During morning rounds in the step-down unit, the medical team evaluates a patient who was … — USMLE Step 2 CK

During morning rounds in the step-down unit, the medical team evaluates a patient who was admitted three days prior for severe, refractory peripheral edema, abdominal fullness, and exertional dyspnea. The patient, a $55$ -year-old individual, has not responded to high-dose intravenous torsemide. Medical history is notable for classical Hodgkin lymphoma in her twenties, which was treated with multi-agent chemotherapy and mantle field radiation, as well as moderate chronic obstructive pulmonary disease.

Vital signs show a blood pressure of $112/74\text{ mm Hg}$ , pulse of $92/\text{min}$ , and respiratory rate of $18/\text{min}$ . Oxygen saturation is $96\%$ on room air. Physical examination demonstrates marked jugular venous distention that paradoxically rises when the patient takes a deep breath. A sharp, high-frequency sound is heard along the left sternal border occurring approximately $0.10\text{ seconds}$ after the second heart sound. The liver edge is palpable $4\text{ cm}$ below the right costal margin. Lungs are clear to auscultation without wheezing.

The team decides to perform simultaneous right and left heart catheterization to clarify the hemodynamic profile. Which of the following findings is most expected in this patient?

Discordant right and left ventricular peak systolic pressure changes during respirationAnswer
B
Blunted $y$ -descent and a prominent $x$ -descent on the right atrial pressure waveform
C
Marked exaggeration of the normal inspiratory fall in systemic blood pressure exceeding $10\text{ mm Hg}$
D
Concordant decrease in both right and left ventricular peak systolic pressures during inspiration
E
Equalization of the right and left ventricular end-diastolic pressures at approximately $4\text{ mm Hg}$

Answer

Discordant right and left ventricular peak systolic pressure changes during respiration

The correct answer identifies the phenomenon of ventricular interdependence, which is the pathognomonic catheterization finding for constrictive pericarditis. The patient's history of mantle field radiation strongly predisposes her to this condition. The physical exam confirms it through the presence of Kussmaul sign (lack of normal inspiratory fall in jugular venous pressure) and a pericardial knock (an early diastolic sound caused by the sudden cessation of ventricular filling). Because the fibrotic pericardium restricts the total cardiac volume, the normal inspiratory increase in venous return to the right ventricle forces the interventricular septum to shift into the left ventricle. Consequently, right ventricular pressure increases while left ventricular pressure simultaneously decreases, which is recorded as discordant peak systolic pressures during simultaneous left and right heart catheterization.

Step-by-Step Solution

Analyze the patient's history and physical examination findings.

Identified a history of mantle field radiation, Kussmaul sign (paradoxical rise in jugular venous pressure with inspiration), and a pericardial knock (early diastolic sound).

These findings are the classic triad for constrictive pericarditis, differentiating it from purely primary pulmonary or right heart failure pathologies.

Evaluate the underlying pathophysiology of constrictive pericarditis.

Determined that the scarred, rigid pericardium creates a fixed total cardiac volume, preventing the heart from expanding outward normally.

Understanding the fixed volume constraint is essential for predicting intracardiac pressure behaviors during the respiratory cycle.

Determine the hemodynamic consequences of inspiration given the fixed total cardiac volume.

Concluded that increased venous return to the right heart during inspiration forces the interventricular septum to bow to the left.

This septal shift increases right ventricular volume and pressure while simultaneously decreasing left ventricular volume and pressure (ventricular interdependence), manifesting as discordant peak systolic pressures.

Key Concept

In constrictive pericarditis, a rigid pericardium causes a fixed total cardiac volume, leading to pronounced ventricular interdependence. This is demonstrated on catheterization by discordant changes in right and left ventricular peak systolic pressures during respiration.

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