Cardiovascular Genetic Testing Guidelines Get a Technology Makeover

June 08, 2022

After more than a decade, the authors of what are still regarded as the definitive guidelines on use of genetic testing to diagnose and manage inherited cardiovascular diseases have revised their recommendations in accordance with 2022 testing technology. Here is a high-level briefing of the new testing guidelines.

The Diagnostic Challenge

Genetic testing of patients with inherited cardiac conditions has proven effective in the diagnosis, prognosis, and treatment of patients with inherited cardiac conditions. Such conditions fall into two basic categories: Mendelian disorders and complex inheritance disorders.

Mendelian disorders are caused by the inheritance of one or two genetic variants and typically cluster in families. Genetic testing has been recommended for early detection of Mendelian cardiovascular disorders that can prove fatal or extremely harmful upon first manifestation, such as sickle cell disease and aortic dissection. Genetic testing is used to identify at-risk carriers of the familial pathogenic variant (and non-carriers who are unlikely to develop disease) via cascade screening to track the genetic variant(s) associated with the disease.

The vast majority of inherited cardiovascular diseases are not Mendelian but complex inheritance disorders involving multiple genetic variants and for which familial clustering is less pronounced. These variants are detected via genome-wide association studies (GWAS) that compare the prevalence of millions of genetic variants, genome-wide, between affected individuals and controls.

The rapid evolution of genetic testing has created the need for definitive clinical guidelines. In 2011, a group of cardiology organizations from around the world, including the European Society of Cardiology (ESC), Heart Rhythm Society (HRS) (US-based), Asia Pacific Heart Rhythm Society (APHRS), and Latin American Heart Rhythm Society (LAHRS), got together to publish the Expert Consensus Statement on the State of Genetic Testing for the Channelopathies and Cardiomyopathies.

Although the 2011 consensus statement is still considered the reference document for determining the need for genetic testing to manage inherited cardiovascular conditions, since its publication, genetic testing has expanded beyond single-gene testing into whole exome and whole genome sequencing.

The New Consensus Statement

Now the groups have reconvened to revise their seminal guidance. Published online in journals EP Europace, Heart Rhythm, and multiple other journals on April 4, the new consensus statement brings the guidelines into line with 2022 genetic testing technology.

“This is now the reference document that all clinicians should use to decide whether genetic testing is indicated for patients with inherited cardiac diseases and their relatives,” noted lead author and professor of cardiology at Amsterdam Medical Centers (Netherlands) Arthur Wilde in an ESC statement.

Cardiovascular Genetic Testing Methods

The new consensus statement outlines the kinds of different cardiovascular genetic test methods that are currently available and makes recommendations about which ones to use in what context and when to perform them, including with regard to multiplex ligation-dependent probe amplification, polymerase chain reaction (PCR), single nucleotide polymorphism (SNP), genotyping arrays, copy number variant (CNV), structural variant (SV), whole exome sequencing (WES), and whole genome sequencing.

Overview of Different Genetic Testing Methods

Technology	Strengths	Limitations	Example diagnostic application
Sequencing approaches
Sanger sequencing	Accuracy Low cost per reaction	Not scalable Insensitive to large SVs	Single gene test Single variant testing—for a pre-specified variant during cascade family evaluation
Panel sequencing	Balances reasonably comprehensive coverage (e.g., all genes associated with a particular phenotype) against cost Often highly optimized for complete and uniform capture of region of interest	Usually exonic only Needs updating as knowledge changes (e.g., new gene-disease associations discovered)	First line diagnostic test for proband
WES	Comprehensive coverage of all genes Off-the-shelf design Can run a single wet-lab workflow, and introduce specificity at analysis stage Can update analysis to incorporate new knowledge without regenerating data—adaptable Enables analyses for secondary findings	Larger target requires more sequencing (c.f. panels) May be less optimized than more focused panel More costly and complex to store and process data (c. 10–100× more data than panel) Will not detect non-coding variants May not detect all variant classes	Diagnosis in proband for very heterogeneous conditions (e.g., pediatric and syndromic cardiomyopathies) Second line test if panel negative in specific circumstances, for example, with informative family structure
WGS	Comprehensive genetic characterization—all genes, all elements, all variant types Will also detect common variants for PRS, pharmacogenetics and other applications Enables analyses for secondary findings	More costly and complex to store and process data (∼100× more data than WES)	Diagnosis in proband for very heterogeneous conditions Second line test if panel negative Definitive and future-proof genetic characterization if funds permit—e.g., hold data in medical record for iterative targeted interpretation according to clinical needs
Non-sequencing approaches
Allele-specific PCR	Quick, cheap, accurate	Pre-specified variants only	Testing a single variant in a large family (more likely Sanger sequencing now)
Array comparative genomic hybridization	Cheap screening for SVs/CNVs High-resolution (compared with cytogenetic approaches)	Insensitive to other variant classes	Screening for structural variants, including aneuploidy, e.g., in structural congenital heart disease
Droplet digital PCR	Low cost, high-sensitivity detection of genome dose for SV/CNV detection at a pre-specified locus	Scalability limited by multiplexing of pre-specified PCR amplicons targeting regions of interest	Confirmation of putative CNVs detected in high-throughput sequence data
DNA SNP arrays	Genome wide Relatively cheap	Pre-specified variants only Accuracy poor for many rarer variants	Recreational ancestry analysis Polygenic risk Pharmacogenetics

Source: EHRA/HRS/APHRS/LAHRS Expert Consensus Statement on the state of genetic testing for cardiac diseases

Polygenic Risk Score Tests

Polygenic risk score (PRS) tests are also working their way into clinical practice, the statement notes, but remain something of a work in progress. “Eventually, PRS may hopefully be able to provide information not only on disease risk but also disease mechanism and therapeutic efficacy,” according to the statement. Use of PRS also “depends on the availability of genomic technology and on regional reimbursement policy,” the statement acknowledges.

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This article originally appeared in G2 Intelligence, Diagnostic Testing & Emerging Technologies, May 2022.

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