ECG Challenge: Hypotension in a Man With Acute MI

Blood pressure is 115/78 mm Hg; heart rate, 65 beats per minute; and respiration rate, 30 breaths per minute. Neck veins are markedly distended; lung fields are clear. A 12-lead ECG (A) shows sinus rhythm with ST-segment elevation in leads II, III, and aVF; ST-segment depression is evident in leads I and aVL. These ECG findings are interpreted as acute inferior wall myocardial infarction (MI) with reciprocal ST-segment depression in the lateral leads. The patient is given aspirin and sublingual nitroglycerin (0.4 mg) while an intravenous line is placed. Moments later, the patient vomits. Blood pressure is undetectable; heart rate is 90 beats per minute; ECG monitoring continues to show normal sinus rhythm. While intravenous saline is administered, a second ECG is obtained; it does not reveal interval change from the first. Then a third ECG, using right-sided precordial leads, is obtained (B). To what diagnosis do these ECG tracings point? WHAT THE ECG SHOWS This patient sustained an inferior wall MI with right ventricular infarction. The typical approach to diagnosis and management of acute coronary syndromes focuses on different anatomic segments of the left ventricle (eg, the inferior wall). Right ventricular MI is a distinct acute coronary syndrome. Right ventricular MI is defined as hypotension, elevated jugular venous pressure, and shock in the presence of clear lung fields in patients with acute coronary syndrome.1 Clinically recognized right ventricular MI usually occurs in the setting of an acute left ventricular ST-segment elevation MI (STEMI). Isolated right ventricular MI is rare. ASSOCIATION WITH INFERIOR OR LATERAL WALL MI In most patients with right ventricular MI, the inferior wall of the left ventricle is involved (usually in the form of a STEMI) as a result of occlusion of the right coronary artery proximal to the right ventricular branch. However, in a few patients (about 10% of those in whom right ventricular MI develops), the left circumflex artery supplies the right ventricle and a lateral wall STEMI occurs. The incidence of right ventricular MI varies significantly, depending on the method used to detect such injury. ECG studies have consistently shown that right ventricular MI occurs in about one third of patients with inferior wall STEMI.2-4 However, autopsy studies reveal that right ventricular MI occurs in more than half of patients with acute MI.