Exploring the association between genetic markers and ICD discharge rate in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant disorder with a pathogenic mutation identified in approximately 50% of cases. The MYH7 and MYBPC3 genes account for over half of these cases, while dozens of other genes can be pathogenic(1). Genetic test results are not independently used to determine which people with HCM benefit from implanted cardiac defibrillators (ICDs)(2, 3). Little is known about the additive role of genetic testing results to existing indications for ICD insertion.

This study aims to examine the interaction between genetic testing results and existing ICD indications and imaging results on defibrillator discharge rates in HCM.

Patients who underwent an ICD for HCM, who underwent a cardiac magnetic resonance (CMR) study and who underwent genetic testing were included across 3 sites. The outcome was the incidence rate of appropriate ICD discharges, calculated using cox regression controlling for current age and primary vs secondary prevention. Interaction analysis between genetic risk factors and existing ICD indications, and with CMR quantification of LGE and septal thickness, was performed, and stratum specific estimates calculated using linear computation.

177 patients were included in the study, of whom 70 (39.55%) had a pathogenic mutation, 5 (2.82%) had a variant likely pathogenic (VLP), 44 (24.86%) had a variant of undetermined significance (VUS) and 58 (39.55%) had no identifiable mutation. The event rate was 3.32 {2.28 to 4.84) per 100 person years. There was no association between genetic variables and ICD discharge rate. There was an 80% reduction in ICD discharge rate in people who underwent ICD insertion exclusively for family history of sudden cardiac death or for syncope who had no pathogenic or likely pathogenic mutation, however this change was not statistically significant (table 2).

There is no strong association between genetic characteristics and ICD discharge rates among people with hypertrophic cardiomyopathy with an existing ICD indication. There is a nonsignificant trend towards fewer ICD discharges among people who underwent ICD insertion for family history alone or for a history of syncope and did not have a pathologic variant.Table 1  Table 2