Cardiomyopathy, hypertrophic
Cardiomyopathy, hypertrophic: Excerpt from Handbook of Diseases
A primary disease of the cardiac muscle, hypertrophic cardiomyopathy is characterized by disproportionate, asymmetric thickening of the interventricular septum in relation to the free wall of the left ventricle (3:1 ratio). With hypertrophic cardiomyopathy — previously known as idiopathic hypertrophic subaortic stenosis—cardiac output may be low, normal, or high, depending on whether stenosis is obstructive or nonobstructive.
The natural history of hypertrophic cardiomyopathy varies. Some patients may remain asymptomatic for years. The dyspnea that results is primarily due to markedly impaired diastolic compliance rather than systolic dysfunction. Sudden death, especially during exercise, may be the initial event, as has occurred with certain athletes (attributed to 36% who died suddenly).
Causes
Despite being designated as idiopathic in almost all cases, hypertrophic cardiomyopathy may be inherited as a non-sex-linked autosomal dominant trait. Most patients have obstructive disease, resulting from effects of ventricular septal hypertrophy and the movement of the anterior mitral valve leaflet into the outflow tract during systole. Eventually, left ventricular dysfunction, from rigidity and decreased diastolic compliance, causes pump failure.
Signs and symptoms
The primary signs and symptoms of hypertrophic cardiomyopathy are exertional dyspnea (90% of patients), angina (75% of patients), and syncope. The chest pain is atypical in that it usually occurs at rest, is prolonged, has no relation to exertion, and isn’t relieved by a nitrate. When sudden death occurs, it may be the first indication of the disease.
Signs and symptoms of the disorder may not appear until it’s well advanced, when atrial dilation and, possibly, atrial fibrillation abruptly reduce blood flow to the left ventricle. Reduced inflow and subsequent low output may produce angina pectoris, arrhythmias, dyspnea, orthopnea, syncope, heart failure, and death.
Clinical tip The most common symptoms of hypertrophic cardiomyopathy are dyspnea and chest pain. Syncope is also common, usually occurring after exertion.
Auscultation reveals a medium-pitched systolic ejection murmur along the left sternal border and at the apex. This murmur increases with Valsalva’s maneuver and decreases with squatting. Palpation reveals a peripheral pulse with a characteristic double impulse (pulsus biferiens) and, with atrial fibrillation, an irregular pulse and loud S4.
Diagnosis
❑ Echocardiography (most useful) shows increased thickness of the intraventricular septum and abnormal motion of the anterior mitral leaflet during systole, occluding left ventricular outflow in obstructive disease.
❑ Cardiac catheterization reveals elevated left ventricular end-diastolic pressure and, possibly, mitral insufficiency.
❑ Electrocardiography usually demonstrates left ventricular hypertrophy, T-wave inversion, left anterior hemiblock, Q waves in precordial and inferior leads, ventricular arrhythmias and, possibly, atrial fibrillation.
Treatment
The goals of treatment are to relax the ventricle and to relieve outflow tract obstruction. Beta-adrenergic blockers slow the heart rate and increase ventricular filling by relaxing the obstructing muscle, thereby reducing angina, syncope, dyspnea, and arrhythmias. However, they may aggravate symptoms of cardiac decompensation. Atrial fibrillation necessitates cardioversion to treat the arrhythmias and, because of the high risk of systemic embolism, anticoagulant therapy. Calcium channel blockers (such as verapamil) may improve diastolic dysfunction until fibrillation subsides.
Surgical alternatives
If drug therapy fails, surgery may be indicated. Ventricular myotomy (resection of the hypertrophied septum) alone or combined with mitral valve replacement may ease outflow tract obstruction and relieve symptoms. However, ventricular myotomy may cause complications, such as complete heart block and ventricular septal defect, and is experimental.
Dual-chamber pacing may prevent progression of hypertrophy and obstruction. Implantable defibrillators may be used in patients with malignant ventricular arrhythmias.
Special considerations
❑ Because syncope or sudden death may follow well-tolerated exercise, warn patients against any strenuous physical activity, such as running and weight lifting.
Clinical TIP Avoid nitroglycerin, digoxin, and diuretics because they can worsen obstruction.
❑ If the patient is to have dental work or surgery, administer prophylaxis for subacute bacterial endocarditis beforehand.
❑ Provide psychological support. If the patient is hospitalized for a long time, be flexible with visiting hours.
❑ Refer the patient for psychosocial counseling to help him and his family accept his restricted lifestyle and the poor prognosis.
❑ If the patient is a child, have his parents arrange for him to continue his studies in the facility.
❑ Because sudden cardiac arrest is possible, urge the patient’s family to learn cardiopulmonary resuscitation.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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