Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Norwegian South East Health Authorities
Introduction
Resynchronization therapy effectively restores myocardial function. No measures exist that specifically quantifies resynchronization. A parameter that quantifies resynchronization should be able to detect effective resynchronization and should not respond to changes in contractility caused by heterometric regulation. Left ventricular pacing (LVP) is associated with dyssynchronous contraction patterns, while biventricular pacing (BIVP) promotes resynchronization dependent on the pacing position of the LV electrode.
Purpose
We compared the acute differences between BIVP and LVP with regards to the preload dependent maximum rate of the LV pressure rise (dP/dtmax), and time to peak dP/dt (Td) to determine which better reflect dyssynchrony and resynchronization.
Methods
Twenty nine patients in heart failure with LBBB underwent CRT implantation with continuous LV pressure registration. The LV lead was first placed in either apical or anterior position followed by a permanent placement in a lateral position. Sequential LVP and BIVP pacing were performed for one minute, at a rate 10% above intrinsic heart rate, before dP/dtmax measurements were recorded. For LVP, BIVP and RVP a patient specific AV delay was used to avoid fusion with intrinsic conduction. Td was defined as the time from pacemaker stimuli to peak dP/dt. Mixed linear models were used for statistics, numbers are estimated marginal means ± SEM and are only reported when with significance set at p < 0.05.
Results
We found no differences in dP/dtmax between BIVP (899 ± 37mmHg/s) and LVP (910 ± 37mmHg/s), while RVP (799 ± 37mmHg/s) was lower. Td was lower with BIVP (165 ± 4ms) than LVP (178 ± 4ms) and RVP (184 ± 4ms). We found no differences in dP/dtmax between lateral (890 ± 35mmHg/s) and anterior (874 ± 38mmHg/s) while apical (824 ± 38mmHg/s) was lower. Td was lower in lateral (171 ± 4ms) than in anterior (179 ± 4ms) and apical (182 ± 4ms) positions. BIVP in lateral position (158 ± 4ms) was lower than any other pacingmode*position, with BIVP*anterior at 173 ± 4ms) and LVP*lateral at 170 ± 2ms. No difference was seen in dP/dtmax between (BIVP + LVP)*(lateral + anterior) that was higher than all other pacingmode*positions.
Conclusion
Td shortens with BIVP and lateral position, and even more so with BIVP in lateral position and thus reflects resynchronization compared to all other combinations tested. DP/dtmax did not reflect resynchronization as BIVP/LVP and lateral/anterior performs equally good. There are no differences between dP/dtmax with any combination of pacing mode (BIVP + LVP) with position (anterior + lateral). This suggests that Td reflects resynchronization while dP/dtmax does not. Resynchronization with biventricular pacing in lateral position translates into a shorter Td and hence links electrical and mechanical events. Td could be the missing link between electrical and mechanical dyssynchrony and may serve as a biomarker for cardiac resynchronization therapy.
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