Background: QRS transition zone is related to the electrical axis of the heart in the horizontal plane and is easily determined from the precordial leads of a standard 12-lead ECG. However, whether delayed QRS transition, or clockwise rotation of the heart, carries prognostic implications and predicts sudden cardiac death (SCD) is unclear.
Objective: The purpose of this study was to study whether delayed transition is associated with mortality and SCD.
Methods: We evaluated 12-lead ECGs of 10,815 Finnish middle-aged subjects from the general population (52% men, mean age 44 ± 8.5 years) and followed them for 30 ± 11 years. Main end-points were mortality and SCD.
Results: Delayed QRS transition at lead V4 or later occurred in 1770 subjects (16.4%) and markedly delayed transition at lead V5 or later in 146 subjects (1.3%). Delayed transition zone was associated with older age, male gender, higher body mass index, hypertension, baseline cardiovascular disease, leftward shift of the frontal QRS axis, wider QRS-T angle, and ECG left ventricular hypertrophy. After adjusting for several clinical and ECG variables, delayed transition was associated with overall mortality (hazard ratio [HR] 1.15, 95% confidence interval [CI] 1.07-1.22, P < .001) and SCD (HR 1.23, 95% CI 1.03-1.47, P = .029). Markedly delayed transition at V5 or later predicted significantly SCD (HR 1.89, 95% CI 1.18-3.03, P = .008) and all-cause mortality (HR 1.30, 95% CI 1.07-1.58, P = .01). However, further adjustments for repolarization abnormalities attenuated this effect.
Conclusion: Delayed QRS transition in the precordial leads of an ECG seems to be a novel ECG risk marker for SCD. In particular, markedly delayed transition was associated with significantly increased risk of SCD, independent of confounding factors.
Keywords: Clockwise rotation; Electrocardiography; Population; QRS transition; Sudden cardiac death.
Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.