MD Cardiovascular System Pathophysiology 2 — Questions and Answers
Question 1: A 65-year-old man with hypertension develops left ventricular hypertrophy. Which hemodynamic change most directly drives this adaptation?
- Increased preload due to volume overload
- Increased afterload due to elevated systemic vascular resistance (Correct answer)
- Decreased contractility due to beta-receptor downregulation
- Increased heart rate due to sympathetic activation
Correct answer: Increased afterload due to elevated systemic vascular resistance
Chronic pressure overload from elevated afterload (e.g., systemic hypertension) stimulates concentric left ventricular hypertrophy.
Question 2: During myocardial ischemia, anaerobic metabolism leads to intracellular acidosis. What is the primary consequence of this acidosis on cardiac function?
- Increased calcium sensitivity of troponin
- Inhibition of phosphofructokinase reducing glycolytic ATP (Correct answer)
- Decreased sodium-potassium ATPase activity
- Enhanced beta-adrenergic receptor sensitivity
Correct answer: Inhibition of phosphofructokinase reducing glycolytic ATP
Intracellular acidosis inhibits phosphofructokinase, a key glycolytic enzyme, further limiting ATP production during ischemia.
Question 3: A patient with mitral stenosis develops pulmonary hypertension. Which mechanism initially elevates pulmonary arterial pressure in this condition?
- Primary pulmonary arteriolar vasospasm
- Passive back-transmission of elevated left atrial pressure (Correct answer)
- Pulmonary vein thrombosis
- Right ventricular systolic dysfunction
Correct answer: Passive back-transmission of elevated left atrial pressure
Mitral stenosis obstructs flow from left atrium to left ventricle, raising left atrial pressure that is passively transmitted backward to the pulmonary vasculature.
Question 4: Which ion channel abnormality is most responsible for the triggered arrhythmias seen in digoxin toxicity?
- Potassium channel blockade prolonging repolarization
- Sodium-potassium ATPase inhibition causing intracellular calcium overload (Correct answer)
- L-type calcium channel activation
- HCN channel hyperpolarization shift
Correct answer: Sodium-potassium ATPase inhibition causing intracellular calcium overload
Digoxin inhibits Na⁺/K⁺-ATPase, raising intracellular Na⁺, which reduces Na⁺/Ca²⁺ exchanger activity, leading to calcium overload and delayed afterdepolarizations.
Question 5: A 72-year-old woman develops acute aortic regurgitation after bacterial endocarditis. Why does she develop acute pulmonary edema while a patient with chronic aortic regurgitation is compensated?
- Acute AR causes higher systemic vascular resistance
- The unprepared left ventricle cannot accommodate the sudden volume load (Correct answer)
- Acute AR causes more severe mitral regurgitation
- Bacterial toxins directly depress myocardial contractility
Correct answer: The unprepared left ventricle cannot accommodate the sudden volume load
In acute AR, the normal-sized left ventricle has poor compliance and cannot accommodate the sudden regurgitant volume, causing abrupt elevation in LV end-diastolic pressure and pulmonary edema.
Question 6: In hypertrophic obstructive cardiomyopathy (HOCM), the outflow tract gradient worsens with which intervention?
- IV fluid bolus
- Phenylephrine infusion
- Passive leg elevation
- Valsalva maneuver (Correct answer)
Correct answer: Valsalva maneuver
The Valsalva maneuver reduces venous return and preload, decreasing LV cavity size and worsening dynamic LVOT obstruction in HOCM.
Question 7: A patient in cardiogenic shock has a pulmonary capillary wedge pressure of 28 mmHg and cardiac index of 1.6 L/min/m². Which pathophysiologic finding best explains the elevated lactate?
- Hepatic glycogenolysis stimulated by catecholamines
- Inadequate oxygen delivery causing anaerobic metabolism in peripheral tissues (Correct answer)
- Renal tubular acidosis from diuretic use
- Respiratory alkalosis from mechanical ventilation
Correct answer: Inadequate oxygen delivery causing anaerobic metabolism in peripheral tissues
Low cardiac output in cardiogenic shock results in inadequate systemic oxygen delivery, forcing peripheral tissues to generate ATP anaerobically with lactate as a byproduct.
MD Cardiovascular System Pathophysiology 2
A 65-year-old man with hypertension develops left ventricular hypertrophy.
Which hemodynamic change most directly drives this adaptation?