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 that is typically inherited in an autosomal dominant fashion with variable penetrance and variable expressivity. The disease has complex symptomatology and potentially devastating consequences for patients and their families. The disorder has a variable presentation and carries a high incidence of sudden death. In fact, HCM is the leading cause of sudden cardiac death in both preadolescent and 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. This hypertrophy can occur in any region of the left ventricle but frequently involves the interventricular septum, which results in an obstruction of flow through the left ventricular (LV) outflow tract.

Decades ago, HCM was written about and known as idiopathic hypertrophic subaortic stenosis (IHSS). It also was written about and known as asymmetric septal hypertrophy (ASH). These terms were replaced by the current term, HCM, because the segmental hypertrophy can occur in any segment of the ventricle, not just the septum. Furthermore, this entity can present without subaortic obstruction to flow, yet still carry the same ominous risk of arrhythmogenic sudden death and many of its clinical symptoms.

HCM can be separated into obstructive and nonobstructive types. Obstructive HCM is due to midsystolic obstruction to flow through the LV outflow tract as a result of a Bernoulli effect–induced systolic anterior mitral valve movement toward the septum. The significance of this obstruction, as it relates to the clinical presentation, and, more significantly, as it relates to the treatment and prognosis, is highly controversial. Some investigators and experts believe the obstruction to flow through the outflow tract of the left ventricle has less to do with the overall hemodynamic and pathophysiologic manifestations of this entity, and that the inappropriate segmental hypertrophy, with its increased myocardial oxygen consumption and substrate for fatal ventricular arrhythmias, has much more significance in the overall clinical picture of this entity and the treatment and prognosis of HCM.

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 an already small outflow tract (by the marked asymmetric septal hypertrophy and possibly an abnormal location of the mitral valve) by the systolic anterior motion of the mitral valve against the hypertrophied septum. The likely cause of this is a Venturi effect resulting from increased ejection velocity produced by the abnormal LV outflow tract orientation and geometry.

In addition, most patients have abnormal diastolic function, whether a pressure gradient is present or not. This diastolic dysfunction impairs ventricular filling and increases filling pressure, despite a normal or small ventricular cavity. These patients have abnormal calcium kinetics and subendocardial ischemia, which are related to the profound hypertrophy and myopathic process.

The molecular basis for HCM is defects in several of the genes encoding for the sarcomeric proteins, such as myosin heavy chain, actin, tropomyosin, and titin. Multiple mutations have been identified, with genotype-specific risks of mortality and degree of hypertrophy. Interestingly, the genetic basis of ventricular hypertrophy does not directly correlate with prognostic risk stratification. Patients with some mutations, such as specific tropomyosin substitutions, have only a mild degree of ventricular hypertrophy, with little or no LV outflow tract obstruction, but they still carry a disproportionately high risk of sudden death.

Frequency

United States

HCM is reported in 0.5% of the outpatient population referred for echocardiography. The overall prevalence of HCM is low and 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. Genetic testing still is in the early stages of research development but can be used to identify asymptomatic family members with the same mutation as the proband (index case).

Mortality/Morbidity

• Sudden death: Most patients are asymptomatic. Unfortunately, the first clinical manifestation of the disease in such individuals may be sudden death, likely from ventricular tachycardia or fibrillation. Younger patients, particularly children, have a much higher mortality rate. Children have a much greater degree of ventricular hypertrophy and are much more symptomatic early on in the disease course. These findings most likely are because more malignant genotypes are present earlier in life, whereas the more benign mutations do not elicit a clinical or echocardiographic phenotype or symptoms in the pediatric population. Death often is sudden, unexpected, and typically is associated with sports or vigorous exertion. Early diagnosis is of prime importance in order to prescribe an appropriate level of safe activity. Screening of first-degree relatives is useful to identify additional affected family members prior to the onset of significant symptoms or sudden death.
• Arrhythmia: Patients can have a myriad of arrhythmias, including atrial fibrillation, atrial flutter, ventricular ectopy, ventricular tachycardia, and ventricular fibrillation. These patients are among the highest-risk group for ventricular fibrillation and pose difficult therapeutic decisions for risk reduction.
• Heart failure: These patients have a high likelihood of recurrent heart failure resulting from both mitral regurgitation and profound diastolic dysfunction. HCM is a progressive condition that worsens over time, as does the gradient across the LV outflow tract if left untreated. Systolic function usually is well preserved until the late stages of the disease. Angina is rare in children but common in adults. Syncope and presyncope are common and may identify individuals at high risk for sudden death.

Sex

• HCM is slightly more common in males than in females. However, the genetic inheritance pattern is autosomal dominant, without sex predilection. Modifying genetic, hormonal, and environmental factors may lead to a higher likelihood of identification in males, increased symptomatology, or higher degrees of LV outflow obstruction, with more prominent findings upon physical examination.
• HCM usually presents at a younger age in females. Females tend to be more symptomatic and are more likely to be disabled by their symptoms than males.

Age

• HCM has a bimodal peak of occurrence. The most common presentation is in the third decade of life, but it may present in persons of any age, from newborns to elderly individuals.
• In the inherited form in children, cases are found in an age range from newborn (ie, stillborn babies) to adult. The peak incidence is in the second decade of life.
• In adults, the peak distribution is in the fourth through the sixth decades of life.

CLINICAL

Section 3 of 11  

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History

Symptoms can include sudden cardiac death, dyspnea, syncope and presyncope, angina, palpitations, orthopnea, paroxysmal nocturnal dyspnea, congestive heart failure, and dizziness.

• Sudden cardiac death
• • This is the most devastating presenting manifestation of HCM. It has the highest incidence in preadolescent and adolescent children and is particularly related to extreme exertion. The risk of sudden death in children is as high as 6% per year.
  • In more than 80% of cases, the arrhythmia that causes sudden death is ventricular fibrillation. Many of these cases degenerate into ventricular fibrillation from rapid atrial arrhythmias, such as fibrillation, supraventricular tachycardia, or Wolff-Parkinson-White syndrome, while others result from ventricular tachycardia and low cardiac output hemodynamic collapse.
• Dyspnea
• • This is the most common presenting symptom, occurring in as many as 90% of symptomatic patients.
  • Dyspnea largely is a consequence of elevated LV diastolic filling pressures (and transmission of those elevated pressures back into the pulmonary circulation). The elevated LV filling pressures principally are caused by impaired diastolic compliance as a result of marked hypertrophy of the ventricle.
• Syncope
• • Syncope is a very common symptom, resulting from inadequate cardiac output upon exertion or from cardiac arrhythmia. It occurs more commonly in children and young adults with small LV chamber size and evidence of ventricular tachycardia upon ambulatory monitoring.
  • Alternatively, syncope may be caused by arrhythmias, either tachycardias or bradycardias. Some patients with HCM have abnormalities in sinus node function, leading to sick sinus syndrome with alternating tachyarrhythmias and bradyarrhythmias or severe bradyarrhythmias.
  • Syncope and presyncope identify patients at high risk of sudden death and warrant an urgent workup and aggressive treatment.
• Presyncope
• • Presyncope includes "graying-out" spells that occur in the erect posture and can be relieved by immediately lying down.
  • They occur quite commonly and identify patients at high risk for sudden death.
  • These symptoms are exacerbated by vagal stimulation. Presyncope also may occur with nonsustained atrial or ventricular tachyarrhythmias.
• Angina
• • Typical symptoms of angina are quite common in patients with HCM and may occur in the absence of detectable coronary atherosclerosis.
  • Impaired diastolic relaxation and markedly increased myocardial oxygen consumption are caused by ventricular hypertrophy that results in subendocardial ischemia, particularly during exertion.
• Palpitations
• • Palpitations are common.
  • These result from arrhythmias, such as premature atrial and ventricular beats, sinus pauses, atrial fibrillation, atrial flutter, supraventricular tachycardia, and ventricular tachycardia.
• Orthopnea and paroxysmal nocturnal dyspnea
• • These are early signs of congestive heart failure and, while relatively uncommon, are observed in patients with severe HCM and result from impaired diastolic function and elevated LV filling pressure.
  • Orthopnea and paroxysmal nocturnal dyspnea result from pulmonary venous congestion.
• Congestive heart failure
• • This is relatively uncommon but is observed in patients with severe HCM.
  • It may occur as a result of a combination of impaired diastolic function and subendocardial ischemia.
  • Systolic function in these patients almost always is well preserved.
• Dizziness
• • Dizziness is common in patients with HCM with elevated pressure gradients across the LV outflow tract. It is worsened by exertion and may be exacerbated by hypovolemia following high levels of exertion or increased insensible fluid loss (eg, during extreme heat).
  • Dizziness also may occur as a result of maneuvers, such as rapid standing or Valsalva during defecation, or certain medications, such as diuretics, nitroglycerin, and vasodilating antihypertensive agents, that decrease preload and afterload and increase the pressure gradient across the LV outflow tract.
  • Dizziness also may be secondary to arrhythmia-related hypotension and decreased cerebral perfusion. Nonsustained arrhythmias often cause symptoms of dizziness, lightheadedness, and presyncope, whereas sustained arrhythmias are more likely to lead to syncope, collapse, and/or sudden cardiac death.

Physical

• Double apical impulse results from a forceful left atrial contraction against a highly noncompliant left ventricle. This occurs quite commonly in adults.
• Triple apical impulse results from a late systolic bulge that occurs when the heart is almost empty and is performing near-isometric contraction. This is a highly characteristic finding of HCM; however, it occurs less frequently than the double apical impulse.
• First heart sound is normal.
• Second heart sound usually is normally split, but in some patients with severe outflow gradients, it is paradoxically split.
• An S₃ gallop is common in children, but it does not have the same ominous significance as in patients with valvular aortic stenosis. When it occurs in adults, it signifies decompensated congestive heart failure.
• A fourth heart sound, an S₄, frequently is heard and results from atrial systole against a highly noncompliant left ventricle.
• Jugular venous pulse reveals a prominent a wave caused by diminished right ventricular compliance secondary to massive hypertrophy of the ventricular septum.
• Double carotid arterial pulse is common. The carotid pulse rises quickly because of the increased velocity of blood through the LV outflow tract and into the aorta. The carotid pulse then declines in mid systole as the gradient develops. This is followed by a secondary rise in carotid pulsation during late systole.
• Apical precordial impulse frequently is displaced laterally and usually is abnormally forceful and enlarged.
• Systolic ejection murmur typically is a systolic ejection crescendo-decrescendo murmur, which is best heard between the apex and left sternal border and 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, Mueller maneuver, squatting) or increase in afterload (eg, handgrip). The murmur and the gradient increase with any decrease in preload (eg, Valsalva maneuver, nitrate administration, diuretic administration, standing) or with any decrease in afterload (eg, vasodilator administration).
• Holosystolic murmur at the apex and axilla of mitral regurgitation is heard 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 patients, although mild aortic regurgitation can be detected by Doppler echocardiography in 33% of patients.

Causes

• Abnormal calcium kinetics
• • The actual cause of HCM is defects in the genes encoding for several of the sarcomeric proteins. Additional data link abnormal myocardial calcium kinetics as the cause of the inappropriate myocardial hypertrophy and specific features of HCM, particularly in patients with diastolic functional abnormalities.
  • Abnormal myocardial calcium kinetics and abnormal calcium fluxes result in an increase in intracellular calcium concentration and occur as a consequence of an increase in the number of calcium channels. This, in turn, may produce hypertrophy and cellular disarray.
• Genetic causes
• • Familial HCM occurs as an autosomal dominant Mendelian-inherited disease in approximately 50% of cases. Some, if not all, of the sporadic forms of the disease may be caused by spontaneous mutations.
  • At least 6 different genes on at least 4 chromosomes are associated with HCM, with more than 50 different mutations discovered thus far. Familial HCM is a genetically heterogenous disease in that it can be caused by genetic defects at more than one locus.
  • In 1989, Seidman and collaborators first reported the genetic basis for HCM. They reported the existence of a disease gene located on the long arm of chromosome 14. Subsequently, they found this to be the gene encoding for beta cardiac myosin heavy chain.
  • Wide variation exists in the phenotypic expression of a given mutation of a given gene, with variability in clinical symptoms and the degree of hypertrophy expressed. Phenotypic variability is related to the differences in genotype, with specific mutations associated with particular symptoms, the degree of hypertrophy, and the prognosis.
• Other suggested causes
• • Abnormal sympathetic stimulation: Heightened responsiveness of the heart to the excessive production of catecholamines or the reduced neuronal uptake of norepinephrine might cause HCM.
  • Abnormally thickened intramural coronary arteries: These do not dilate normally, which leads to myocardial ischemia. This progresses to myocardial fibrosis and abnormal compensatory hypertrophy.
  • Subendocardial ischemia: This is related to abnormalities of the cardiac microcirculation that deplete the energy stores essential for the sequestration of calcium during diastole. Subendocardial ischemia results in persistent interaction of the contractile elements during diastole and increased diastolic stiffness.
  • Cardiac structural abnormalities: These include a catenoid configuration of the septum, which results in myocardial cell hypertrophy and disarray.

DIFFERENTIALS

Section 4 of 11  

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Other Problems to be Considered

Aortic stenosis, supravalvular

WORKUP

Section 5 of 11  

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• Follow-up
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Lab Studies

• No specific laboratory blood tests are required in the workup of HCM.
• Genetic testing is not widely available at this time but is becoming increasingly available in this disease setting. In research situations or in larger pedigrees, genotyping is informative for the identification of additional family members once the proband's genotype has been determined.

Imaging Studies

• Two-dimensional echocardiography and Doppler studies
• • Two-dimensional echocardiography is diagnostic for HCM. Color Doppler flow studies typically reveal mitral regurgitation.
  • Spectral continuous-wave Doppler studies in patients with obstructive HCM reveal an elevated flow velocity across the LV outflow tract. Severe obstructive HCM typically has a flow velocity greater than 4 m/s, and a gradient across the LV outflow tract of greater than 50 mm Hg is considered severe.
  • Echocardiography also typically reveals diastolic dysfunction with reduced LV compliance and a mitral valve ratio of E wave to A wave of less than 1 (usually <0.8). Systolic function is good, and, in fact, the LV ejection fraction usually is 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 leaflet and asymmetric septal hypertrophy with a ratio of septal wall thickness to posterior wall thickness of greater than 1.4:1.
  • The septum not only is relatively thicker than the posterior wall, it also typically is at least 4-6 mm thicker than normal for each age group. Massive hypertrophy with septal wall thickness of greater than 25 mm has been noted in rare cases, particularly in infants with glycogen storage defects, as are observed in patients with 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 that have been observed in pathological studies.
  • A narrowing of the LV outflow tract occurs in many patients with HCM. This contributes to the creation of a pressure gradient in a small number of patients.
  • The hallmark of HCM associated with a pressure gradient is the abnormal systolic motion of the anterior leaflet of the mitral valve (ie, systolic anterior motion) and, in rare cases, the systolic motion of the posterior leaflet. Three explanations for the systolic anterior motion of the mitral valve have been offered, as follows:
    • The mitral valve is pulled against the septum by contraction of the papillary muscles, which occurs because of the valve's abnormal location and septal hypertrophy altering the 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 (Venturi effect).
  • Several other echocardiographic findings may be present, as follows:
    • A small LV cavity may be present secondary to marked hypertrophy of the myocardium and encroachment into the LV cavity.
    • Reduced septal motion and thickening during systole may occur, particularly of the upper septum, resulting from disarray of the myofibrillar architecture and abnormal contractile function.
    • The motion of the posterior wall may be normal or increased.
    • The rate of closure of the mitral valve in mid diastole may be reduced secondary to a decrease in LV compliance or abnormal transmitral flow during diastole.
    • Mitral valve prolapse, a rare echocardiographic occurrence in HCM, may be present.
  • Partial systolic closure or, more commonly, coarse systolic fluttering of the aortic valve related to turbulent blood flow in the outflow tract may occur. 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.
  • The presence of mitral regurgitation virtually always is confirmed by Doppler echocardiography in patients with HCM who have a systolic gradient.
  • In general, a summary of echocardiography findings includes abnormal systolic anterior leaflet motion of the mitral valve, LV hypertrophy, left atrial enlargement, small ventricular chamber size, septal hypertrophy with septal-to-free wall ratio greater than 1.4:1, mitral valve prolapse and mitral regurgitation, decreased mid aortic flow, and partial systolic closure of the aortic valve in mid systole.
• Chest radiograph
• • Chest radiograph (CXR) findings are variable. The cardiac silhouette may range from normal to markedly increased.
  • Left atrial enlargement frequently is observed, especially when significant mitral regurgitation is present. This is manifested by a "double-density" appearance on CXR.
• Radionuclide imaging
• • Radionuclide imaging with thallium or technetium may show reversible defects, mostly in the absence of coronary artery disease.
  • Thallium or technetium scintigraphy may reveal defects in myocardial perfusion, even in the setting of angiographically normal coronary arteries.
  • These reversible defects evident on radionuclide scanning are more common in children and adolescents with a history of sudden death or syncope, which suggests that myocardial ischemia is a significant factor in the mechanism of the demise of younger patients with HCM.

Other Tests

• Electrocardiography
• • Common findings include ST-T wave abnormalities and LV hypertrophy. Other findings observed on ECG include axis deviation (right or left), conduction abnormalities (P-R prolongation, bundle-branch block), sinus bradycardia with ectopic atrial rhythm, and atrial enlargement. One mutation has been identified that is associated with both HCM and Wolff-Parkinson-White syndrome.
  • Uncommon findings include an abnormal and prominent Q wave in the anterior precordial and lateral limb leads, short P-R interval with QRS suggestive of preexcitation, atrial fibrillation (poor prognostic sign), and a P-wave abnormality, including left atrial enlargement.
• Holter monitoring and event electrocardiography: Findings commonly include atrial and ventricular ectopy, sinus pauses, wandering atrial pacemaker, atrial tachycardia, atrial fibrillation and/or flutter, and nonsustained ventricular tachycardia.

Procedures

• Cardiac catheterization
• • A diagnostic hemodynamic catheterization is useful to determine the degree of outflow obstruction, diastolic characteristics of the left ventricle and LV anatomy, and, particularly, the coronary arterial anatomy.
  • Therapeutic interventions also have been performed, including transcatheter septal alcohol ablation to relieve the LV outflow obstruction.
• Electrophysiology studies
• • A diagnostic electrophysiology study using programmed electrical stimulation may identify conduction abnormalities, sinus node dysfunction, and the potential for inducible arrhythmias.
  • The prognostic correlation of inducible arrhythmias with spontaneous clinical arrhythmias and/or sudden death is not entirely clear. Several studies have shown a relationship between electrophysiology study results and risk stratification for sudden cardiac death, but other studies have not been able to demonstrate a direct relationship.

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 occur in almost all patients with HCM. Fibrosis is prominent and may be extensive enough to produce grossly visible scars. Abnormal intramural coronary arteries, with a reduction in the size of the lumen and thickening of the vessel wall, are common in patients with HCM and occur in more than 80%. This abnormality most frequently occurs in the ventricular septum and accompanies extensive fibrosis in the affected walls of the heart.

TREATMENT

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Medical Care

• Evaluation usually can be conducted on an outpatient basis. Inpatient studies and surgical treatment also may be necessary.
• Medical and surgical therapy is used to reduce ventricular contractility or increase ventricular volume, increase ventricular compliance and outflow tract dimensions, and, in the case of obstructive 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.

Surgical Care

• 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 those patients with severe mitral regurgitation due to systolic anterior movement of the mitral valve, particularly in those individuals who develop either congestive heart failure, largely due to mitral regurgitation (large regurgitant fraction), or those who develop pulmonary hypertension as a result of severe mitral regurgitation.
• Pacemaker implantation
• • 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.
  • Many patients feel an improvement in symptoms and can have a reduction in prescribed medications.
  • 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.
• Catheter septal ablation
• • Transvenous catheter ablation of the septal region has been performed using selective arterial ethanol infusion to destroy myocardial tissue.
  • 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 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 symptoms, particularly in the incidence of heart failure.
  • In many centers, it is the surgical procedure of choice for HCM.
• Implantable cardioverter defibrillator
• • 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 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 several recent, large, well-designed prospective studies in adults with coronary artery disease and low ejection fraction surviving myocardial infarction, the ICD has been demonstrated to be superior to antiarrhythmic drug therapy.
  • 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 HCM and arrhythmias, aborted sudden death, malignant genotype or family history, and other factors that may increase mortality and, particularly, sudden arrhythmic death risk.

Consultations

• Cardiologist
• Cardiothoracic surgeon
• Cardiac electrophysiologist
• Geneticist

Diet

• No special diet is required.
• The patient should avoid excessive weight gain.

Activity

• 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 HCM
  • Identified malignant genotype

MEDICATION

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The purpose of pharmacologic therapy is to reduce the pressure gradient across the LV outflow tract by reducing the inotropic state of the left ventricle, improving compliance of the left ventricle, and reducing diastolic dysfunction. To date, only one pharmacologic agent, amiodarone (Cordarone), has been shown to reduce the incidence of arrhythmogenic sudden cardiac death.

Drug Category: Beta-adrenergic blocking agents

Reduce inotropic state of left ventricle. Decrease diastolic dysfunction and increase LV compliance, thereby reducing pressure gradient across LV outflow tract. Decrease myocardial oxygen consumption, thereby reducing myocardial ischemia potential. Decrease heart rate, thus reducing myocardial oxygen consumption and reducing myocardial ischemia potential.

Drug Category: Antiarrhythmics

These agents alter the electrophysiologic mechanisms responsible for arrhythmia.

Drug Category: Calcium channel blockers

Alternative to beta-blockers, they decrease inotropic state of the left ventricle, decrease gradient across the LV outflow tract, decrease diastolic dysfunction, and increase diastolic filling of the left ventricle by improving LV diastolic relaxation. May have a better effect on exercise performance.

Drug Category: Natriuretic peptides

Dilate veins and arteries.

FOLLOW-UP

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Further Inpatient Care

• Admit for testing and 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.
• Use antitussives may be administered as needed to avoid coughing.
• Avoid inotropic drugs if possible.
• 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.
• Avoid diuretics because of their 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 a total abstinence of these activities.

Complications

• Congestive heart failure
• Ventricular and supraventricular arrhythmias
• Infective mitral endocarditis
• Atrial fibrillation with mural thrombosis formation
• Sudden death

Prognosis

• Mortality rate is 4% per year. Sudden death is the most common reason.
• This is a chronic illness with lifestyle restrictions.

Patient Education

• Family members should learn cardiopulmonary resuscitation.
• Refer the patient and family for psychosocial counseling.
• Impose activity restrictions that include total abstinence from highly competitive athletic activities and very strenuous physical exertion, such as lifting heavy objects, lifting weights, and shoveling snow.
• Refer children of patients with HCM, especially those in the pediatric age range, for urgent echocardiography and genetic testing if echocardiogram does not yet reveal overt disease.
• For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education article Palpitations.

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, is a potential pitfall.
• Failure to inform patient and family of exercise restrictions may lead to litigation. Deviation from the strongest of recommendations that the patient refrain from all high-intensity competitive sports is not acceptable due to the high risk of arrhythmogenic sudden cardiac death.
• Failure to recognize signs and symptoms of HCM may lead to legal problems.
• Failure to screen (or recommend screening) first-degree relatives once an index case is identified can be a medicolegal pitfall.

Special Concerns

• Many patients, particularly children, may not be symptomatic. Careful evaluation of a heart murmur may reveal HCM.

MULTIMEDIA

Section 10 of 11  

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Media file 1:  Hypertrophic cardiomyopathy.
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Media type:  CT

REFERENCES

Section 11 of 11

• Authors and Editors
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• Armstrong AT, Binkley PF, Baker PB, et al. Quantitative investigation of cardiomyocyte hypertrophy and myocardial fibrosis over 6 years after cardiac transplantation. J Am Coll Cardiol. Sep 1998;32(3):704-10. [Medline].
• Blanchard DG, Ross J Jr. Hypertrophic cardiomyopathy: prognosis with medical or surgical therapy. Clin Cardiol. Jan 1991;14(1):11-9. [Medline].
• Bonne G, Carrier L, Richard P, et al. Familial hypertrophic cardiomyopathy: from mutations to functional defects. Circ Res. Sep 21 1998;83(6):580-93. [Medline].
• Bonow RO. Left ventricular diastolic function in hypertrophic cardiomyopathy. Herz. Feb 1991;16(1):13-21. [Medline].
• Bonow RO, Maron BJ, Leon MB, et al. Medical and surgical therapy of hypertrophic cardiomyopathy. Cardiovasc Clin. 1988;19(1):221-39. [Medline].
• Brandenburg RO. Syncope and sudden death in hypertrophic cardiomyopathy. J Am Coll Cardiol. Apr 1990;15(5):962-4. [Medline].
• Braunwald E, Wynne J. The Cardiomyopathies and Myocarditides. In: Heart disease: A textbook of cardiovascular medicine. 5th ed. Philadelphia, Pa: WB Saunders; 1997:. 1414-26.
• Braunwald E. Hypertrophic cardiomyopathy--continued progress. N Engl J Med. Mar 23 1989;320(12):800-2. [Medline].
• Counihan PJ, McKenna WJ. Low-dose amiodarone for the treatment of arrhythmias in hypertrophic cardiomyopathy. J Clin Pharmacol. May 1989;29(5):436-8. [Medline].
• Davies MJ, McKenna WJ. Hypertrophic cardiomyopathy: an introduction to pathology and pathogenesis. Br Heart J. Dec 1994;72(6 Suppl):S2-3. [Medline].
• DeRose JJ Jr, Banas JS Jr, Winters SL. Current perspectives on sudden cardiac death in hypertrophic cardiomyopathy. Prog Cardiovasc Dis. May-Jun 1994;36(6):475-84. [Medline].
• Dilsizian V, Bonow RO, Epstein SE, Fananapazir L. Myocardial ischemia detected by thallium scintigraphy is frequently related to cardiac arrest and syncope in young patients with hypertrophic cardiomyopathy. J Am Coll Cardiol. Sep 1993;22(3):796-804. [Medline].
• Elliott PM, Brecker SJ, McKenna WJ. Diastolic dysfunction in hypertrophic cardiomyopathy. Eur Heart J. Aug 1998;19(8):1125-7. [Medline].
• Fananapazir L, Chang AC, Epstein SE, McAreavey D. Prognostic determinants in hypertrophic cardiomyopathy. Prospective evaluation of a therapeutic strategy based on clinical, Holter, hemodynamic, and electrophysiological findings. Circulation. Sep 1992;86(3):730-40. [Medline].
• Fananapazir L, Leon MB, Bonow RO, et al. Sudden death during empiric amiodarone therapy in symptomatic hypertrophic cardiomyopathy. Am J Cardiol. Jan 15 1991;67(2):169-74. [Medline].
• Fananapazir L, Epstein SE. Hemodynamic and electrophysiologic evaluation of patients with hypertrophic cardiomyopathy surviving cardiac arrest. Am J Cardiol. Feb 1 1991;67(4):280-7. [Medline].
• Fananapazir L, Cannon RO 3rd, Tripodi D, Panza JA. Impact of dual-chamber permanent pacing in patients with obstructive hypertrophic cardiomyopathy with symptoms refractory to verapamil and beta-adrenergic blocker therapy. Circulation. Jun 1992;85(6):2149-61. [Medline].
• Hayashida W, Kumada T, Kohno F, et al. Left ventricular regional relaxation and its nonuniformity in hypertrophic nonobstructive cardiomyopathy. Circulation. Oct 1991;84(4):1496-504. [Medline].
• Hintringer F, Nesser HJ, Niel J, et al. Pacing in distal left ventricular hypertrophic cardiomyopathy. Pacing Clin Electrophysiol. Sep 1998;21(9):1828-30. [Medline].
• Losi MA, Betocchi S, Manganelli F, et al. Pattern of left ventricular filling in hypertrophic cardiomyopathy. Assessment by Doppler echocardiography and radionuclide angiography. Eur Heart J. Aug 1998;19(8):1261-7. [Medline].
• Louie EK, Edwards LC 3rd. Hypertrophic cardiomyopathy. Prog Cardiovasc Dis. Jan-Feb 1994;36(4):275-308. [Medline].
• Maki S, Ikeda H, Muro A, et al. Predictors of sudden cardiac death in hypertrophic cardiomyopathy. Am J Cardiol. Sep 15 1998;82(6):774-8. [Medline].
• Maron BJ, Roberts WC, Epstein SE. Sudden death in hypertrophic cardiomyopathy: a profile of 78 patients. Circulation. Jun 1982;65(7):1388-94. [Medline].
• Maron BJ. Hypertrophic cardiomyopathy. Curr Probl Cardiol. Nov 1993;18(11):639-704. [Medline].
• Maron BJ, Peterson EE, Maron MS, Peterson JE. Prevalence of hypertrophic cardiomyopathy in an outpatient population referred for echocardiographic study. Am J Cardiol. Mar 15 1994;73(8):577-80. [Medline].
• Maron BJ, Gardin JM, Flack JM, et al. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Echocardiographic analysis of 4111 subjects in the CARDIA Study. Coronary Artery Risk Development in (Young) Adults. Circulation. Aug 15 1995;92(4):785-9. [Medline].
• Maron BJ, Isner JM, McKenna WJ. 26th Bethesda conference: recommendations for determining eligibility for competition in athletes with cardiovascular abnormalities. Task Force 3: hypertrophic cardiomyopathy, myocarditis and other myopericardial diseases and mitral valve prolapse. J Am Coll Cardiol. Oct 1994;24(4):880-5. [Medline].
• Maron BJ. Q waves in hypertrophic cardiomyopathy: a reassessment. J Am Coll Cardiol. Aug 1990;16(2):375-6. [Medline].
• Maron BJ, Cecchi F, McKenna WJ. Risk factors and stratification for sudden cardiac death in patients with hypertrophic cardiomyopathy. Br Heart J. Dec 1994;72(6 Suppl):S13-8. [Medline].
• Maron BJ, Klues HG. Surviving competitive athletics with hypertrophic cardiomyopathy. Am J Cardiol. Jun 1 1994;73(15):1098-104. [Medline].
• Maron BJ. Appraisal of dual-chamber pacing therapy in hypertrophic cardiomyopathy: too soon for a rush to judgment?. J Am Coll Cardiol. Feb 1996;27(2):431-2. [Medline].
• McDonald KM, Maurer B. Permanent pacing as treatment for hypertrophic cardiomyopathy. Am J Cardiol. Jul 1 1991;68(1):108-10. [Medline].
• McKenna WJ, Camm AJ. Sudden death in hypertrophic cardiomyopathy. Assessment of patients at high risk. Circulation. Nov 1989;80(5):1489-92. [Medline].
• Piacenza JM, Kirkorian G, Audra PH, Mellier G. Hypertrophic cardiomyopathy and pregnancy. Eur J Obstet Gynecol Reprod Biol. Sep 1998;80(1):17-23. [Medline].
• Robinson K, Frenneaux MP, Stockins B, et al. Atrial fibrillation in hypertrophic cardiomyopathy: a longitudinal study. J Am Coll Cardiol. May 1990;15(6):1279-85. [Medline].
• Seiler C, Hess OM, Schoenbeck M, et al. Long-term follow-up of medical versus surgical therapy for hypertrophic cardiomyopathy: a retrospective study. J Am Coll Cardiol. Mar 1 1991;17(3):634-42. [Medline].
• Shapiro LM. Hypertrophic cardiomyopathy in the elderly. Br Heart J. May 1990;63(5):265-6. [Medline].
• Shirani J, Maron BJ, Cannon RO 3rd, et al. Clinicopathologic features of hypertrophic cardiomyopathy managed by cardiac transplantation. Am J Cardiol. Aug 15 1993;72(5):434-40. [Medline].
• Spirito P, Maron BJ. Relation between extent of left ventricular hypertrophy and diastolic filling abnormalities in hypertrophic cardiomyopathy. J Am Coll Cardiol. Mar 15 1990;15(4):808-13. [Medline].
• Spirito P, Bellone P. Natural history of hypertrophic cardiomyopathy. Br Heart J. Dec 1994;72(6 Suppl):S10-2. [Medline].
• Spirito P, Lakatos E, Maron BJ. Degree of left ventricular hypertrophy in patients with hypertrophic cardiomyopathy and chronic atrial fibrillation. Am J Cardiol. May 1 1992;69(14):1217-22. [Medline].
• Watkins H. Multiple disease genes cause hypertrophic cardiomyopathy. Br Heart J. Dec 1994;72(6 Suppl):S4-9. [Medline].
• Webb JG, Sasson Z, Rakowski H, et al. Apical hypertrophic cardiomyopathy: clinical follow-up and diagnostic correlates. J Am Coll Cardiol. Jan 1990;15(1):83-90. [Medline].
• Wigle ED. Impaired left ventricular relaxation in hypertrophic cardiomyopathy: relation to extent of hypertrophy. J Am Coll Cardiol. Mar 15 1990;15(4):814-5. [Medline].
• ten Berg JM, Suttorp MJ, Knaepen PJ, et al. Hypertrophic obstructive cardiomyopathy. Initial results and long-term follow-up after Morrow septal myectomy. Circulation. Oct 1994;90(4):1781-5. [Medline].

Article Last Updated: Jul 18, 2006