A 63-year-old man comes to the emergency department due to a 1-week history of progressively worsening shortness of breath and cough. The shortness of breath is exacerbated when the patient lies flat in bed; he has to prop himself up with 3 pillows to sleep well at night. He was treated for a myocardial infarction 2 weeks ago and had 2 stents placed in the left anterior descending artery. The patient's other medical conditions include long-standing hypertension and type 2 diabetes mellitus. Blood pressure is 120/80 mm Hg, pulse is 92/min, and respirations are 22/min. Pulse oximetry is 89% on room air. Physical examination reveals bilateral crackles at the lung bases and an S3. Which of the following is most likely present in this patient?

Question

A 63-year-old man comes to the emergency department due to a 1-week history of progressively worsening shortness of breath and cough.  The shortness of breath is exacerbated when the patient lies flat in bed; he has to prop himself up with 3 pillows to sleep well at night.  He was treated for a myocardial infarction 2 weeks ago and had 2 stents placed in the left anterior descending artery.  The patient's other medical conditions include long-standing hypertension and type 2 diabetes mellitus.  Blood pressure is 120/80 mm Hg, pulse is 92/min, and respirations are 22/min.  Pulse oximetry is 89% on room air.  Physical examination reveals bilateral crackles at the lung bases and an S3.  Which of the following is most likely present in this patient?

Quizplus · Accepted Answer

This patient's dyspnea, orthopnea, bibasilar crackles, and S3 suggest left-sided heart failure due to recent myocardial infarction (MI). Atherosclerotic plaque rupture in the left anterior descending or left circumflex artery can infarct large areas of the left ventricular myocardium, leading to decreased contractility and reduced cardiac output. This can result in elevation of end-diastolic pressure that impairs diastolic return from the pulmonary veins, leading to increased hydrostatic pressure in the pulmonary capillaries with transudation of fluid into the lung parenchyma (pulmonary edema). Pulmonary edema in the alveoli impairs ventilation and causes intrapulmonary shunting. In addition, edema in the lung interstitium makes the lungs heavy and stiff, restricting pulmonary expansion during inspiration. This decreased lung compliance can mimic that seen with other causes of restrictive lung physiology (eg, interstitial lung disease). (Choice A) Surfactant decreases the surface tension of the fluid layer that lines alveolar cells, helping prevent alveolar collapse. Pulmonary edema dilutes pulmonary surfactant, increasing both alveolar surface tension and the tendency for alveolar collapse. (Choice C) Ventilation-perfusion (V/Q) mismatch exists on a spectrum with intrapulmonary shunting (perfusion without ventilation) and dead space ventilation (ventilation without perfusion) on either end. Pulmonary edema causes V/Q mismatch via increased intrapulmonary shunting with a corresponding decrease in dead space ventilation. V/Q mismatch via increased dead space ventilation is seen with pulmonary embolism. (Choice D) Functional residual capacity is the volume of air in the lungs at the end of normal expiration. It is increased in conditions with increased lung compliance (eg, chronic obstructive pulmonary disease) and decreased in conditions such as pulmonary edema that reduce lung compliance. (Choice E) Interventricular septal rupture is a mechanical complication of MI that causes left-to-right cardiac shunting. However, this complication usually occurs within 3-5 days following MI and precipitates a dramatic and acute, rather than gradual, presentation of heart failure. Educational objective: Left-sided heart failure is common following myocardial infarction affecting the left ventricle. The resulting accumulation of edema in the pulmonary interstitium makes the lungs heavy and stiff, restricting inspiratory expansion and decreasing lung compliance.

A 63-Year-Old Man Comes to the Emergency Department Due to a 1-Week