A 66-year-old man with diabetes mellitus is brought to the hospital due to sudden-onset chest pain and nausea. Blood pressure is 70/60 mm Hg and pulse is 60/min. Lungs are clear on auscultation. ECG shows ST-segment elevation in leads II, III, and aVF. Chest x-ray is unremarkable. The patient is diagnosed with an inferior wall myocardial infarction. Emergent cardiac catheterization reveals complete occlusion of the proximal right coronary artery. He is persistently hypotensive in the cardiac catheterization laboratory. Which of the following hemodynamic findings is most likely to be observed in this patient?

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This patient is in cardiogenic shock after suffering an inferior wall myocardial infarction. The inferior wall of the left ventricle (LV) is supplied by the posterior descending artery, which arises off the dominant right coronary artery. Because the right coronary artery also gives off marginal branches that supply most of the right ventricle (RV), inferior wall myocardial infarction is often associated with right ventricular infarction. Right-sided heart failure typically presents with hypotension and distended jugular veins, but the lungs are clear unless significant left-sided heart failure is also present. This patient's lack of crackles on lung auscultation and absence of pulmonary edema on chest x-ray is indicative of isolated RV dysfunction. Right ventricular infarction decreases RV stroke volume, which in turn leads to diminished LV filling and cardiac output despite preserved LV systolic function, resulting in hypotension and shock. Because left-sided filling pressures are reduced, pulmonary capillary wedge pressure (PCWP) also decreases as it reflects left atrial pressure. In addition, patients have elevated central venous pressure due to impaired forward flow and backup of blood into the systemic venous system. (Choices B and D) LV anterior wall infarcts (eg, due to left anterior descending artery occlusion) are more likely than inferior wall infarcts to cause LV systolic dysfunction, resulting in decreased cardiac output, elevated left-sided filling pressures (eg, increased PCWP), and cardiogenic pulmonary edema. Initially, central venous pressure may be normal; however, persistently high left-sided pressures may lead to right-sided heart failure, resulting in elevated central venous pressure. (Choice E) Increased cardiac output with decreased PCWP and central venous pressure is characteristic of distributive shock due to sepsis. Educational objective: The dominant right coronary artery perfuses both the inferior wall of the left ventricle and the majority of the right ventricle. Proximal occlusion can cause right ventricular myocardial infarction, which presents with hypotension (reduced cardiac output) and distended jugular veins (elevated central venous pressures). The lungs will be clear on auscultation and x-ray (lack of pulmonary edema) unless concomitant left-sided heart failure is also present. __________ References: Acute right ventricular infarction. (http://www.ncbi.nlm.nih.gov/pubmed/22548813) Right ventricular myocardial infarction: from pathophysiology to prognosis. (http://www.ncbi.nlm.nih.gov/pubmed/24294033)

A 66-Year-Old Man with Diabetes Mellitus Is Brought to the Hospital