Hypertrophic Cardiomyopathy is a hereditary disorder that is typically inherited in an autosomal dominant fashion with variable penetrance and expressivity. The hallmark of the disorder is myocardial hypertrophy that is inappropriate, often asymmetrical, and occurs in the absence of an obvious inciting hypertrophy stimulus. This hypertrophy can occur in any region of the left or right ventricle, but frequently involves the interventricular septum, which in nearly quarter of patients results in an obstruction of flow through the left ventricular outflow tract. Mutations involving genes coding for sarcomeric proteins accounts for most cases of HCM.
ECG manifestations of HCM:
- Ventricular Hypertrophy which may affect one or more of the following regions i.e, The interventricular septum, The left free wall, The apical and paraseptal regions, The right ventricle.
- Intraventricular Conduction Defects like Left anterior Hemiblock and Left Bundle Branch Block
- Atrial abnormality
- WPW like manifestation in ECG
- Prolongation of the QT interval
- Disturbances of cardiac rhythm
Role of ECG in screening of HCM
While ECG has only limited value in determining Left Ventricular outflow obstruction, level of hypertrophy, genetic mutation and risk stratification, it is an invaluable tool in mass screening of population where 2D Echocardiography is not cost effective.
ECG manifestations may be the initial finding of HCM appearing even before the LV hypertrophy is visible in ECHOCARDIOGRAPHY.
ECG is also found to be more sensitive than ECHOCARDIOGRAPHY during family screening for identifying non-hypertrophic carriers of certain mutations like TnT, TnI and MBPC i.e, Myosin Binding Protein C.
Pathological Q waves and repolarising abnormalities are highly specific, and are often present in children with sarcomere protein gene mutations before the development of echocardiographic LV hypertrophy.