New System Reclassifies Cardiomyopathy in Children

By Will Boggs MD

June 28, 2019

NEW YORK (Reuters Health) - A new scientific statement from the American Heart Association (AHA) proposes a new classification scheme for cardiomyopathy in children.

"Our new classification systems are controversial," Dr. Steven E. Lipshultz of the University at Buffalo Jacobs School of Medicine and Biomedical Sciences, in New York, told Reuters Health by email. "We follow a hierarchical classification of cardiomyopathy in children that places morphofunctional characteristics higher than genetic and nongenetic causes of disease."

"This places children with syndromes known to be associated with their heart disease, such as Noonan syndrome patients with a hypertrophied left ventricle, within rather than outside of this classification scheme, as their structural heart disease meets the phenotypic definition of hypertrophic cardiomyopathy," he said. "This also places children with a genotypic predisposition, such as pathogenic MYH7 mutation, outside of rather than within this classification scheme if they show no cardiomyopathy phenotype."

With an estimated incidence of one case per 100,000 person-years, cardiomyopathy in children is rare, yet it is the primary indication for heart transplantation during childhood. The causes are established in very few cases.

Dr. Lipshultz and colleagues, on behalf of the AHA Council on Cardiovascular Disease in the Young, Council on Clinical Cardiology, and Counsel on Genomic and Precision Medicine, developed this scientific statement "to help cardiologists who are caring for these children identify the known causes of cardiomyopathy in their patients and also to help determine future research priorities in order to achieve earlier diagnosis, improved clinical outcomes, and better quality of life for these children and their families."

The statement proposes classifying pediatric cardiomyopathy into five main groups:

- Dilated cardiomyopathy (DCM), defined by the presence of a dilated left ventricle with systolic dysfunction in the absence of a hemodynamic cause that can produce the existent dilation and dysfunction.

- Hypertrophic cardiomyopathy (HCM), defined by the presence of a hypertrophied, non-dilated ventricle in the absence of a hemodynamic cause that is capable of producing the existent magnitude of wall thickening (i.e., excluding both physiological hypertrophy and pathological hypertrophy secondary to hypertension and other disorders).

- Restrictive cardiomyopathy (RCM), defined by the presence of abnormal compliance without another predominant phenotype of right ventricular or left ventricular dilatation, hypertrophy, or systolic dysfunction.

- Left ventricular myocardial noncompaction (LVNC) cardiomyopathy, defined by the distinctive appearance of prominent left ventricular trabeculations and deep intratrabecular recesses detected on imaging studies or pathological examination.

- Cardiomyopathy associated with arrhythmia (AVC), an autosomal-dominantly inherited heart disease characterized pathologically by fibrofatty replacement of the myocardium and clinically by ventricular arrhythmias and impaired ventricular systolic function.

Each of these main groups is further subdivided into different phenotypes and, for some, into primary and secondary causes and genetic categories, the authors explain in Circulation, online May 28.

Suitable modalities for evaluating pediatric cardiomyopathies include echocardiography, cardiac MRI and cardiac CT, whereas cardiac catheterization is used rarely to assess morphology and more commonly to assess hemodynamics, obtain endomyocardial biopsies and for intervention in patients with amenable lesions.

The statement also describes the genetics of pediatric cardiomyopathies and discusses methods of genetic testing, interpretation and application of test results, and the limitations of genetic testing.

The statement does not attempt to provide a step-by-step approach or decision-making algorithm to the diagnostic evaluation, because finding a cause "is often elusive and may require the participation of multiple subspecialists, such as electrophysiologists, geneticists, mitochondria-metabolism experts, and endocrinologists."

"The diagnosis of cardiomyopathy in children often warrants a comprehensive and multidisciplinary approach," Dr. Lipshultz said. "Advanced cardiac imaging and genetic testing, in particular, play an increasingly important role in the care of children with cardiomyopathy."

"Although, like most pediatric heart disease, these are rare disorders, the frequency of poor outcomes results in a disproportionate number of deaths in children," he said. "For these reasons, much more research in pediatric cardiomyopathy is urgently needed. Recent advances in our understanding of many forms of these diseases also mean that there has never been a more exciting time to participate in such research and thus improve the outlook for children living with cardiomyopathy."

Dr. John Lynn Jefferies of the University of Tennessee Health Science Center, in Memphis, Tennessee, who studies pediatric cardiomyopathy, told Reuters Health by email, "The pediatric-cardiomyopathy field as a whole has lagged behind adult cardiology regarding AHA statements, consistency of care, and unified nomenclature for non-congenital heart disease. This publication brings us to a comparable level of the adult cardiomyopathy literature with the understanding that the pediatric literature is much less robust and established given the smaller cohort of patients and heterogeneity of care."

"This statement offers clarity to clinicians regarding a consistent manner to classify cardiomyopathies in children," he said. "Now, providers have a pathway to have conversations with families and referring providers that use a 'common language.' This will facilitate care partnerships with local cardiologists and cardiomyopathy cardiologists and allow for accurate and precise discussions resulting in more consistent and predictable care."

SOURCE: https://bit.ly/30X6Drr

Circulation 2019.

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