Clinical and genetic characteristics and course of congenital long QT syndrome: A ten-year single center experience

Funding Acknowledgements Type of funding sources: None. Background Long QT syndrome (LQTS) is an inherited primary arrhythmia syndrome associated with life-threatening ventricular arrhythmia. Objective To report the clinical and genetic characteristics and outcome of LQTS patients in single center inherited arrhythmia clinic. Methods Retrospective review of patients diagnosed LQTS and evaluated by ECG, 12 lead holter, exercise test and genetic testing in inherited arrhythmia clinic from January 212 to January 2022. Results 101 patients (32 families) were included, mean age 24.3± 17 years. Thirteen patients (12.8%) were diagnosed after previous cardiac arrest and six patients (6%) had syncope. Seventy (69.3%) were identified as having LQTS during family screening. 97 patients (97%) were confirmed to have a pathogenic mutation for LQTS genes. Beta blockers were recommended to 74 patients (73%), flecainide to 20 (19.8%). Nine patients (8.9%) received an ICD for secondary prevention and one patient (1%) for primary prevention. During 5.8 ± 2.7 years, dose of beta-blockers increased from propranolol 70 ±42 mg to 105 ±60.3 mg (p= 0.0004), QTC shortening (479 ± 36.9 to 466 ±30.1 msec, p=0.01) in ECG and maximal QTC measured in 12 lead holter (521± 43.9 to 505± 37.8 msec, p=0.01). Maximal heart rates measured in 12 lead holter and exercise test were reduced ( 130± 24.5 to 116 ± 20.2 beats/min p=0.0001 and 152.6±22 to 145± 20.58 beats/min, p=0.043). Seven patients (6.9%) experienced ventricular arrhythmia, five received appropriate ICD shock and two patients that declined beta blockers experienced syncope due to polymorphic ventricular tachycardia and cardiac arrest. The one patient that had the ICD for primary prevention, experienced polymorphic ventricular tachycardia that was successfully treated by the ICD. Conclusions Intensive clinical follow up and an optimal medical therapy in a specialized arrhythmia clinic is associated with a relatively low incidence of sudden cardiac death and a low rate of ICD utilization in LQTS patients.