MD Cardiovascular System Pathophysiology 3 — Questions and Answers
Question 1: A 55-year-old man undergoes cardiac catheterization after a large anterior STEMI. Which coronary artery territory is most likely occluded?
- Right coronary artery (RCA)
- Left circumflex artery (LCX)
- Left anterior descending artery (LAD) (Correct answer)
- Posterior descending artery (PDA)
Correct answer: Left anterior descending artery (LAD)
The LAD supplies the anterior wall, apex, and anterior interventricular septum, making it the vessel most responsible for anterior ST-elevation myocardial infarction.
Question 2: Which compensatory mechanism in heart failure leads to cardiac remodeling and ultimately worsens long-term prognosis?
- Increased atrial natriuretic peptide secretion
- Chronic neurohormonal activation via RAAS and sympathetic nervous system (Correct answer)
- Peripheral vasodilation to reduce afterload
- Increased erythropoietin secretion
Correct answer: Chronic neurohormonal activation via RAAS and sympathetic nervous system
Chronic RAAS and sympathetic activation causes maladaptive cardiac remodeling—fibrosis, hypertrophy, and chamber dilation—that progressively worsens heart failure.
Question 3: Electrical alternans on ECG in a patient with hypotension and elevated JVP most likely indicates which condition?
- Hypertrophic cardiomyopathy
- Constrictive pericarditis
- Cardiac tamponade (Correct answer)
- Pulmonary embolism
Correct answer: Cardiac tamponade
Electrical alternans—beat-to-beat variation in QRS amplitude—results from the heart swinging within a large pericardial effusion, characteristic of cardiac tamponade.
Question 4: A patient with long-standing hypertension develops diastolic heart failure. The primary pathophysiologic abnormality is:
- Reduced ejection fraction due to systolic dysfunction
- Impaired ventricular relaxation and increased chamber stiffness (Correct answer)
- Mitral annular dilation causing regurgitation
- Decreased sympathetic tone reducing heart rate
Correct answer: Impaired ventricular relaxation and increased chamber stiffness
Hypertensive heart disease causes concentric LV hypertrophy with increased collagen deposition, impairing active relaxation (lusitropy) and passive compliance.
Question 5: In a patient with pulmonary embolism, the right ventricle fails acutely despite normal baseline function. What is the critical mechanism?
- Direct compression of RV by the embolus
- Sudden increase in RV afterload exceeding its adaptive capacity (Correct answer)
- Systemic hypoxia suppressing RV contractility
- Left ventricular underfilling causing septal shift
Correct answer: Sudden increase in RV afterload exceeding its adaptive capacity
The thin-walled RV, unlike the LV, cannot acutely adapt to sudden pressure overload from massive PE, leading to acute RV failure and obstructive shock.
Question 6: Which finding differentiates restrictive cardiomyopathy from constrictive pericarditis on hemodynamic catheterization?
- Elevated right-sided filling pressures in restriction only
- Discordance of LV and RV pressures with respiration in restriction (Correct answer)
- Square root sign (dip-and-plateau) in restriction only
- Equalization of diastolic pressures in restriction only
Correct answer: Discordance of LV and RV pressures with respiration in restriction
In constrictive pericarditis, the fixed pericardial shell dissociates intrathoracic from intracardiac pressure, causing concordant respiratory variation; restriction shows discordant ventricular pressure changes.
Question 7: A patient develops Wolff-Parkinson-White syndrome with atrial fibrillation. Why is AV nodal blockade with diltiazem potentially lethal?
- It causes direct myocardial depression leading to asystole
- Slowing AV node conduction preferentially routes impulses down the accessory pathway at dangerously fast rates (Correct answer)
- It prolongs the QT interval causing torsades de pointes
- It causes paradoxical acceleration of AV nodal conduction
Correct answer: Slowing AV node conduction preferentially routes impulses down the accessory pathway at dangerously fast rates
Blocking the AV node in WPW-AF directs all impulses through the unprotected accessory pathway, which can conduct at rates exceeding 300 bpm, potentially degenerating into ventricular fibrillation.
MD Cardiovascular System Pathophysiology 3
A 55-year-old man undergoes cardiac catheterization after a large anterior STEMI.
Which coronary artery territory is most likely occluded?