“Epidemiology of Short QT Interval in Phase I of Kherameh Cohort Study: A Population-based Study on 4,363 Subjects in Southern Iran”

Aims: Short QT-interval is a condition that bear the suspicion of short QT syndrome (SQTS). SQTS is known to increase risk of life-threatening arrythmias and sudden cardiac death (SCD). Due to the insufficient population-based studies and use of various QT cut-off values it accounts for as an undiagnosed condition. In this study, we sought for prevalence of short QT interval in Kherameh cohort study, one of the southern sectors of the Prospective Epidemiological Research Studies in Iran (PERSIAN). Methods: Data of 4,363 adult subjects were analyzed from phase 1 of the cohort during 2014-2017. The corrected QT (QTc) intervals were calculated and electrocardiograms (ECGs) with QTc of less than 370 milliseconds (msec) were reanalyzed for bradycardia, early repolarization, atrial fibrillation (AF), arrhythmias, and other electrical conduction abnormalities. Results: Seventy-two subjects (1.65%) had a QTc of less than 370msec (mean QTc of 360.72±11.72). A male predominance and a lower mean heart rate observed in SQTS susceptible group (M/F of 1/0.26 vs. 1/1.145, p -value<0.0001; 58.389±9.787 vs. 70.899±11.775; p -value<0.0001) compare to the subjects with normal QTc. At least, 2 subjects with high-probability SQTS and 3 with intermediate-probability SQTS identified. The frequency of AF, syncope, bradycardia, early repolarization, low voltage ECG, and infantile SCD in first- and second-degree relatives were 16.67, 4.17, 33.33, 11.11, 6.94, 11.11%, respectively. Conclusion: The prevalence of short QT interval in our cohort was in line with previous studies. The higher proportions of cardiac symptoms, familial SCDs and ECG derived specific findings amongst SQTS-susceptible index persons than non-short QT interval normal population might implicate in gene study and family screening.