A 68-year-old man is evaluated in the outpatient clinic for worsening shortness of breath … — USMLE Step 2 CK

A 68-year-old man is evaluated in the outpatient clinic for worsening shortness of breath over the past week. He reports progressive difficulty walking short distances and a persistent, non-productive cough that is most prominent when he lies down to sleep. Medical history includes long-standing essential hypertension, obesity, and a 40-pack-year smoking history. Current medications are lisinopril and amlodipine. Vital signs are temperature $37.0^\circ C$ , blood pressure $168/95 \text{ mm Hg}$ , pulse $92\text{/min}$ , and respirations $22\text{/min}$ . Oxygen saturation is $92\%$ on room air. Physical examination reveals an obese man with mild respiratory effort. Jugular venous pressure is estimated at $9 \text{ cm H}_2\text{O}$ above the sternal angle. Pulmonary auscultation demonstrates bilateral end-expiratory wheezes and scattered bibasilar crackles. Cardiac examination reveals a regular rhythm with a distinct fourth heart sound (S4). Trace bilateral lower extremity edema is noted. Bedside spirometry indicates an $FEV_1/FVC$ ratio of $78\%$ . Which of the following pathophysiologic mechanisms best explains this patient's current symptoms?

Impaired left ventricular active relaxation and increased chamber stiffnessAnswer
B
Chronic inflammation and hypersecretion of mucus in the tracheobronchial tree
C
Protease-mediated destruction of alveolar walls and permanent airspace enlargement
D
Right ventricular failure secondary to chronic hypoxic pulmonary vasoconstriction
E
Reversible smooth muscle bronchospasm triggered by environmental allergens

Answer

Impaired left ventricular active relaxation and increased chamber stiffness

The correct answer identifies the pathophysiology of Heart Failure with Preserved Ejection Fraction (HFpEF). This patient's presentation of orthopnea, elevated JVP, bibasilar crackles, and an S4 gallop in the setting of long-standing hypertension and obesity is classic for HFpEF. The wheezing represents 'cardiac asthma,' which is caused by peribronchial edema resulting from elevated left-sided filling pressures. Despite his smoking history, his normal

FEV_1/FVC

ratio rules out a primary obstructive airway disease like COPD.

Step-by-Step Solution

Analyze the patient's presenting symptoms and vital signs.

The patient has progressive dyspnea, orthopnea (coughing when lying down), and elevated blood pressure.

Identifying the core clinical syndrome is the first step in differentiating between cardiac and pulmonary etiologies.

Evaluate the physical examination findings.

Elevated JVP, bibasilar crackles, wheezes, and an S4 gallop are present.

An S4 gallop indicates a stiff, non-compliant left ventricle. Crackles and elevated JVP point to volume overload backing up into both pulmonary and systemic circuits.

Interpret the objective diagnostic data (spirometry).

The

FEV_1/FVC

ratio is

78\%

, which is normal (greater than

70\%

A normal ratio effectively rules out chronic obstructive pulmonary disease (COPD) as the primary cause of his wheezing, despite his heavy smoking history.

Synthesize the findings to determine the underlying pathophysiology.

The patient has Heart Failure with Preserved Ejection Fraction (HFpEF) presenting with 'cardiac asthma'.

HFpEF is driven by impaired active relaxation and increased left ventricular stiffness, leading to elevated filling pressures that cause peribronchial edema (wheezing) and alveolar fluid (crackles).

Key Concept

Heart Failure with Preserved Ejection Fraction (HFpEF) vs. COPD

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