A 71-year-old male is evaluated in the emergency department due to severe shortness of bre… — USMLE Step 2 CK

A $71$ -year-old male is evaluated in the emergency department due to severe shortness of breath that has progressively worsened over the last two days. The patient reports that his breathing becomes especially difficult when he lies flat in bed, requiring him to sleep in a recliner chair. His medical history includes hypertension and a $45$ -pack-year smoking history. He currently takes amlodipine. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $172/98$ mmHg, pulse is $112$ /min, and respirations are $28$ /min. Pulse oximetry shows $89\%$ on room air. Physical examination reveals an anxious patient in mild respiratory distress. Auscultation of the lungs demonstrates diffuse, bilateral expiratory wheezes and a prolonged expiratory phase. Cardiac auscultation reveals a regular tachycardia; an extra, low-pitched heart sound is heard shortly after the second heart sound at the cardiac apex. The apical impulse is displaced laterally. There is trace bilateral pitting edema of the lower extremities. Bedside chest radiography shows an enlarged cardiac silhouette, prominent pulmonary vasculature, and prominent septal lines. Which of the following is the most likely primary underlying mechanism for this patient's acute respiratory symptoms?

Increased left ventricular filling pressureCevap
B
Bronchial smooth muscle constriction
C
Irreversible enlargement of distal airspaces
D
Increased pulmonary vascular resistance
E
Increased pulmonary capillary permeability

Cevap

Increased left ventricular filling pressure

This patient's presentation of progressive dyspnea, orthopnea, and wheezing in the setting of hypertension strongly suggests acute decompensated heart failure (ADHF). The presence of an S3 gallop (an extra, low-pitched heart sound heard shortly after S2), a laterally displaced apical impulse (indicating cardiomegaly), and chest radiograph findings of an enlarged cardiac silhouette with prominent septal lines (Kerley B lines) confirm left-sided volume overload. In ADHF, left ventricular systolic or diastolic dysfunction leads to increased left ventricular end-diastolic pressure (filling pressure). This elevated hydrostatic pressure is transmitted backward to the left atrium and pulmonary veins, causing fluid to leak into the pulmonary interstitium. This resulting peribronchial edema compresses the small airways, leading to wheezing (often termed 'cardiac asthma').

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Analyze the patient's presenting symptoms and risk factors.

The patient has acute, severe dyspnea, orthopnea, and wheezing in the context of long-standing hypertension and a significant smoking history.

Establishing the acute respiratory presentation and risk factors sets the foundation for differentiating between a primary pulmonary versus cardiac etiology.

Evaluate the physical examination and bedside imaging findings.

Key findings include an S3 gallop (extra low-pitched sound after S2), a laterally displaced apical impulse (cardiomegaly), and chest radiography showing prominent pulmonary vasculature and septal lines (Kerley B lines).

These objective findings definitively point to left-sided volume overload and cardiomegaly, which are not seen in primary obstructive lung diseases.

Correlate the clinical findings with the underlying pathophysiology.

The patient is experiencing acute decompensated heart failure (ADHF). Left ventricular dysfunction leads to increased left ventricular end-diastolic pressure (filling pressure), which transmits backward to the lungs, causing peribronchial edema and subsequent wheezing (cardiac asthma).

Connecting the diagnosis (ADHF) to the specific hemodynamic mechanism answers the question asked in the stem.

Anahtar Kavram

Acute decompensated heart failure can present with wheezing (cardiac asthma) due to peribronchial edema. It is differentiated from a COPD exacerbation by clinical signs of left-sided volume overload, such as an S3 gallop, a displaced apical impulse, and pulmonary edema on chest radiography, all of which are driven by increased left ventricular filling pressures.

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