Combined Fixed and Dynamic Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy Due to a...

Introduction: Hypertrophic cardiomyopathy (HCM) is a common myocardial disease worldwide and is associated with heart failure symptoms and sudden cardiac death. In a subset of patients, it may produce dynamic left ventricular outflow tract obstruction (LVOTO) and systolic anterior motion (SAM)-related mitral valve dysfunction through drag forces and altered mitral-septal geometry. In contrast, subaortic stenosis caused by a subaortic membrane is an uncommon congenital lesion that may lead to fixed subvalvular LVOTO in adulthood. The coexistence of these entities is rare and can substantially complicate diagnosis and management. Case presentation: A 51-year-old woman with HCM, paroxysmal atrial fibrillation, and heart failure presented with acute decompensation and cardiogenic shock. After initial hemodynamic stabilization and cardioversion for atrial fibrillation with rapid ventricular response, multimodality imaging with transthoracic and transesophageal echocardiography, coronary computed tomography angiography, and cardiac magnetic resonance demonstrated dual LVOTO, with a dynamic component related to HCM/SAM physiology and a fixed component caused by an elongated subaortic membrane, accompanied by severe SAM-related mitral regurgitation. Echocardiography showed a resting peak LVOT gradient of 49 mmHg, increasing to 85 mmHg with the Valsalva maneuver. After exclusion of obstructive coronary artery disease and evaluation for selected phenocopies, the patient underwent septal myectomy, subaortic membrane resection, and adjunctive mitral valve plication. Early postoperative echocardiography showed reduction in the maximum provoked LVOT gradient to 38 mmHg and improvement of mitral regurgitation from severe to mild. At 3-month follow-up, she remained in sinus rhythm, improved to New York Heart Association functional class II, and had no documented readmissions for heart failure. Conclusions: Combined fixed and dynamic LVOTO due to concomitant subaortic membrane and HCM is exceedingly rare. Accurate diagnosis requires a high index of suspicion and a multimodality imaging strategy to define the obstructive mechanisms and support mechanism-based surgical management and avoid incomplete treatment when a coexisting fixed lesion is present.