Evaluation of CACNA1C-Positive Patients Evaluated in a Tertiary Genetic Heart Rhythm Clinic.

Genetic variants in CACNA1C are associated with several cardiac and neurologic conditions. We conducted a retrospective review of patients evaluated and treated who presented with a pathogenic (P), likely pathogenic (LP), or variant of uncertain significance (VUS) in CACNA1C. Among 4,774 patients, 49 had P, LP, or VUS variants (55% female; median age 15 years; mean QTc 481 ms). Of these, 22 had long QT syndrome type 8, 8 had Timothy syndrome, 2 had cardiac only Timothy syndrome, and 9 had no cardiac phenotype. Ten patients exhibited extracardiac findings. Thirty-one patients were treated with a beta-blocker, 21 patients had an implantable cardioverter-defibrillator (ICD). Nine patients were on intentional non-therapy. Six patients had at least 1 breakthrough cardiac event on follow-up. Overall, CACNA1C-positive patients present with diverse diagnoses and severity. Treatments vary by phenotype, however management with preventative measures only presents a reasonable option for some phenotype-negative, genotype-positive patients.