Purpose: In this sub-study from the Danish randomized, controlled, multicenter study to assess the efficacy of Implantable cardioverter defibrillator in patients with non-ischemic Systolic Heart failure on mortality (DANISH) study, we aimed to assess the association between ?QRSd after implantation of CRT and mortality in a large cohort of patients with non-ischemic cardiomyopathy.
Methods: We included all patients from the DANISH study who received a CRT system (CRT-defibrillator or CRT-pacemaker). The last ECG before implantation and the first available ECG after implantation were used for calculation of ?QRSd. Patients without ECG data were excluded. ?QRSd did not meet the proportional hazards assumption in the Cox model. The association between ?QRSd and the primary endpoint, all-cause mortality was therefore investigated in two time-intervals: 0-1 year, and beyond one year after CRT
Results: 640 patients were treated with CRT and ECGs were available in 572 patients. Median age was 66 years, 390 (68%) were men and QRSd was 160 milliseconds (ms; IQR 146-180). An ECG was recorded 48 days (IQR 33-85) after implantation and showed that CRT had resulted in QRSd of 145 ms (IQR 125-160) i.e. ?QRSd of median -14 ms (IQR -38 - 3). Patients were followed for median 4.6 years (IQR 3.0 – 6.1). During the first year of implantation 20 patients died and in this time-interval an 18% reduction in mortality was observed per 10 ms reduction of QRSd (HR 0.82, CI: 0.69 – 0.98, p=0.03). Beyond one year, 86 patients died, but ?QRSd was not associated with additional reduction of mortality (HR 1.07, CI: 0.90-1.04, p=0.14).
Conclusion: In a large cohort of patients with non-ischemic cardiomyopathy reduction of QRSd early after implantation of CRT was associated with reduced mortality within the first year of treatment. Changes in QRSd was not associated with additional mortality reduction beyond the first year.