How is left ventricular hypertrophy and hypertrophic obstructive myocardium diagnosed? Left ventricular wall thickness is measured in late diastole and is normally 6-11 mm. left ventricular wall hypertrophy is diagnosed if any part of the left ventricular wall is >11 mm thick. Hypertrophic cardiomyopathy is a common autosomal dominant heart disease (echocardiographic phenotype 1/500 in the population). In addition to hypertrophic cardiomyopathy myocardial hypertrophy, there are many other causes such as hypertensive disease, athlete’s heart, congenital aortic stenosis, aortic constriction, cardiac amyloidosis and Fabry’s disease that can lead to hypertrophy of the left ventricular wall. The latest ACC/AHA guidelines for the diagnosis and treatment of hypertrophic cardiomyopathy clearly state that hypertrophic cardiomyopathy can be diagnosed when the left ventricular wall thickness exceeds 15 mm at any site, excluding secondary factors of cardiac hypertrophy. The clinical symptoms and signs of hypertrophic cardiomyopathy vary greatly depending on the location of the hypertrophic myocardium. Otto et al. classified the hypertrophic myocardium at different locations into seven types: (1) diffuse; (2) septal hypertrophy; (3) apical hypertrophy; (4) papillary hypertrophy; (5) inferior posterior wall hypertrophy; (6) hypertrophic obstruction; and (7) right ventricular hypertrophy. Whether the left ventricular outflow tract is obstructed or not is of great importance for clinical treatment decisions. A peak pressure difference in the left ventricular outflow tract >30 mmHg is defined as left ventricular outflow tract obstruction, whether by resting or evoked test, and if the mean pressure difference in the left ventricular outflow tract exceeds 50 mmHg, it is an indication for surgical treatment, or selective chemical ablation therapy, and pacemaker implantation asynchronous therapy.