What is obstructive hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac condition. It is characterised by thickening of the heart muscle.

Its prevalence is 1 in 500 people in the general population (Source: Cardiomyopathy UK, accessed Jan 2019).

Hypertrophic cardiomyopathy is frequently associated with left ventricular outflow tract obstruction (LVOTO). LVOTO is caused by the thickened heart muscle obstructing the flow of blood leaving the left ventricle, and the abnormal movement of the mitral valve. This is the main reason for debilitating symptoms in HCM patients, such as palpitations, chest pain, dizziness or fainting, breathlessness and tiredness.

HCM is also one of the risk factors for sudden cardiac death, especially in young patients. In the long-term, it causes enlargement of the left atrium and increases the risk of atrial fibrillation (AF).

How to prepare for obstructive hypertrophic cardiomyopathy management

Left ventricular outflow tract obstruction (LVOTO)

The LVOTO management programme at Guy’s and St Thomas’ Specialist Care is at the highest level of diagnostic expertise and offers all the internationally available management options. LVOTO interventions are considered appropriate in patients with a significant degree of LVOT obstruction, who are not improving on medication and have symptoms limiting their daily activities.

The 2 techniques currently available are alcohol septal ablation and surgical myectomy. Before a patient undergoes intervention, they will have a series of tests, including a dynamic echocardiogram and a cardiac MRI, to assess the LVOTO and the anatomy and geometry of both the left ventricle and the mitral valve.

Surgical myectomy

Surgical myectomy for the management of obstructive hypertrophic cardiomyopathy is a procedure which entails surgical muscle resection to eliminate LVOTO.

The surgery is planned carefully with the assistance of specialist imaging to assess the LVOTO and the anatomy of the left ventricle and the mitral valve. During the procedure the surgeon will reach the inside of the heart, through the aorta and the aortic valve. The inner surface of the heart muscle will then be resected under direct vision in order to relieve the blockage in the areas where it is thickened.

The amount of muscle removed varies between 3-15g and the resection is carefully planned and carried out taking into account all the individual anatomical characteristics of the patient’s heart. Occasionally, the resection of the muscle is not sufficient and then a repair or replacement of the mitral valve may become necessary.

Alcohol septal ablation

Alcohol septal ablation (ASA) is a nonsurgical reduction of the thickness of the ventricular muscle in the area of the outflow tract. It is a clinically efficient therapeutic option in selected cases. The procedure involves the tip of a catheter being wedged into a small artery that supplies blood to the thick muscle. Then the area of blood supply is carefully checked with specialised imaging.

If appropriate, an infarction is generated in the area by injecting a small amount of ethanol (alcohol) through the catheter. This results in scarring and shrinking of the wall thickness, which reduces or even eliminates the obstruction. However, the improvement may not manifest itself immediately after the procedure.

ASA can only address the muscle thickness and not the other components of the internal anatomy of the heart, and the amount of muscle mass reduction is also limited. In cases where a large reduction of the wall thickness would be required, it would mean inducing a large myocardial infarction that may increase the risk of the procedure.

Benefits of treatment for obstructive hypertrophic cardiomyopathy

Although hypertrophic cardiomyopathy is a condition for which there is not a definitive cure, patients experience major symptomatic improvement after successful management of LVOTO. Data suggests that significant reduction or elimination of LVOTO improves survival and long-term outcome. Following surgery, a patient can be discharged from hospital within 7 days. ASA patients benefit from a shorter hospital stay and more rapid recovery.

The benefits to the patient include:

  • relief from symptoms such as fainting, fatigue, tightening of the chest and breathlessness
  • substantial improvement of the quality of life
  • reduced risk of sudden cardiac arrest, particularly in the young
  • reduced risk of other complications related to LVOTO (left atrial dilatation, atrial fibrillation, pulmonary hypertension)
  • clinical evidence suggests that it improves long-term survival and outcome

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