Strength of patient cohorts and biobanks for cardiomyopathy research.

In 2011 the Netherlands Heart Foundation allocated funding (CVON, Cardiovasculair Onderzoek Nederland) to stimulate collaboration between clinical and preclinical researchers on specific areas of research. One of those areas involves genetic heart diseases, which are frequently caused by pathogenic variants in genes that encode sarcomere proteins. In 2014, the DOSIS (Determinants of susceptibility in inherited cardiomyopathy: towards novel therapeutic approaches) consortium was initiated, focusing their research on secondary disease hits involved in the onset and progression of cardiomyopathies. Here we highlight several recent observations from our consortium and collaborators which may ultimately be relevant for clinical practice.

The Netherlands Arrhythmogenic Cardiomyopathy Registry: design and status update.

BACKGROUND: Clinical research on arrhythmogenic cardiomyopathy (ACM) is typically limited by small patient numbers, retrospective study designs, and inconsistent definitions. AIM: To create a large national ACM patient cohort with a vast amount of uniformly collected high-quality data that is readily available for future research. METHODS: This is a multicentre, longitudinal, observational cohort study that includes (1) patients with a definite ACM diagnosis, (2) at-risk relatives of ACM patients, and (3) ACM-associated mutation carriers. At baseline and every follow-up visit, a medical history as well information regarding (non-)invasive tests is collected (e. g. electrocardiograms, Holter recordings, imaging and electrophysiological studies, pathology reports, etc.). Outcome data include (non-)sustained ventricular and atrial arrhythmias, heart failure, and (cardiac) death. Data are collected on a research electronic data capture (REDCap) platform in which every participating centre has its own restricted data access group, thus empowering local studies while facilitating data sharing. DISCUSSION: The Netherlands ACM Registry is a national observational cohort study of ACM patients and relatives. Prospective and retrospective data are obtained at multiple time points, enabling both cross-sectional and longitudinal research in a hypothesis-generating approach that extends beyond one specific research question. In so doing, this registry aims to (1) increase the scientific knowledge base on disease mechanisms, genetics, and novel diagnostic and treatment strategies of ACM; and (2) provide education for physicians and patients concerning ACM, e. g. through our website ( www.acmregistry.nl ) and patient conferences.

Large next-generation sequencing gene panels in genetic heart disease: yield of pathogenic variants and variants of unknown significance.

BACKGROUND: Genetic heterogeneity is common in inherited cardiac diseases. Next-generation sequencing gene panels are therefore suitable for genetic diagnosis. We describe the results of implementation of cardiomyopathy and arrhythmia gene panels in clinical care. METHODS: We present detection rates for variants with unknown (class 3), likely (class 4), and certain (class 5) pathogenicity in cardiogenetic gene panels since their introduction into diagnostics. RESULTS: In 936 patients tested on the arrhythmia panel, likely pathogenic and pathogenic variants were detected in 8.8% (4.6% class 5; 4.2% class 4), and one or multiple class 3 variants in 34.8%. In 1970 patients tested on the cardiomyopathy panel, likely pathogenic and pathogenic variants were detected in 19.8% (12.0% class 5; 7.9% class 4), and one or multiple class 3 variants in 40.8%. Detection rates of all different classes of variants increased with the increasing number of genes on the cardiomyopathy gene panel. Multiple variants were detected in 11.7% and 28.5% of patients on the arrhythmia and cardiomyopathy panels respectively. In more recent larger versions of the cardiomyopathy gene panel the detection rate of likely pathogenic and pathogenic variants only slightly increased, but was associated with a large increase of class 3 variants. CONCLUSION: Overall detection rates (class 3, 4, and 5 variants) in a diagnostic setting are 44% and 61% for the arrhythmia and cardiomyopathy gene panel respectively, with only a small minority of likely pathogenic and pathogenic variants (8.8% and 19.8% respectively). Larger gene panels can increase the detection rate of likely pathogenic and pathogenic variants, but mainly increase the frequency of variants of unknown pathogenicity.

Congenital hydrocephalus in clinical practice: a genetic diagnostic approach.

Congenital hydrocephalus is a common and often disabling disorder. The etiology is very heterogeneous. Little is known about the genetic causes of congenital hydrocephalus. A retrospective survey was performed including patients with primary congenital hydrocephalus referred to the Department of Clinical Genetics between 1985 and 2010 by perinatologists, (child) neurologists or pediatricians. Patients with hydrocephalus secondary to other pathology were excluded from this survey. We classified patients with primary congenital hydrocephalus into two main groups: non-syndromic hydrocephalus (NSH) and syndromic hydrocephalus (SH). Seventy-five individuals met the inclusion criteria, comprising 36% (27/75) NSH and 64% (48/75) SH. In 11% (8/75) hydrocephalus was familial. The cause of hydrocephalus was unknown in 81% (61/75), including all patients with NSH. The male-female ratio in this subgroup was 2.6:1, indicating an X-linked factor other than the L1CAM gene. In the group of SH patients, 29% (14/48) had a known cause of hydrocephalus including chromosomal abnormalities, L1 syndrome, Marden-Walker syndrome, Walker-Warburg syndrome and hemifacial microsomia. We performed this survey in order to evaluate current knowledge on the genetic etiology of primary congenital hydrocephalus and to identify new candidate genes or regulatory pathways for congenital hydrocephalus. Recommendations were made concerning the evaluation and genetic workup of patients with primary congenital hydrocephalus. We conclude that further molecular and functional analysis is needed to identify new genetic forms of congenital hydrocephalus.