| Objective（s）:Atrioventricular block（AVB）is a slow-onset arrhythmia for which cardiac pacing is the most effective treatment,and postoperative programmed optimization must focus on the atrioventricular interval（AVI）,which should be set physiologically to maximize cardiac function after pacing.Currently,there is no standardized method or accepted optimal value for programmed optimization of AVI,and it is dependent on individual physician experience,with significant variation in efficacy across different levels of hospitals and physicians.To this end,we designed this study to validate the efficacy and safety of the USCOM,an ultrasound Doppler hemodynamic monitoring device,through a prospective randomized controlled trial,with the ultimate goal of discovering a safe,effective,practical,convenient,and easily replicable method of AVI optimization,promoting the"standardization"of AVI optimization techniques,and improving the overall condition of the patients involved.Methods:Patients with a diagnosis of second-degree type II,high,III AV block who had a permanent dual-chamber pacemaker implanted and were randomized to the study and control groups were included in our hospital during the period2020-2022.were included and randomized to the study and control groups.In the study group,the AVI was set individually by USCOM,and the programmed Sensed AV interval（SAV）/Paced AV interval（PAV）was set to eight levels:（1）90/120ms,（2）120/150ms,（3）150/180ms,（4）180/210ms,（5）210/240ms,（6）240/270ms,（7）270/300ms,（8）300/330ms,and the AVI with the highest cardiac output measured by USCOM was the best AVI,and the programmed parameter was retained;the control group was programmed with SAV/PAV at 150/180 ms as usual.At the follow-up time of 1 month,baseline and review clinical data were collected to compare the symptoms,cardiac structure and cardiac function indexes between the two groups,and to analyze the factors affecting cardiac structure and function after pacing.Data entry and statistical analysis were performed with SPSS.Results:1.Baseline demographic characteristics and clinical data:A total of 80patients were included,including 51 males and 29 females.There were 48 cases in the study group and 32 cases in the control group.There were no statistically significant differences between the two groups in terms of age,diagnosis,disease history,weight,systolic blood pressure and NT-pro BNP,and statistically significant differences in terms of gender（males35（72.9%）vs 13（females27.1%）,P<0.05）,height 166.08±7.38cm vs 161.03±9.23cm,P<0.05 and body surface area 1.78±0.14 m2vs 1.79±0.18m2,P<0.05 with statistically significant differences.Patients in the study group were taller than the control group and had a larger body surface area than the control group.2.Baseline cardiac ultrasound:The left atrial diameter（LAD）、left ventricular end diastolic dimension（LVEDD）、Left ventricular ejection fraction（LVEF）and aortic internal diameter of the overall population were 34±4.86 mm,46.48±6.28 mm,63.27±6.56%and 20.48±2.12 mm;respectively;There were 29 cases of no mitral regurgitation,There were 23 cases of no tricuspid regurgitation,50 case of mild regurgitation,7 case of moderate regurgitation.There were no statistically significant differences in baseline cardiac cardiac ultrasound indicators between the two groups.47 case of mild regurgitation,3 case of moderate regurgitation,and 1 case of severe regurgitation.3.Baseline pacing and ECG-related indicator:The overall population in this study had 4 cases of right ventricular electrode implantation in the apical region and 76cases of septal implantation.The Atrial threshold was 0.6（0.5,0.8）v,the sensing was3.14±1.67m V,impedance was 622.35±166.48Ω;The Ventricular threshold was 0.8（0.5,1.1）v,the sensing was 9.23±4.80m V,and the impedance was.（745.73±216.87Ω）;The intrinsic QRS durrtion（IQRSd）was（112.75±26.67ms）,and the pacing QRS duration（PQRSd）was130.37±27.27ms;The percentage of atrial pacing was 7.8（1.9,28.2）%and the percentage of ventricular pacing was 99（63,100）%.There was a statistically significant difference between the two groups comparing their intrinsic QRS wave durrtion,which was prolonged in the study group compared with the control group 117.54±27.63ms vs 105.32±23.63ms,P<0.05.The rest of the above indicators were not statistically significant differences.4.Comparison of USCOM parameters after pacing program control:each USCOM parameter in the overall population was as follows:Cardiac output（CO）2.44±0.99l/min,Cardiac index（CI）1.40±0.56l/min/m2 Stroke volume（SV）32.68±13.53ml,Systemic vascular resistance（SVI）18.75±7.69ml/m2,HR 74.97±12.03bpm.There was no statistically significant difference in the percentage of ejection time and heart rate between the two groups,and statistically significant differences were found in the remaining paremeters.CO 2.73±1.10l/minvs2.00±0.58l/min,P<0.05,CI 1.54±0.59l/mi n/m2vs1.20±0.43l/min/m2,P<0.05,SV36.56±14.74mlvs26.68±8.62ml,P<0.05,SVI 20.39±8.12ml/min vs16.19±6.26 ml/min,P<0.05.In the study group,CO,CI,peak Velocity of flow（Vpk）,velocity time integral（Vti）,Minute distance（MD）,SV,and SVI were increased,Systemic vascular resistance（SVR）and ystemic vascular resistance index（SVRI）were decreased compared to the control group.5.Cardiac ultrasound and symptom scores at 1 month of follow-up:each parameter of cardiac ultrasound in the overall population was as follows:LAD 33.51±4.25 mm,LVEDD 45.86±4.92 mm,LVEF 63.04±5.83%,aortic internal diameter 20.48±2.12mm),left atrial volume index（LAVI）26.74±7.83 ml/m2,E-peak 65.88±21.24cm.s-1,A-peak 81.56±20.11cm.s-1,E/A 0.84±0.38,E/e’8.95±4.48,deceleration time（DT）145.55±58.59ms.no mitral regurgitation in 27 cases,mild regurgitation in 50 cases,moderate regurgitation in 3 cases;no There were 14 cases of tricuspid regurgitation,63 cases of mild regurgitation,and 3 cases of moderate regurgitation.There was a statistically significant difference in the A-peak between the two groups 77.2±17.19 cm.s-1vs.88.32±22.62 cm.s-1,P<0.05,and the A-peak was lower in the study group.The rest of the above cardiac ultrasound indices showed no statistically significant differences.The total pacemaker symptom score for the overall population was 0（0,1）,with no statistically significant differences in symptom scores between the two groups.6.Correlation analysis of all patients revealed a positive correlation between ventricular pacing QRS wave duration and LVEDD r=0.262,P=0.019 and a negative correlation with LVEF r=-0.235,P=0.036.Conclusion（s）:1.In this study,the optimal SAV/PAV judged by USCOM determina tion of hemodynamic parameters ranged from 120ms/150ms to 240ms/270ms with no fixed value,indicating that the optimal AVI varies significantly between individuals with a large degree of dispersion,making it difficult to determine the optimal value by conventional programming alone.2.USCOM-guided optimization of AVI in dual-chamber pacemakers can improves short-term hemodynamics in patients with atrioventricular block;in addition,in addition,it has an effect on late ventricular diastolic trans mitral blood flow,but the significance of this effect on cardiac structure and function cannot yet be defined.3.The pacing QRS wave duration affects the E-peak flow velocity of mitral valve and is positively correlated with LVEDD and negatively correlated with LVEF,suggesting that the delayed electrical activity associated with right ventricular pacing affects cardiac structure and function,and that the more delayed ventricular depolarization during pacing has a greater the negative effects on cardiac structure and function.4.USCOM-guided physiological AVI optimization of dual-chamber pacemakers in patients with AVB is a safe,feasible and effective new method that deserves clinical promotion. |
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