Cardiomyopathy, dilated
Cardiomyopathy, dilated: Excerpt from Handbook of Diseases
Resulting from extensively damaged myocardial muscle fibers, dilated cardiomyopathy interferes with myocardial metabolism and grossly dilates all four chambers of the heart. This gives the heart a globular appearance. In this disorder, hypertrophy may be present.
Dilated cardiomyopathy leads to intractable heart failure, arrhythmias, and emboli. The prognosis for patients with dilated cardiomyopathy without evidence of heart failure varies: some patients’conditions remain stable, some gradually deteriorate, and others rapidly decline. Once heart failure is apparent, the natural history is similar to that of other causes of heart failure.
Causes
The origin of most cardiomyopathies is unknown. Occasionally, dilated cardiomyopathy results from myocardial destruction by toxic, infectious, or metabolic agents, such as certain viruses, endocrine and electrolyte disorders, and nutritional deficiencies. Other causes include muscle disorders (myasthenia gravis, progressive muscular dystrophy, myotonic dystrophy), infiltrative disorders (hemochromatosis, amyloidosis), and sarcoidosis.
Cardiomyopathy may be a complication of alcoholism. Although the condition may improve if the patient abstains from alcohol, it will recur when he resumes drinking.
How viruses induce cardiomyopathy is unclear, but investigators suspect a link between viral myocarditis and subsequent dilated cardiomyopathy, especially after infection with poliovirus, coxsackievirus B, influenza virus, or human immunodeficiency virus.
Metabolic cardiomyopathies are related to endocrine and electrolyte disorders and nutritional deficiencies. Thus, dilated cardiomyopathy may develop in patients with hyperthyroidism, pheochromocytoma, beriberi (thiamine deficiency), or kwashiorkor (protein deficiency). Cardiomyopathy may also result from rheumatic fever, especially among children with myocarditis.
Antepartal or postpartal cardiomyopathy may develop during the last trimester or within months after delivery. Its cause is unknown, but the condition is most common in multiparous women older than age 30, particularly those with malnutrition or preeclampsia. In these patients, cardiomegaly and heart failure may reverse with treatment, allowing a subsequent normal pregnancy. If cardiomegaly persists despite treatment, the prognosis is extremely poor.
Clinical tip Dilated cardiomyopathy has a 50% mortality after 5 years; 50% of patients improve to normal within the first few months of delivery.
Signs and symptoms
With dilated cardiomyopathy, the heart ejects blood less efficiently than usual. Consequently, a large volume of blood remains in the left ventricle after systole, causing signs and symptoms of heart failure —both left-sided (shortness of breath, orthopnea, exertional dyspnea, paroxysmal nocturnal dyspnea, fatigue, and an irritating dry cough at night) and right-sided (edema, liver engorgement, and jugular vein distention).
Physical examination reveals cardiomegaly, an S3 gallop rhythm and, often, a murmur resulting from functional mitral insufficiency.
Diagnosis
❑ Echocardiography confirms the presence of dilated cardiomyopathy.
❑ Exercise thallium-201 scintigraphy may suggest underlying coronary artery disease.
❑ Electrocardiography (ECG) and angiography are used to rule out ischemic heart disease; ECG may also show biventricular hypertrophy, sinus tachycardia, atrial enlargement and, in 20% of patients, atrial fibrillation and bundle-branch heart block.
❑ Chest X-ray demonstrates cardiomegaly — usually affecting all heart chambers — and may demonstrate pulmonary congestion, pleural or pericardial effusion, or pulmonary hypertension.
Treatment
Therapeutic goals include correcting the underlying causes and improving the heart’s pumping ability with digoxin, a diuretic, oxygen, and a sodium-restricted diet. Other options may involve bed rest and a steroid.
Vasodilators reduce preload and afterload, thereby decreasing congestion and increasing cardiac output. Acute heart failure requires vasodilation with I.V. nitroprusside or I.V. nitroglycerin. Long-term treatment may include hydralazine, isosorbide dinitrate, an angiotensin-converting enzyme inhibitor, and an anticoagulant.
When these treatments fail, therapy may require heart transplantation, though only for carefully selected patients. Cardiomyoplasty, which wraps the latissimus dorsi muscle around the ventricles, helps the ventricle to effectively pump blood. A cardiomyostimulator delivers bursts of electrical impulses during systole to contract the muscle.
Give your patient specific care instructions prior to his dimissal. (See Discharge instructions.)
Special considerations
❑ If the patient has acute failure, monitor him for signs of progressive failure (bilateral crackles, increased neck vein distention) and compromised renal perfusion (oliguria, increased blood urea nitrogen and creatinine levels, electrolyte imbalances). Weigh him daily.
❑ If the patient is receiving a vasodilator, frequently check his blood pressure and heart rate. If he becomes hypotensive, stop the infusion and place him in a supine position, with his legs elevated to increase venous return and to ensure cerebral blood flow.
❑ If the patient is receiving a diuretic, monitor him for signs of resolving congestion (decreased crackles and dyspnea) or too vigorous diuresis. Check the serum potassium level for hypokalemia and renal function for increased creatinine level, especially if therapy includes digoxin.
❑ Before discharge, teach the patient about his illness and its treatment.
Clinical tip Therapeutic restrictions and an uncertain prognosis can cause profound anxiety and depression, so offer support and let the patient express his feelings. Be flexible with visiting hours.
❑ Encourage the patient’s family members to learn cardiopulmonary resuscitation.
Pictures
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.
More About Dilated cardiomyopathy
More Medical Textbooks Online about Dilated cardiomyopathy
Review other book chapters online related to Dilated cardiomyopathy:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
|
|
More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
|
|
» Next page: Cardiomyopathy, hypertrophic (Handbook of Diseases)
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
