Changes in QRS duration are associated with maximal exercise capacity in adult patients with repaired tetralogy of Fallot

Objective: In adult patients with repaired tetralogy of Fallot (TF) QRS duration at rest seems to be a predictor of maximal exercise. We examined the relationship between QRS duration during exercise and exercise performance. Design: In 57 consecutive TF patients QRS duration in V 1 (ms) was measured at rest, at maximal exercise (W max, W), and at peak oxygen consumption (peak VO 2, ml/min). Stroke volume (SV) was calculated from cardiac output, obtained by CO 2 rebreathing. Spearman rank correlation was used to describe the relationship between QRS duration and exercise performance. Statistical significance was defined as P<0.05. Results: Seven patients, who didn't pass the anaerobic threshold, and one outlier (W max=340 W) were excluded, resulting in a sample of 49 patients (75.5% male; median age=24 years, range 16-43 years). QRS duration at rest (median=160 ms, range 78-194 ms) and at maximal exercise (median=153 ms, range 80-193 ms) did not differ significantly. The median change of QRS duration during exercise was -5 ms (range -31 to +83 ms). This was negatively correlated with Peak VO 2 (2081±577 ml/min; ρ=-0.33, P=0.02) and W max (182±53 Watt; ρ=-0.33, P=0.02). In patients with QRS shortening peak VO 2 and the exercise induced increase in SV were significantly higher than in patients with QRS shortening. Conclusions: This study indicates that QRS shortening during exercise in TF patients is related with a better exercise performance. Lower increase in stroke volumes may be responsible for this difference. Further research is needed to elaborate these findings. © 2005 Elsevier Ireland Ltd. All rights reserved.