Abstract
1.1.1 Aims- To determine whether a reduction in bulk activation time results in the optimisation of cardiac resynchronisation therapy (CRT) patient outcome.
- To investigate and compare the echocardiographic technique and Electrocardiographic Imaging (ECGi) for obtaining ventricular activation time for the optimisation of CRT in subjects
- To analyse the effect of changing the spacing vectors on ventricular activation time when quadripolar leads are used with ECGi.
- To use ECGi for serial non-invasive assessment of the effects of CRT on electrical activation concerning the underlying electrical substrate.
1.1.2 Methods
Recruitment of twenty-one patients was done based on established CRT criteria. After implantation, patients went through echo-guided optimisation of the AVD and VVD. ECGi was also performed on patients during this procedure. ECGi maps were constructed for each AVD and VVD. Offline analysis of these maps was done. Optimal AVD and VVD timings were calculated with the help of the total ventricular activation time (TVaT) and a ventricular activation time index (VaT10-90Index). Optimal values were the ones that gave minimal TVaT and VaT10-90Index values. These electrical timings were also correlated with cardiac output.For 19 patients, quadripolar leads were a part of the CRT system, activation maps were constructed for the available vectors and TVaT and VaT10-90Index were calculated.For the remaining 11 patients, activation maps were created through ECGi on the day immediately after the implant and also at the 6-month follow-up visit.
1.1.3 Results
A 20% reduction in bulk activation time (VaT10-90 Index) was seen when optimisation was done with ECGi as compared to echocardiographic programming optimisation. Improved ventricular hemodynamics indicated rapid ventricular activation. A marked reduction in ventricular activation times (particularly in VaT10-90Index) between the most and least synchronous vectors was observed when quadripolar lead was a part of the CRT system.Both total and bulk ventricular activation times significantly decreased when the CRT system was turned on during day 1. After 6 months, a stable decrease in TVaT was observed. This was different from VaT10-90Index. CRT caused a reduction in total and bulk activation times in non-ischaemic subjects. Electrical remodelling exhibited by volumetric responders after 6 months, was not evident in non-responders
1.1.4 Conclusions
CRT response may show significant improvement due to ECGi optimisation because ECGi guided programming may achieve superior fusion of activation waveforms. Ventricular activation timings in both ischaemic and non-ischaemic patients are significantly affected by a change in the configuration of an LV quadripolar lead. Ischaemic patients and volumetric responders show rapid bulk myocardium activation and synchronisation with regards to CRT. This leads us to the conclusion that reverse electrophysiological remodelling in the bulk myocardium may be happening as a result of CRT, but not in late-activating ischaemic or fibrotic regions.
| Date of Award | 1 May 2021 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Steven Niederer (Supervisor) & Christopher Aldo Rinaldi (Supervisor) |