How can the rate-adaptive atrioventricular delay be programmed in atrioventricular block pacing?

AIM: To optimize recommendations for programming of the rate-adaptive atrioventricular (AV) delay. METHODS AND
RESULTS: Optimal AV delay (AVD(opt)) is the net effect of the pacemaker-related interatrial conduction time (IACT), duration of the left-atrial electromechanical action (LA-EAC(long)) and duration of left-ventricular latency (S(V)-EAC(short)). It can be calculated by AVD(opt) = IACT + LA-EAC(long)-S(V)-EAC(short). We measured these three components in 20 DDD pacemaker patients (EF >45%) with the third degree AV block (AVB) at rest and submaximal ergometric exercise load of 71 +/- 9 W which resulted in a 31.5 +/- 9.9 bpm rate increase. Between exercise and rest, the components of and the final AVD(opt) showed no significant differences. Interatrial conduction time in VDD and DDD pacing varied by 2.3 +/- 8.4 ms and 1.4 +/- 8.8 ms, respectively, S(V)-EAC(short) changed by -2.6 +/- 21.8 ms and AVD(opt) by -3.5 +/- 33.3 ms and -4.3 +/- 37.8 ms in VDD and DDD operation, respectively. The greatest variation was of LA-EAC(long) by -8.4 +/- 32.7 ms. Linear regressions of the rate-dependent variations (Deltaf) in VDD operation yielded DeltaIACT(f) = 0.04Deltaf + 0.95 ms, DeltaLA-EAC(long) = -0.59Deltaf + 10.1 ms, and DeltaS(V) - EAC(short) = 0.14Deltaf -7.2 ms which resulted in DeltaAVD(opt) = -0.69Deltaf + 18.2 ms.
CONCLUSION: A recommendation for programming of rate-adaptive AV delay in AV block patients cannot be given.