While rounding in the oncology unit, a physician is urgently called to evaluate a patient … — USMLE Step 3

While rounding in the oncology unit, a physician is urgently called to evaluate a patient who developed abrupt-onset dyspnea and profound lightheadedness. The patient has a history of advanced lung cancer and recently underwent radiation therapy. Current vital signs demonstrate sinus tachycardia at $122\text{ /min}$ , respiratory rate of $24\text{ /min}$ , and a narrowed pulse pressure with a blood pressure of $88/72\text{ mm Hg}$ . The extremities are cool to the touch, and the lungs are clear to auscultation bilaterally. Given the high suspicion for a rapidly progressive hemodynamic complication characterized by the accumulation of fluid in the pericardial space, which of the following physical examination findings would most accurately support this specific diagnosis? (Select 3 findings)

An exaggerated drop in systolic blood pressure of greater than $10\text{ mm Hg}$ during inspirationAnswer
B
An inspiratory elevation of jugular venous pressure
C
A high-pitched, early diastolic sound occurring shortly after the second heart sound
Elevated jugular venous pressure exhibiting a prominent $x$ descent and an absent $y$ descentAnswer
Distant and muffled heart sounds on precordial auscultationAnswer
F
A third heart sound ( $S_3$ ) gallop accompanied by bilateral crackles at the lung bases

Answer

The physical examination findings supporting acute cardiac tamponade are an exaggerated drop in systolic blood pressure during inspiration (pulsus paradoxus), elevated jugular venous pressure with a prominent

x

descent and an absent

y

descent, and distant/muffled heart sounds.

The correct findings directly reflect the pathophysiology of cardiac tamponade. The accumulation of fluid in the pericardial space equalizes pressures across all cardiac chambers. This leads to Beck's triad, which includes distant and muffled heart sounds. Because the heart is compressed, early diastolic filling is severely impaired, resulting in a loss of the normal

y

descent on the jugular venous waveform (while the systolic

x

descent remains). Furthermore, the fixed pericardial volume causes enhanced ventricular interdependence; during inspiration, the increased right heart filling bows the intraventricular septum to the left, decreasing left ventricular stroke volume and causing an exaggerated drop in systolic blood pressure of

>10\text{ mm Hg}

(pulsus paradoxus).

Step-by-Step Solution

Analyze the clinical presentation and vital signs.

The patient exhibits hypotension, a narrowed pulse pressure, tachycardia, and clear lungs in the setting of lung cancer.

These findings point toward obstructive shock, specifically malignant pericardial effusion leading to acute cardiac tamponade.

Identify the classic diagnostic triad for this condition.

Beck's triad consists of hypotension, elevated jugular venous pressure (JVP), and muffled heart sounds.

Muffled heart sounds confirm one of the correct physical examination findings.

Evaluate the hemodynamic effects of the pericardial fluid on the cardiac cycle.

The increased intrapericardial pressure restricts right ventricular filling, leading to enhanced ventricular interdependence (pulsus paradoxus) and altered JVP waveforms (absent

y

descent).

This confirms the remaining two correct physical examination findings specific to tamponade rather than other pericardial diseases.

Key Concept

Cardiac tamponade presents with Beck's triad (hypotension, jugular venous distention, muffled heart sounds), pulsus paradoxus, and a distinct JVP waveform featuring a prominent

x

descent with a loss of the

y

descent.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic