Surgical Septal Myectomy and Atrial Myxoma Resection: Two Diseases, One Heart, and a Case Report.

BACKGROUND The coexistence of cardiac myxoma and hypertrophic cardiomyopathy is exceedingly rare and poses diagnostic and therapeutic challenges. While atrial myxomas may cause acute hemodynamic compromise, concomitant left ventricular outflow tract obstruction (LVOTO) due to hypertrophic cardiomyopathy can remain clinically underestimated, raising uncertainty regarding the optimal timing of septal reduction therapy. CASE REPORT A 38-year-old man was admitted with acute dyspnea and hypoxemia. Imaging revealed pulmonary congestion and a large left atrial mass causing functional mitral stenosis. Transthoracic echocardiography demonstrated asymmetric septal hypertrophy (maximum thickness 25 mm) with dynamic LVOTO and a mobile left atrial mass consistent with myxoma. The patient underwent surgical resection of the tumor with concomitant septal myectomy. Histopathology confirmed atrial myxoma and myocardial hyperplasia. Postoperatively, complete atrioventricular block required permanent dual-chamber pacemaker implantation. At short-term follow-up, the patient was asymptomatic with mild residual LVOTO. CONCLUSIONS This case underscores the importance of comprehensive structural and functional assessment in patients with intracardiac tumors. In young patients with favorable prognostic features and significant left atrial dilatation, early septal myectomy performed concomitantly with tumor resection may be justified, even when resting LVOT gradients are below conventional thresholds. This strategy aligns with the latest American and European guidelines on cardiomyopathies and may prevent delayed intervention and disease progression. The case also highlights atrioventricular block as a relevant complication of surgical myectomy, reinforcing the need for careful perioperative planning. Overall, this report provides an instructive example of individualized surgical decision-making in complex cardiomyopathy presentations.