Maximizing efficiency of alternation algorithms for hemodynamic optimization of the AV delay of cardiac resynchronization therapy.

BACKGROUND: During optimization of the atrioventricular (AV) delay of cardiac resynchronization therapy (CRT), it is not known exactly which windows of time around the transition are most informative for identification of the optimum. METHOD AND RESULTS: IN 22 patients with CRT, we performed AV delay optimization using continuous noninvasive hemodynamics. We used signal-to-noise ratio to determine the most efficient averaging window location and width. We found that it is most efficient to position the averaging windows immediately before and immediately after the transition in AV delay. For example, skipping five beats after the transition decreases signal-to-noise ratio by 17.5% (P < 0.0001). Similarly, skipping five beats immediately before the transition reduces signal-to-noise ratio by 11.7% (P < 0.0001). The best choice of "fixed" averaging window width was found to be six beats, with signal-to-noise ratio falling by, for example, 41% for a one-beat window (P = 0.0002). However, even better was to set the window width for each patient to match one respiratory cycle. We observed that the pre- and posttransition signal-to-noise ratio traces begin to diverge three beats after the transition in AV delay. We believe this represents the time taken for the peripheral response to pacing-induced changes in stroke volume to occur. CONCLUSIONS: THE most efficient way to use alternating transitions for the hemodynamic optimization of CRT is to use an averaging window of one respiratory cycle, and not to skip any beats between the pretransition and posttransition averaging windows.

Efficiency, reproducibility and agreement of five different hemodynamic measures for optimization of cardiac resynchronization therapy.

BACKGROUND: Several hemodynamic measures have been used for optimization of the AV delay of cardiac resynchronization therapy (CRT), including pulse pressure (PP), systolic blood pressure (SBP) and cardiac output (CO). We aimed to determine whether these measures identify the same optimum and whether they have the same efficiency and reproducibility at identifying this optimum. METHODS AND RESULTS: In 22 patients with cardiac resynchronization therapy, we adjusted the AV delay while atrially pacing at 110 bpm and simultaneously recording SBP, diastolic blood pressure (DBP), PP, mean arterial pressure (MAP) and CO. SBP, PP and CO all had essentially the same signal-to-noise ratios (15.4+/-5.4, 15.5+/-6.4, 15.3+/-7.4 respectively p=NS). In contrast, MAP and DBP had significantly worse signal-to-noise ratios than SBP (14.2+/-5.6, p=0.003 and 12.1+/-4.4, p<0.0001 respectively). The optimal AV delay was very similar between SBP, PP, MAP and DBP. For example, the optima identified by SBP correlated strongly with those identified by PP (r=0.94), MAP (r=0.96) and DBP (r=0.90). In contrast, the optima detected by CO was poorly related to these (e.g. r=0.36 with SBP optima). Reproducibility was best for optima detected by SBP followed by MAP and PP. CONCLUSIONS: Essentially the same AV optimum is identified, regardless of whether the parameter chosen for maximization is SBP, PP, MAP or DBP. We conclude that optimizing the CRT AV delay using SBP gives the best combination of efficiency and reproducibility, with PP and MAP being reasonable alternatives.