title: Subaortic membrane mimicking hypertrophic cardiomyopathy.
abstract: A 34-year-old man was referred for progressive angina and exertional dyspnoea refractory to medical therapy, with a presumptive diagnosis of hypertrophic cardiomyopathy (HCM). Transthoracic echocardiography (TTE) revealed asymmetric septal hypertrophy without systolic anterior motion of the mitral valve leaflet and with no dynamic left ventricular outflow tract (LVOT) obstruction. However, the LVOT velocity was elevated at rest as well as with provocation, without the characteristic late peaking obstruction seen in HCM. Focused TTE to evaluate for suspected fixed obstruction demonstrated a subaortic membrane 2.2 cm below the aortic valve. Coronary CT angiography confirmed the presence of the subaortic membrane and was negative for concomitant coronary artery disease. Surgical resection of the subaortic membrane and septal myectomy resulted in significant symptomatic relief and lower LVOT velocities on postoperative TTE. This case reminds the clinician to carefully evaluate for alternative causes of LVOT obstruction, especially subaortic membrane, as a cause of symptoms mimicking HCM.
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Mark Joseph
authors.initials: MJ
authors.lastname: Anderson
authors.affiliation: Department of Medicine/Cardiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Adelaide
authors.initials: A
authors.lastname: Arruda-Olson
authors.affiliation: Department of Medicine/Cardiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Bernard
authors.initials: B
authors.lastname: Gersh
authors.affiliation: Department of Medicine/Cardiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Geske
mesh_terms: D000328:Adult; D000789:Angina, Unstable / Q000209:etiology; D001018:Aortic Diseases / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis*; D003937:Diagnosis, Differential; D004417:Dyspnea / Q000209:etiology; D004452:Echocardiography; D006801:Humans; D008297:Male