Abstract 13256: Heart Failure Patients with IVCD Who Respond to CRT May be Differentiated from Nonresponders by QRS Frequency Content
Cardiac resynchronization therapy (CRT) is controversial in patients with nonspecific intraventricular conduction defect (IVCD) due to high non-response rates. However, this constitutes a significant portion of CRT candidates. We have previously identified QRS signal properties distinguishing left bundle branch block (LBBB) patients responders to CRT (ie upward shift in QRS frequency content), from nonresponders (no change). We hypothesized that IVCD patients undergoing CRT would exhibit similar changes in the frequency spectrum.
Methods: We examined the QRS frequency content of 30 CRT responder patients (R) and 37 nonresponders (NR) with baseline IVCD before and after CRT. We utilized a custom made computer algorithm for QRS isolation and Fourier analysis. In order identify a unique value to characterize the frequency content, we derived the median frequency (F50), where 1/2 the total frequency power of the QRS lies on either side of that value. CRT response was defined as a reduction in the LV end systolic volume by 10% after at least 6 months of CRT pacing. F50 values were then computed from the standard ECG for leads I, AVF and V3. F50 values were compared between the R and NR groups, before and after implantation (nonparametric Mann-Whitney test).
Results: No differences were appreciated in leads I or AVF. However, lead V3 exhibited significant differences between the two IVCD groups at baseline and post-CRT (Figure). The F50 in the R group trended higher than the NR group at baseline. However, after CRT the F50 of the R group trended higher still while the NR group F50 decreased (p<0.05). This resulted in a significant difference between the two groups after CRT (p<0.01).
Conclusions: IVCD responders to cardiac resynchronization therapy show similar changes in QRS frequency content to LBBB responders (increased frequency) after implantation. This suggests that QRS frequency analysis may aid candidate selection for CRT and may aid selection of LV lead position.
- © 2012 by American Heart Association, Inc.