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    Is individualised Cardiac Resynchronisation Therapy (CRT) programming superior to conventional programming with respect to QRS narrowing?

    Broadhurst, Lucy (2021) Is individualised Cardiac Resynchronisation Therapy (CRT) programming superior to conventional programming with respect to QRS narrowing? Doctoral thesis (Other), Manchester Metropolitan University.


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    Introduction: QRS narrowing is emerging as a key marker of successful Cardiac Resynchronisation Therapy (CRT) (Cleland et al, 2013; Jastrzebski et al, 2018). Individualised CRT programming, via fusion pacing, such as SyncAV) or multipoint pacing (MPP), has been shown to narrow QRS and give acute benefit (Varma et al, 2018; Forleo et al, 2017). Combining technologies may augment the benefit but there is little evidence to support this (O’Donnell et al, 2016). Accurate measurement of QRS duration (QRSd) is critical in CRT, but different methods are used in clinical practice. This study aims to establish whether individualised CRT programming is superior to conventional programming with respect to QRS narrowing. A secondary aim is to determine whether abbreviated global QRS methodology is comparable to single lead measurement for assessing QRS duration. Method: This observational study (n=28) compared five CRT programming strategies [Mode 1=Best single point pacing, Mode 2=Nominal SyncAV, Mode 3=Individualised SyncAV, Mode 4=MPP, Mode 5=Individualised Sync AV +MPP]. Optimal CRT was considered as narrowest QRSd (ms). QRSd was assessed by both individual ECG lead measurement and abbreviated global QRS methodology (QRS_aGlobal) over 5 leads. Patient response to CRT was assessed after a five-month follow-up period, using clinical and functional measures. Results: All CRT modes reduced QRSd compared to baseline (p<0.0001). Largest mean QRSd reductions were obtained with individualised programming modes. Mode 3 showed greater reduction in QRS when compared to Mode 1 (p=0.0036) and Mode 2 (p=0.0001). Mode 5 also reduced QRSd when compared to Mode 1 (p=0.0146), 2 (p=0.0301) and 4 (p=0.0049). QRSd measurements varied within the individual leads of the 12 Lead ECG; maximum standard deviation (SD) 21.6 ms, minimum SD 3.98 ms. Comparison of QRS_aGlobal and individual lead methodologies showed mean differences in QRSd ranging from 5.9 ms (V2) to 14.2 ms (Lead I) with broader limits of agreement 27.1 ms (QRS_Mean) to 37.5 ms (Lead II). QRS_aGlobal methodology demonstrated intra-operator variability of 4.8 ms ± 9.5 ms and inter-operator variability of 7.9 ms ± 15.5 ms. Assessment of response was limited by COVID19. Conclusion: This study supports the view that individualised CRT programming can produce maximal QRS narrowing. SyncAV appeared to have the greatest contribution to QRS narrowing. Further research is required as to whether individualised programming can influence patient outcomes. This study recommends standardisation of the methodology for measuring QRSd; different methods should not be used interchangeably. Abbreviated global QRSd is a pragmatic alternative to individual lead QRSd measurement using the Abbott programmer.

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