Comparison of different invasive hemodynamic methods for AV delay optimization in patients with cardiac resynchronization therapy: implications for clinical trial design and clinical practice.

BACKGROUND: Reproducibility and hemodynamic efficacy of optimization of AV delay (AVD) of cardiac resynchronization therapy (CRT) using invasive LV dp/dtmax 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: 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; R(2)=0.45) as did delayed absolute (SDD 39 ms; R(2)=0.50). Multiple relative had better reproducibility: SDD 23 ms, R(2)=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--and might be advisable for future study designs. With optimal AVD, instead of nominal, the hemodynamic increment of CRT is approximately doubled.