Cardiac remodelling and functional status after cardiac resynchronisation therapy: comparison between de-novo implantation and upgrade from right ventricular pacing
H L Bjerre, E A Frandsen, A Sommer, C Stephansen, N Risum, S H Poulsen, J C Nielsen, M B KronborgAbstract
Background
Patients with heart failure induced or worsened by chronic right ventricular (RV) pacing commonly undergo upgrade to a cardiac resynchronization therapy device (CRT). In the modern era of heart failure therapy, it remains unclear whether patients with an RV paced QRS who are upgraded to CRT derive similar benefits as patients with intrinsic conduction who undergo a de novo CRT procedure.
Purpose
The purpose of this study was to compare the effect size of improvement in cardiac function and functional capacity from CRT implantation to 6-month follow-up between patients with RV pacing and intrinsic conduction at baseline. We hypothesized that patients with RV pacing and intrinsic conduction at baseline would derive similar improvements in both cardiac function and functional capacity following CRT.
Methods
We included patients from three randomized controlled trials; the ImagingCRT (1), ElectroCRT (2) and DANISH-CRT (3) trials. Inclusion criteria were age ≥40 years, left ventricular (LV) ejection fraction (LVEF) ≤35% and prolonged QRS. All patients received biventricular CRT. The primary endpoint was change in LV end-systolic volume (LVESV) from baseline to 6-month follow-up. Secondary endpoints included change in QRS duration, LVEF, LV end-diastolic volume, LV mass index, left atrial volume index, N-terminal prohormone of brain natriuretic peptide, six-minute walk test, quality of life questionnaires, New York Heart Association functional class and use of loop diuretics.
Results
We included 592 patients; 97 (16.4%) with RV pacing and 495 (83.6%) with intrinsic conduction at baseline. Patients with RV pacing at baseline were older and more likely to have ischemic heart disease and atrial fibrillation. On the primary endpoint we found significant relative reduction in LVESV from baseline to 6-month follow-up for patients with RV pacing (-34±25%) and intrinsic conduction (-32±26%) with no between-group difference (mean difference -2%, 95% CI [-8;4], p=0.469). There was a significant absolute improvement in LVEF in patients with RV pacing (14±9) and intrinsic conduction (13±9) at baseline, with no difference between them (mean difference 1, 95% CI [-1;3], p=0.356). Reduction in QRS duration was larger with RV pacing compared with intrinsic conduction (-38±26 versus -26±24 ms, p<0.001). We found significant improvements in the remaining secondary endpoints, with no difference between the groups.
Conclusion
Patients with RV paced QRS morphology who are upgraded to a CRT device derive substantial improvement in cardiac function and functional capacity, comparable to patients with intrinsic conduction undergoing CRT.