Mr. J, aged 27 years, was diagnosed with a heart condition 10 years earlier and was placed on a beta blocker. Since his initial diagnosis, he received limited surveillance monitoring for his condition and was no longer taking the beta blocker. He had recently moved to another state, and his new employer requested a cardiac evaluation.
Mr. J reported occasional palpitations with physical activity and mild dyspnea after climbing a flight of stairs. Family history included a brother and father with heart problems. There was a family history of sudden cardiac death (SCD). Mr. J did not use tobacco or recreational drugs. He played noncompetitive racquetball and softball on a regular basis.
The patient’s ECG revealed normal sinus rhythm with ST-T wave changes in anterolateral leads and no Q waves. Physical exam revealed a 2/6 mid-systolic murmur at the left-upper-sternal border that increased with the Valsalva maneuver. Mr. J’s exercise echocardiogram showed severe left atrial enlargement, mild mitral valve insufficiency, septal thickness 2.8 cm (an increase from 1.8 cm over the past three years), and left ventricular outflow gradient of 15 mm Hg at rest, increasing to 32 mm Hg with Valsalva.
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During the treadmill, Mr. J. demonstrated good exercise tolerance with an abnormal BP response with exercise. A 24-hour Holter monitor revealed one premature beat and no arrhythmias or ventricular tachycardia. A stress cardiac MRI revealed normal cardiac function, myocardial scarring of the intraventricular septum of 10%, severe asymmetric left ventricular hypertrophy (LVH), septal thickness of 3.2 cm, no perfusion abnormalities, and mild mitral insufficiency.
Mr. J. was referred to an electrophysiologist for evaluation of his risk for SCD. The electrophysiologist recommended placement of an implantable cardioverter-defibrillator (ICD). After a lengthy discussion regarding his risk for SCD and the recommendation for ICD, Mr. J opted to defer his decision for the time being. He was given a prescription for a beta blocker, instructed to report any related symptoms immediately or go to the emergency department, and to return to clinic in six months for follow-up.
1. Description
Cardiomyopathies are a group of diseases characterized by dysfunction of the myocardium. Hypertrophic cardiomyopathy (HCM) is predominantly a hereditary condition typified by increased thickening of the myocardium, stiffness of the left ventricle, mitral valve changes, and cellular deficiencies. The thickened myocardium becomes stiff, making it hard for the heart to relax and allowing for inadequate filling of the heart chambers. As a result of the filling defects, the heart does not pump enough blood, especially during exercise. Many people with HCM are asymptomatic and lead normal lives, while others are symptomatic with a decreased quality of life. A small number of people with HCM will die suddenly.
2. Incidence
HCM is the second most prevalent form of heart muscle disease, affecting an estimated 600,000 to 1.5 million Americans, or one in every 500 persons. Generally, younger people diagnosed with HCM have a relative with either asymptomatic or undiagnosed disease. Accurately defining a population at risk becomes difficult since the cause of HCM varies.
3. Etiology
The three major forms of HCM are (1) familial, (2) sporadic, and (3) those associated with unknown causes. The familial form, or primary cause of HCM, is usually more severe and tends to be diagnosed mainly in young persons. In this patient population, it is thought that HCM is caused by a defect with gene mutation that controls heart-muscle growth. There are many gene mutations that can lead to HCM, thus the type of HCM that develops will vary within families.
The sporadic form, or secondary cause of HCM, is usually seen in older individuals and is attributable to high BP, valvular heart disease, congenital heart defects, or the aging process.
Rarely, HCM is diagnosed without evidence of cause.
4. Pathophysiology
Thickening or hypertrophy of the myocardium most commonly occurs at the septum but can occur in other areas of the heart, such as the apex within the right and left ventricle. As the septum becomes thickened, narrowing reduces the flow of blood from the left ventricle to the aorta. The result is a condition called outflow tract obstruction, commonly referred to as hypertrophic obstructive cardiomyopathy, which ultimately obstructs blood flow. The ventricles become weakened by the increased pumping needed to overcome the narrowed passage.
As the myocardium thickens, cellular changes occur within the heart, leading to a stiff left ventricle. The left ventricle is unable to relax properly, and inadequate filling results. With less blood in the ventricle at filling, less oxygenated blood is then pumped to other organs and muscles. This results in increased pressures within the heart and associated symptoms.
Mitral-valve changes take place as the result of narrowing of the left ventricular outflow tract, leading to obstruction and increased pressures within the left ventricle. Mitral regurgitation or leaking of the valve occurs, causing backflow of blood from the left ventricle back into the left atrium of the heart.
On microscopic examination, the cells of the heart in HCM patients appear irregular and disorganized. These changes can cause electrical disturbances or ventricular arrhythmias as the electrical conduction travels through the lower chambers of the heart.
In rare cases, the myocardium will thin and the left ventricle will dilate, leading to a decline in heart function and the development of heart failure. This is known as dilated cardiomyopathy.
5. Clinical features
The presentation and progression of HCM varies greatly. Among children, HCM may cause no or mild symptoms in some, while others may have more profound symptoms, such as heart failure. As the youngster approaches late childhood and early adolescence, symptoms of HCM may manifest due to rapid growth and development. The symptoms of HCM often become apparent with exercise associated with competitive sports. In the presence of obstruction, the first sign of HCM may be a systolic heart murmur that increases with Valsalva maneuvers.
The severity of HCM symptoms varies with the location and extent of hypertrophy, presence of obstruction, occurrence of heart failure, or arrhythmias. Associated symptoms of HCM include:
Shortness of breath and fatigue, especially with exercise.This symptom can be associated with the backup of pressure in the left atrium and lungs.
Angina pectoris or chest pain.This can occur with or without exercise, and frequently after eating.
Presyncope or syncope.This can be idiopathic in nature or may occur as the result of irregular heart rhythms or the inadequacy of blood vessels during exercise.
Palpitations. This symptom can be associated with such rhythm abnormalities as atrial fibrillation (AF) or ventricular tachycardia. (The risks for blood clots and heart failure increase with AF.)
SCD.This can be the presenting symptom of persons with HCM.
Whereas many people with HCM can live a productive life without debilitating symptoms, others may develop conditions that shorten their lives or have negative effects on their quality of life.
The occurrence of ventricular fibrillation or ventricular tachycardia can lead to sudden cardiac arrest or loss of heart function. If not properly treated with immediate CPR and defibrillation, SCD occurs. Although most people with HCM are at relatively low risk for SCD, it is more prominent among young athletes and people under the age of 30 years.
Despite thickening of the myocardium, the heart is usually able to pump adequately in people with HCM. In some cases, stiffness of the myocardium may occur, forcing the heart to work harder and leading to heart failure.
6. Diagnosis
In the absence of a prior diagnosis of HCM, a history of symptoms or evidence of familial SCD associated with HCM may raise suspicions. Auscultation of distant heart sounds or detection of a cardiac murmur may also raise your antennae. Once assumed, the diagnosis of HCM is further differentiated by several diagnostic tests:
ECG may reveal evidence of LVH and abnormal Q waves present in anterolateral and inferior leads.
Chest x-ray can be normal or reveal cardiomegaly.
Echocardiography is used for detecting muscle thickness, the degree of obstruction, and the presence of valvular abnormality.
A 24-hour Holter monitor is worn to determine presence of cardiac arrhythmias (mainly nonsustained ventricular tachycardia).
An exercise treadmill test is used to objectively diagnose exercise tolerance, BP response, and heart rate and rhythm.
Cardiac MRI is an evolving tool used in the initial diagnosis of HCM and used to accurately identify persons who are at risk for SCD.
Cardiac MRI is unmatched for assessing myocardial structure, function, and such tissue characteristics as myocardial scarring in persons with HCM. Cardiac MRI has a more precise measurement technique for wall thickness and greater predictability for SCD than echocardiography.
7. Treatment options
Before deciding on optimal therapy for HCM, perform a thorough medical exam. Treatment options are focused on reducing symptoms associated with HCM and preventing SCD. Such medications as beta blockers or calcium channel blockers help relax the heart muscle, allowing for adequate filling and better pumping capacity to improve symptoms. If arrhythmias are present, anti-arrhythmic drugs may be indicated. In the presence of AF, anticoagulants may be needed for antithrombotic effect.
In cases in which obstruction is present, a permanent pacemaker can relieve some of the obstruction and associated symptoms. The effectiveness of this treatment is less than 40% and is usually reserved for older patients who do not want to undergo more invasive therapy, such as surgical myectomy or septal ablation.
Surgical myectomy is an open-heart procedure in which the septal muscle blocking the flow of blood is surgically removed. For persons with severe symptoms of HCM and obstruction, this is considered the recommended treatment. Surgical myectomy has a success rate of 90% to 95%. The majority of surgical myectomy patients are able to return to normal activities.
In septal ablation, a catheter inserted into the groin injects alcohol into the arteries supplying the thickened myocardium. Over time, the alcohol will destroy that portion of the thickened myocardium, reducing the obstruction and associated symptoms of HCM. The success rate of this procedure is limited because it is often difficult to identify the artery distribution that supplies blood to the thickened myocardium. Post-procedure complications include heart block, and the long-term effects of septal ablation have not been determined.
Beyond the cardiac issues, the psychiatric components associated with HCM must also be recognized and treated. Panic attacks and depression are common among HCM patients. The fear of SCD is emotionally isolating for some patients and can alter their sense of identity.
Treatment for panic attacks and depression includes medication and/or psychotherapy and patient education. Choose the type of drug treatment carefully, since some psychiatric agents may cause hypotension, worsening HCM. Selective serotonin reuptake inhibitors—mainly citalopram (Celexa) and sertraline (Zoloft)—have the least effect on lowering BP and can be beneficial in the treatment of depression. Some patients with HCM may require the help of a psychiatrist. Provide the patient with accurate information about SCD to calm his or her fears. Some studies show a trend toward improvement of cardiac outcomes through recognition and treatment of depression, panic attacks, and other psychiatric illnesses.
8. Prognosis
The majority of people with HCM are able to maintain a normal lifestyle and life span. Symptoms may develop gradually, suddenly, or not at all. It is important for clinicians to identify patients who are at a higher risk for SCD, which include:
- Those who have a family history of SCD caused by HCM
- Those in whom the onset of symptoms manifests early in childhood and are associated with episodes of presyncope or syncope
- Those who have an abnormal BP response of <20 mm Hg increase in systolic pressure during exercise
- Those who experience such arrhythmias as nonsustained ventricular tachycardia
- Those with outflow tract obstruction and/or LVH >20 mm (With LVH >30 mm, the risk of SCD is 20% at 10 years and 40% at 20 years, doubling every 10 years.)
- Those with significant left-atrial enlargement
- Those with severe symptoms and decrease in heart function
- Those with myocardial scarring >10% as detected by cardiac MRI (more scarring correlates to an increased risk of arrhythmias and SCD)
When two or more SCD risk factors are present, such preventive measures as anti-arrhythmia medication and placement of an ICD are warranted.
9. General guidelines and considerations
People diagnosed with HCM should not engage in strenuous activities or competitive sports and should limit activity to mild aerobic exercise. Dehydration can exacerbate the symptoms of HCM. Administer antibiotics before dental or surgical procedures to prevent infective endocarditis. Since HCM can be hereditary and manifest at different stages of life, family members of individuals diagnosed with HCM should be screened every three years in adolescence and every five years in adulthood. Family members of HCM patients should learn CPR. People with hypertension should maintain adequate BP control. HCM patients should notify their clinician immediately if any unusual symptoms occur.
10. Conclusion
Five months after clinical evaluation, Mr. J’s young son found him dead in the garage. Mr. J had three risk factors for SCD: a thickened intraventricular septum >30 mm, severe left-atrial enlargement, and abnormal BP response with exercise, making a strong case for an ICD.
The risk of SCD had been identified in Mr. J and recommended options for management had been explained in detail to him. For unknown reasons the patient declined ICD placement. It is unclear whether Mr. J continued his beta-blocker therapy or intended to comply with follow-up instructions.
Management of people with HCM must be individualized according to many variables, including symptoms and risk of SCD, the person’s perception of disease and emotional issues, and the provider’s evaluation and knowledge of the disease process.
Both the control of symptoms associated with the disease and the prevention of SCD have a profound impact on patient outcome. The health-care team must have a basic understanding of the multifaceted nature of HCM to provide appropriate care to this patient population.
