MD Cardiovascular System Pathophysiology 5 — Questions and Answers
Question 1: A 70-year-old man with calcific aortic stenosis has a peak-to-peak gradient of 55 mmHg and valve area of 0.7 cm². He is asymptomatic. What is the most critical pathophysiologic event that signals the need for intervention?
- Onset of any of: angina, syncope, or heart failure symptoms (Correct answer)
- Decline in ejection fraction below 60%
- Gradient increase by more than 5 mmHg per year
- Development of left bundle branch block
Correct answer: Onset of any of: angina, syncope, or heart failure symptoms
The classic symptom triad of severe AS—angina, syncope, and heart failure—marks the inflection point at which survival drops sharply without valve replacement.
Question 2: Which pathophysiologic change most directly causes the elevated BNP levels in patients with decompensated heart failure?
- Renal failure impairing BNP clearance
- Myocardial wall stress from increased ventricular filling pressure stretching cardiomyocytes (Correct answer)
- Hepatic congestion reducing BNP metabolism
- Sympathetic activation stimulating BNP gene transcription
Correct answer: Myocardial wall stress from increased ventricular filling pressure stretching cardiomyocytes
Elevated ventricular wall stress from high filling pressures mechanically stretches cardiomyocytes, triggering cleavage of proBNP into BNP and NT-proBNP.
Question 3: A 60-year-old with diabetes and chronic kidney disease develops accelerated atherosclerosis. Which mechanism most distinguishes uremia-associated vascular disease from traditional atherosclerosis?
- LDL oxidation exclusively in uremia
- Medial calcification from calcium-phosphate deposition and vascular smooth muscle transdifferentiation (Correct answer)
- Foam cell formation from monocyte-derived macrophages
- Endothelial dysfunction from oxidized LDL
Correct answer: Medial calcification from calcium-phosphate deposition and vascular smooth muscle transdifferentiation
Uremia promotes vascular calcification via hyperphosphatemia and FGF-23 signaling, causing vascular smooth muscle cells to transdifferentiate into osteoblast-like cells depositing calcium in the media.
Question 4: A patient develops cardiac tamponade after pericardiocentesis reveals bloody fluid. Her blood pressure equalizes across all four cardiac chambers during diastole. This equalization of diastolic pressures explains which clinical sign?
- Electrical alternans
- Pulsus paradoxus (Correct answer)
- Kussmaul sign
- Ewart sign
Correct answer: Pulsus paradoxus
Equalized diastolic pressures from pericardial compression cause inspiratory-dependent ventricular competition, reducing LV stroke volume and SBP by >10 mmHg with each breath.
Question 5: In the setting of acute myocardial infarction, early reperfusion can paradoxically cause cell death through which mechanism?
- Re-entry arrhythmias from restored conduction
- Reperfusion injury from calcium overload, reactive oxygen species, and mitochondrial permeability transition pore opening (Correct answer)
- Hyperemia causing mechanical rupture of infarcted myocytes
- Sudden normalization of pH inactivating contractile proteins
Correct answer: Reperfusion injury from calcium overload, reactive oxygen species, and mitochondrial permeability transition pore opening
Restored blood flow delivers oxygen to cells with depleted antioxidant defenses, generating ROS that open the mitochondrial permeability transition pore, leading to additional cardiomyocyte death.
Question 6: A 45-year-old with dilated cardiomyopathy has functional mitral regurgitation. What is the primary mechanism of MR in this setting?
- Calcification and immobility of the mitral leaflets
- Papillary muscle rupture from ischemia
- Annular dilation and leaflet tethering from LV remodeling displacing papillary muscles (Correct answer)
- Primary leaflet prolapse from myxomatous degeneration
Correct answer: Annular dilation and leaflet tethering from LV remodeling displacing papillary muscles
Dilated cardiomyopathy causes spherical LV remodeling that displaces papillary muscles laterally and apically, tethering the mitral leaflets and preventing coaptation.
Question 7: Which finding on echocardiography is most specific for acute rejection after cardiac transplantation?
- New mitral regurgitation
- Diastolic dysfunction with elevated E/e' ratio and new restrictive filling pattern (Correct answer)
- Pericardial effusion
- Right ventricular dilation
Correct answer: Diastolic dysfunction with elevated E/e' ratio and new restrictive filling pattern
Acute cellular rejection causes myocardial edema and inflammation that impairs diastolic function; a new restrictive filling pattern with elevated E/e' is an early, relatively specific echo marker.
MD Cardiovascular System Pathophysiology 5
A 70-year-old man with calcific aortic stenosis has a peak-to-peak gradient of 55 mmHg and valve area of 0.7 cm².
He is asymptomatic.
What is the most critical pathophysiologic event that signals the need for intervention?