Association between pre-operative prolonged corrected QT interval and all-cause mortality after non-cardiac surgery.

Background: Prolonged corrected QT interval (QTc) has been linked to risk of arrhythmias and mortality in the general population. Pre-operative electrocardiography is often obtained for patient-and procedural cardiovascular risk assessment. The aim of this study was to investigate the association of pre-operative QTc and all-cause mortality in a non-cardiac surgical cohort.

Methods: A retrospective study of all patients over 18 years undergoing non-cardiac surgery at Landspitali-the National University Hospital in Iceland between 2 January 2005 to 31 December 2015, with follow-up through 20 May 2016. Patients were separated into five categories according to their pre-operative QTc interval ≤ 379, 380-439 (reference group), 440-479, 480-519 and ≥520 ms. Primary outcome was long-term mortality and secondary outcome was 30-day mortality.

Results: A total of 10,209 surgeries for 10,209 individuals were included. The median follow-up for mortality was 2691 days (interquartile range [IQR] 1620-3705 days). Patients with longer QTc interval had a higher comorbidity burden, were more likely to undergo emergency surgery and were often prescribed cardiac medications. After adjustment for confounding variables, the hazard ratio (HR) for long-term mortality compared with reference (QTc 380-439 ms) was 0.85 [CI: 0.66-1.09] for QTc ≤379, 1.08 [CI: 0.99-1.17] for QTc 440-479 ms, 1.26 [CI: 1.10-1.43] for QTc between 480 and 519 ms and 0.97 [CI: 0.78-1.21] for QTc ≥520 ms. When compared with reference, only patients with QTc interval between 480 and 519 ms had higher odds ratio for 30-day mortality as odds ratio for other groups were following; 1.12 [CI: 0.18-3.8] for ≤379 ms, 1.03 [CI: 0.70-1.51] for QTc 440-479 ms, 1.64 [CI: 1.02-2.60] for QTc 480-519 ms and 0.98 [0.44-2.06] for QTc ≥520 ms.

Conclusion: Pre-operative QTc between 480 and 519 ms is associated with both higher long-term and 30-day mortality after non-cardiac surgery. The results suggest that this could reflect an underlying cardiovascular risk.