Treatment for Hypertrophic Cardiomyopathy

There are several forms of treatment available that are directed toward improving heart function, relieving symptoms, and preventing complications in HCM patients. Many individuals who have very mild or no symptoms do not require treatment, unless they are judged to be at high-risk for sudden death. For those patients who do require therapy, one or more of the following treatment strategies should be considered.

Drugs

Drugs (medications) are usually the first line of treatment for patients with shortness of breath or chest pain associated with exertion. Many patients realize benefit from medications with reduction in their symptoms. A variety of drugs are currently used in treating HCM and new drugs are likely to become available in the future. The need for drug treatment and the precise choice of medication has to be made by a physician on an individual basis, and could change in any patient over time. The most commonly used drugs are described below.

Beta-blockers
Beta-blockers slow the heartbeat and probably improve filling of the ventricles in diastole, reduce the force of contraction, and may also decrease obstruction during exercise.

Calcium channel blockers
The second major group of drugs used are the calcium channel blockers, which appear to relax the heart and improve filling of the ventricles. 

Antiarrhythmic drugs
These drugs might be used when an arrhythmia such as ventricular tachycardia or atrial fibrillation is detected and judged to be important to an individual patient. The most commonly used antiarrhythmic drugs in HCM are used either to reduce the chances of recurrent atrial fibrillation, or to reduce the risk of sudden death.

Diuretics
Some severely symptomatic patients develop fluid retention and, in this situation, diuretics (water tablets), which increase urine flow, may be administered.

Anticoagulants
Most patients with episodic or persistent atrial fibrillation are placed on anticoagulants (blood thinners) to prevent stroke, which may result if clot forms in the atria and a portion breaks off and travels through the arterial blood stream to the brain. Such treatment requires monitoring with a blood test on a monthly basis. Given the potential complications of anticoagulation (i.e., brain hemorrhage as a consequence of trauma), the decision of whether to begin anticoagulants may be a difficult one and obviously should be made in close consultation with the cardiologist.

Implantable defibrillators

Those HCM patients clearly at high-risk for sudden death may be candidates for an implantable cardioverter-defibrillator (ICD), a sophisticated device which is permanently implanted internally. The ICD has the capability of sensing potentially lethal arrhythmias and then introducing a shock (or antitachycardia pacing) to terminate these arrhythmias and restore normal heart rhythm. At the same time, an ECG recording is generated directly by the device to precisely document the event. Recently, there has been much more experience with, and interest in, the ICD for high-risk patients with HCM, and we believe this device has favorably changed the clinical course of the disease for many patients.



The implantable cardioverter-defibrillator (ICD). When an HCM patient is judged to be at high-risk this device can be permanently implanted to automatically detect and terminate arrhythmias that can be lethal. A small box about the size of a pacemaker is placed under the skin just below the clavicle, and is attached to wires (called leads) introduced into the heart which are responsible for sensing (and recording) the heart rhythm...and delivering the shock, if necessary, which restores normal electrical activity.

Over the last few years these devices have become smaller and much easier to implant in unobtrusive positions on the chest, requiring in most instances only an overnight hospital stay without major surgery. The ICD leads can now be introduced through the veins (and are therefore present inside the heart chamber) and the generator is placed just under the clavicle. Even a few high-risk children have now had ICDs implanted.

Patients must be aware of the possible complications associated with ICDs such as false shocks due to fast heart rates that are actually benign. Furthermore, there is a small chance of infection, and problems with the leads, usually related to breakage, are not uncommon.

As the risk period in HCM is characteristically very long (theoretically 20 to 50 years in some patients), the ICD is likely to be a long-term or life-long treatment, thereby creating the crucial necessity for careful and consistent maintenance and interrogation of the device including regular battery replacement. We have knowledge of several HCM patients in whom the ICD discharged appropriately for the first time as long as four to nine years after it was implanted, emphasizing the unpredictable timing of these events.

In the future, we expect that ICDs will be offered as life-saving protection to many more HCM patients. However, it is important to note the ICD is not a treatment intended for all HCM patients, but only for those who are judged by their cardiologist to be truly at high-risk. Most HCM patients are at low (or no) risk for sudden death, including those with only mild thickening of the heart wall and those without a family history of sudden death. At present there does not seem to be much use for antiarrhythmic drugs as alternatives to the ICD in high-risk patients. After all, these medications have not been proven to be completely effective in these circumstances, and may also have important side effects over the long-term.

Surgery

Surgery (ventricular septal myotomy-myectomy) is reserved for those patients with marked outflow obstruction who have severe symptoms that are unresponsive to drugs or other treatment. Specifically, surgery is the preferred treatment in those patients with obstructive gradients (of 50 millimeters of mercury [mm Hg] or more) and symptoms that persist even after all drugs or other options have been exhausted. Several surgical techniques have been used in HCM, but the one which is most accepted is the ventricular septal myotomy-myectomy operation in which the surgeon removes a small portion of the thickened muscle from the upper portion of ventricular septum, thereby widening the left ventricular cavity in that region and relieving the obstruction.



Surgery in HCM (the ventricular septal myotomy-myectomy operation; Morrow procedure). After the patient is placed under cardiopulmonary bypass the surgeon opens the aorta and performs surgery through that exposure. A. First, two vertical parallel incisions are made in the top portion of the ventricular septum. A third incision is then made, connecting the two parallel incisions. B. This section of muscle is then removed. C. At completion of the myotomy-myectomy, a rectangular channel is evident extending from just below the aortic valve to a point just beyond where obstruction occurs (where the mitral valve contacts the septum). It should be emphasized that the surgeon does not, in fact, open the left ventricle as shown here only for illustrative purposes only.

Surgery for HCM should be performed only by surgeons sufficiently experienced with this operation, and experienced surgeons are generally found at tertiary referral institutions. Therefore, HCM patients requiring surgery must frequently travel outside of their home communities for treatment. In experienced centers operative mortality is low, with most patients reporting a long-lasting and measurable improvement in symptoms after operation. Surgery can be performed safely in children and older patients with HCM. Operative risk for HCM appears to be increased only if additional heart surgery (such as coronary artery bypass grafting) must also be performed at the same time.

If the operation is performed properly, obstruction under resting conditions will not return. Occasionally, in selected patients, instead of a myotomy-myectomy, the surgeon may choose to replace the mitral valve with an artificial valve. There is no reason to perform both a myectomy and valve replacement.

Of course, some patients who meet the clinical criteria for surgery are not, in fact, optimal candidates for operation, either because of other complicating diseases, geographic inaccessibility to an experienced surgeon, disability from other complicating diseases, advanced age, lack of motivation on the part of the patient, or other factors. Indeed, these issues are fundamental to any consideration for alternatives to myotomy-myectomy surgery.

Alcohol septal ablation (non-surgical myectomy)

A new experimental procedure for patients with outflow obstruction which has been devised to reduce hypertrophy of the upper septum (and thereby outflow obstruction), without the need for open-heart surgery, in severely symptomatic patients who no longer benefit from drugs (or pacing). This technique involves injecting a small amount of absolute alcohol solution into a small branch of the coronary artery that supplies the upper portion of the ventricular septum. This destroys and thins that part of the heart wall and, in effect, produces a myocardial infarction (heart attack) and healed scar. This technique is performed as part of a cardiac catheterization under local anesthetic. Although in relatively early stages of development, this technique may well represent a useful addition to the nonsurgical therapies available to patients with severe HCM symptoms.

Most HCM physicians do not regard alcohol septal ablation, at present, as either a cure or a primary treatment strategy for HCM, but rather as a potentially useful addition to the available treatment strategies for selected patients. Alcohol septal ablation leaves patients with a heart scar, which theoretically may predispose them to important arrhythmias later in life (unlike myotomy-myectomy, which leaves no such scar). For this reason, at the present time, we do not recommend septal ablation to young patients. Indeed, some referral institutions perform alcohol septal ablation only in operative candidates who otherwise are not optimal subjects for surgery, either because of associated medical conditions, strong patient preference against operation, or advanced age.

Pacemakers

Pacemakers have been used in HCM for several reasons. Occasionally, when the normal electrical signal fails to traverse the ventricles, either because of sinus node failure or heart block, implantation of a pacemaker is appropriate and necessary. This involves placing a small box containing a battery in the chest under the skin and passing fine wires through the veins to the heart in order to deliver the necessary signals so that the heart is automatically paced.

As a treatment alternative to the septal myotomy-myectomy operation, many severely symptomatic patients with HCM and obstruction have received dual-chamber pacemakers to relieve symptoms and outflow obstruction. Pacing can reduce the degree of obstruction in many patients but usually much less than is achieved with operation. In addition, much of the symptom improvement perceived by many patients is probably due to a placebo effect, rather than real change in the disease state. It is essential to keep in mind that the most important issue in the treatment of any patient with HCM is whether an intervention (including pacing) improves symptoms and quality of life, and not its precise effect on the degree of obstruction. Certainly, pacemakers should not be regarded as a primary treatment for most patients with HCM, and the selection of which particular patients are likely to benefit from pacing is most important. At present, it appears that HCM patients older than age 65 with show the most convincing positive effects from pacing.

Heart transplantation

For a small minority of HCM patients, heart transplantation may be recommended. Heart transplantation is an option when there is severe disability and limiting symptoms, marked impairment in the pumping action of the ventricles, and enlargement of the heart chambers and thinning of the wall, which become unresponsive to other treatment. This facet of HCM is often referred to as the "end-stage" (or "dilated" or "burned-out" phase), and is the only generally accepted indication for heart transplantation within the HCM disease spectrum. The "end-stage" ultimately affects only about five to ten percent of patients. Spontaneously, and without a prior clinical event, the heart undergoes anatomic and functional changes, that result in a form of heart failure more reminiscent of other heart diseases with greatly enlarged chambers (such as the dilated form of cardiomyopathy). As a result, the treatment for this type of heart failure clearly differs that usually employed in HCM.

HCM is not a homogeneous disease and, certainly, that concept applies directly to treatment options. The disease spectrum of HCM is diagrammed in the figure below.



Depiction of the very broad overall HCM disease spectrum. Note, in particular, that many patients develop no or only mild symptoms, do not necessarily require treatment, and may achieve normal longevity in statistical terms. ICD = implantable cardioverter-defibrillator.

Adapted from Hypertrophic Cardiomyopathy: For Patients, Their Families, and Interested Physicians, by Barry J. Maron, MD, et al., Copyright 2001, with permission from Futura Media Services, Inc., Armonk, New York