Background
Reproducibility and hemodynamic efficacy of optimization of AV delay (AVD) of cardiac resynchronization therapy (CRT) using invasive LV dp/dt
max are unknown.
Method and results
25 patients underwent AV delay (AVD) optimisation twice, using continuous left ventricular (LV) dp/dtmax, systolic blood pressure (SBP) and pulse pressure (PP). We compared 4 protocols for comparing dp/dtmax between AV delays:
Immediate absolute: mean of 10 s recording of dp/dtmax acquired immediately after programming the tested AVD,
Delayed absolute: mean of 10 s recording acquired 30 s after programming AVD,
Single relative: relative difference between reference AVD and the tested AVD,
Multiple relative: averaged difference, from multiple alternations between reference and tested AVD.
We assessed for dp/dtmax, LVSBP and LVPP, test-retest reproducibility of the optimum.
Optimization using immediate absolute dp/dtmax had poor reproducibility (SDD of replicate optima = 41 ms; R2 = 0.45) as did delayed absolute (SDD 39 ms; R2 = 0.50). Multiple relative had better reproducibility: SDD 23 ms, R2 = 0.76, and (p < 0.01 by F test).
Compared with AAI pacing, the hemodynamic increment from CRT, with the nominal AV delay was LVSBP 2 % and LVdp/dtmax 5 % , while CRT with pre-determined optimal AVD gave 6 % and 9 % respectively.
Conclusions
Because of inevitable background fluctuations, optimization by absolute dp/dtmax has poor same-day reproducibility, unsuitable for clinical or research purposes. Reproducibility is improved by comparing to a reference AVD and making multiple consecutive measurements. More than 6 measurements would be required for even more precise optimization ¡ª and might be advisable for future study designs. With optimal AVD, instead of nominal, the hemodynamic increment of CRT is approximately doubled.
