A 65-year-old man comes to the clinic with a 3-month history of progressive exertional dys… — USMLE Step 2 CK

A $65$ -year-old man comes to the clinic with a $3$ -month history of progressive exertional dyspnea, lower extremity swelling, and abdominal fullness. He has a $30$ -pack-year smoking history and mild chronic obstructive pulmonary disease. Twenty years ago, he was diagnosed with Hodgkin lymphoma and treated with chemotherapy and mantle field radiation.

Vital signs show a blood pressure of $115/75$ mm Hg, pulse of $92$ /min, and respirations of $18$ /min. Pulse oximetry is $96\%$ on room air.

Physical examination reveals an elevated jugular venous pulsation at $11$ cm H $_2$ O that paradoxically increases during inspiration. Auscultation of the heart reveals a regular rhythm and a high-frequency sound just after S $_2$ . The lungs are clear to auscultation bilaterally. The abdomen is distended with shifting dullness, and there is 2+ bilateral pitting edema to the knees.

Laboratory results are as follows:
Thyroid-stimulating hormone (TSH): $2.1$ $\mu$ U/mL (Normal: $0.4$ - $4.0$ $\mu$ U/mL)
Free T $_4$ : $1.0$ ng/dL (Normal: $0.9$ - $2.4$ ng/dL)
Total T $_3$ : $60$ ng/dL (Normal: $80$ - $200$ ng/dL)

Which of the following is the most likely primary pathophysiologic mechanism responsible for this patient's current presentation?

Restricted diastolic filling of the ventricles due to a rigid pericardiumAnswer
B
Pulmonary arterial vasoconstriction secondary to chronic alveolar hypoxia
C
Left ventricular systolic dysfunction resulting in elevated pulmonary capillary wedge pressure
D
Decreased myocardial contractility secondary to impaired pituitary hormone production
E
Exaggerated drop in intrathoracic pressure during inspiration leading to decreased left ventricular stroke volume

Answer

Restricted diastolic filling of the ventricles due to a rigid pericardium

This patient's clinical presentation is highly characteristic of constrictive pericarditis, a known late complication of mediastinal radiation therapy (often used for Hodgkin lymphoma). The radiation causes chronic inflammation, leading to a thickened, fibrotic, and rigid pericardial sac. This rigid pericardium restricts the diastolic filling of the ventricles, causing blood to back up into the systemic venous system, which manifests as right-sided heart failure (elevated jugular venous pressure, hepatomegaly, ascites, and peripheral edema). Classic physical examination findings include Kussmaul sign (a paradoxical increase in jugular venous pressure during inspiration, as the right ventricle cannot accommodate the increased venous return) and a pericardial knock (a high-frequency early diastolic sound caused by the sudden cessation of ventricular filling). The patient's clear lungs indicate the absence of left heart volume overload.

Step-by-Step Solution

Analyze the patient's presenting symptoms and physical examination findings.

The patient has signs of right-sided heart failure (elevated jugular venous pressure, ascites, bilateral pitting edema) without signs of left-sided heart failure (clear lungs). He also has a Kussmaul sign (inspiratory increase in jugular venous pressure) and a pericardial knock (high-frequency early diastolic sound).

Identifying the pattern of isolated right heart failure with specific physical exam signs helps narrow the differential diagnosis.

Correlate the physical findings with the patient's past medical history.

The patient had mantle field radiation for Hodgkin lymphoma

20

years ago. This history, combined with Kussmaul sign and a pericardial knock, strongly suggests constrictive pericarditis.

Radiation therapy is a major risk factor for the development of constrictive pericarditis, which can occur years or decades after exposure.

Evaluate the laboratory findings to rule out confounding conditions.

The thyroid panel shows a low total T

_3

but normal TSH and free T

_4

, which is diagnostic of euthyroid sick syndrome (common in chronic heart failure), ruling out a primary or secondary thyroid disorder as the cause of his symptoms.

It is important to ensure that the symptoms are not driven by a correctable metabolic abnormality.

Determine the pathophysiologic mechanism of the confirmed diagnosis.

Constrictive pericarditis is characterized by a scarred, rigid pericardium that restricts the diastolic filling of the ventricles, leading to systemic venous congestion.

This directly answers the question regarding the underlying mechanism of the patient's presentation.

Key Concept

Constrictive Pericarditis

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic