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Early repolarization (ER) is defined as elevation of J point at least 1mm (0.1mV) in two consequent derivations on ECG. Early Repolarization Syndrome (ERS) which is usually seen in people without structural heart disease is considered under the title of ‘J wave syndromes’ because of its similarities with Brugada syndrome (BS). As a result of multi-center studies, the association of ERS with sudden cardiac death (SCD) established and it is now known that ERS is a cause of life threatening ventricular arrhythmias. The studies about genetic basis of ERS have been proceeding however firstly reported KCNJ8 gene mutation, as well as for BS, was also defined for ERS.
We conducted this study in order to determine the patients at risk with arrhythmia markers and search for KCNJ8 gene S422L mutation in patients who had ER.
Study included 100 patients with diagnosis of ERS and 100 subjects with normal ECG as control group. Subjects without coronary artery disease and with normal echocardiography results were included in study. Mean age was 33.1±9.7 in study group and 35.8±9.9 in control group. The existence of arrhythmia, heart rate variability and late potentials were examined in ER group. In both groups, S422L mutation in KCNJ8 gene was genotyped using allele specific PCR.
In our study using ‘ER ECG pattern typing’, 64% of patients with ER were defined as type l, 32% as type 2 and 4% as type 3 ER pattern. It was found that corrected QT interval (QTc) was shorter in ER group than in control group without reaching statistical significance (In ER group mean QTc; 371±28.7 ms, in the control group mean QTc; 381±31.4 ms, p=0.08). No couplet/triplet ventricular premature contractions (VPC) or nonsustained ventricular tachycardia was detected in Holter recordings of ERS group. Heart rate variability was found to be decreased 26% in the patient group, using the time domain methods. By using signal averaged ECG, late potentials were detected in 14% of the patients. These findings were consistent with the results of contemporary studies. History of unexplained syncope was present in two patients with normal neurologic assessment and the association of syncope with ERS was not statistically significant (p=0.15).
The S422L- KCNJ8 gene mutation which was investigated in both groups, was detected only in one subject in the control group, but not in the study group, making the association of mutation with ERS statistically insignificant. Nevertheless, it must be emphasized that the number of ERS patients included in our study was small and neither the patients nor their families had history of sudden cardiac death and most of them were found to be in low risk group.
As a result, we observed that there was not any significant relationship between KCNJ8-S422L mutation and ERS in patients who were mostly in low risk group. Further studies are needed to clarify treatment options and management strategies in those patients.