Hypertrophic = Large size; Obstructive = narrowing causing obstruction; Cardiomyopathy = Affliction of the heart. HOCM is an affliction of the heart where the muscle towards the outflow is large and thick and obstructs blood flow.
There are other names for HOCM such as Asymmetric Septal Hypertrophy or Idiopathic Hypertrophic Subaortic Stenosis and hereditary cardiac dysplasia. It affects between 1/1000 and 1/500 of the general population. Majority of the patients with hypertrophic cardiomyopathy have at least one other affected first degree relative. It affects males more than females.
Most patients with HOCM have no symptoms. Some patients may complain of breathing difficulty or chest pain on exertion. Some patients may have a history of lightheadedness or syncope.
Unfortunately the first presentation for some unlucky people may be a sudden cardiac death.
The most characteristic feature of the disease is the thickening of the walls of the left ventricle. This may be disproportionate towards the interventricular septum relative to the other walls.
The relaxation properties of the left ventricle are impaired due to the thickening of the muscular walls, which decreases the ability of the ventricle to receive blood. In nearly a fourth of the cases there is accompanying obstruction to blood flow from the heart to the body via the aorta due to narrowing of the outflow; in other words a quarter of patients with HOCM suffer from Left Ventricular Outflow Tract Obstruction (LVOTO).
The diagnosis is invariably made on echocardiogram, which shows thickened ventricular wall, a LVOT narrowing with mostly normal contractility of the ventricles. 90-95% of the patients need only medical treatment with beta-blockers or calcium channel blockers. Only 5-10 % of the patients require intervention either by a procedure called Septal ablation where we produce an intentional infarction in the area causing the obstruction or by open-heart surgery where the thickened wall of the ventricle, which is causing obstruction, is remodeled. This procedure is called Septal Myectomy. The operation has been in vogue for a long time and provides excellent long-term results with a very low risk.
A newer procedure called Extended Septal Myectomy provides an even better long tern result and we have developed extensive expertise in this form of surgery. In India however, an alternative and remarkably inferior strategy has been the mainstay of surgery till date. Here, while leaving the Septal abnormality in place, the mitral valve is replaced with a mechanical artificial valve to improve the LVOTO.
An additional problem faced by these patients is leakage across the Mitral Valve. This occurs due to deformation of the valve as a result of dynamic pressure changes in the area that includes the Mitral Valve, Hypertrophied septum and the LVOT. The consensus amongst experienced HOCM surgeons is that since MR is caused by HOCM, relief of HOCM must be the strategy to relieve MR. We have also followed the same doctirine and have observed complete resolution of MR by relief of HOCM only. We have so far not changed or had to repair any mitral valves in HOCM patients.
Significantly delay in surgery can lead to the heart muscle becoming weak and preclude conventional treatments like alcohol ablation or Extended Septal Myectomy; for such patients a transplant is the only recourse.