The evolution of basal septal hypertrophy: From benign and age‐related normal variant to potentially obstructive and symptomatic cardiomyopathy

Localized thickening of the basal portion of the ventricular septum or basal septal hypertrophy ( BSH ) has been identified both at autopsy and by imaging studies for decades; despite numerous investigations, there is no consensus on the significance of this finding and a remarkable lack of consistency in terminology. This paper summarizes the scientific literature on the topic, focusing on recent echocardiographic findings. A case description illustrating some of the complex issues involved in measurement and diagnosis and differentiation from sigmoidal hypertrophic cardiomyopathy ( HCM ) is presented. Criteria are proposed for diagnosing pathologic BSH which include the following: (1) Exertional symptoms compatible with left ventricular outflow tract obstruction ( LVOTO ) such as dyspnea, near‐syncope, and chest discomfort; (2) Documented LVOTO gradient demonstrated at peak bicycle or post‐treadmill exercise >30 mm Hg; and (3) Symptomatic improvement with β‐blocker (or other negative inotropic) therapy (preferably accompanied by documentation of reduction of exercise‐induced LVOT ).