AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Hypertrophic cardiomyopathy (HCM) is a genetic disorder typically inherited in an autosomal dominant fashion with variable penetrance and variable expressivity. HCM has a complex set of symptoms and potentially devastating consequences for both patients and their families. The disorder has a variable presentation; some children with HCM are completely asymptomatic, whereas others have a high incidence of sudden death. In fact, HCM is the leading cause of sudden cardiac death during exertion in adolescent children.

The hallmark of the disorder is myocardial hypertrophy that is inappropriate, often asymmetric, and occurs in the absence of an obvious inciting hypertrophy stimulus. Although any region of the left ventricle (LV) can be involved, hypertrophy frequently involves the interventricular septum, which results in an obstruction in the LV outflow tract. HCM can occur without LV outflow obstruction, and the right ventricle (RV) may also be involved.

Pathophysiology

Since the initial descriptions of HCM, the feature that has attracted the greatest attention is the dynamic pressure gradient across the LV outflow tract. The pressure gradient appears to be related to further narrowing of the outflow tract, already made small by the marked asymmetric septal hypertrophy and the possibly abnormally located mitral valve, by systolic anterior motion of the mitral valve against the hypertrophied septum. This is most likely caused by a Venturi effect as a result of increased ejection velocity produced by the abnormal LV outflow tract orientation and geometry. In addition, most patients with HCM have abnormal diastolic function whether or not a pressure gradient exists. This diastolic dysfunction impairs ventricular filling and increases filling pressure despite a normal or small ventricular cavity. Patients with HCM have abnormal calcium kinetics and subendocardial ischemia, which are related to the profound hypertrophy and myopathic process.

Defects in several of the genes encoding for the sarcomeric proteins (eg, myosin heavy chain, actin, tropomyosin, titin) provide the molecular basis for HCM. More than 200 distinct mutations have been identified, some with genotype-specific risks of mortality and degrees of hypertrophy. Interestingly, the genetic basis of ventricular hypertrophy does not correlate directly with prognostic risk stratification.

Some mutations (eg, specific tropomyosin substitutions) cause only a mild degree of ventricular hypertrophy, with little or no LV outflow tract obstruction; however, particular mutations carry a disproportionately high risk of sudden death. Other nonsarcomeric genes cause a disease that appears similar to HCM but is more of a storage disorder. These diseases, such as Pompe disease (due to mutations in the gene that encodes acid alpha-glucosidase), and other glycogen-storage diseases, such as those that involve protein kinase gamma-2 (PRKAG2) and lysosomal-associated membrane protein 2 (LAMP2), overlap with HCM in the phenotypic expression.

Frequency

United States

HCM is reported in 0.5% of the outpatient population referred for echocardiography. Overall prevalence of HCM is low; the disorder has been estimated to occur in 0.05-0.2% of the population. Morphologic evidence of disease is found by echocardiography in approximately 25% of first-degree relatives of patients with HCM. While still in research development, genetic testing can be used to identify asymptomatic family members with the same mutation as the proband (ie, index case). Commercial gene testing for sarcomeric mutations is not yet widely available.

Mortality/Morbidity

The mortality rate among individuals with HCM is 2-4% per year. Younger patients, particularly children, have a higher mortality rate from HCM than older patients, which may be due in part to particularly malignant genotypes that cause earlier expression of disease prior to the childbearing years. The risk of sudden death in children with HCM is perhaps as high as 4-6% per year. Certain genes (and, therefore, particular families) have a higher risk of death from ventricular arrhythmia.

Race

HCM does not appear to have a race-dependent frequency. It has been reported in all races.

Sex

• HCM is identified slightly more commonly in males than in females. However, the genetic inheritance pattern is autosomal dominant, without gender predilection. Modifying genetic, hormonal, and environmental factors may lead to higher likelihood of identification, more apparent symptoms, or higher degrees of LV outflow obstruction in males, allowing for more prominent physical examination findings.
• HCM usually presents at an earlier age in females than in males. Females with HCM tend to be more symptomatic and are more likely to be disabled by their symptoms.

Age

HCM may occur at any age from newborn to elderly. HCM is a progressive condition that worsens over time, as does the gradient across the LV outflow tract if left untreated.

• HCM has a bimodal peak of incidence. Overall, its most common presentation is in the third decade of life. However, the peak incidence for inherited forms of HCM is in the second decade of life.
• In adults, the peak distribution is in the fourth through sixth decades.

CLINICAL

Section 3 of 11  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

Patients with hypertrophic cardiomyopathy (HCM) may be asymptomatic. Symptoms of HCM can include sudden cardiac death, dyspnea, syncope, presyncope, angina, palpitations, orthopnea, paroxysmal nocturnal dyspnea, congestive heart failure, and dizziness. Children may have a more variable degree of ventricular hypertrophy than adults and are more likely to have symptoms early in the disease course. These findings are most likely due to the fact that the more malignant genotypes present earlier in life, whereas the more benign mutations do not elicit a clinical or echocardiographic phenotype or symptoms in childhood. Cardiac MRI may provide earlier detection of presymptomatic HCM in genotype-positive children or family members.

• Sudden cardiac death
• • This is the most devastating presenting manifestation of HCM.
  • Sudden cardiac death has the highest incidence in preadolescent and adolescent children.
  • Most patients with HCM are asymptomatic; unfortunately, sudden death may be the first clinical manifestation of the disease.
  • Death often is sudden and unexpected and typically is associated with sports or vigorous exertion.
  • The arrhythmia that causes sudden death is ventricular fibrillation in more than 80% of individuals with HCM. For more information, see Ventricular Fibrillation.
  • Many patients with HCM develop ventricular fibrillation following atrial fibrillation, atrial flutter, supraventricular tachycardia associated with Wolff-Parkinson-White syndrome, ventricular tachycardia, and/or low–cardiac-output hemodynamic collapse.
  • Early diagnosis is of prime importance if death is to be prevented by prescription of an appropriate level of safe activity, medications, surgery, and/or an implantable cardioverter defibrillator. As this is an autosomal-dominantly inherited disease, screening of first-degree relatives with physical examination, ECG, and echocardiography is useful to identify additional family members with HCM before onset of significant symptoms or sudden death.
• Dyspnea
• • The most common presenting symptom of HCM, dyspnea occurs in as many as 90% of symptomatic patients.
  • Dyspnea is largely a consequence of elevated LV diastolic filling pressures and transmission of those elevated pressures back into the pulmonary circulation. The elevated LV filling pressures result principally from impaired diastolic compliance as a result of marked hypertrophy of the ventricle.
• Syncope
• • Syncope is a common symptom of HCM, resulting from inadequate cardiac output on exertion or from cardiac arrhythmia, either tachycardia or bradycardia. Syncope occurs more commonly in children and young adults with small LV chamber size and evidence of ventricular tachycardia on ambulatory monitoring. Some patients with HCM have abnormalities in sinus node function, leading to sick sinus syndrome.
  • Syncope identifies children with HCM at significantly increased risk of sudden death and warrants an urgent evaluation and aggressive treatment.
• Presyncope
• • Presyncope refers to "graying out" spells that occur in the erect posture and can be relieved by the individual immediately lying down. These symptoms are exacerbated by vagal stimulation.
  • Presyncope may also occur with nonsustained atrial or ventricular tachyarrhythmias.
  • Presyncope occurs quite commonly in patients with HCM and identifies a subgroup of patients who are at increased risk for sudden death. Like syncope, presyncopal episodes warrant an urgent workup and aggressive treatment.
  • However, dizziness and presyncope are common symptoms in teenagers and may simply represent vasodepressor reaction or a common faint. A thorough investigation is warranted to rule out potential malignant symptoms.
• Angina
• • Typical symptoms of angina are seen in children with HCM and occur in the absence of detectable coronary atherosclerosis.
  • Impaired diastolic relaxation and markedly increased myocardial oxygen consumption due to ventricular hypertrophy result in subendocardial ischemia, particularly during exertion.
• Palpitations
• • Palpitations are common in HCM.
  • Palpitations usually are due to arrhythmia, such as premature atrial and ventricular beats, sinus pauses, intermittent AV block, atrial fibrillation, atrial flutter, supraventricular tachycardia, and ventricular tachycardia. Nonsustained ventricular tachycardia is another marker for higher risk of sudden death.
• Orthopnea and paroxysmal nocturnal dyspnea
• • While uncommon in children, these early signs of congestive heart failure are observed in individuals with severe cases of HCM.
  • These symptoms occur when impaired diastolic function and elevated LV filling pressure result in pulmonary venous congestion.
• Congestive heart failure
• • While relatively uncommon in children, congestive heart failure is observed in individuals with severe cases of HCM.
  • It may occur as a result of a combination of impaired diastolic function and subendocardial ischemia.
  • Systolic function in children with HCM is almost always well preserved, at least until the late stages of the disease.
  • Patients with CHF have a high likelihood of recurrent heart failure due to both mitral regurgitation and profound diastolic dysfunction.
• Dizziness
• • Dizziness is common in children with HCM who have elevated pressure gradients across the LV outflow tract. Worsened by exertion, dizziness may be exacerbated by hypovolemia following high levels of exertion or increased insensible fluid loss (eg, during or after exposure to extreme heat).
  • Dizziness may be caused by medications or maneuvers (eg, rapid standing, Valsalva during defecation) that decrease preload and afterload and increase the pressure gradient across the LV outflow tract.
  • Dizziness also may be caused by arrhythmia-related hypotension and decreased cerebral perfusion. Nonsustained arrhythmias often cause symptoms of dizziness, giddiness, and presyncope, whereas sustained arrhythmias more likely lead to syncope, collapse, and sudden cardiac death.

Physical

• Patients with HCM can have a myriad of arrhythmias, including atrial fibrillation, atrial flutter, ventricular ectopy, ventricular tachycardia, and ventricular fibrillation.
• Double apical impulse, resulting from a forceful left atrial contraction against a highly noncompliant LV, occurs quite commonly in children with HCM.
• Triple apical impulse, resulting from a late systolic bulge that occurs when the heart is almost empty and is performing near-isometric contraction, is a highly characteristic finding in individuals with HCM; however, triple apical impulse is less frequent than double apical impulse.
• First heart sound is normal in individuals with HCM.
• Second heart sound is usually split; however, in some patients with HCM and extreme outflow gradients, second heart sound is split paradoxically.
• A third heart sound gallop is common in persons with HCM, but it does not have the same ominous significance as in patients with valvular aortic stenosis or in adults.
• A fourth heart sound is heard frequently in individuals with HCM and is due to atrial systole against a highly noncompliant LV.
• Jugular venous pulse reveals a prominent a wave due to diminished right ventricular compliance secondary to massive hypertrophy of the ventricular septum.
• Double carotid arterial pulse is common in persons with HCM. The carotid pulse rises quickly because of increased velocity of blood through the LV outflow tract into the aorta. The carotid pulse then declines in mid systole as the gradient develops, followed by a secondary rise in carotid pulsation during systole.
• Apical precordial impulse frequently is displaced laterally and usually is abnormally forceful and enlarged.
• Typical in individuals with HCM, systolic ejection crescendo-decrescendo murmur is heard best between the apex and left sternal border; it radiates to the suprasternal notch but not to the carotid arteries or neck. The murmur and the gradient across the LV outflow tract diminish with any increase in preload (eg, Valsalva maneuver, Müller maneuver, squatting) or increase in afterload (eg, handgrip). The murmur and the gradient increase with any decrease in preload (eg, that elicited by nitrate medications, diuretics, standing) or with any decrease in afterload (eg, that elicited by vasodilators).
• Holosystolic murmur of mitral regurgitation is heard at the apex and left axilla in patients with systolic anterior motion of the mitral valve and significant LV outflow gradients.
• Diastolic decrescendo murmur of aortic regurgitation is heard in 10% of children with HCM, though mild aortic regurgitation can be detected by Doppler echocardiography in 33% of patients with the disorder.

Causes

The actual cause of HCM is defects in the genes encoding for several of the sarcomeric proteins. Other causes are as follows:

• Abnormal calcium kinetics
• • Additional data point to abnormal myocardial calcium kinetics as the cause of the inappropriate myocardial hypertrophy and specific features of HCM, particularly the diastolic functional abnormalities.
  • Abnormal myocardial calcium kinetics and abnormal calcium fluxes increase intracellular calcium concentrations and occur as a consequence of an increase in the number of calcium channels; in turn, this may produce hypertrophy and cellular disarray.
• Genetic causes
• • Familial HCM occurs as an autosomal dominant inherited disease in approximately 50% of individuals with the disorder. Some, if not all, of the sporadic forms of the disease may be due to spontaneous mutations.
  • At least 12 different genes on at least 6 chromosomes are associated with HCM, and more than 200 different mutations have been discovered. Most of these genes encode for sarcomeric proteins such as myosin heavy chain, actin, titin, myosin-binding protein, tropomyosin, and others. Thus, familial HCM is a genetically heterogenous disease because it is caused by defects at multiple genetic loci.
  • In 1989, Jarcho et al reported the genetic basis for HCM and the existence of a disease gene located on the long arm of chromosome 14. Subsequently, they found this to be the gene encoding for the beta cardiac myosin heavy chain.
  • The phenotypic expression of a particular mutation of a particular gene varies widely, with variability in clinical symptoms and degree of hypertrophy expressed. Phenotypic variability is related to differences in genotype, with specific mutations associated with particular symptoms, degree of hypertrophy, and prognosis.
• Other suggested causes
• • Abnormal sympathetic stimulation, caused by heightened responsiveness of the heart to catecholamines, excessive production of catecholamines, or reduced neuronal uptake of norepinephrine, may cause HCM.
  • Abnormally thickened intramural coronary arteries do not dilate normally, which leads to myocardial ischemia. This progresses to myocardial fibrosis and abnormal compensatory hypertrophy.
  • Subendocardial ischemia is related to abnormalities of the cardiac microcirculation that deplete the energy stores essential for the sequestration of calcium during diastole, resulting in persistent interaction of the contractile elements during diastole and increased diastolic stiffness.
  • Cardiac structural abnormalities include catenoid configuration of the septum, which results in myocardial cell hypertrophy and disarray.

DIFFERENTIALS

Section 4 of 11  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

WORKUP

Section 5 of 11  

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• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• No specific laboratory blood tests are required in the workup of patients with hypertrophic cardiomyopathy (HCM).
• Presently, genetic testing for HCM is not widely available. However, in research situations or in larger pedigrees, genotyping of sarcomeric protein genes is informative in the identification of additional family members with HCM, particularly once the genotype of the proband has been determined.

Imaging Studies

• Two-dimensional echocardiography reveals LV hypertrophy and is diagnostic for HCM.
• • In patients with a systolic gradient, color Doppler flow echocardiography typically reveals mitral regurgitation, which may be accompanied by left atrial enlargement.
  • Spectral continuous wave Doppler echocardiography reveals an elevated flow velocity across the LV outflow tract. Severe HCM typically has a flow velocity greater than 4.0 m/s, and a gradient greater than 50 mm Hg is considered severe.
  • Echocardiography also typically reveals diastolic dysfunction with reduced LV compliance and a mitral valve E/A ratio less than 1.0 (usually <0.8). Systolic function is good; in fact, the LV ejection fraction is usually high to normal at the time of diagnosis. The LV diameter is at the lower limit of normal or smaller than normal.
• The hallmarks of the obstructive type of HCM consist of systolic anterior motion of the anterior mitral valve and asymmetric septal hypertrophy, with a septal wall thickness-to-posterior wall thickness ratio greater than 1.4:1. In rare individuals with HCM, systolic motion of the posterior leaflet also is observed. Three explanations for systolic anterior motion of the mitral valve have been offered.
  • The mitral valve is pulled against the hypertrophic septum by contraction of the papillary muscles because of the abnormal location of the valve and the abnormal orientation of the papillary muscles.
  • The mitral valve is pushed against the septum because of its abnormal position in the outflow tract.
  • The mitral valve is drawn toward the septum because of the lower pressure that occurs as blood is ejected at high velocity through a narrowed outflow tract (ie, Venturi effect).
• The septum in individuals with HCM is not only relatively thicker than the posterior wall, it is also typically at least 4-6 mm thicker than normal for each age group. Massive hypertrophy with septal wall thickness greater than 25 mm has been noted in rare individuals with the disorder, particularly in infants with glycogen storage defects (eg, Pompe disease).
• An unusual echocardiographic pattern consisting of a ground-glass appearance has been noted in portions of the hypertrophied myocardium in some patients with HCM. This pattern may be related to the abnormal cellular architecture and myocardial fibrosis observed in pathologic studies.
• The LV outflow tract is narrowed in many patients with HCM. This contributes to the creation of a pressure gradient in a small number of children.
• Partial systolic closure or, more commonly, coarse systolic fluttering of the aortic valve is related to turbulent blood flow in the outflow tract. Abnormalities in diastolic function may be demonstrated by echocardiography and Doppler recordings in approximately 80% of patients with HCM, independent of the presence or absence of a systolic pressure gradient.
• Other echocardiographic findings in individuals with HCM may include the following:
  • Small LV cavity due to marked hypertrophy of the myocardium and encroachment into the LV cavity
  • Reduced septal motion and thickening during systole, particularly of the upper septum, due to the disarray of the myofibrillar architecture and abnormal contractile function
  • Normal or increased motion of the posterior wall
  • Reduced rate of closure of the mitral valve in mid diastole due to a decrease in LV compliance or abnormal transmitral flow during diastole
  • Mitral valve prolapse, a rare echocardiographic occurrence in persons with HCM
  • Left atrial enlargement
  • Decreased mid aortic flow
• Chest radiographic findings vary in individuals with HCM.
• • Cardiac silhouette may range from normal to markedly increased.
  • Left atrial enlargement is observed frequently, especially when significant mitral regurgitation is present.
• Radionuclide imaging with thallium or technetium may demonstrate reversible defects.
• • Most of these reversible defects are in the absence of coronary artery disease.
  • These reversible defects on radionuclide scanning are more common in children and adolescents with a history of sudden death or syncope, which suggests that myocardial ischemia plays a significant factor in the mechanism of the deaths of younger patients with HCM.

Other Tests

• Electrocardiography
• • Common findings in individuals with HCM include ST-T wave abnormalities and LV hypertrophy. Other findings observed on ECG include axis deviation (right or left), conduction abnormalities (ie, PR prolongation, bundle branch block), sinus bradycardia with ectopic atrial rhythm, and atrial enlargement. In a genetic syndrome due to mutations in AMP-activated PRKAG2, HCM has been associated with inherited Wolff-Parkinson-White syndrome and conduction defects.
  • Uncommon findings in persons with HCM include an abnormal and prominent Q wave in the anterior precordial and lateral limb leads, short PR interval with QRS suggestive of preexcitation, atrial fibrillation (poor prognostic sign), and P wave abnormalities including left atrial enlargement.
• Holter monitoring: Findings in individuals with HCM commonly include atrial and ventricular ectopy, sinus pauses, wandering atrial pacemaker, intermittent or variable AV block, and nonsustained atrial and/or ventricular arrhythmias.

Procedures

• Cardiac catheterization
• • A diagnostic hemodynamic catheterization may be useful to determine the degree of outflow obstruction, diastolic characteristics of the LV, and ventricular and, particularly, coronary arterial anatomy.
  • Therapeutic interventions such as transcatheter septal alcohol ablation to relieve the LV outflow obstruction have been performed. This minimally invasive catheter-based technique may be useful for relief of symptoms associated with LV outflow obstruction and may be an alternative procedure to surgical myomectomy. The main drawbacks are risks of inadvertent AV block and extension of the alcohol-induced infarct, leading to myocardial dysfunction or iatrogenic ventricular septal defects.
• Electrophysiology studies
• • A diagnostic electrophysiologic study may identify conduction abnormalities, sinus node dysfunction, and the potential for inducible arrhythmias using programmed electrical stimulation. However, the prognostic correlation of inducible arrhythmias with spontaneous clinical arrhythmias or sudden death is not entirely clear.
  • Several studies have demonstrated a relationship between electrophysiologic study results and risk stratification, although others have not been able to demonstrate a direct relationship. Electrophysiology studies may also be used to identify a substrate that is amenable to catheter ablation, such as atrial flutter or ventricular tachycardia.

Histologic Findings

Myocardial hypertrophy and gross disorganization of the muscle bundles result in a characteristic whorled pattern; cell-to-cell disarray and disorganization of the myofibrillar architecture within a given cell occurs in almost all patients with HCM. Fibrosis is prominent and may be extensive enough to produce grossly visible scars. Abnormal intramural coronary arteries, with reduced lumen sizes and thickening of the vessel wall, are common in individuals with HCM, occurring in more than 80% of patients. This abnormality occurs most frequently in the ventricular septum and accompanies extensive fibrosis in the affected walls of the heart.

TREATMENT

Section 6 of 11  

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Medical Care

Patients with arrhythmias are among the groups with highest risk for ventricular fibrillation and pose difficult therapeutic decisions for risk reduction.

• Evaluation of the individual with hypertrophic cardiomyopathy (HCM) usually can be conducted on an outpatient basis. Inpatient studies and surgical treatment may be necessary as well.
• Medical and surgical therapy is used to reduce ventricular contractility or increase ventricular volume, increase ventricular compliance and outflow tract dimensions, and, in obstructive HCM, reduce the pressure gradient across the LV outflow tract. Paramount to any therapy for an individual with HCM is reduction in the risk of sudden death (by early identification of the disorder), effective medical care, and implantation of either a pacemaker or an automatic cardioverter defibrillator.

Surgical Care

• Left ventricular myomectomy
• • Left ventricular myomectomy is used for patients with HCM who have severe symptoms refractory to therapy and an outflow gradient of more than 50 mm Hg either with provocation or at rest.
  • The procedure is typically successful in abolishing the outflow gradient; most patients with HCM have symptomatic improvement for at least 5 years. However, the reduction in LV outflow gradient may not correlate with a reduction in the risk of 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.
• Pacemaker implantation
• • Transvenous dual-chamber pacing has been used for patients with HCM. The right ventricular (RV) septal preexcitation induced by RV 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. Many patients with HCM and pacemaker implantation feel that their symptoms improve, allowing a reduction in prescribed medication. However, a reduction in LV outflow tract gradient does not mean necessarily a reduction in vulnerability to ventricular arrhythmias and sudden death.
  • Therefore, some investigators have used permanent pacing in some patients with HCM as adjunctive rather than primary treatment. The reported results vary widely, with a significant placebo effect and variability in patient outcomes.
• Catheter septal ablation
• • Transvenous catheter ablation of the septal region has been performed using selective arterial ethanol infusion to destroy myocardial tissue in individuals with HCM.
  • The procedure is analogous to a surgical myomectomy in attempting to decrease the amount of septal ventricular myocardium, thereby reducing the LV outflow tract gradient. Complications include heart block and myocardial infarction.
• Implantable cardioverter defibrillator
• • The implantable cardioverter defibrillator (ICD) has been used for prevention of sudden arrhythmic death. Transvenous placement is similar in technique to permanent pacemaker implantation and can be performed in the electrophysiology laboratory or operating room. An ICD automatically detects, recognizes, and treats tachyarrhythmias and bradyarrhythmias using tiered therapy (ie, bradycardia pacing, overdrive tachycardia pacing, low-energy cardioversion, high-energy shock defibrillation).
  • ICD therapy has been demonstrated to be lifesaving. In several recent, large, well-designed, prospective studies in adults with coronary artery disease and low ejection fraction who survived myocardial infarction, the ICD has been well demonstrated as superior to antiarrhythmic drug therapy. Ongoing studies are being performed to assess the value of ICD therapy in cardiomyopathy. Several studies have demonstrated that patients (including children) with HCM who have an ICD receive appropriate shocks for ventricular tachycardia and ventricular fibrillation.
  • Smaller studies in children as well as personal and anecdotal experience appear strongly to favor using the ICD in patients with HCM and arrhythmias, aborted sudden death, malignant genotype or family history of the disease, and other factors that may increase mortality, particularly sudden arrhythmic death risk.
  • Clearly, in patients who have had an aborted sudden death event or documented sustained ventricular tachyarrhythmias, the ICD is indicated as secondary prevention.
  • In adults, primary prevention therapy is also being used for patients with HCM, but without a documented ventricular tachyarrhythmia or aborted sudden death event. Although this is a reasonable indication, the appropriate shock rate is significantly lower in these primary prevention patients.
  • Additional markers of higher risk (eg, LV wall thickness, nonsustained ventricular tachycardia, abnormal exercise blood pressure response, genotyping or malignant family history, other stratifying tests) would be useful to identify patients who have greater ventricular arrhythmia vulnerability.
  • The main downsides to implanting an ICD are the relatively high rate of inappropriate shocks (for sinus tachycardia, supraventricular tachycardia, or lead problems) and a high lead fracture rate, particularly in younger patients.
  • The devices last approximately 4-5 years because of either battery depletion or lead failure, and these young patients require multiple ICD device replacements and lead extraction procedures, which carry additional surgical risks. For more information, see Pacemaker Therapy.

Consultations

• Cardiologist
• Cardiothoracic surgeon
• Cardiac electrophysiologist
• Geneticist

Diet

• No special diet is required in individuals with HCM.
• Advise the patient with HCM to avoid excessive weight gain.

Activity

• Advise the individual with HCM to avoid strenuous and/or anaerobic exercise. Do not permit competitive level sports if any of the following are present in individuals with HCM:
• • Significant outflow gradient
  • Significant ventricular or supraventricular arrhythmia
  • Marked LV hypertrophy
  • History of sudden death in relatives with HCM
  • Confirmed malignant genotype

MEDICATION

Section 7 of 11  

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Beta-blockers and calcium channel blockers are effective therapies in children with hypertrophic cardiomyopathy (HCM). In individuals with significant tachyarrhythmias, amiodarone and other class III-type antiarrhythmic agents also have been used.

Drug Category: Beta-adrenergic blocking agents

These agents may decrease outflow obstruction and increase ventricular compliance. No clear evidence indicates that they decrease sudden death. Approximately one half of patients with HCM who use beta-blockers feel improvement in symptoms.

Drug Category: Calcium channel blockers

These agents are an alternative to beta-blockers. Calcium channel blockers improve diastolic filling by improving diastolic relaxation and decreasing outflow gradient due to depression of cardiac contractility.

Drug Category: Antiarrhythmics, miscellaneous

Amiodarone is categorized as a class III antiarrhythmic agent but has antiarrhythmic effects that overlap all 4 Vaughn-Williams antiarrhythmic classes. Its use is generally reserved for potentially life-threatening ventricular arrhythmias.

FOLLOW-UP

Section 8 of 11  

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• Follow-up
• Miscellaneous
• Multimedia
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Further Inpatient Care

• Admit for testing, electrophysiology procedures, and/or surgical intervention.

Further Outpatient Care

• Carefully monitor medication dose and adverse effects.

In/Out Patient Meds

• Medications include beta-blockers, calcium channel blockers, and, rarely, diltiazem, amiodarone, and disopyramide.
• Avoid administration of inotropic drugs.
• Avoid nitrates and sympathomimetic amines except in patients with hypertrophic cardiomyopathy (HCM) and concomitant coronary artery disease.
• Avoid digitalis, because glycosides are contraindicated except in patients with uncontrolled atrial fibrillation.
• Avoid diuretics because of their effect on LV myotomy and ventricular volume.

Transfer

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

Deterrence/Prevention

• Advise individuals with HCM to avoid strenuous activity, anaerobic exercise such as weightlifting, and high-level competitive sports.

Complications

• Congestive heart failure
• Arrhythmia
• Infective mitral endocarditis
• Atrial fibrillation with mural thrombosis formation
• Sudden death

Prognosis

• Mortality rate in individuals with HCM is 4% per year. Sudden death is the most common cause.
• HCM is a chronic illness with lifestyle restrictions.

Patient Education

• Family members of persons with HCM should learn cardiopulmonary resuscitation (CPR).
• Refer the family and patient with HCM for psychosocial counseling.
• Impose activity restrictions for individuals with HCM.
• For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education article Palpitations.

MISCELLANEOUS

Section 9 of 11  

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• Miscellaneous
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Medical/Legal Pitfalls

• Failure to recognize associated conditions, such as essential hypertension, mitral regurgitation, mitral valve prolapse, and angina pectoris
• Failure to inform family and patient with hypertrophic cardiomyopathy (HCM) of exercise restrictions
• Failure to recognize signs and symptoms of HCM
• Failure to screen (or recommend screening of) first-degree relatives once an index case of HCM is identified
• Failure to effectively treat or prevent malignant arrhythmias
• Failure to have serious discussions regarding the risks, benefits, and decisions regarding the implantation of a cardioverter defibrillator

Special Concerns

• Children with HCM may not be symptomatic. Careful evaluation of a heart murmur may reveal HCM.
• Careful screening of first-degree relatives should be recommended, including physical examination, ECG, and echocardiography.

MULTIMEDIA

Section 10 of 11  

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• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Hypertrophic cardiomyopathy. Image courtesy of Michael E. Zevitz, MD
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Media file 2:  Sarcomeric genes involved in hypertrophic cardiomyopathy (adapted from Priori 1999).
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Media type:  Image

Media file 3:  ECG of a 16-year-old with hypertrophic cardiomyopathy (HCM), demonstrating left ventricular hypertrophy pattern and "pseudo-preexcitation."
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Media type:  ECG

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
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• Differentials
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• Follow-up
• Miscellaneous
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• References

• Adabag AS, Casey SA, Kuskowski MA, et al. Spectrum and prognostic significance of arrhythmias on ambulatory Holter electrocardiogramin hypertrophic cardiomyopathy. J Am Coll Cardiol. Mar 1 2005;45(5):697-704. [Medline].
• Almquist AK, Montgomery JV, Haas TS, Maron BJ. Cardioverter-defibrillator implantation in high-risk patients with hypertrophiccardiomyopathy. Heart Rhythm. Aug 2005;2(8):814-9. [Medline].
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Article Last Updated: Aug 18, 2006