Impact of prolonged and short QT intervals on immediate risks of newly diagnosed arrhythmias and mortality

The relationship between corrected QT (QTc) intervals and short-term clinical outcomes remains insufficiently investigated. This study examined correlations between QTc intervals and risks of arrhythmia or mortality over a 3-month follow-up period. This retrospective study analyzed de-identified electronic medical records from the TriNetX Network. Adult patients with at least 2 electrocardiogram assessments were categorized into 5 QTc interval groups: long QTc (>500 milliseconds [ms]), borderline QTc (460–500 ms), high-normal QTc (420–460 ms), control QTc (370–420 ms), and short QTc (200–370 ms). Primary outcomes were 3-month risks of new-onset atrial fibrillation (AF) or ventricular arrhythmia (VA), with secondary focus on 3-month mortality risk. Among 145, 111 patients, a U-shaped pattern was observed in AF risk across QTc interval categories. The hazard ratio for AF risk was 7.384 (95% confidence interval: 5.911–9.224) in the long QTc group and 7.735 (95% confidence interval: 4.237–14.122) in the short QTc group compared to controls. Similar U-shaped correlations were observed between QTc intervals and VA or mortality risks. Sensitivity analyses confirmed the U-shaped association for AF. However, sensitivity analyses showed that the association between short QTc intervals and the risk of VA or mortality was attenuated and no longer statistically significant after excluding patients exposed to QTc-prolonging medications or in pre-pandemic cohorts. Our findings revealed a U-shaped correlation between QTc intervals and the occurrence of AF, VA, and mortality within a 3-month observation period, underscoring the potential of QTc intervals as short-term prognostic predictors.