P890Gene carriers of hypertrophic cardiomyopathy, what to expect over time
Abstract Background Data on the natural history of genotype positive/phenotype negative (G+/P-) hypertrophic cardiomyopathy (HCM) patients identified as a part of genetic cascade screening in different age groups is limited. Purpose To describe the rate of conversion to overt HCM phenotype in G+/P- subjects in relation with the age who were identified in a specialized clinic in a single center. Methods We retrospectively identified 56 consecutive HCM G+/P− subjects followed in our center specialized clinic between Jan 2012-Jan 2019. Demographics, family history of sudden cardiac death (SCD) and presence of symptoms were collected. All of them underwent baseline investigations including ECG, echocardiogram and/or cardiac magnetic resonance (CMR) and 24 hour monitor at baseline and during follow up. Overt HCM phenotype was defined as left ventricular hypertrophy (LVH) ≥13mm in the echocardiogram or CMR. Results We identified 56 HCM G+/P− subjects from 34 different families. 22 subjects were ≤18 years old with a mean age of 11.6±0.9 years (IQR [P25-P75] 9–16 years) and 32 subjects were >18 years old with a mean age of 38.1±2.2 years (IQR [P25-P75] 27–48 years). Mean time of follow up was 35.2±34.4 months (IQR [P25-P75] 4.25–50.25 years). 60.7% (34) of them were female and 82.1% (46) were of Caucasian ethnicity. Most of the subjects with no evidence LVH were asymptomatic but small number had symptoms, 8.9% (5), and 3.6% (2) were treated with betablockers for palpitations. Family history of SCD was present in 57.1% (32) of the subjects and 35.7% (20) had a relative with an implantable cardiac defibrillator (ICD). MYBPC3 gene mutations were identified in 62.5% (35) of subjects, followed by MYH7 gene mutation in 23.2% (13) of the cases. None of the subjects under 18 year old developed HCM during the period of observation, however 7 subjects (21.9%), mean age 48.6±10.5 years, 71.4% (5) females, showed progression to HCM in the >18 years old group. All of them had pathogenic MYBPC3 gene variants. No differences were found in gender, ethnicity, symptoms or family history of SCD in the G+/P− vs HCM group. There were no differences on the presence of ECG abnormalities and no episodes of NSVT were recorded in any of the groups. Baseline E/e' values of those with new HCM vs G+/P− were higher (8.2±3.3 vs 5.6±1.7, p=0.014). Conclusions In our cohort, rate of progression to HCM phenotype was 21.9% of >18 years old HCM G+/P- subjects. The mean age at the time of developing the phenotype was 48.6±10.5 years old and all the patients were asymptomatic for cardiac symptoms. Echocardiographic E/e' values were increased. This data supports the need of life long follow up of this group of patients with ongoing clinical evaluation. Acknowledgement/Funding ESC clinical grant