Dilated cardiomyopathy
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Dilated cardiomyopathy or DCM (also known as congestive cardiomyopathy), is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is dilated, often without any obvious cause. About one in three cases of congestive heart failure (CHF) is due to dilated cardiomyopathy. Harrison's Principles of Internal Medicine, 16th edition. Kasper, Braunwald, Fauci, Hauser, Longo, Jameson. ISBN 0-07-139140-1
A cardiomyopathy is any disease that primarily affects the muscle of the heart. In DCM, left and/or right ventricular systolic pump function of the heart is impaired, leading to progressive cardiac enlargement and hypertrophy, a process called remodeling. Harrison's Principles of Internal Medicine, 16th edition. Kasper, Braunwald, Fauci, Hauser, Longo, Jameson. ISBN 0-07-139140-1
Dilated cardiomyopathy is the most common form of cardiomyopathy. It occurs more frequently in men than in women, and is most common between the ages of 20 and 60 years.Robbins Basic Pathology, 7th edition. Kumar, Cotran, Robbins. ISBN 0-7216-9274-5
Although no cause is apparent in many cases, dilated cardiomyopathy is probably the end result of myocardial damage produced by a variety of toxic, metabolic, or infectious agents. It may be the late sequel of acute viral myocarditis, possibly mediated through an immunologic mechanism. Alcohol abuse is also strongly associted with the development of dilated cardiomyopthy in some cases. Autoimmune mechanisms are also suggested as a cause for dilated cardiomyopathy.San Martin MA, Garcia A, Rodriguez FJ, Terol I. Dilated cardiomyopathy and autoimmunity: an overview of current knowledge and perspectives. Rev Esp Cardiol. 2002 May;55(5):514-24. PMID 12015932
A reversible form of dilated cardiomyopahty may be found with alcohol abuse, pregnancy, thyroid disease, cocaine use, and chronic uncontrolled tachycardia.
Genetics
About 20-40% of patients have familial forms of the disease, with mutations of genes encoding cytoskeletal, contractile, or other proteins present in myocardial cells.Ross J Jr. Dilated cardiomyopathy: concepts derived from gene deficient and transgenic animal models. Circ J. 2002 Mar;66(3):219-24. PMID 11922267 The disease is genetically heterogenous, but the most common form of its transmission is an autosomal dominant pattern. Autosomal recessive, X-linked, and mitochondrial inheritance of the disease is also found.Schonberger J, Seidman CE. Many roads lead to a broken heart: the genetics of dilated cardiomyopathy. Am J Hum Genet. 2001 Aug;69(2):249-60. Epub 2001 Jul 6. PMID 11443548Although the disease is more common in African-Americans than in whites, it may occur in any patient population.
Associated symptoms
For many affected individuals, Dilated Cardiomyopathy is a condition which will not limit the quality or duration of life. A minority, however, experience significant symptoms and there is sometimes a risk of sudden death. Evaluation by a cardiologist is recommended to confirm the diagnosis and to assess the outlook and particularly the risk of complications. In some pations symptoms of left- and right-sided congestive heart failure develop gradually. Left ventricular dilatation may be present for months or even years before the patient becomes symptomatic.Vague chest pain may be present, but typical angina pectoris is unusual and suggests the presence of concomitant ischemic heart disease. Syncope due to arrhythmias, and systemic embolism may occur.
Physical examination
The patients may present variable degrees of cardiac enlargement, and findings of congestive heart failure. In advance stages of the disease, the pulse pressure is narrowed and the jugular venous pressure is elevated. Third and fourth heart sounds are common. Mitral or tricuspid regurgitation may occur, presented by systolic murmurs upon auscultation (see mitral regurgitation and tricuspid insufficiency for more details about the findings).Laboratory examinations
Generalized enlargement of the heart is seen upon normal chest X-ray. Pleural effusion may also be noticed, which is due to pulmonary venous hypertension.The electrocardiogram often shows sinus tachycardia or atrial fibrillation, ventricular arrhythmias, left atrial abnormality, and sometimes intraventricual conduction defects and low voltage. Echocardiogram shows left ventricular dilatation with normal or thinned walls and reduced ejection fraction. Cardiac catheterization and coronary angiography are often performed to exclude ischemic heart disease.
Treatment
Years ago the statistic was that the majority of patients, particularly those over 55 years of age, died within 3 years of the onset of symptoms (stage 5 of CHF) – and such figures can still be found in some textbooks. The situation has improved dramatically in recent years with drug therapy that can slow down progression and in some cases even improve the heart condition. Death is due to either congestive heart failure or ventricular tachy- or bradyarrhythmias.Patients are given the standard therapy for heart failure, including salt restriction, angiotensin-converting enzyme (ACE) inhibitors, diuretics, and digitalis. Anticoagulants may also be used. Alcohol should be avoided. Artificial pacemakers may be used in patients with intraventricular conduction delay, and implantable cardioverter-defibrillators in those at risk of arrhythmia. These forms of treatment have been shown to improve symptoms and reduce hospitalization.
In patients with advanced disease who are refractory to medical therapy, cardiac transplantation should be considered.
Alternative treatment
Some tested and untested alternative treatments are promoted by some, including food supplements Coenzyme Q10, L-Carnitine, Taurine and D-Ribose.The benefits of Coenzyme Q10 in treating of cardiomyopathy and heart failure are supported by some scientific studies such as:
[University of Texas, 1992, testing Q10 on eleven exemplary transplant candidates]
[Department of Medicine, Scott & White Clinic, Temple, Texas, 1990, testing Q10 on 143 patients]
[Buzzi Hospital, Italy, 1994, testing Q10 on 3600 patients]
Dilated cardiomyopathy in dogs
Dilated cardiomyopathy is a heritable disease in some dog breeds, including the Boxer, Dobermann, and St Bernard. Treatment is based on medication, including ace inhibitors, loop diuretics and phosphodiesterase inhibitors.
References
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