Hypertrophic Cardiomyopathy Treatment & Management

Evaluation usually can be conducted on an outpatient basis. Inpatient studies and surgical treatment also may be necessary. Medical and surgical therapy are used to reduce ventricular contractility or increase ventricular volume, increase ventricular compliance and outflow tract dimensions, and, in the case of obstructive hypertrophic cardiomyopathy (HCM), reduce the pressure gradient across the LV outflow tract. Paramount to any therapy is reduction in the risk of sudden death by identification of these patients early on and effective medical and/or surgical implantation of an automatic defibrillator.^[19]

Medications include beta blockers, calcium channel blockers, and, rarely, diltiazem, amiodarone, and disopyramide. Use antitussives may be administered as needed to avoid coughing.

Avoid inotropic drugs if possible; also avoid nitrates and sympathomimetic amines, except in those patients with concomitant coronary artery disease. Avoid digitalis, because glycosides are contraindicated except in patients with uncontrolled atrial fibrillation. Cautious use of diuretics should be exercised because of their potential adverse effect on the LV outflow gradient and ventricular volume.

Transfer

Transfer may be required for further diagnostic evaluation and electrophysiologic device or surgical intervention.

Deterrence/prevention

Patients must abstain from highly strenuous competitive athletic activity and highly strenuous physical exertion, such as shoveling snow or lifting very heavy objects, due to the high risk of arrhythmogenic sudden cardiac death. No acceptable medical recommendation deviates from total abstinence from these activities.

Consultations

Consultations may be indicated with the following:

• Cardiologist
• Cardiothoracic surgeon
• Cardiac electrophysiologist
• Geneticist

Diet

No special diet is required. However, the patient should avoid excessive weight gain.

Left ventricular myomectomy

LV myomectomy is used for patients with severe symptoms refractory to therapy and an outflow gradient of more than 50 mm Hg, either with provocation or with rest. The procedure typically is successful in abolishing the outflow gradient; most patients have symptomatic improvement for at least 5 years.

The reduction in LV outflow gradient may not correlate with a risk reduction for sudden death or overall mortality. Furthermore, the outflow gradient may increase gradually over time and return to the same level as before, requiring a repeat procedure or additional medical therapy.

Mitral valve replacement

Mitral valve replacement is reserved for patients with severe mitral regurgitation due to systolic anterior movement of the mitral valve, particularly when mitral regurgitation (large regurgitant fraction) is associated with the development congestive heart failure, largely due to), or pulmonary hypertension.

The ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities recommend permanent pacing for SND or AV block in patients with hypertrophic cardiomyopathy (HCM) and may be considered in medically refractory symptomatic patients with HCM and significant resting or provoked LV outflow tract obstruction.^[20]

Transvenous dual-chamber pacing has been used for patients with HCM. The right ventricular septal preexcitation induced by right ventricular apical pacing leads to a "pulling away" of the septum from the outflow region, allowing for an increase in flow with a decrease in LV outflow tract obstruction.^[21]

Many patients feel an improvement in symptoms with pacemaker implantation and can have a reduction in prescribed medication.

Note again that a reduction in LV outflow tract gradient does not necessarily mean a reduction in vulnerability to ventricular arrhythmias and sudden death. Therefore, permanent pacing in patients with HCM has been used as adjunctive therapy by some investigators rather than as primary treatment. The reported results are widely variable, with a significant placebo effect and variability in patient outcomes.^{[22, 23]}

Transvenous catheter ablation of the septal region has been performed using selective arterial ethanol infusion to destroy myocardial tissue.^[24] The procedure involves infusing 96% ethanol down the first septal branch of the left anterior descending artery and inducing a therapeutic infarction of the proximal interventricular septal myocardium.

This leads to a remodeling of the septum, which decreases the marked septal thickening characteristic of hypertrophic cardiomyopathy (HCM) and results in a decrease of the gradient across the LV outflow tract. In this manner, the procedure is analogous to a surgical myomectomy, in attempting to decrease the amount of septal ventricular myocardium and thereby reducing the LV outflow tract gradient.

The procedure has been used in clinical practice since the early 1990s and the reported results have been excellent, with significant reduction in symptoms, particularly in the incidence of heart failure.^{[25, 26]} In many centers, it is the surgical procedure of choice for HCM.

The implantable cardioverter defibrillator (ICD) has been used for the prevention of sudden arrhythmic death. Transvenous placement is similar in technique to permanent pacemaker implantation and can be performed in either the electrophysiology laboratory or the operating room.

An ICD automatically detects, recognizes, and treats tachyarrhythmias and bradyarrhythmias using tiered therapy (ie, bradycardia pacing, overdrive tachycardia pacing, low-energy cardioversion, and high-energy shock defibrillation).

ICD therapy has been shown to be life saving. In large, well-designed, prospective studies in adults with coronary artery disease and low ejection fraction who survived myocardial infarction, the ICD has been demonstrated to be superior to antiarrhythmic drug therapy.^[27]

Ongoing studies are being performed to assess the value of ICD therapy in cardiomyopathy. Smaller studies in children and personal and anecdotal experience appear to strongly favor utilization of the ICD in patients with hypertrophic cardiomyopathy (HCM) and arrhythmias, aborted sudden death, malignant genotype or family history, and other factors that may increase mortality and, particularly, sudden arrhythmic death risk.

Avoid strenuous exercise. Competitive-level sports should not be permitted if any of the following is present:

• Significant outflow gradient
• Significant ventricular or supraventricular arrhythmia
• Marked LV hypertrophy
• History of sudden death in relatives with hypertrophic cardiomyopathy (HCM)
• Identified malignant genotype
• Young age (< 30 years)
• Abnormal blood pressure response to exercise
• History of syncope, particularly in children

Although avoidance of intense physical exertion is probably appropriate, participation in noncompetitive-level recreational sports activities is not believed to be contraindicated.

Cardiovascular screening before participation in competitive sports appears to reduce the frequency of unexpected sudden death from HCM, although whether large-scale screening of athletes is administratively feasible or cost-effective remains to be determined.^{[28, 29]}

Sudden death often occurs during exercise, but it also demonstrates a circadian distribution, with clustering of deaths in the morning and early evening.