Spectre of HCM

September 12, 2018 0 By CH Unnikrishnan

Dr Shivanee Shah

A 32-year-old man, Nikhil (name changed), brought his 2 sons to the one-of-its-kind Hypertrophic Cardiomyopathy Centre at Amrita Institute of Medical Sciences (AIMS), Kochi, to be screened for hypertrophic cardiomyopathy (HCM). While Nikhil’s boys, aged 6 and 2, had no obvious symptoms, he himself had been an HCM patient since his teen years and had come to ascertain the fate of his children. The HCM history went beyond Nikhil; his mother also had been diagnosed with the same condition, and at the age of 28, had sadly collapsed while working and died of sudden cardiac arrest.

Nikhil, the only son, had undergone ECG and echo studies at VSM Hospital, Mavelikkara, and was diagnosed with HCM. During a follow-up examination, it was observed that his condition had worsened considerably, and by age 17, his myocardial thickness had increased to such an extent that there were overt signs of obstructive hypertrophic cardiomyopathy that could no longer be controlled by medication. Nikhil underwent a septal myectomy at Amrita Institute of Medical Sciences. “It was probably the very first septal myectomy done at Amrita”, says Dr. Hisham Ahamed, Associate Professor of Cardiology, AIMS, Kochi. Dr. Ahamed, along with Dr. Praveen Varma, Clinical Professor and Head, Department of Cardiovascular and Thoracic Surgery at AIMS, have been instrumental in setting up the first hypertrophic cardiomyopathy unit in the country at Amrita.

HCM is an autosomal dominant, inherited disease, earlier thought to afflict 1 in every 500 individuals. The disease is caused due to mutations in proteins important for the structure of the cardiac muscles and the subsequent thickening of the heart muscle, especially of the septum between the ventricles. With the advent of genetics, it has been possible to accurately diagnose the condition and it now appears that the actual prevalence of this condition is closer to 1 in 200. While many people with HCM have no or minor symptoms and live normal lives; for some, the condition can progress aggressively and even result in sudden cardiac death as seen for Nikhil’s mother. With these alarming prevalence rates, it is very important to accurately diagnose and treat such individuals to prevent sudden death. One such avenue to treat HCM patients is to develop focused centers such as the Hypertrophic Cardiomyopathy Center at Amrita Hospital where a comprehensive team is dedicated to screening, diagnosing, treating, and following up such patients.

Now, after 15 years, Nikhil came back to have his children screened. ECG and echo were done for Nikhil and his 2 sons. As it turns out, while his 6-year-old son showed no features of hypertrophic cardiomyopathy via ECG and echo, his
2-year-old son showed substantial thickening of the myocardial wall. However, there was no obstruction and HCM symptoms had not set in. Due to the familial history of sudden cardiac death, Nikhil and his son fall under a high-risk group which warrants genotyping to identify the causative mutation and to screen for the same mutation in other first degree relatives in the family. Next-generation sequencing using a cardiomyopathy panel was done and showed that both Nikhil and his 2-year-old son carried
a mutation in the MYH7 gene. MYH7 encodes a protein called myosin
heavy chain 7, that is vital for muscle contraction. Mutations in MYH7 are thought to account for around 35% of familial hypertrophic cardiomyopathy cases and result in the thickening of the cardiac muscles. For Nikhil and his son, the mutation was found to be Arg719Gln (cytogenetic location: 14q11.2), which is known for its aggressive traits. Genetic testing confirmed that both Nikhil and his son are in a
high-risk group for sudden cardiac death and would need to be strictly followed-up. For Nikhil’s 2-year-old son, serial echo will be done, and his condition will be closely monitored. Once he is older, cardiac MRI will also be done to monitor his condition.

Nikhil also underwent a follow-up echo. His latest echo showed severe thickening of the myocardial wall of around 3 cms. Considering the aggressive mutation and the history of sudden cardiac death in the family, Dr. Ahamed’s team has suggested placing an implantable cardioverter defibrillator (ICD). While Nikhil awaits this procedure, the HCM team is considering a cardiac MRI to assess the degree of scar tissue formation in the heart.