A 68-year-old woman comes to the emergency department due to sudden-onset chest pain associated with 2 episodes of vomiting. Medical history includes hypertension and chronic obstructive pulmonary disease. The patient smoked a pack of cigarettes per day for 30 years and quit 5 years ago. Blood pressure is 80/50 mm Hg, pulse is 60/min, and respirations are 14/min. Examination shows diaphoresis and elevated jugular venous pressure. S1 and S2 are normal. A grade 2/6 lower left parasternal systolic murmur is heard and increases with inspiration but does not radiate. The lungs are clear to auscultation. ECG reveals 2-mm ST-segment elevation in leads II, III and aVF and 1-mm ST-segment depression in leads I and aVL. Which of the following is the most likely cause of this patient's hypotension?

Question

A 68-year-old woman comes to the emergency department due to sudden-onset chest pain associated with 2 episodes of vomiting.  Medical history includes hypertension and chronic obstructive pulmonary disease.  The patient smoked a pack of cigarettes per day for 30 years and quit 5 years ago.  Blood pressure is 80/50 mm Hg, pulse is 60/min, and respirations are 14/min.  Examination shows diaphoresis and elevated jugular venous pressure.  S1 and S2 are normal.  A grade 2/6 lower left parasternal systolic murmur is heard and increases with inspiration but does not radiate.  The lungs are clear to auscultation.  ECG reveals 2-mm ST-segment elevation in leads II, III and aVF and 1-mm ST-segment depression in leads I and aVL.  Which of the following is the most likely cause of this patient's hypotension?

Quizplus · Accepted Answer

11ec25c8_d358_c688_bc81_853fa0cfca79_MD0003_00 This patient has an ST-segment elevation myocardial infarction (MI) affecting the inferior myocardial wall, which is recognized by ST-segment elevation in ECG leads II, III, and aVF. Inferior wall MI classically presents with chest or epigastric pain and commonly involves vagal symptoms (eg, diaphoresis, nausea, vomiting). Because the inferior wall is usually supplied by the right coronary artery, which also usually supplies the sinoatrial and atrioventricular nodes, bradyarrhythmias (eg, sinus bradycardia, atrioventricular block) are common. Inferior wall MI can affect the inferior and posterior portions of the left ventricle, but it often primarily affects the right ventricle. leads II, III, and aVF Right ventricular MI (RVMI) involves characteristic features that differ from left ventricular MI. There is abruptly decreased RV contractility with increased RV preload that causes jugular venous distension (JVD) and sometimes a murmur of secondary tricuspid regurgitation (resulting from RV dilation). The failing RV is unable to pump adequate blood through the pulmonary circulation to the left atrium, resulting in decreased left ventricular preload (with clear lungs), reduced cardiac output, and often profound hypotension. Unlike left ventricular MI, which benefits from a reduction in RV preload (eg, with nitroglycerin), a reduction in RV preload can significantly worsen hypotension with RVMI. Intravenous normal saline to further increase RV preload is often needed to aid left ventricular filling and improve hypotension. (Choice B) The reduced cardiac output and hypotension with RVMI (eg, right-sided heart failure) causes a reflexive increase in systemic vascular resistance. right-sided heart failure (Choice C) Increased intrapericardial pressure occurs in cardiac tamponade, which involves impaired RV filling and can present similarly to RVMI with hypotension, JVD, and clear lungs. However, distant heart sounds and tachycardia are expected, and tamponade does not explain a tricuspid regurgitation murmur. (Choice D) Interventricular septum rupture is a mechanical complication of MI that causes left-to-right interventricular shunting. Patients typically develop biventricular failure with pulmonary edema. The associated systolic murmur is expected to decrease with inspiration (due to increased right-sided pressure and reduced shunting through the septal defect). (Choice E) Acute pulmonary embolism (PE) can cause obstruction of RV outflow and can present similarly to RVMI with hypotension, JVD, and clear lungs. However, tachycardia is expected. Nonspecific ST-segment and T-wave changes are common with PE, but ST-segment elevation is highly unusual. Educational objective: Inferior wall myocardial infarction commonly involves vagal symptoms (eg, nausea) and bradyarrhythmias and often primarily affects the right ventricle. Right ventricular myocardial infarction presents with jugular venous distension, clear lungs, and often profound hypotension caused by impaired delivery of blood to the left ventricle. References: Right heart ischemia: pathophysiology, natural history, and clinical management. (http://www.ncbi.nlm.nih.gov/pubmed/9449958)

A 68-Year-Old Woman Comes to the Emergency Department Due to Sudden-Onset