LAUSR

Long QT interval elevates risks of life-threatening arrhythmias, cardiovascular mortality and all-cause mortality. The prevalence of prolonged QTc among Caucasians is approximately 8.7%. In Thai population, the prevalence and prognosis of prolonged QTc remain unexplored. 1. To identify the prevalence of long QT interval in the Thai population without prior cardiovascular disease. 2. To evaluate the association between long QT interval and long-term cardiovascular (CV) event and all-cause mortality. A total of 2756 participants from the Electricity Generating Authority of Thailand (EGAT) study from 1997 to 2015 were studied. Among those, 2456 participants had completed EKGs and were included into the final analysis. The long QT interval was defined as QTc longer than 450 milliseconds (ms) in male and 460 ms in female respectively. Mortality endpoints included CV event and all-cause mortality were collected. Multivariable cox-proportional hazard model adjusted for all major CV risk factors was used to determine the association between prolonged QTc and outcomes. The majority of the population are male (N=1941, 79%). The mean QT interval calculated by Bazett's formula is 424±28.27 ms. Prolonged QTc was observed 12.5% in male and 17.7% in female. There were 509 (20.7%) deaths during the follow-up period. After 18 years of follow up, 10.5% of the prolonged QTc group had cardiovascular events, compared with 6.8% in the normal QTc group (P=0.09). All-cause mortality occurred in 30% of the prolonged QTc group and 19.3% in the normal QTc group (adjusted HR 1.33, 95% CI 1.05–1.68, P=0.018). After dividing QTc into deciles, the lowest mortality was observed in the 3rd to 7th deciles (17.6%, 19.7%, 16.3%, 23.2% and 18.9% respectively) and the highest mortality was observed in the 2nd deciles (22.09%) and the 8th to 10th deciles (22%, 27.15% and 28.38% respectively). Hazard function of prolonged QTc 1. In this worker cohort from Thailand, prolonged QTc was observed in 14% of the population. 2. During 18 years follow up, prolongation of QT interval is an independent risk factor for all-cause mortalities but not cardiovascular mortality. 3. There was a J-curve effect in association between the duration of QT interval and all-cause mortality.