Objective: Prolongation of corrected QT interval (QTc) is associated with increased morbidity and mortality. We examined the predictors of the use of QTc prolonging medications (QTPM).
Methods: We included 15,792 ARIC participants with a resting, standard 12-lead electrocardiogram and ≥ 1 measure of QTc over up to four triennial examinations between 1987 and 1998 (54,638 person-visits). Participants with missing data were excluded (n=1,668). To optimize clinical applicability, QTc was calculated using Bazett’s equation. At each visit, we identified participants using ≥ 1 CredibleMeds classified QTPMs, age > 65 years, females, and those with LVH, or QTc > 500 ms at the prior visit. We used linear regression (random and fixed effects models) for 37,233 person-visit observations from visits 2-4 to determine predictors of the use of QTPMs. The following known risk factors and potential predictors for QTc lengthening were assessed: age, female sex, LVH, and QTc at the prior visit. Standard errors were corrected for repeat observations per person. Additional risk factors will be assessed in future analyses.
Results: Among person-visit observations from Visit 2-4 (mean age 59.7, 55% female, 9% LVH, mean QTc 431), 16% (n= 5,153) of participants were using one or more QTPM. Preliminary results suggest three of the four identified risk factors predicted use of QTPMs: age, sex, and QTc at prior visit. Prolonged QTc at prior visit was associated with a lower probability of using QTPM. In contrast, use of QTPMs was positively associated with a joint effect of age and female sex. The latter is concerning given older females are at increased risk for QTc prolongation.
Conclusions: In this preliminary analysis, several predictors of QTPM use emerged. Future analyses will include additional predictors and assessment of outcome will adjust for these predictors.