Clinical Study Of The Av Interval And Pacing Site

PartⅠInfluence of Different Atrial Ventricular delay on left ventricular functionBackground:For a long time DDD pacing is considered as physiological pacing for patients of atrialventricular block whose sinus node function is normal. Usually atrial and ventricular leads have been positioned in the right atrial appendage and in the right ventricular apex(RVA),respectively.RVA pacing altered ventricular depolarization vector and increased ventricular asynchronous,which resulted in deterioration of left ventricular function.Sensed atrioventricular delay(SAV) is a critical parameter to maximaize hemodynamics in atrialventricular block patients With DDD pacemakers.So how to program optimal SAV is paticully important.Objective:Using tissue Dopple imaging and conventional echocardiographic technique,and surface electrocardiography(ECG),we evaluate optimal SAV by different methods.Optimal SAV was achieved by providing the longest left ventricular filling time(FT),the highest VTI_AO and the minimum myocardial performance(MPI).We also examined the ventricular synchrony by Ts of left and right ventricule.Methods:1.Thirty-one patients(11 men and 20 women,58±14 years)with a DDD PM for third-degree AV block were studied.2.Different SAV were programmed ranged from 70ms to 170ms by steps of 20ms. At every SAV the following parameters were measured:FT,VTI_AO and MPI.Optimal AV delay was achieved by providing the longest FT,the highest VTI_AO and the minimum MPI.Compared MPI at optimal SAV and nominal AVD(150ms).3.Optimal SAV delay was achieved by programming a delay of 100ms from the end of the sensed wave to peak/nadir of the paced ventricular complex.First,a long SAV delay of 200ms was programed(long AVD).Optimal SAV=long SAV+100-T. T=the interval from the end of the P wave to the peak/nadir of the paced ventricular complex.Compare the MPI of optimal AVD and SAV 150ms.4.Compare time to peak systolic velocity(Ts) lateral wall and right wall at optimal SAV achieved by MPI and SAV 150ms.Results:FT,VTI_AO and MPI derived optimal SAV were significantly different (87.7±17.3ms,118q-27ms and 80±9.8ms).MPI decreased significantly at Optimal SAV achieved by MPI vs SAV delay 150ms(0.53±0.18 vs 0.78±0.21,p＜0.01 ).△Ts of left lateral wall and right wall were decreased at Optimal SAV(88.3±23.4ms vs 109.6±28.9ms,P＜0.01 ).MPI at Optimal SAV derived by surface ECG was decreased significantly(0.59±0.18 vs 0.78±0.21,P＜0.01).Conclusions:Different methods derived different optimal SAV.At MPI optimized SAV,systolic and diastolic performance of myocardial was highest. Optimal SAV achieved by surface ECG is a simple method that improved the cardiac function. PartⅡClinical Study of Right Ventricular Outflow Tract PacingBackground:Pacing from the right ventricular apex(RVA) is associated with an increased incidence of left ventricular dysfunction and atrial fibrillation and death,altered ventricular depolarization vector and increased ventricular asynchronous contraction.Right ventricular outfow tract(RVOT) pacing may provide better performance of the heart because it has an almost normal ventricular activation and conduction sequence.RVOT pacing may provide a shorter total ventricular activation time and reducing the adverse effects of RVA pacing,paticully for the third AV block patients.Objective:To compare the contraction synchrony and cardiac performance between different pacing sites:RVA and RVOT.Methods:Forty-five patients(16 men,58±16years) were studied.The patients were randomized into RVA group(n=31) and RVOT group(n=14).Optimal SAV was achieved by MPI method.After optimaized,ventricular synchrony and cardiac performance were further evaluated by comparing the different pacing sites.Results:Optimal SAV for RVA and RVOT pacing group were(80±9.8 ms vs 92±18ms,P＜0.01).IVD was 46.7±14.6ms for RVA pacing and 30.6±10.2ms for RVOT pacin(P＜0.01).△Ts of left lateral wall and septum were(89.5±25.7ms vs 27.9+10.5ms,P＜0.001) and left lateral wall and right wall were(88.3±23.4ms vs 29.5±16.7ms,P＜0.001) of RVA pacing and RVOT pacing.The contraction synchrony of RVOT pacing imprvoed significantly vs RVA pacing. Conclusions:RVOT pacing improved left ventricular contraction synchrony and cardiac performance compared RVA pacing.The advantage of RVOT pacing is correlated with pacing site. PartⅢAtrial Pacing:The Impact on Ventricular PacingBackground:Sick sinus syndrome(SSS) and atrial ventricular(AV) block are mostly common diseases for DDD pacing.Pacing at the right atrial appendage is known to delay left atrial contraction due to interatrial conduction time(PIACT). Left atrial activtion and conduction time delayed sinus rhythm for about 20-70ms. Activation and conduction time from atrial to ventricul was shorter than programed AV interval,which may increase the percentage of ventricular pacing.Objective:To evaluate the intrinsic AV conduction time in atrial pacing and in atrial sensing mode.To observe the influense of atrial pacing on the percentage ventricular pacing.Methods:This is a prospective own control study.Sixteen patients (7men,9women,61.8±9.7years) implanted with Medtronic Kapppa 700 pacemakers for SSS.Base rate was programed for 60 beats/min or 40 beats/min randomly after implantation.To compare the percentage of ventricular pacing at atrial pacing or atrial sensing and the percentage of VS from search.To determin the atrialventricular conduction time of atrial pacing and atrial sensing on marker channel on programer.Results:Time from AP to VS is 240.7±17.33ms,and from AS to VS is 174.2±18.46ms,atrial pacing may delay intrinsic AV conduction time for about 66.5±18.67ms.The percentage of Ventricular pacing(VP) at Atrial pacing(AP) and atrial sensing(AS) were(63.65±30.43%vs 9.68±10.81%,P=0.002) separately.Vs from search are(25.23±33.85%vs 85.71±22.26%,P=0.001 ) separately.The percentage of VP at nominal and optimized were(73.33±34.15%vs 6.29±8.02%, P＜0.001) separately.Conclusions:Atrial pacing increased the percentage of ventricular pacing. Optimized AVD individualy decreaed the ratio of ventricular pacing significantly.