QRS narrowing and prediction of res-ponse to cardiac resynchronization therapy

Şipal et al. (1) have reported that surface electrocardiogram (ECG) can be used to guide left ventricular (LV) lead placement in patients with multiple target veins. In this prospective study, they demonstrated that LV lead placement guided by ECG improves response to cardiac resynchronization therapy (CRT). In this well-presented article by Şipal and colleagues, they randomized 80 patients into two groups at a 1:1 ratio. In group 1, they placed the LV lead at the site with the narrowest BiV-paced QRS, as intraprocedurally measured using surface ECG. In group 2 (control), the patients un¬derwent standard CRT implantation without ECG guidance, preferentially in a lateral, posterior, or posterolateral vein. In group 1, they observed that ECG duration 6 months postoperatively was shorter than that at the baseline. In group 2, they observed that ECG duration 6 months postoperatively was similar to that at the baseline. Nonetheless, functional class improved in both the groups. Korantzopoulos et al. (2) have demonstrated that QRS narrowing was a positive predictor of response to CRT. Lecoq et al. (3) have shown that the extent of QRS shortening (DeltaQRS) associated with biventricular stimulation was the only independent predictor of response to CRT. In the light of this knowledge, it might be beneficial to describe why patients in study group 2 showed a better functional status despite no change in the ECG duration.