Transesophageal Echocardiogram With Isoproterenol to Unmask Previously Occult Left Ventricular Outflow Tract Obstruction.

Thorough and accurate evaluation of left ventricular outflow tract (LVOT) obstruction is critical in the assessment and management of patients with hypertrophic cardiomyopathy (HCM). Although Doppler echocardiography has become the initial modality to assess LVOT obstruction, it may not identify all patients with labile obstruction. In patients with a high clinical suspicion of LVOT obstruction, further provocative testing is needed. In HCM patients with poor transthoracic echocardiogram windows or who are unable to exercise, isoproterenol-guided transesophageal echocardiogram (TEE) remains a viable option to assess for systolic anterior motion (SAM) and LVOT obstruction. We report 4 individuals in whom there was no obvious SAM or LVOT obstruction at rest but who had severe LVOT obstruction unmasked by isoproterenol-guided TEE.