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Hypertrophic Cardiomyopathy: A Review of Etiology and Treatment

Jurynec, Jennifer MS, APRN, ACNP

The Journal of Cardiovascular Nursing: January-February 2007 - Volume 22 - Issue 1 - p 65-73
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Hypertrophic cardiomyopathy (HCM) is a congenital cardiac disease with an estimated prevalence of 1:500 in the population. Individuals with HCM can present with clinical manifestations that include left ventricular outflow obstruction, cardiac dysrhythmias, diastolic heart failure, cardiac angina, and sudden cardiac death. Current treatments include pharmacologic intervention to reduce heart rate and ventricular contractility as well as surgery or septal alcohol ablation to reduce myocardial septal size. Implantable cardiac defibrillators are considered a treatment option in individuals with HCM who are at an increased risk for sudden cardiac death. The identification of persons at risk for complications related to HCM is important for reducing mortality and morbidity in this population. In addition, diagnosis of HCM in an individual allows the healthcare provider caring for these patients to screen, educate, and institute timely preventative measures in other members of the family. The purpose of this review is to provide clinicians caring for cardiac patients with a guide for recognition, diagnosis, prevention, and treatment of HCM.

Jennifer Jurynec, MS, APRN, ACNP LDS Hospital, Cardiovascular Services Division, Salt Lake City, Utah.

Corresponding author Jennifer Jurynec, MS, APRN, ACNP, 1351 Roberta St., Salt Lake City, UT 84115 (e-mail: jenabbyadams@yahoo.com).

Hypertrophic cardiomyopathy (HCM) is a familial genetic cardiovascular disorder amenable to intervention. In the past 50 years, there has been an abundance of research on the genetics, screening, treatment, and follow-up of HCM, yet there is little clinical information published in the nursing literature. Clinicians working in primary or secondary care settings must be aware of HCM and know how to screen, treat, educate, and follow patients and their family members diagnosed with HCM. Advanced practice nurses are in a unique position to detect, educate, and treat familial genetic diseases. As expert clinicians, they assess disorders from a holistic perspective using comprehensive physical examination and detailed history, including assessment of family history, psychosocial influences, and functional abilities. The purpose of this article is to provide clinicians with a guide to detection, treatment, and prevention of complications related to HCM.

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Problem

Hypertrophic cardiomyopathy is a genetic cardiovascular disorder that presents with diverse clinical manifestations. Clinical presentation of HCM ranges from an asymptomatic individual with a strong family history to someone with exercise intolerance, heart failure (HF), syncope, dysrhythmias, or sudden cardiac death (SCD).1,2 Hypertrophic cardiomyopathy is frequently quoted as the most common reason for SCD in athletes.1,3,4 It is most commonly characterized by left ventricular hypertrophy with preferential nonconcentric hypertrophy of the septum and presence of dynamic obstruction of the left ventricular outflow tract (LVOT).5 Systolic anterior motion of the mitral valve is present in 25% of people with HCM.6 Aside from the phenotypical manifestations of HCM, many other clinical problems can exist, including ventricular and atrial dysrhythmias,7 myocardial ischemia,8 and HF.2 Although HCM is a diverse clinical disease with varying presentation and outcomes, these sequela are conditions that healthcare providers caring for these patients can recognize and treat.

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Genetics of HCM

Hypertrophic cardiomyopathy is an autosomal dominant disorder primarily affecting genes encoding cardiac sarcomere proteins.7 Due to the autosomal dominant nature of this mutation, persons who have a parent with a positive mutation in one of these genes has a 50% chance of inheriting the mutation themselves.9 When there is not a clear familial history, the mutations are thought to arise as spontaneous somatic mutations.9 Despite the identification of genetic mutations leading to this disorder, HCM remains a genetically diverse and poorly understood disorder with more than 200 known mutations in 10 genes.7 A definitive model that explains mechanisms that lead to septal hypertrophy has not been identified.10 Possible mechanisms proposed include reduced contractile function leading to compensatory hypertrophy of the cardiac myocytes, insufficient levels of muscle ATP resulting in improper sarcomere function,10 and sarcomeric abnormalities leading to the induction of growth factors that stimulate hypertrophy and fibrosis.9 Mechanisms for the other complications encountered in patients with HCM are myofibril disarray that can lead to myocardial scarring and act as an dysrhythmogenic substrate, ischemia caused by myocardial bridging, coronary artery fibrosis, and coronary artery disease and mitral regurgitation resulting from systolic anterior motion of the mitral valve.2,6,7

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Epidemiology

Hypertrophic cardiomyopathy was first identified as a distinct clinical entity in the 1950s. After this period, considerable research was done to define the underlying genetic mechanisms of the disease. This research served as a guide for clinicians on how to screen and treat affected individuals.10 The initial estimates of prevalence and incidence of SCD in adolescents, minorities, and women were gleaned from a population of patients that were referred to tertiary care centers and therefore are not considered to be representative of the general population. In more recent studies, there has been some attempt to identify the risk for HCM in various populations. Some of these data are presented below.

Recent studies have assessed risk in adolescents, minorities, nonreferral-based communities, and women.7,11,12 Generalizations cannot be made based on these few studies, but some trends can be appreciated. Hypertrophic cardiomyopathy is estimated to have a prevalence of 1:500 in the general population.4,7,13 Severity of clinical symptoms and presentation may be influenced by the particular mutation carried, but because there is no currently sensitive diagnostic genetic testing available to the average practitioner, there is no way to use this information to assess a patient's risk for adverse outcomes.8,9,14 The documented incidence of a 4% to 6% chance of SCD in young athletes and children versus 1% to 2% annual chance of SCD in adults1 suggests that HCM is a disease in which SCD occurs primarily in adolescents and teens. Asymptomatic people younger than 35 years seem to experience SCD relatively more often, yet the risk extends beyond adolescence and middle age to the elderly.7,11,13,15

Hypertrophic cardiomyopathy is referenced as the most common cause of SCD among athletes, yet recent studies present conflicting data.1,3,4 One study of Italian athletes found that only 2% of sudden death among athletes were due to HCM compared with 7.3% in the nonathlete group.3 A similar study of American Army recruits involved in intensive basic training found that among 64 recruits that experienced SCD, only 13% of sudden death were due to HCM and 61% were due to anomalous coronary artery insertion.16 In contrast, a study looking at SCD among American football and basketball players found 102 (36%) of all deaths were due to HCM.17

A recent study examining the relationship between gender and HCM found that women differ in physical complications and clinical severity. Women suffer stroke more often, progress to HF with New York Heart Association class III to IV 50% more, are older at presentation, and have a greater degree of left ventricular outflow obstruction.11 Because of the array of symptoms, presentation, natural course of disease, and lack of homogeneity in this disorder, multiple clinical parameters have been developed to help the clinician assess a given patient with HCM and attempt to determine risk for complications and SCD.1,2,7,8

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Pathophysiology and Clinical Findings

The histology of the myocardium in a patient with HCM often shows myocellular disarray, coronary vessel narrowing, coronary fibrosis, myocardial scarring, coronary vessel bridging, and nonconcentric septal hypertrophy.6,8 Clinical findings can include septal hypertrophy with systolic anterior motion of the mitral valve, ventricular and atrial dysrhythmias, diastolic dysfunction, syncope, myocardial ischemia, and HF.4,13

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Septal Hypertrophy and Systolic Anterior Motion

The primary feature of individuals with HCM is nonsymmetric septal hypertrophy that commonly involves the apex.13 Approximately 25% of those with HCM will present with LVOT obstruction with or without systolic anterior motion of the mitral valve.4,5,13 Obstruction of the LVOT is due to partial obliteration of the LVOT diameter related to the hypertrophied septal muscle. This obstruction results in a resting pressure gradient between the aorta and LVOT. In systole, the septal wall partially obstructs the diameter of the LVOT and reduces stroke volume. Systolic anterior motion occurs when a leaflet of the mitral valve is pulled into the LVOT during systole, adding to obstruction of the LVOT. Because the mitral valve leaflet that is pulled into the LVOT is open during systole, a mitral regurgitation murmur can be appreciated in this group of patients.10

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Ventricular and Atrial Dysrhythmias

Ventricular dysrhythmias are presumed to be the primary cause of SCD in individuals with HCM, whereas atrial fibrillation is the most common sustained dysrhythmia and occurs in 20% to 25% of patients.1,13 Atrial fibrillation is primarily thought to be due to left atrial enlargement. Ventricular dysrhythmias are possibly due to myocardial scarring, creating an irritable focus or reentrant circuit on the ventricular myocardium.7,8 Data from 24-hour Holter monitoring in individuals with HCM show that 90% of these patients experienced ventricular dysrhythmias that were primarily premature ventricular complexes with nonsustained bursts of ventricular tachycardia occurring in 30% of them.7

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Diastolic Dysfunction

The HCM patient with diastolic dysfunction can present in 2 ways. One is related to the inability of the ventricle to relax because of a restrictive pattern in the ventricle presumably due to myocardial scarring. The other is due to a dilated-hypokinetic ventricle.13,18 Identifying which form is present is important because, a dilated-hypokinetic ventricle in a patient with HCM leads more frequently to New York Heart Association class III or IV HF symptoms. It is also the primary reason for heart transplant in the patient with HCM.18

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Syncope

Syncope in individuals with HCM is heterogeneous in origin. Possible explanations of syncope include ventricular or atrial dysrhythmias, outflow obstruction that leads to reduced cardiac output, autonomic dysfunction, abnormal peripheral vasodilatation response, myocardial ischemia, and diastolic dysfunction.2,7

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Myocardial Ischemia

Atypical chest pain is a frequent complaint of patients with HCM. Patients with HCM have the same risk factors for coronary artery disease as the general population, but their mortality and morbidity profile is significantly worse due to their concomitant left ventricular dysfunction.19 Possible explanations for atypical chest pain and myocardial ischemia in this population include myocardial bridging, coronary vessel narrowing, impairment of normal compensatory vasodilatation, impaired coronary reserve, and an imbalance in the number of coronary vessels perfusing a hypertrophied ventricular wall.7,8,19

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Heart Failure

Heart failure in patients with HCM is primarily thought to be due to a diastolic restrictive pattern.13 Increased stiffness from myocardial scarring in the left ventricle leads to decreased filling of the left ventricle in diastole. Blood flow backs up into the left atrium and pulmonary arteries leading to left atrial enlargement and symptoms of left-sided HF. Only approximately 15% to 20% of all patients with HCM progress to HF. Historically, HF was a clinical complication thought to be primarily present in elderly individuals with HCM,13 but a recent study of children with HCM ages 1 to 10 years found that the presenting symptom in 7.5% of the these children was HF. During 10 years of follow-up, 50% of the deaths among children in this group were due to HF.15 Approximately 5% of individuals with HCM will develop a form of HF known as the "end stage, burnt out stage or dilated stage."7 This stage is characterized by ventricular remodeling, myocardial wall thinning, and chamber enlargement.7 These patients are often refractory to medical treatment and become candidates for heart transplantation.

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Diagnosis and Clinical Exam

Hypertrophic cardiomyopathy remains a difficult disease to definitively diagnose with genetic testing at this time.14 Therefore, diagnosis rests on echocardiography, physical examination, hemodynamic testing, assessment of family history, and symptoms.

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Echocardiography

Left ventricular hypertrophy greater than 15 mm in the absence of other mechanical, metabolic, or genetic causes for hypertrophy is considered sufficient to diagnose individuals with HCM (Figure 1).4,7 Septal wall hypertrophy is usually greater than the posterior free wall of the left ventricle.4 Because not all people with HCM present with septal hypertrophy, this is neither a sensitive measure nor a specific measure of definitively diagnosing HCM.7 Pressure gradients between the aorta and left ventricle of greater than 30 mm Hg by echocardiography are a sign of severe LVOT7 obstruction, and these patients, approximately 25% of the population of HCM patients, more frequently progress to HF or experience SCD.6,7,20 In individuals with LVOT obstruction, it is not unusual to see systolic anterior motion of the mitral valve on echocardiogram and moderate to severe mitral regurgitation.5,13

FIGURE 1

FIGURE 1

The 2 most common diseases that can reproduce the HCM phenotype are amyloidosis and hypertensive cardiomyopathy; ruling them out as possible etiology of cardiac hypertrophy is important.21 Being able to distinguish normal physiologic changes associated with excellent physical conditioning in athletes from pathologic HCM is also important, considering the dire consequences of one versus the other.3 In general, athletes with extreme physical conditioning may have some degree of normal hypertrophy that does not exceed 12 mm and preserved systolic and diastolic function.22 In athletes with extreme physical conditioning that play combination sports using multiple muscle groups and forms of exercise, it may be difficult to distinguish hypertrophic adaptation from pathologic cardiomyopathy. Therefore, diagnosis requires more sophisticated echocardiography studies such as tissue Doppler and measurement of blood velocity gradients across the myocardial wall. These patients should be referred or managed in conjunction with a congenital cardiologist.10

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Physical Examination

Physical examination includes provocative maneuvers to assess the degree of LVOT obstruction and auscultation. Common findings include a systolic ejection murmur at the left sternal edge radiating to the aortic and mitral areas, and sometimes a pan systolic murmur from mitral regurgitation that radiates to the axilla.5,13 Maneuvers and drugs that affect preload or afterload will affect the loudness of the murmur (Table 1). Exercise testing will help to assess the degree of LVOT obstruction by resulting in a paradoxical response to exercise. With severe LVOT obstruction, the patient's blood pressure will not rise more than 25 points systolically from baseline, or there is a paradoxical response where blood pressure drops with exercise. This finding correlates with the degree of obstruction.7 Further physical inspection can reveal an exaggerated A wave of the jugular venous pulse, rapid upstroke of the carotid arterial pulsation, pulsus bisferiens, double or triple precordial impulse, and a fourth heart sound.5

TABLE 1

TABLE 1

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Electrocardiography

The most common findings on a 12-lead electrocardiogram are consistent with left ventricular hypertrophy and may also often show left atrial enlargement, repolarization abnormalities, pathological Q waves in the inferior leads, and in subsets of this population, giant negative T waves are present or short PR intervals with a slurred QRS upstroke.5,10,13 A 24-hour Holter monitors can reveal paroxysmal atrial fibrillation, supraventricular tachycardia, or ventricular dysrhythmias, which occur frequently in this population.7

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Hemodynamic Testing

Abnormal peripheral vasodilatation in response to exercise is present in up to 25% of people with HCM.10 This manifests as an inability to raise the systolic blood pressure greater than 20% to 25% from baseline or, there is a paradoxical response and blood pressure, falls with exercise. Abnormal exercise response is considered a severe sign of LVOT obstruction and portends a poor prognosis and greater risk of SCD.7,23 Many individuals with LVOT obstruction are asymptomatic at rest and therefore require provocation to assess pressure gradients. Patients with an increased gradient are at a much greater risk of proceeding to HF and therefore benefit from early intervention.6 The American College of Cardiology/European Society of Cardiology consensus statement suggests that exercise testing is the only sensitive way to determine if there is a gradient present.7 Using other inotropic agents like dobutamine to increase myocardial contractility is known to increase gradients in patients with cardiac disease not related to HCM. Therefore, it is not a sensitive measure for diagnosis or determination of LVOT obstruction in individuals with HCM.7

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Family History

Only a few individuals with HCM have a family history of HCM, since up to 60% of mutations are thought to be de novo sporadic mutations.24 The importance of determining whether an individual has HCM based on family history, although not a sensitive measure of diagnosis, guides decisions regarding prophylactic use of an implantable cardiac defibrillator (ICD) to prevent SCD. In addition, appropriate screening can be completed in first-degree relatives if a diagnosis is confirmed. Due to the familial nature of detected HCM, screening of first-degree relatives is necessary. The screening examination includes a thorough history and physical, 12-lead electrocardiogram, and echocardiogram.13 If HCM is suspected in any of the first-degree relatives, further testing should include 24-hour Holter monitoring to rule out dysrhythmias and exercise testing to look for latent LVOT obstruction.13

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Screening

Hypertrophic cardiomyopathy is a disorder that usually presents in the adolescent or late adolescent period perhaps because of the increased somatic growth that occurs during this period.7 Current guidelines suggest initially screening children who are at risk for HCM based on physical evidence or family history with 24-hour Holter monitoring, echocardiography, 12-lead electrocardiogram, exercise testing, and physical examination.13 After initial workup, asymptomatic individuals should undergo annual echocardiogram until they are 18 years old. After age 18, and if they remain asymptomatic, screening echocardiogram can be done every 5 years.4,13

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Treatment

Treatment options for HCM are 4-fold; pharmacologic therapy to increase diastolic filling and reduce the LVOT gradient, surgery to permanently reduce the LVOT obstruction and gradient, pacemaker therapy, and ICD device therapy (Figures 2 and 3). The following discussion will cover these 4 modalities.

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

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Pharmacological Treatment

Pharmacologic therapy is indicated for patients exhibiting symptoms of chronic HF with or without LVOT obstruction. Pharmacologic therapy consists of beta-blockers, calcium channel blockers, and the antidysrhythmic disopyramide.

The choice of whether to first start a beta-blocker or calcium channel blocker is at the discretion of the prescriber. In general, it is recommended that beta-blockers are started first and if they are not effective in reducing symptoms, then the calcium channel blocker verapamil can be started. Using both in conjunction is not recommended. Disopyramide, although it can be the only medication prescribed to a HCM patient, is usually used in conjunction with a low dose of beta-blocker.7

Beta-blockers work by decreasing cardiac inotropy and heart rate. The beneficial effects of this are a prolongation in diastolic ventricular filling, a reduction in cardiac contractility, and a reduction in myocardial oxygen demand. These lead to reduced LVOT outflow gradient and obstruction with exercise. Beta-blockers can be used in patients with or without obstruction but seem to be effective in reducing sympathetic tone associated with exercise. Therefore, they are particularly indicated in patients who exhibit symptoms with exertion. Contraindications for beta-blockers include patients with reactive airway disease. In these patients, a calcium channel blocker may be a better option. Another concern is the use of beta-blockers in children. Their use has been associated with growth retardation, depression, and learning impairments, and use in children must be carefully monitored.7,10,13

Calcium channel blockers work effectively by reducing cardiac inotropy and heart rate through a different mechanism than beta-blockers. They are also effective in promoting ventricular relaxation and slowing heart rate to improve ventricular filling.13 The calcium channel blocker verapamil is recommended for use in HCM patients because it has been studied the most in this group of patients.13 Verapamil is started when patients have contraindications to beta-blockers or when beta-blockers were not effective in reducing symptoms. Calcium channel blockers generally produce coronary vascular smooth muscle relaxation and coronary vasodilatation. As a result, in patients who have severe LVOT obstruction or significant outflow gradients, calcium channel blockers can cause hemodynamic compromise and are therefore not recommended in these patients.7,10,13

Disopyramide is an antidysrhythmic drug whose properties include negative inotropy, peripheral vasoconstriction, and reduction in heart rate. It can be used safely in patients who have significant outflow obstruction or gradients. Disopyramide has a risk of increasing atrioventricular node conduction. Therefore, it is frequently used in conjunction with a beta-blocker for heart rate control.7,10,13

Amiodarone hydrochloride is used in individuals with HCM and atrial fibrillation. Beta-blockers and calcium channel blockers may be used for heart rate control. Patients with HCM who are in atrial fibrillation have an increased risk of stroke and progression to HF.7 In patients with hemodynamic decompensation due to atrial fibrillation, every attempt should be made to convert the patient to normal sinus rhythm by electrical or chemical cardioversion. In addition to use of amiodarone hydrochloride in these individuals, consideration should be given to use of warfarin to prevent stroke.

The clinician caring for the decompensated HCM patient should maintain adequate volume status, reduce inotropy, and reduce myocardial oxygen demand.10,24 In acute treatment of hemodynamic decompensation from HCM, efforts should be made to avoid beta-agonist drugs like dobutamine or dopamine because they worsen LVOT obstruction with their positive chronotropic and inotropic properties. Nitrates can be used in the treatment of ischemia but should be used with caution because they can reduce preload and exacerbate LVOT obstruction. If the patient is hypotensive and addition of a beta-blocker would be detrimental acutely, use of a purely alphaadrenergic agonist such as phenylephrine should be used instead of a mixed beta/alpha-adrenergic agonist drug like epinephrine or dopamine.4 Management of volume status is crucial in patients with severe LVOT or outflow gradients because they are dependent on adequate preload for good cardiac output and reducing the occurrence of the hypertrophied septum collapsing on itself in systole.

As previously mentioned, 5% of patients will reach end-stage HF or the "burnt out" stage.7 At this stage, it is acceptable to treat these patients with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, spironolactone, digitalis, diuretics, and betablockers as per standard of care for patients with HF. Ultimately, these patients end up needing heart transplantation.7,10

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Surgical Treatment

Surgery is recommended in drug refractory patients with severe LVOT obstruction. Surgery is generally considered a palliative measure that improves morbidity but not mortality.20 Having said this, patients with LVOT obstruction have greater ventricular and atrial wall stress, increased myocardial oxygen demands, increased mitral regurgitation, and increased left atrial size. Their risk of developing atrial fibrillation is increased with these complications, and therefore, surgery may help reduce the risk of atrial fibrillation and stroke in these patients, in addition to reducing symptoms related to LVOT obstruction.20 The goal of surgery is to reduce LVOT obstruction by reducing the size of the ventricular septum. This can be done through septal myectomy or septal alcohol ablation. Septal myectomy involves a sternotomy incision and general anesthesia. A small amount of tissue is removed from the interventricular septum immediately abolishing the LVOT gradient. Advantages to this approach include additional repair of abnormal mitral valve leaflets or mitral valve replacement at the same time if indicated.7 Alcohol ablation is less invasive and can be done in the catheterization laboratory. It involves infusion of alcohol through the septal perforator artery resulting in necrosis of interventricular myocardial cells. Abolishment of the gradient is not immediate but depends on necrosis of septal myocardial cells over time.

Despite the relative ease of septal alcohol ablation in skilled hands, septal myectomy remains the gold standard. Complications of septal myectomy are death in 1% to 2% of patients postoperatively, a 1% to 2% chance of complete atrioventricular block requiring a pacemaker, the risk of general anesthesia, and a risk of bleeding, which is generally low.7 The benefits include immediate reduction in the LVOT gradient with a gradient at rest of less than 10 mm Hg, reduction in mitral regurgitation, reduction in myocardial oxygen demand, reduction in ventricular/atrial wall stress, and improvement both objectively and subjectively in exercise tolerance.7,25 Septal ablation is a newer procedure and has the same postoperative 1% to 2% risk of death but has a much higher rate of complete atrioventricular block, 5% to 10%, and less reduction in LVOT gradient at rest (25 mm Hg).7 Success of septal alcohol ablation depends on the anatomical correctness of the septal perforator artery that is used for access to the septum. In up to 20% of people,4 the septal perforator artery may not feed the correct part of the septum that needs to be ablated. In addition, septal alcohol ablation carries the risk of aortic dissection, massive myocardial infarction, and myocardial scarring creating arrhythmogenic substrate.4,7,13 Symptomatic and objective relief is not always immediate with alcohol ablation as it is with septal myectomy. The reason for this is that the effectiveness of septal alcohol ablation depends on necrosis of myocardial cells and ventricular remodeling, which can take up to 3 to 6 months to be complete.6

In individuals not eligible for surgery or alcohol ablation because of age, comorbidities, or personal preference, dual chamber pacemakers have been found to offer some relief from symptoms associated with LVOT obstruction. The positive effects of these pacemaker are thought to be due to excitation of the ventricle, which pulls it away from the opposing wall and reduces the LVOT gradient.6 However, the effectiveness of these pacemakers in patients with LVOT obstructions has not been determined across several randomized trials, and current use is based on primarily anecdotal evidence.7 Dual chamber pacemakers may provide symptomatic relief in up to 50% of individuals. They do not improve objective exercise tolerance, and the measured LVOT gradients are only minimally improved or even worsened. For these reasons, dual-chamber pacemakers are considered a last line choice for elderly individuals who are symptomatic, refractory to drug therapy, and not candidates for septal myectomy or septal alcohol ablation.4,6,7,10

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Bacterial Endocarditis Prevention

The risk for infective endocarditis is increased in individuals with intrinsic mitral valve disease or LVOT obstruction at rest. Therefore, prophylactic antibiotics are advised before these patients receive any dental procedures or surgical procedure in which there is break in skin integrity and risk of contact with blood.7,10

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Prevention of SCD

Significant research has been done examining SCD treatment and prophylaxis (Figure 3). Accepted treatments are placement of ICD and use of amiodarone hydrochloride. Major risk factors exposing an individual to SCD are previous history of sustained ventricular dysrhythmias, aborted cardiac arrest, family history of SCD, unexplained syncope, left ventricular thickness greater than 30 mm, abnormal blood pressure response with exercise, and documented nonsustained ventricular tachycardia. Minor risk factors include atrial fibrillation, myocardial ischemia, LV outflow obstruction, and chronic HF.1,3,4,7,10,13 Placement of an ICD to abort SCD is indicated for individuals who have major risk factors or multiple minor risk factors.13 One study followed patients for 3 years, finding that potentially lethal ventricular dysrhythmias were aborted in 25% of ICD patients. Those receiving shocks were usually younger than 40 years, emphasizing the importance of early screening and prevention.13 Amiodarone hydrochloride has been used with some success prophylactically in individuals at risk for SCD. The results of amiodarone use are not predictable; it requires careful monitoring and has significant risk for side affects.7

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Conclusion

Hypertrophic cardiomyopathy is a genetic cardiovascular disorder that presents with a diverse and difficult clinical spectrum of symptoms and treatment options to clinicians. The clinician caring for patients with HCM has the imperative to detect, treat, and provide education about HCM to prevent SCD and life-threatening complications from LVOT obstruction. This review is intended to fill the knowledge gap in the nursing and advanced practice nursing literature. It should also serve as a guide on how to recognize, screen, diagnose, educate, and treat individuals with HCM.

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Acknowledgment

The author acknowledges Dr Nancy Staggers, Dr Alexa Doig, Dr Kevin Whitehead, and Dr Michael Jurynec for their assistance and critical reading of this manuscript.

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REFERENCES

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17. Maron BJ, Carney KP, Lever HM, et al. Relationship of race to sudden cardiac death in competitive athletes with hypertrophic cardiomyopathy. J Am Coll Cardiol. 2003;41(6):974-980.
18. Biagini E, Coccolo F, Ferlito M, et al. Dilated-hypokinetic evolution of hypertrophic cardiomyopathy: prevalence, incidence, risk factors, and prognostic implications in pediatric and adult patients. J Am Coll Cardiol. 2005;46(8):1543-1550.
19. Sorajja P, Ommen SR, Nishimura RA, Gersh BJ, Berger PB, Tajik AJ. Adverse prognosis of patients with hypertrophic cardiomyopathy who have epicardial coronary artery disease. Circulation. 2003;108(19):2342-2348.
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National Kidney Foundation 2007 Clinical Meetings

April 10-14, 2007

Walt Disney World Swan and Dolphin Hotel in Orlando, FL

Register online at www.nkfclinicalmeetings.org

CM.07 offers innovative educational opportunities for Physicians, Fellows and Residents, Pharmacists, Physician Assistants, Nurse Practitioners, Nephrology Nurses and Technicians, Renal and Clinical Dietitians, and Nephrology Social Workers. The program is designed to create an interactive environment to encourage the flow of ideas between all members of the kidney healthcare team.

The National Kidney Foundation is the major voluntary health organization dedicated to preventing kidney and urinary tract diseases, improving the health and well-being of individuals and families affected by these diseases, and increasing the availability of all organs for transplantation.

Keywords:

advanced practice nurse; cardiomyopathy; hypertrophic cardiomyopathy; sudden cardiac death

© 2007 Lippincott Williams & Wilkins, Inc.