Hypertrophic cardiomyopathy is a disorder of the heart muscle in which the heart muscle gets grossly thickened, sometimes causing obstruction to the flow of blood from the heart to the body. If there is obstruction to blood flow, that variety is known as hypertrophic obstructive cardiomyopathy (HOCM). The non obstructive variety is known as hypertrophic non obstructive cardiomyopathy (HNOCM). Both varieties come under the common heading of hypertrophic cardiomyopathy (HCM). In some varieties only the tip of the heart muscle in the left ventricle (lower muscular chamber of the heart) is thickened. This form is known as apical hypertrophic cardiomyopathy. The usual hallmark of hypertrophic cardiomyopathy is that the interventricular septum (wall separating two lower muscular chambers of the heart) is more thickened than rest of the left ventricle. This is known as asymmetric septal hypertrophy (ASH).
Risk of sudden death
Hypertrophic cardiomyopathy sometimes catches the attention of press due to sudden death of an athlete. Heavy physical activity can cause sudden changes in the heart rhythm in hypertrophic cardiomyopathy, sometimes leading to cardiac arrest (stoppage of the heart) and sudden death. When this occurs in a young athlete, it often receives a lot of public attention. Hence many screening programs have been considered for pre participation screening of athletes for disorders like this.
Another important feature of hypertrophic cardiomyopathy is the propensity of genetic transmission. It is transmitted in an autosomal dominant pattern. That would mean that if an individual has hypertrophic cardiomyopathy, fifty percent of first degree relatives are likely to have the same gene and hence have the disorder. Even though there is fifty percent chance of genetic transmission, all individuals with the gene may not manifest the disease at the same period in life. Most cases manifest only later in life as it takes time for the heart muscle to get thickened. While screening for the disease, even if children are not detected to be affected initially they have to be evaluated later in life for the manifestations.
Detection of hypertrophic cardiomyopathy
Apart from physical examination of the individual concerned, ECG (electrocardiogram) and echocardiography (ultrasound scanning of the heart) are two simple tests which can give an indication of the disease. ECG gives an indication of the disease by showing electrical evidence of thickening of the heart muscle. It can also detect abnormalities in the cardiac rhythm if any. Echocardiography is the usual investigation used to document the thickening of the heart muscle and obstruction to blood flow if any. Echocardiography can also be done at the bedside using portable or even hand held scanners. Cardiac magnetic resonance (CMR) imaging is also useful in documenting the disorder of the heart muscle, though it is seldom used due to the higher costs and lower availability.