OPTIMIZING THE AV DELAY IN DDD-PACEMAKER PATIENTS WITH PRESERVED AV-CONDUCTION

There is conflicting data on whether or not intrinsic AV-conduction (i c) should be preserved in patients (pt) paced with dual chamber device s (DDD-PM) in the absence of overt high degree AV block. In 32 pt with DDD-PM implanted for sick sinus syndrome (n = 25), syncope with bifas cicular block (n = 5) and intermittent high degree AV block (n = 2), i mpedance cardiography (ICG) was used to determine the AV delay (AVD) w hich yielded the maximum stroke volume (MSV). At the time of the study no pt showed high degree AV block. With steps of 20 - 30 ms the AV de lay was prolonged until ic took place. Programmed pacing modes were DV I only (n = 21), DVI and VAT (n = 9) and VAT only (n = 2), resulting i n 41 AVD optimization procedures (AVO). In the VAT group the PR interv al for sinus rhythm without ventricular tracking was 205 25 ms (ms). I n the DVI group the corresponding interval between the atrial stimulus and the beginning of QRS was 250 30 ms. In 10 AVOs, MSV was seen with ic, even if a bifascicular block was present (3 out of 10). In 31 stu dies, MSV was associated with ventricular pacing at an AV delay of 90 51 ms (VAT, n = 9) and 135 44 ms (DVI, n = 22), respectively, includin g pt with normal intrinsic QRS duration (18 out of 31). The hemodynami c benefit of ventricular pacing increased with the difference between the intrinsic conduction time and the optimum AV delay. DDD pacing in pt without overt high degree AV block does not necessarily show maximu m hemodynamic benefit from preserving intrinsic ventricular depolariza tion. There are no simple rules for AV delay programming in this subse t. The individually optimal AVD may be found by ICG, but further evalu ation is necessary.