Subvalvular aortic stenosis, also known as subaortic stenosis (SAS), is a significant form of left ventricular outflow tract (LVOT) obstruction characterized by fixed anatomical narrowing immediately below the aortic valve. Although valvular aortic stenosis remains the most common cause of LVOT obstruction, SAS represents a meaningful subset of congenital heart disease—particularly in infants, children, and young adults—and poses unique diagnostic, surgical, and long-term management challenges. The chronic pressure overload created by this fixed subvalvular obstruction promotes the development of concentric left ventricular hypertrophy (LVH), which, when untreated, increases the risk of myocardial ischemia, malignant arrhythmias, and ultimately congestive heart failure, adversely impacting long-term survival. As such, SAS requires ongoing surveillance and timely intervention to interrupt the progressive cascade of myocardial remodeling and its downstream complications. Anatomically, SAS manifests in 3 principal morphologic forms. The discrete membranous subtype, accounting for approximately 70% of cases, consists of a thin fibrous membrane attached to the upper interventricular septum and extending toward the anterior mitral leaflet, typically forming a crescent-shaped ridge (see Image. Discrete Subaortic Stenosis on Computed Tomography). A related but thicker variant, the fibromuscular ridge, produces similar hemodynamic consequences. Less commonly, tunnel-type SAS (<30%) presents as diffuse fibromuscular narrowing extending from the left ventricular (LV) cavity to the hypoplastic aortic annulus, often accompanied by septal thickening and requiring more extensive surgical approaches, such as the Konno procedure. Rarely, accessory mitral valve tissue may protrude into the LVOT, contributing to obstruction. Importantly, the distance between the obstructive membrane and the aortic valve is prognostic; distances of less than 5 mm are associated with increased risk of aortic valve injury and higher recurrence rates following resection. The natural history of SAS is one of gradual but persistent progression. Turbulent, high-velocity systolic flow is directed toward the structurally normal aortic valve cusps, leading over time to cusp thickening, fibrosis, and the development of secondary aortic regurgitation (AR), a hallmark of disease evolution. This combination of fixed subvalvular obstruction and progressive AR perpetuates substantial LV pressure overload, fueling further LVH and raising the risk of adverse cardiac outcomes. Early recognition and strategic intervention are therefore crucial to limiting the long-term consequences of sustained pressure burden and preventing irreversible ventricular remodeling.

Accessory mitral valve tissue (AMVT) is a rare congenital anomaly that is typically diagnosed during childhood and overlooked in elderly patients presenting with left ventricular outflow tract (LVOT) obstruction. A 73-year-old man presented with exertional presyncope and a systolic murmur. Transthoracic echocardiography revealed a mobile sac-like structure protruding into the LVOT, causing a 74 mm Hg gradient despite a normal aortic valve. Multimodal imaging confirmed a type IIB2 AMVT with dynamic prolapse. Surgical resection and histological analysis confirmed valve-like tissues. At the 3-year follow-up, the patient had remained asymptomatic with no recurrence. This case shows that AMVT, although congenital, can rarely present in elderly individuals. A crescendo systolic murmur with beat-to-beat variability aids diagnosis. Multimodal imaging is critical for diagnosis and surgical planning. Prompt excision and careful perioperative management ensure durable relief and favorable long-term outcomes. AMVT, although congenital, can present as LVOT obstruction, even in elderly patients. A crescendo systolic murmur with beat-to-beat variability is a clinical sign of dynamic obstruction caused by AMVT.

Left atrial mitral valve (MV) accessory chord and accessory MV tissue are rare congenital anomalies that may mimic more common pathologies. A 30-year-old man presented with dyspnea, weight loss, and an outpatient transthoracic echocardiogram concerning for infective endocarditis. Transesophageal echocardiography revealed a chordlike structure extending from the limbus of the interatrial septum to the anterior MV leaflet, continuing through the left ventricular outflow tract, across the aortic valve, and into the ascending aorta. These findings were associated with moderate mitral regurgitation and severe aortic regurgitation. Surgical resection confirmed the diagnosis of accessory MV tissue with a left atrial MV accessory chord. Patients may present with heart failure or malperfusion symptoms due to valvopathy or left ventricular outflow tract obstruction. Multimodal imaging and surgical resection with valve repair are key to diagnosis and management. Chordal anomalies can mimic endocarditis and cause dual-valve disease. Early transesophageal echocardiography and surgical intervention are critical to avoid misdiagnosis.