DCM is a progressive ventricular wall thinning and dilatation accompanied with gradual functional impairment. It should not be a final diagnosis but rather a basis for further in-depth investigations. DCM is far less common than CAD and arterial hypertension, DCM is the third cause of heart failure. In a majority of patients, dilated cardiomyopathy involves the inflammatory process and genetics however the causes are usually largely unknown.

• Cardiomyopathy is a myocardial disorder; Types - Dilated (DCM), hypertrophic (HCM) restrictive (RCM), and arrhythmogenic right ventricular (ARVC). Echocardiography is used to establish the type of cardiomyopathy. However, types may, as end-stage (dilated) HCM, or ARVC with predominantly left ventricular involvement often overlap each other or mimic one other. 

• The phenotype of DCM is established by means of imaging studies – echocardiography being the most common. (American Society of Echocardiography's Guidelines and Standards Committee; European Association of Echocardiography. J Am Soc Echocardiogr. 2005 Dec;18(12):1440-63.) The cardiomyopathy is considered dilated if the following criteria can be observed in echocardiography; 1) left ventricular end-diastolic diameter (LVEDd) > 117% of the age and body surface 2) left ventricular systolic dysfunction (LVSD) defined by left ventricular ejection fraction (LVEF)<45% and/or 3) fractional shortening (FS) < 25%. 

• DCM is a major cause of sudden death in young adults (Long-term prognostic impact of therapeutic strategies in patients with idiopathic dilated cardiomyopathy: changing mortality over the last 30 years. Merlo M1, ... , Sinagra G. Eur J Heart Fail. 2014 Mar;16(3):317-24. doi: 10.1002/ejhf.16.) and is currently the most frequent diagnosis in patients referred for heart transplantation. Dilated cardiomyopathy is a severe myocardial disease that results in high morbidity and mortality, especially in young adults. The course of the disease is unpredictable, from relatively mild to severe and rapid, progressing to death.

• DCM often unmasks during the first or secound trimester. The few cases of classical DCM in pregnancy describe marked deterioration. LVEF <40% predicts high risk and if LVEF is <20%, maternal mortality is very high & termination of pregnancy should be considered. (ESC guideline 2011; CVD during pregnancy)

Stage I – Screening (green arrow)

• Exclusion of CAD, HTA, valvular heart disease or congenital heart disease.

 

Stage II – Identification of “diagnosable” causes (red arrow)

• Other forms of cardiomyopathies that may mimic and/or lead to DCM include: end-stage HCM, RCM, peripartum cardiomyopathy, stress-induced cardiomyopathy (Tako-tsubo syndrome), left ventricular non-compaction.

• Toxins-induced cardiomyopathy; ethanol, cocaine, amphetamines, anthracyclines, cyclophosphamide, and trastuzumab.

• Infiltrative disease – include amyloidosis, sarcoidosis, and hemochromatosis.

• Connective tissue diseases include systemic lupus erythematosous, scleroderma, giant cell arthritis, etc. Endocrinologic disorders that may rarely lead to the phenotype of DCM include thyroid hormone excess or deficiency, pheochromocytoma, Cushing’s disease.

• Rare causes; Neuromuscular diseases (Duchenne’s muscular dystrophy, myotonic dystrophy, Friedreich’s ataxia), celiac disease, extensive chest radiation, nutritional deficiencies (thiamine, selenium, and L-carnitine), obstructive sleep apnea.

 

Stage III – Establishing the etiology of idiopathic DCM

• At the end of Stage II, DCM will be classified as idiopathic dilated cardiomyopathy.

• Appropriate examinations such as echocardiographic studies of family members, genetic studies, histopathological or immunochemistry studies of cardiac samples could be performed to differentiate between main causes of idiopathic DCM.

Diagnostic Algorithm

To simplify the DCM patient flow, a three-staged diagnostic algorithm has been proposed and is presented below. ( The diagnostic work up of genetic and inflammatory dilated cardiomyopathy, Dr. Pawel Rubis, e-journal of the ESC Council for Cardiology Practice VOL.13,N°19 - 07 APR 2015)

Idiopathic DCM

At the end of Stage II, DCM will be classified as idiopathic dilated cardiomyopathy as no other detectable causes of DCM have been identified. 

Familial

• Idiopathic DCM is considered familial (genetic) when more than one first-degree relative has been diagnosed with DCM. It is estimated that familial DCM can be diagnosed in 20 to over 50% of patients with an initial diagnosis of IDC. The great majority of familial DCM is transmitted in an autosomal dominance inheritance pattern. (Recent progress in the genetics of cardiomyopathy and its role in the clinical evaluation of patients with cardiomyopathy. Ghosh N1, Haddad H. Curr Opin Cardiol. 2011 Mar;26(2):155-64. doi: 10.1097)

• Unlike hypertrophic cardiomyopathy which is primarily a disease of sarcomeric proteins, the genetic and molecular basis of DCM is more heterogeneous. (The role of sarcomere gene mutations in patients with idiopathic dilated cardiomyopathy. Møller DV1, ..., Køber L. Eur J Hum Genet. 2009 Oct;17(10):1241-9. doi: 10.1038 )

• In the 2009 Guidelines of the American Heart Failure Society, genetic testing for HCM and ARVC is well validated. Nevertheless, genetic evaluation in DCM is also recommended. Confirmation of the causative mutation from detailed genetic analysis and positive family history are necessary to establish the diagnosis. (Familial dilated cardiomyopathy: evidence for genetic and phenotypic heterogeneity. Heart Muscle Disease Study Group. Mestroni L1, ..., Camerini. J Am Coll Cardiol. 1999 Jul;34(1):181-90)

Non familial

• Dilated cardiomyopathy due to inflammation and sub-sequent autoimmunisation is probably more common than was previously thought.

• Inflammatory dilated cardiomyopathy (DCMI) is a late and serious consequence of the complex interplay of the infectious agent, most often a virus, and the (auto)-immunologic response, which primarily develops in susceptible individuals (according to a genetic factor). (European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2013 Sep;34(33):2636-48, 2648a-2648d. doi: 10.1093) Although the DCMI phenotype is indistinguishable from the typical DCM, the diagnosis of DCMI cannot be made without endomyocardial biopsy. → Histo-pathological examination, immuno-histochemistry and molecular biology techniques.

• DCM can occur at a late stage following cardiac infection and inflammation. In contrast to active or fulminant myocarditis, which is by definition, an acute inflammatory disorder of the heart, often with preserved left ventricular size, inflammatory DCM is defined by the presence of chronic inflammatory cells in association with left ventricular dilatation and reduced ejection fraction; histology and/or immunocytochemistry are, therefore, necessary for the diagnosis. (Classification of the cardiomyopathies: a position statement from the european society of cardiology working group on myocardial and pericardial diseases. eurheartj 4 October 2007)

 

Compilation by Dr. Samad Ali Moradi; "Dilated cardiomyopathy" article from the e-journal of the ESC VOL.13,N°19 - 07 APR 2015, Also according to author's work experience, heart journals and guidelines.