Defibrillation threshold testing does not cause acute electrocardiographic changes in cardiomyopathy patients undergoing insertion of an implantable cardioverter defibrillator

Abstract

and repeated five times at 2-week intervals. T-wave morphology descriptors [TCRT, T-wave morphology dispersion (TMD) and CRA parameter] were calculated every 5 seconds in overlapping 10-second ECG segments. Recordings with fewer than total 1000 analyzable segments or fewer than 100 segments during the first or the last hour of the recording were excluded. Results: A total of 187 intradialytic recordings were included in the final analysis containing on average 2699 ± 592 ECG segments. Mean intradialytic values were as follows: CRA 0.204 ± 0.101, TMD 32.14 ± 21, and TCRT 0.282 ± 0.583.There was a positive correlation between CRA and TMD (p = 0.000, CE .528) and CRA and TCRT (0.312, p = 0.000). Comparison between averaged values during the first and after the third hours of recordings showed statistically significant differences in CRA, TCRT and TMD [independent-sample t test p b 0.05 for 182 (97.3%), 179 (95.7%) and 180 (96.3%) of comparisons respectively]. Intradialytic changes were expressed as (last hour value − first hour value)/first hour value and denoted as CRAD, TMDD and TCRTD. More than 10% intradialytic increase was noted in 55.5%, 41.8 %, and 55.5% while more than 10% decrease in 8.2%, 35% and 12.3% of the overall recordings for CRA, TCRT and TMD, respectively. There was a positive relationship between intradialytic change of CRA and TMD (correlation coefficient of 0.211, p = 0.05). Repeated-measures ANOVA of average CRA, TMD, TCRT and their intradialytic changes (CRAD, TMDD and TCRTD) in subjects with five consecutive analyzable recordings showed intrasubject stability (CRA F = 0.558, p = 0.694; TMD F = 0.770, p = 0.483; TCRT F = 1.966, p = 0.135; CRAD F = 0.356, p = 0.839; TMDD F = 0.533, p = 0.630; TCRTD F = 1.498, p = 0.239). Pre-dialysis hyponatremia was associated with higher intradialytic changes in CRA (independent-sample t test p = 0.019). Conclusion: T-wave morphology descriptors exhibit differential subject specific dynamic profiles in response to fluid and electrolyte changes on dialysis. Predialysis hyponatremia may have a role in intradialytic CRA changes.