational change that inhibits the pump's activity.

Question 1032: What is the mechanism of action of nicorandil?

A. Cl- channel blocker
B. K+ channel blocker
C. K+ channel opener (Correct Answer)
D. Na+ channel blocker

Explanation: ***K+ channel opener*** - **Nicorandil** acts as a **potassium channel opener**, specifically targeting ATP-sensitive potassium channels (K-ATP channels) in vascular smooth muscle - Opening these channels leads to **hyperpolarization** of the cell membrane, causing relaxation of smooth muscle and **vasodilation** - Nicorandil also has a **nitrate-like effect**, providing a dual mechanism for its antianginal action - This mechanism makes it effective in **stable angina** and **coronary vasospasm** *K+ channel blocker* - Potassium channel blockers (e.g., certain antiarrhythmics like amiodarone) inhibit potassium efflux, leading to **prolonged repolarization** and increased action potential duration - This mechanism is opposite to nicorandil's action and is used for **antiarrhythmic purposes**, not for vasodilation - Would cause vasoconstriction rather than the vasodilation seen with nicorandil *Na+ channel blocker* - Sodium channel blockers (e.g., local anesthetics, Class I antiarrhythmics) inhibit sodium influx, thereby **stabilizing cell membranes** and reducing excitability - This mechanism does not explain the **vasodilation** characteristic of nicorandil - Primarily used for arrhythmias, local anesthesia, or neurological conditions *Cl- channel blocker* - Chloride channel blockers are not a primary mechanism for drugs producing **vasodilation** like nicorandil - Their effects are typically related to **fluid secretion** or **cell volume regulation** (e.g., in cystic fibrosis or secretory diarrhea) - This mechanism is distinct from nicorandil's cardiovascular actions

Question 1033: Which of the following is a contraindication for the use of triptans?

A. Hepatic failure
B. Controlled hypertension
C. Ischemic heart disease (Correct Answer)
D. None of the options

Explanation: ***Ischemic heart disease*** - Triptans are **serotonin 5-HT1B/1D receptor agonists** [1] that cause **vasoconstriction**, including of coronary arteries [2] - This is an **absolute contraindication** - coronary vasoconstriction can precipitate angina, myocardial infarction, or coronary vasospasm in patients with compromised cardiac blood flow [2] - Other absolute cardiovascular contraindications include previous MI, coronary artery vasospasm (Prinzmetal angina) [2], and **uncontrolled/severe hypertension** *Controlled hypertension* - Patients with **well-controlled hypertension** can generally use triptans safely with appropriate monitoring - While triptans may cause transient blood pressure elevation due to vasoconstriction, this is clinically insignificant when baseline BP is adequately controlled - **Uncontrolled or severe hypertension** (BP >140/90 mm Hg or severe elevations) is an absolute contraindication, but controlled hypertension is not *Hepatic failure* - Most triptans undergo hepatic metabolism, so **severe hepatic impairment** requires dose reduction or avoidance of certain triptans - This is a **precaution or relative contraindication** requiring dose adjustment, not an absolute contraindication like ischemic heart disease - Some triptans (e.g., sumatriptan) have alternative elimination routes and may be preferred in hepatic disease *None of the options* - This is incorrect because **ischemic heart disease** is a definitive absolute contraindication for all triptans [2] - The vasoconstrictive mechanism makes triptans unsafe in any condition with compromised coronary blood flow [2]

Question 1034: Which of the following antiarrhythmic drugs can cause Long QT syndrome?

A. All of the options (Correct Answer)
B. Dofetilide
C. Sotalol
D. Ibutilide

Explanation: ***All of the options*** - **Dofetilide**, **sotalol**, and **ibutilide** are all Class III antiarrhythmic agents that primarily block potassium channels, thereby prolonging the **repolarization phase** of the action potential. - This prolongation of repolarization can increase the duration of the **QT interval** on an electrocardiogram, predisposing patients to **Torsades de Pointes**, a life-threatening polymorphic ventricular tachycardia. *Dofetilide* - **Dofetilide** is a selective **potassium channel blocker** (Class III antiarrhythmic) known to prolong the QT interval in a dose-dependent manner. - Its use requires careful monitoring of the QT interval due to the significant risk of inducing **Torsades de Pointes**. *Sotalol* - **Sotalol** has both **beta-blocking** (Class II) and **potassium channel blocking** (Class III) properties. - Its Class III activity, specifically the blockade of the **delayed rectifier potassium current**, leads to QT prolongation and the risk of proarrhythmia. *Ibutilide* - **Ibutilide** is a Class III antiarrhythmic that acts primarily by activating a **slow inward sodium current** and blocking the rapid component of the delayed rectifier potassium current (IKr). - This dual action strongly prolongs the action potential duration and effective refractory period, resulting in a significant risk of **QT prolongation** and **Torsades de Pointes**, especially when converted from atrial rhythm.

Question 1035: Mechanism of action of Torcetrapib is ?

A. Bile acid sequestrant
B. Sterol absorption inhibitor
C. Lipoprotein lipase activator
D. CETP inhibitors (Correct Answer)

Explanation: ***CETP inhibitors*** - **Torcetrapib** is a **cholesteryl ester transfer protein (CETP) inhibitor** designed to increase HDL cholesterol levels by preventing the transfer of cholesteryl esters from HDL to VLDL and LDL. - Despite its mechanism aiming to raise HDL, **Torcetrapib** significantly **failed in clinical trials** due to an unexpected increase in cardiovascular events and mortality, possibly linked to off-target effects like elevated blood pressure. *Bile acid sequestrant* - **Bile acid sequestrants** (e.g., cholestyramine) work by binding to **bile acids in the intestine**, preventing their reabsorption and increasing their fecal excretion. - This leads to an **upregulation of hepatic LDL receptors** to synthesize new bile acids from cholesterol, thereby lowering plasma LDL levels. *Sterol absorption inhibitor* - **Sterol absorption inhibitors** (e.g., ezetimibe) act by **blocking the Niemann-Pick C1-like 1 (NPC1L1) protein** in the small intestine. - This mechanism specifically **reduces the absorption of dietary and biliary cholesterol**, leading to decreased delivery of cholesterol to the liver and subsequent lowering of LDL-C. *Lipoprotein lipase activator* - A **lipoprotein lipase (LPL) activator** would increase the activity of LPL, an enzyme that **hydrolyzes triglycerides** in chylomicrons and VLDL. - This action would primarily lead to a **reduction in triglyceride-rich lipoproteins** and an increase in HDL, but **Torcetrapib** does not function through LPL activation.

Question 1036: Which of the following antilipidemic drugs is a sterol absorption inhibitor?

A. Gemfibrozil
B. Simvastatin
C. Nicotinic acid
D. Ezetimibe (Correct Answer)

Explanation: ***Ezetimibe*** - **Ezetimibe** acts by inhibiting the **Niemann-Pick C1-like 1 (NPC1L1) protein**, which is responsible for the absorption of cholesterol and phytosterols in the small intestine. - This mechanism directly reduces the amount of dietary and biliary cholesterol absorbed, leading to a decrease in **LDL-C** levels. *Gemfibrozil* - **Gemfibrozil** is a **fibrate**, primarily acting as a **PPAR-α agonist** to increase lipoprotein lipase activity. - Its main effects are reducing **triglycerides** and increasing **HDL-C**, not directly inhibiting sterol absorption. *Simvastatin* - **Simvastatin** is an **HMG-CoA reductase inhibitor** (statin), which reduces cholesterol synthesis in the liver. - It works by blocking the rate-limiting step in cholesterol biosynthesis, not by inhibiting sterol absorption from the gut. *Nicotinic acid* - **Nicotinic acid** (niacin) primarily works by inhibiting **hepatic VLDL secretion** and decreasing the catabolism of HDL. - Its main effects are increasing **HDL-C** and lowering **triglycerides** and **LDL-C**, through a mechanism distinct from sterol absorption inhibition.

Question 1037: Which of the following is NOT a side effect of amiodarone?

A. Corneal microdeposits
B. Photosensitivity
C. Tachycardia (Correct Answer)
D. Pulmonary fibrosis

Explanation: ***Tachycardia*** - **Amiodarone** is an antiarrhythmic drug primarily used to treat and prevent **tachyarrhythmias**, meaning it generally slows down heart rate and is not associated with causing tachycardia. - Its main effect is to prolong the **refractory period** in myocardial cells, which helps to stabilize abnormal heart rhythms, rather than inducing them. *Pulmonary fibrosis* - **Amiodarone** is well-known for its potential to cause **pulmonary toxicity**, including **interstitial lung disease** and **pulmonary fibrosis**, which can be severe and even fatal. - This side effect is thought to be dose-dependent and can manifest as shortness of breath and cough, requiring careful monitoring. *Corneal microdeposits* - **Corneal microdeposits**, often described as **whorl keratopathy** or **cornea verticillata**, are a very common and usually benign side effect of **amiodarone**. - These deposits typically do not affect vision but can cause blurred vision or halos around lights in some patients. *Photosensitivity* - **Photosensitivity** is a common dermatological side effect of **amiodarone**, leading to an exaggerated sunburn reaction or a grayish-blue skin discoloration in sun-exposed areas. - Patients are advised to use **sunscreen** and protective clothing while on **amiodarone** to minimize this risk.

Question 1038: Which of the following medications is most commonly associated with bradycardia?

A. Propranolol (Beta Blocker) (Correct Answer)
B. Lisinopril (ACE Inhibitor)
C. Amlodipine (Calcium Channel Blocker)
D. Digitalis (Digoxin)

Explanation: ***Propranolol (Beta Blocker)*** - Propranolol is a **non-selective beta-blocker** that blocks both β1 and β2 adrenergic receptors. - By blocking **β1 receptors in the heart**, it directly reduces heart rate (negative chronotropic effect) and is **most commonly associated with bradycardia** among the given options. - Bradycardia is a **predictable and common therapeutic effect** of beta-blockers, occurring even at therapeutic doses. - Beta-blockers are the **classic drug class** taught as causing bradycardia in medical pharmacology. - Other effects include reduced contractility (negative inotropic) and slowed AV conduction. *Digitalis (Digoxin)* - Digoxin inhibits the **Na+/K+ ATPase pump** and increases **vagal tone**, which can slow AV nodal conduction. - While digoxin CAN cause bradycardia, this typically occurs in **toxicity or overdose** rather than as a common therapeutic effect. - At therapeutic doses, digoxin is used for its positive inotropic effect and rate control in atrial fibrillation. - Bradycardia from digoxin is less commonly encountered compared to beta-blockers in routine clinical practice. *Lisinopril (ACE Inhibitor)* - Works by inhibiting **angiotensin-converting enzyme**, causing vasodilation and reducing blood pressure. - Acts on the **renin-angiotensin-aldosterone system** and does not typically affect heart rate. - Not associated with bradycardia. *Amlodipine (Calcium Channel Blocker)* - A **dihydropyridine calcium channel blocker** that primarily causes peripheral vasodilation. - Unlike **non-dihydropyridine CCBs** (verapamil, diltiazem), amlodipine has minimal effect on the **SA and AV nodes**. - May actually cause **reflex tachycardia** due to vasodilation rather than bradycardia.

Question 1039: Which of the following can prolong QT interval?

A. Gatifloxacin (Correct Answer)
B. Nalidixic acid
C. Pefloxacin
D. Ofloxacin

Explanation: ***Gatifloxacin*** - This **fluoroquinolone antibiotic** is known to cause **significant QT prolongation**, which can lead to serious cardiac arrhythmias like **Torsades de Pointes** [1]. - Among fluoroquinolones, gatifloxacin carries the **highest risk** of QT interval prolongation. - Its use has been **withdrawn or restricted** in many countries due to these **serious cardiac side effects** and dysglycemia, especially in patients with pre-existing cardiac conditions. - This is the **best answer** as it has the most clinically significant association with QT prolongation. *Nalidixic acid* - This is a **first-generation quinolone** primarily used for **urinary tract infections**. - While it can theoretically prolong QT interval, the **clinical significance is much lower** compared to fluoroquinolones. - It is **rarely implicated** in clinically significant QT prolongation in practice. *Ofloxacin* - Ofloxacin is a **second-generation fluoroquinolone** with a **moderate risk** of QT prolongation. - All fluoroquinolones carry a **class warning** for QT effects, but ofloxacin has **significantly lower risk** compared to gatifloxacin, moxifloxacin, and sparfloxacin. - It is considered **relatively safer** within the fluoroquinolone class for cardiac effects. *Pefloxacin* - Pefloxacin is another **second-generation fluoroquinolone** with **moderate QT prolongation potential**. - Like ofloxacin, it has a **comparatively lower risk** than gatifloxacin. - The **clinical incidence** of significant QT prolongation is **much less** than with newer fluoroquinolones.

Question 1040: Which of the following changes in ECG is most commonly associated with Digitalis use?

A. Tall T waves
B. ST segment elevation
C. Prolonged QT interval
D. Prolonged PR interval (Correct Answer)

Explanation: ***Prolonged PR interval*** - Digitalis increases **parasympathetic tone** and slows **AV nodal conduction**, leading to a prolonged PR interval [1], [2]. - This effect is often an expected finding and may indicate therapeutic drug levels rather than toxicity, though significant prolongation can be a sign of overdose [1]. *Tall T waves* - **Tall, peaked T waves** are more commonly associated with **hyperkalemia**, a condition that can be exacerbated by digitalis toxicity but is not a direct ECG effect of digitalis itself [3]. - Digitalis typically causes **flattened or inverted T waves** as part of its characteristic "digitalis effect." *ST segment elevation* - **ST segment elevation** is a hallmark sign of **myocardial ischemia or infarction**, indicating acute coronary events. - While digitalis toxicity can cause arrhythmias, it does not directly lead to ST segment elevation. *Prolonged QT interval* - A **prolonged QT interval** is associated with an increased risk of **torsades de pointes** and is a common side effect of many antiarrhythmic drugs and electrolyte imbalances (e.g., hypokalemia, hypomagnesemia). - Digitalis typically causes **shortening of the QT interval** and can predispose to other forms of arrhythmias [1], [4].

Practice by Chapter

Antihypertensive Agents

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Drugs for Heart Failure

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Antiarrhythmic Drugs

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Antianginal Agents

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Lipid-Lowering Drugs

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Anticoagulants and Antiplatelet Drugs

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Thrombolytic Agents

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Drugs Used in Pulmonary Hypertension

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Drugs Used in Shock

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Cardiovascular Effects of Non-Cardiovascular Drugs

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