Impacts Of Right Ventricular Apical Pacing On Cardiac Function And Left Ventricular Systolic Synchrony

Objective: To acquire patients'parameters of left ventricular function and systolic synchronism including left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular ejection fraction(LVEF) and stroke volume(SV) by real-time three-dimensional echocardiography(RT-3DE),test the brain natriuretic peptide(BNP) concentration,compare these parameters pre-operative and post-operative,assess impacts of RVA pacing on cardiac structure and function.By progrmming of AV-delay,we investigate RT-3DE at V-pace and V-sense mode respectively,assess impacts of different pacing mode on cardiac structure and function,observe the variation of BNP concentration during different pacing mode,evaluate the value and significance of RT-3DE and BNP during the follow-up of pacemaker,and explore the mechanism of RVA pacing on patients'hemodynamic.Methods: Seventy-one patients with sick sinus syndrom who received dual-chamber pacemaker during 2007 September to 2009 July in our hospital were selected.Atrial leads and ventricular leads were placed at right atrial appendage and right ventricular apex respectively.All patients had normal heart LVEF of >50%.Before pacing BNP concentration was tested.During prophase postoperative,we investigated RT-3DE at pacing and non-pacing respectively.After keeping parameters of pacemaker at acquiescence condition for three months, RT-3DE and BNP were repeated.After prolonging AV-delay for another three months,we test BNP and performed RT-3DE at RVA pacing(V-pace) and intrinsic conduction(V-sense) mode.Subjects were stratified into two groups according to whether they had developed systolic dyssynchrony when programmed to V-pace, then compared the clinical character of the two groups.All data was analysed by SPSS13.0. Results: 1. At prophase postoperative,there was increase in the standard deviation of the time to minimal regional volume of 16 left ventricular segments(Tmsv-16SD) at V-pace but no significance (13.8±8.2ms vs. 11.7±5.4ms,P<0.001), but significant increase in QRS duration(168±23ms vs.98±15ms,P<0.001),as well as enlargement in LVESV(26.7±6.3ml vs. 22.7±6.2ml,P<0.01),decrease in SV (34.4±10.2ml vs. 36.7±11.8ml, P<0.05)and LVEF(57.0±7.1% vs. 61.7±6.5%,P<0.01),but no significant change in LVEDV,Transmitral E velocity,Transmitral A velocity,E/A ratio,Deceleration time of E wave E,Isovolumic relaxation time and Left atrium diameter compared with patients at V-sense.2.The mean percentage of pacing was 59±34% three months after pacing.Significant enlargement was induced in LVESV (30.2±7.5ml vs. 22.7±6.2ml,P<0.05),Left atrium diameter (40±4mm vs. 35±5mm,P<0.05),with increase in Tmsv-16SD (22.7±7.6ms vs. 11.7±5.4ms,P<0.01) and BNP (153.6±35.1 pg/ml vs. 81.2±21.4 pg/ml,P<0.01) compared with baseline,whereas decrease in SV(31.4±9.7ml vs. 36.7±11.8ml,P<0.05),LVEF(50.9±10.3% vs. 61.7±6.5%,P<0.01);But no significant change in Transmitral E velocity,Transmitral A velocity,E/A ratio,Deceleration time of E wave E.3. The mean percentage of pacing was 15±14% six months after pacing. This time there was significant decrease in LVEF(53.6±6.1% VS. 61.3±6.5%, P<0.01),but increase in BNP(p<0.01) and Tmsv-16SD (15.9±6.9ms vs. 11.7±5.4ms, P<0.01),and no significant change in other parameters compared with baseline,;Compared with three months post-operative,significant decrease was induced in LVESV(25.2±5.9ml vs. 30.2±7.5, P<0.01),Tmsv-16SD(18.9±6.9ms vs. 22.7±7.6, P<0.01)and BNP level(125.0±28.3 pg/ml vs. 153.6±35.1 pg/ml, P<0.05),but increase in SV(35.8±10.4ml vs. 31.4±9.7ml, P<0.05),LVEF(53.6±6.1% vs. 47.8±10.3%, P<0.05),no significant change in other parameters.4. 43.0% (28 out of 65)patients developed systolic dyssynchrony six months after pacing.When programmed to V-pace,this group was found to have enlargement in LVEDV (66.0±12.1ml vs. 62.7±12.9ml, P<0.05),decrease in LVEF(51.8±5.1% VS. 54.0±5.3%, P<0.05)and SV (34.2±8.6ml vs. 33.8±8.4, P<0.05);Compared with no dyssynchrony group,the amplitude of LVEF(-2.2±4.2 vs. -1.1±3.0, P<0.01),LVESV(2.9±1.6 vs. 1.2±2.0, P<0.01)and SV(-2.9±2.0 vs. -0.6±4.9, P<0.001) were significantly greater in patients who developed significant dyssynchrony when programmed from V-sense to V-pace mode;At V-sense,patients with pacing-induced systolic dyssynchrony also had significantly larger LVESV (28.9±6.8ml vs. 22.2±5.3ml,P=0.01),low LVEF (54.0±5.3% vs. 63.4±5.9,P<0. 01),as well as left ventricular SV (33.0±8.4ml vs. 38.6±9.9ml,P<0.05);When compared between V-sense and V-pace mode,LVEF decreased to <50% in 6 out of 28(21.4%) in those who developed systolic dyssynchrony,but in none of the 37 patients without systolic dyssynchrony.Furthermore,the cumulative percentage of ventricular pacing in last six months was higher in patients stratified to dyssynchrony group(54±36%vs. 22±19%,P<0.001).No significant change was found in QRS duration, LVEDV and left atrium diameter at V-pace and V-sense mode in the two groups.5.There was no marked change in patients pacing threshold ,threshol of perception current and impedance of ventricular during follow-up.The parameters of pacing electrodes were stable and safe.Conclusion:①RVA pacing may have adverse impacts on systolic function in patients with preserved LVEF,but its impacts on diastolic function is determined.②Nearly half of the patients developed left ventricular systolic dyssynchrony six months after pacing in patients with preserved LVEF;③The independent determinants of systolic dyssynchrony included the low normal EF,pre-existing LV hypertrophy,and the cumulative amount of RVA pacing>40% in the past six months;④RT-3DE could accomplish most patients's image conversion;⑤BNP could well reflect left ventricular dysfunction;⑥RVA pacing was not the best choose though with normal LVEF.