Dilated and Restrictive Cardiomyopathies

Dilated and Restrictive Cardiomyopathies



Cardiomyopathies are diseases of the myocardium associated with cardiac dysfunction.1 Table 1 lists the five types of cardiomyopathy: dilated, hypertrophic, restrictive, arrhythmogenic right ventricular, and unclassified. Many conditions manifest as one form of cardiomyopathy and progress to another. For example, hypertensive heart disease can begin with a hypertrophic pattern and subsequently become a dilated cardiomyopathy. Some diseases have features of more than one type of cardiomyopathy (e.g., sarcoidosis can have features of restrictive and dilated cardiomyopathy at different times in the course of the disease).


Table 1 World Health Organization Classification of Cardiomyopathies



























Type of Cardiomyopathy Features Causative Factors
Dilated Dilated left or both ventricle(s), with impaired contraction Ischemic, idiopathic, familial-genetic, immune, alcoholic, toxic, valvular
Hypertrophic Left or right ventricular hypertrophy, or both Familial, with autosomal dominant inheritance (see elsewhere in this section, “Hypertrophic Cardiomyopathy”)
Restrictive Restrictive filling and reduced diastolic filling of one or both ventricles; normal or near-normal systolic function Idiopathic, amyloidosis, endomyocardial fibrosis
Arrhythmogenic right ventricular cardiomyopathy Fibrofatty replacement of right ventricular myocardium, Uhl’s anomaly (parchment heart) Unknown; familial, usually autosomal dominant inheritance, with incomplete penetrance; possible autosomal recessive inheritance; rare forms associated with typical phenotype (e.g., Naxos disease)
Unclassified Not typical for previous four groups Fibroelastosis, noncompacted myocardium, systolic dysfunction with minimal dilation, mitochondrial disease

Data from Richardson P, McKenna W, Bristow M, et al: Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the definition and classification of cardiomyopathies. Circulation 1996;93:841-842.


Cardiomyopathy often results in the heart failure syndrome, with a number of systemic manifestations. On the other hand, many systemic conditions have cardiac involvement and manifest primarily as heart failure. The cardiomyopathies represent a diverse group of conditions whose final common pathway is myocardial dysfunction. With few exceptions, histologic findings are nonspecific and include myocyte hypertrophy, cellular necrosis, and fibrosis.


There are many known causes of cardiomyopathy. Many systemic diseases have myocardial involvement, which can range from mild to severe (Table 2). The most common cause in developed countries is ischemic cardiomyopathy. In other areas, such as equatorial Africa, infiltrative disease is the leading cause.


Table 2 Causes of Cardiomyopathy



























Cause Disorder
Cardiovascular





Metabolic


Infectious, inflammatory


Toxic Alcohol, cocaine, amphetamines, chemotherapy
Genetic





Tachycardia Tachycardia-induced cardiomyopathy
Pregnancy Peripartum cardiomyopathy

In this chapter, discussion is confined to the definition, prevalence, signs and symptoms, and diagnosis of cardiomyopathies, with the exclusion of hypertrophic cardiomyopathy. Treatment is discussed in the chapter on heart failure.



DILATED CARDIOMYOPATHY




Prevalence


It is difficult to assess the prevalence of cardiomyopathy accurately. Many cases go undiagnosed and patients with undiagnosed cardiomyopathy can present with sudden cardiac death. Strict diagnostic criteria are lacking. Approximately 5 million Americans have symptomatic heart failure, but it has been estimated that 50 million Americans fulfill American Heart Association–American College of Cardiology definitions of classes A and B heart failure (Table 3)2 and are either at risk for or have established structural heart disease in the absence of heart failure symptoms. It is unclear how many people fall into stages B, C, and D combined (those with structural heart disease, with or without heart failure symptoms); most of these people have cardiomyopathies.


Table 3 American Heart Association/American College of Cardiology Staging of Heart Failure


















Stage Definition
A Patients at risk of heart failure, with no structural heart disease
B Patients with structural heart disease, without symptoms of heart failure
C Patients with past or present heart failure symptoms
D Patients with advanced disease (e.g., inotropic support)

Adapted from Hunt SA, Abraham WT, Chin MH, et al; American College of Cardiology; American Heart Association Task Force on Practice Guidelines; American College of Chest Physicians; International Society for Heart and Lung Transplantation; Heart Rhythm Society: ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure): Developed in collaboration with the American College of Chest Physicians and the International Society for Heart and Lung Transplantation: Endorsed by the Heart Rhythm Society. Circulation 2005;112:e154-e235.


The estimated prevalence of idiopathic dilated cardiomyopathy is 0.4 per 1000 of the general population. However, in the future, as more causes are elucidated and more patients are found to have genetic or familial cardiomyopathy, the number of patients with idiopathic disease, a diagnosis of exclusion, will decrease.




Specific Types



Ischemic Cardiomyopathy


Ischemic cardiomyopathy (ICM) is the most commonly identified specific cause of dilated cardiomyopathy, accounting for more than 60% of patients with symptomatic heart failure and many more with asymptomatic left ventricular dysfunction. There are several mechanisms by which coronary artery disease can result in ICM.


Myocardial infarction causes localized myocyte necrosis, with resultant scar formation and loss of contractile function in the ventricular segment perfused by the culprit artery. In addition, the myocardium distal to the area of infarction develops increased wall stress, adverse remodeling, and chamber dilation, so that a cardiomyopathic process occurs in adjacent nonischemic areas.


Another mechanism for myocardial dysfunction is hibernation, in which areas of myocardium are chronically underperfused and metabolically less active. These areas remain metabolically intact but do not contribute to the mechanical activity of the heart. Identification of these areas and restoration of their perfusion through revascularization might improve the ejection fraction and long-term prognosis.


Additional features of ICM include the development of mitral valvular regurgitation, which may be caused by papillary muscle dysfunction or functional factors, such as failure of mitral valve leaflets to coapt in a dilated ventricle. This further increases the volume overload state, increasing myocardial energy demands and causing a vicious cycle of worsening systolic dysfunction.


Atrial and ventricular arrhythmias occur commonly in ICM and include atrial fibrillation, which can further compromise contractile function. The development of atrioventricular conduction delays with the necessity for permanent pacemaker insertion can also cause pacing-induced dyssynchrony when pacing is performed from the right ventricular apex alone.


ICM is generally ascribed to epicardial coronary atherosclerosis, but it can also occur in any vasculitic process (e.g., Takayasu’s arteritis), congenital abnormalities (including aberrant coronary arteries), embolic conditions (e.g., atrial fibrillation, endocarditis, thrombophilic states), cardiac allograft vasculopathy, and microvascular ischemia.



Idiopathic Dilated Cardiomyopathy


The term idiopathic dilated cardiomyopathy is applied to most patients with nonischemic cardiomyopathy. With progress in the field of gene analysis, it is likely that many patients with idiopathic cardiomyopathy will receive a specific molecular or genetic diagnosis in the future.


Acute myocarditis may be a more common prelude to dilated cardiomyopathy than was once believed. The natural history of acute myocarditis is largely unknown because it is rarely symptomatic. It is most commonly caused by Coxsackie group B viruses. Overall, approximately 50% of patients who receive a diagnosis of acute viral myocarditis develop dilated cardiomyopathy. Up to 76% of patients with nonischemic dilated cardiomyopathy who have had a clinically recognized episode of myocarditis have genomic viral DNA persistence in myocardial samples. Despite this, endomyocardial biopsy (EMB) rarely shows myocarditis in patients with new-onset cardiomyopathy. Most have nonspecific histologic findings by light microscopy. There is significant interobserver variability in the pathologic diagnosis of myocarditis.4


No specific genetic abnormality is recognized as causing dilated cardiomyopathy. Numerous abnormalities have been found. There are many putative mechanisms in the development of familial cardiomyopathy beyond the scope of this chapter; all forms of mendelian inheritance have been observed, including autosomal dominant, recessive, X-linked, and mitochondrial (matrilinear).5


Hypertensive heart disease can initially manifest as left ventricular hypertrophy with isolated diastolic dysfunction and preserved systolic function, as assessed by conventional echocardiographic techniques. Because remodeling occurs over time, the hypertrophy can progress to a dilated cardiomyopathy with systolic dysfunction. Atrial fibrillation is a common manifestation of hypertensive heart disease. Hypertensive heart disease is the leading identifiable cause of heart failure in older women.




Toxic Cardiomyopathies


Alcoholic cardiomyopathy may account for approximately 4% of all cardiomyopathies, and men have a significantly worse prognosis.6 The average duration of heavy drinking (more than 90 g/day) in most cohorts is 15 years. Diastolic dysfunction usually precedes any evidence of systolic dysfunction. Left ventricular dilation is an early finding. Hypertension, atrial fibrillation (holiday heart), and coronary disease are more common in heavy drinkers. Identification of alcohol as a potential cause of cardiomyopathy is vital; abstinence can result in an improved ejection fraction in 50% of patients medically treated for heart failure, and continued drinking can result in further deterioration of cardiac function. The mechanism of alcohol-induced cardiomyopathy is unclear but might involve disturbances in intracellular calcium transients, mitochondrial disruption, decreased myofibrillary proteins, and myocyte apoptosis. Histologic findings are nonspecific.


Cocaine and amphetamines (including 3,4-methylenedioxymethamphetamine, or ecstasy) can result in dilated cardiomyopathy with single and chronic use.7 The cause is multifactorial and includes direct myocyte toxicity, tachycardia-induced injury, hypertension, and myocardial infarction.


Doxorubicin can cause cardiomyopathy with characteristic histopathologic features. Trastuzumab, used in the treatment of metastatic breast cancer, can cause a cardiomyopathy. Unlike anthracycline-induced toxicity, it usually responds to standard treatment or the discontinuation of trastuzumab.8 Brain natriuretic peptide (BNP) is proving useful in monitoring cardiac function in patients receiving cardiotoxic chemotherapy, because elevation of the BNP level occurs at an early stage in the condition. Hydroxychloroquine can cause skeletal and cardiac myopathies.


Peripartum cardiomyopathy is dilated cardiomyopathy arising in the last month of pregnancy or within 5 months postpartum.9 Of these cases, 75% occur in the first 2 months after delivery. Risk factors include age older than 30 years, multiparity, twin pregnancy, African descent, and a family history of peripartum cardiomyopathy.10 Its cause is unknown but may be related to reduced suppressor T cell activity, which occurs during pregnancy, and can result in an autoimmune type of myocardial inflammation or activation of myocarditis. Recovery, usually within 6 months, occurs in 50% of patients. Patients should be advised not to have more children. (See the chapter “Pregnancy and Heart Disease.”)

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Jul 18, 2017 | Posted by in GENERAL SURGERY | Comments Off on Dilated and Restrictive Cardiomyopathies

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