Evaluation of cardiomyopathy

The cardiomyopathies are an important, heterogeneous group of heart muscle diseases that make a significant contribution to morbidity and mortality.[1]Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006;113:1807-1816. http://circ.ahajournals.org/content/113/14/1807.full.pdf+html http://www.ncbi.nlm.nih.gov/pubmed/16567565?tool=bestpractice.com They are associated with mechanical and/or electrical dysfunction. Inappropriate ventricular hypertrophy or dilatation is usually present.[1]Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006;113:1807-1816. http://circ.ahajournals.org/content/113/14/1807.full.pdf+html http://www.ncbi.nlm.nih.gov/pubmed/16567565?tool=bestpractice.com Cardiomyopathy involvement may be predominantly limited to the heart (primary cardiomyopathy) or form part of a generalized systemic disorder (secondary cardiomyopathy). Causes vary widely, but genetic etiologies are most common in primary cardiomyopathies. Complications include cardiovascular death and progressive heart failure, with its associated disability.[1]Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006;113:1807-1816. http://circ.ahajournals.org/content/113/14/1807.full.pdf+html http://www.ncbi.nlm.nih.gov/pubmed/16567565?tool=bestpractice.com

Classifications

In 1995, the World Health Organization/International Society and Federation of Cardiology Task Force classified cardiomyopathies as primary myocardial disorders, whereas heart muscle diseases of known etiology or associated with systemic diseases were categorized as secondary or specific heart muscle diseases.[2]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 Mar 1;93(5):841-2. http://circ.ahajournals.org/content/93/5/841.full http://www.ncbi.nlm.nih.gov/pubmed/8598070?tool=bestpractice.com However, as research has improved the understanding of these conditions, working groups have proposed new but different classification systems. 

The scientific statement from the American Heart Association has defined cardiomyopathies as "a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic. Cardiomyopathies either are confined to the heart or are part of generalized systemic disorders, often leading to cardiovascular death or progressive heart failure-related disability."[1]Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006;113:1807-1816. http://circ.ahajournals.org/content/113/14/1807.full.pdf+html http://www.ncbi.nlm.nih.gov/pubmed/16567565?tool=bestpractice.com

• Primary cardiomyopathies are those where the condition is predominantly confined to the heart muscle and where subclassifications of genetic, mixed, and acquired are adopted.

• Secondary cardiomyopathies are those where myocardial involvement occurs as part of a systemic or multiorgan disorder.

The European Society of Cardiology Working Group on Myocardial and Pericardial Diseases has opted to use a clinical rather than genetic classification, where heart muscle disorders are classified according to morphology and function: "a myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality."[3]Elliott P, Andersson B, Arbustini E, et al. Classification of the cardiomyopathies: a position statement from the European Society Of Cardiology Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2008;29:270-276. http://eurheartj.oxfordjournals.org/content/29/2/270.long http://www.ncbi.nlm.nih.gov/pubmed/17916581?tool=bestpractice.com Its members felt that many primary cardiomyopathies have significant extracardiac manifestations and that many secondary cardiomyopathies may involve the heart as the major manifestation.[Figure caption and citation for the preceding image starts]: Diseases that may cause cardiomyopathyElliott P, et al. Eur Heart J 2008; 29: 270-76; used with permission [Citation ends].

It is important to recognize that the traditional classification into hypertrophic, dilated, and restrictive cardiomyopathies mixes anatomical with functional designations, which are not mutually exclusive. [Figure caption and citation for the preceding image starts]: Proposed classification systemElliott P, Andersson B, Arbustini E, et al. Classification of the cardiomyopathies: a position statement from the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2008;29:270-276. Used with permission. [Citation ends].

The American Heart Association published a separate scientific statement in 2019, covering the classification and diagnosis of cardiomyopathy in children.[4]Lipshultz SE, Law YM, Asante-Korang A, et al. Cardiomyopathy in Children: Classification and Diagnosis: A Scientific Statement From the American Heart Association. Circulation. 2019 Jul 2;140(1):e9-e68. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000682 http://www.ncbi.nlm.nih.gov/pubmed/31132865?tool=bestpractice.com This favours a classification for pediatric cases based primarily on the structural and functional phenotype (which forms the basis for diagnosis and management), with genetic and nongenetic causes as lower-level subcategories.