Hypertrophic Cardiomyopathy
Primary hypertrophic cardiomyopathy is a genetic cardiac disease caused by mutations in genes encoding proteins of the sarcomere and represents the most common genetic cardiomyopathy. These patients are at risk of development of severe left ventricular hypertrophy. Hypertrophy preferentially involves the interventricular septum in the basal LV segments but often extends into the lateral wall, posterior septum and LV apex. Although HCM is typically characterized by asymmetric septal hypertrophy, almost any myocardial segment may be involved. M mode measurements are used for accurate quantification of the interventricular septal and left ventricular posterior wall thickness taken at end diastole. In addition, the mitral valve structure can be abnormally thickened or elongated which can lead to narrowing of the left ventricular outflow tract and creation of dynamic obstruction across the left ventricular outflow tract. Complications of HCM include sudden death, ischemia and diastolic dysfunction.
Echocardiographic assessment should focus on the following:
- Assessment of left ventricular outflow tract obstruction
- Assessment the degree and distribution of LV hypertrophy
- Assessment of systolic and diastolic LV function
- Assessment of left atrial size
- Systolic anterior motion – SAM with the presence of dynamic left ventricular outflow tract obstruction
Echocardiographic criteria are used to aid diagnosis of HCM:
- Unexplained maximal wall thickness >15 mm in any myocardial segment
- Septal/posterior wall thickness ratio >1.3 in normotensive patients
- Septal/posterior wall thickness ratio >1.5 in hypertensive patients.
- Systolic anterior motion (SAM) of the mitral valve
- Fixed or dynamic left ventricular outflow tract obstruction
References:
Moss, Arthur J., and Hugh D. Allen. Moss and Adams' Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2008.
Lai, Wyman W. Echocardiography in Pediatric and Congenital Heart Disease: From Fetus to Adult. Chichester, UK: Wiley-Blackwell, 2009.
European Society of Cardiology Focus on echocardiography in hypertrophic cardiomyopathy. ESC Council for Cardiology Practice. Vol. 13, N° 20 - 14 Apr 2015
Risk stratification for sudden cardiac death in hypertrophic cardiomyopathy: systematic review of clinical risk markers. Christiaans, van Engelen K, van Langen IM, Birnie E, Bonsel GJ, Elliott PM, Wilde AA. Europace. 2010 Mar;12(3):313-21
Nagueh et al. American Society of Echocardiography Clinical Recommendations for Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy. (J Am Soc Echocardiogr 2011;24:473-98.)