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Difficulty: HardCardiovascular System

A 74-year-old man presents to the emergency department at 3:00 AM with sudden-onset, severe shortness of breath and wheezing. He has a 45-pack-year smoking history, essential hypertension, and diet-controlled type 2 diabetes mellitus. He reports waking up gasping for air and states that his cough produces frothy sputum. Current medications include amlodipine and metformin. His temperature is 37.0°C (98.6°F), blood pressure is 210/115 mm Hg, pulse is 112/min, and respirations are 28/min. Pulse oximetry shows 88% on room air. Physical examination reveals use of accessory muscles of respiration. Lung auscultation demonstrates diffuse, bilateral end-expiratory wheezes with a prolonged expiratory phase. Cardiac examination reveals a sustained but non-displaced apical impulse and a prominent fourth heart sound (S4). Jugular venous pressure is estimated at 10 cm H2O. There is no lower extremity edema. A chest radiograph reveals peribronchial cuffing, indistinct pulmonary vascular margins, and a normal cardiothoracic ratio. An electrocardiogram demonstrates normal sinus rhythm with voltage criteria for left ventricular hypertrophy. Which of the following pathophysiologic mechanisms is the primary driver of this patient's current respiratory distress?

  1. Decreased left ventricular diastolic complianceAnswer
  2. B
    Right ventricular pressure overload
  3. C
    Decreased left ventricular ejection fraction
  4. D
    Dynamic left ventricular outflow tract obstruction
  5. E
    Increased pulmonary vascular endothelial permeability

Answer

Decreased left ventricular diastolic compliance
This patient is presenting with acute flash pulmonary edema, manifesting clinically as 'cardiac asthma' (wheezing secondary to peribronchial edema compressing the airways). While his smoking history makes COPD a consideration, his extreme hypertension, prominent S4 gallop, normal cardiothoracic ratio, and interstitial edema (peribronchial cuffing) on radiograph strongly indicate cardiogenic pulmonary edema due to Heart Failure with Preserved Ejection Fraction (HFpEF). The primary pathophysiologic driver of HFpEF is decreased left ventricular diastolic compliance (a stiff ventricle). When blood pressure spikes, the non-compliant ventricle requires exceedingly high filling pressures, which rapidly transmit backward into the left atrium and pulmonary venous system, resulting in acute pulmonary edema.

Step-by-Step Solution

1
Analyze the patient's presentation and vital signs.
The patient presents with sudden-onset nocturnal dyspnea, wheezing, frothy sputum, extreme hypertension (210/115 mm Hg), and hypoxia.
To establish the acuity of the presentation and identify the primary physiologic derangements.
2
Evaluate the physical examination and diagnostic findings.
Exam shows an S4 gallop, non-displaced apical impulse, and wheezing. CXR shows peribronchial cuffing and a normal heart size. ECG shows left ventricular hypertrophy.
To differentiate between cardiac and pulmonary etiologies of wheezing and dyspnea.
3
Synthesize the data to form a clinical diagnosis.
The findings indicate acute cardiogenic pulmonary edema (flash pulmonary edema) secondary to a hypertensive emergency. The wheezing is 'cardiac asthma' caused by peribronchial interstitial edema.
Despite the smoking history, the extreme blood pressure, S4, and CXR findings confirm a cardiac source rather than a primary COPD exacerbation.
4
Identify the subtype and mechanism of the heart failure.
The normal heart size and S4 point to Heart Failure with Preserved Ejection Fraction (HFpEF), which is driven by decreased left ventricular diastolic compliance.
Concentric left ventricular hypertrophy creates a stiff ventricle that requires high filling pressures, leading to rapid fluid backup into the lungs during acute hypertensive episodes.

Key Concept

Heart Failure with Preserved Ejection Fraction (HFpEF) / Cardiac Asthma
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Topics

Cardiovascular System

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