Isolated dynamic left ventricular outflow tract obstruction can cause hypotension that rapidly responds to intravenous beta blockade.

Dynamic left ventricular outflow tract obstruction occurs in hypertrophic cardiomyopathy, stress cardiomyopathy, acute coronary syndromes, and with inotrope use. We describe three critical care patients who developed "isolated" left ventricular outflow tract obstruction with hypotension in the absence of these precipitants. Systolic anterior motion of anterior mitral valve leaflet with peak left ventricular outflow tract gradients of greater than 120 mmHg was noted in Cases 1 and 2. Under close supervision, intravenous (IV) β blocker was initiated with 5 mg metoprolol repeated every 5 minutes up to 15 mg and continued to maintain heart rate less than 70 beats/min. IV fluids were replaced aggressively. Bedside Doppler echocardiogram confirmed near normalization of left ventricular outflow tract gradient with improvement in systolic anterior motion and hypotension within minutes after IV β blocker confirming its specific therapeutic effect. Isolated left ventricular outflow tract obstruction can occur in the absence of recognized precipitants. Early recognition is crucial because this potentially fatal condition responds well to adequate β blocker and IV fluids with rapid relief of hypotension and symptoms. (C) 2011 Lippincott Williams & Wilkins, Inc.