CP14: OPTIMIZING OF AV DELAY BY INTERAPEX PREEXCITATION TIME (IAPT) DETERMINATION IN OBSTRUCTIVE HYPERTROPHIC CARDIOMYOPATHY.

Background The effectiveness of DDD pacing in the case of hypertrophic obstructive cardiomyopathy (HOCM) depends on the optimal AV delay (AVD) programming. There are no criterions of appropriate AVD calculation. We hypothesized that the optimal AVD may depend on the interapex preexcitation time (IAPT). The present study exemines if DDD pacing efficathy is depends upon an IAPT magnitude. Methods IAPT measurement was performed in 21 HOCM patients with LV OT SPG>30 mm Hg. IAPT was determined with the help of step-by-step AVD shortening with RVA pacing from the sensing of RVA's own excitation by pacemaker (initial AVD) up to the moment of shortening of AV interval on the LVA catheter. That is the IAPT is the necessary RVA pre-excitation period needed to achieve LVA pre-excitation. Outflow tract systolic pressure gradient (SPG) was assesed by Echocardiography. Results The maximum SPG reduction (ranging from 30% to 100% of initial values) occurred with AVD shortening by 80-120 ms from initial AVD and persisted up to the moment of mitral valve wedging. The onset of this period gradient decrease coincided with the IAPT end phase, which appeared to be a stabile value of 100-120 ms in adults and 80-100 ms in children. The efficient DDD pacing therapy of HOCM was possible only if the IAPT was smaller than the AV interval of RVA and can launch LVA pre-excitation after the left atrial systole providing time for its complete contraction. Conclusion The clarification of IAPT enables reliable AVD programming in HOCM patients. All you need is to determine the real AV conductance time with atrium faster-thansinus-rhythm pacing (DDD-regime) and with atrial excitation detection (VDD-regime) and to subtract the time of interapical preexcitation. To secure a reliable ALV preexcitation on various systolic frequencies one needs to correctly program the physiological frequencydependent AV interval linear shortening. [ABSTRACT FROM PUBLISHER]