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/dt max are unknown. Method and results 25 patients underwent AV delay (AVD) optimisation twice, using continuous left ventricular (LV) dp/dt max , systolic blood pressure (SBP) and pulse pressure (PP). We compared 4 protocols for comparing dp/dt max between AV delays: Immediate absolute: mean of 10s recording of dp/dt max acquired immediately after programming the tested AVD, Delayed absolute: mean of 10s recording acquired 30s 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/dt max , LVSBP and LVPP, test–retest reproducibility of the optimum. Optimization using immediate absolute dp/dt max had poor reproducibility (SDD of replicate optima=41ms; R 2 =0.45) as did delayed absolute (SDD 39ms; R 2 =0.50). Multiple relative had better reproducibility: SDD 23ms, 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/dt max 5%, while CRT with pre-determined optimal AVD gave 6% and 9% respectively. Conclusions Because of inevitable background fluctuations, optimization by absolute dp/dt max 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.