A 63-year-old man is brought to the emergency department due to an episode of syncope. The patient was recently discharged back to a nursing home after being hospitalized for a urinary tract infection. He has a history of coronary artery disease and takes aspirin, clopidogrel, and atorvastatin. His other medical conditions include type 2 diabetes mellitus and hypertension. The patient does not use tobacco, alcohol, or illicit drugs. Blood pressure is 68/32 mm Hg and pulse is 118/min. Invasive hemodynamic monitoring reveals an elevated right atrial pressure of 17 mm Hg and a pulmonary capillary wedge pressure of 7 mm Hg (normal: 8-10 mm Hg). Which of the following is the most likely cause of this patient's current condition?

Question

A 63-year-old man is brought to the emergency department due to an episode of syncope.  The patient was recently discharged back to a nursing home after being hospitalized for a urinary tract infection.  He has a history of coronary artery disease and takes aspirin, clopidogrel, and atorvastatin.  His other medical conditions include type 2 diabetes mellitus and hypertension.  The patient does not use tobacco, alcohol, or illicit drugs.  Blood pressure is 68/32 mm Hg and pulse is 118/min.  Invasive hemodynamic monitoring reveals an elevated right atrial pressure of 17 mm Hg and a pulmonary capillary wedge pressure of 7 mm Hg (normal: 8-10 mm Hg). Which of the following is the most likely cause of this patient's current condition?

Quizplus · Accepted Answer

11ec160b_38dc_84a8_9249_913775bc6932_MD0001_00 This patient is in shock (eg, severe hypotension, end organ dysfunction [syncope]) due to an unknown cause. Hemodynamic monitoring (eg, pulmonary artery catheterization) shows decreased pulmonary capillary wedge pressure (PCWP) and increased right atrial pressure (RAP), which indicate impaired blood flow from the right ventricle to the left side of the heart (right-sided heart failure). Common causes of right-sided heart failure include obstruction of pulmonary circulation (eg, pulmonary arterial hypertension, pulmonary embolism) and right ventricular infarction (likely in this patient due to multiple cardiovascular risk factors). In right ventricular infarction, the right ventricle is unable to effectively pump blood forward into the pulmonary arteries, causing increased pressure in the right atrium (ie, elevated central venous pressure). The decreased right ventricular outflow also lowers PCWP (an indicator of left-sided preload), which subsequently reduces cardiac output and causes hypotension. A reflexive increase in heart rate is mostly intact in this patient, though it is often impaired in right ventricular infarction due to frequent ischemic involvement of the conduction system. (Choices A and D) Anaphylactic shock and septic shock are associated with peripheral vasodilation and massive fluid shift to the extravascular space. The depleted intravascular volume lowers the mean circulatory filling pressure, reducing both RAP and PCWP, while hypotension caused by widespread peripheral vasodilation leads to a compensatory increase in cardiac output. (Choice B) Gastrointestinal bleeding can cause hypovolemic shock with decreased RAP, PCWP, and cardiac output. Decreased cardiac output triggers an increase in sympathetic tone with peripheral vasoconstriction (increased systemic vascular resistance) to help maintain perfusion pressure. (Choice E) Aortic stenosis causes left ventricular outflow obstruction and would increase pressure in the left atrium (increased PCWP) and pulmonary circulation. In severe cases, right-sided heart failure can also develop, leading to increased RAP. Systemic vascular resistance is increased with aortic stenosis in response to a reduction in cardiac output. Educational objective: Right ventricular infarction (right-sided heart failure) can lead to shock via impaired forward blood flow to the left heart, which lowers left-sided preload (decreased pulmonary capillary wedge pressure) and decreases cardiac output. The reduced right ventricular output also raises right atrial and central venous pressure.

A 63-Year-Old Man Is Brought to the Emergency Department Due