Disturbed Atrial Mechanical Function In CIED-detected Atrial High-rate Episode,A Speckle Tracking Study

Background:Cardiac implantable electrophysiology devices(CIED)are designed to treat diseases such as bradyarrhythmia and monitor cardiac electrical activity in real time and in long term.CIED can detect atrial high-rate episodes(AHRE)by sensing the depolarizing electrical activities of the local myocardium with the leads fixed in atrium.At present the intrinsic connection between atrial high-rate episodes and stroke or systemic thromboembolic events is still unclear.And the potential myocardial changes which come up with AHRE are mysterious.Methods:From June 2017 to December 2017,we prospectively enrolled 97 patients who were in sinus rhythm and planned to get implantation of dual-chamber CIED for their first time in the First Affiliated Hospital of Zhejiang University.We excluded the patients with implantable automatic defibrillator(ICD)or cardiac resynchronization therapy(CRT)and kept only those with DDD pacemaker in study.All the eligible patients were followed up for 3 months.82 patientes were followed up successfully and 3 missed.Then all the patients were divided into 2 groups,depending on whether AHRE occured within 3 months after implantation.Echocardiographic dynamic grayscale images were acquired before and 3 months after the implantation.Simpson’s method was applied to gain the volume of left atrium to assess the degree of structural modeling,including left atrium end-diastole volume(LAEDV)and left atrium end-diastole volume index(LAEDVI).And off-line speckle tracking echocardiography(STE)analysis was performed in three-chamber view(left ventricular long-axis view,APLAX),two-chamber view(CH2)and four-chamber view(CH4)to gain the strain varibles of the atrium to assess the degree of functional remodelingn.Strain varibles included the global varibles,such as(1)global longitudinal booster strain during late diastole(GLSa),time to booster strain during late diastole(TBS).(2)global longitudinal reservoir strain during systole(GSLs),time to reservoir strain during systole(TRS).(3)global longitudinal conduit strain during early diastole(GLSe).And we measured the negative maximum value of strain and strain rate of atrial basal segment,middle segment and distal segrnent,which were defined according the distance from atrial segment to the atrioventricular valve to reflect cantraction of local myocardial:(1)left atrial anterior strain(LAAS)and left atrial anterior strain rate(LAASr).(2)left atrial inferior strain(LAIS)and left atrial inferior strain rate(LAISr).(3)left atrial posterior strain(LAPS)and left atrial posterior strain rate(LAPSr).(4)left atrial lateral strain(LALS)and left atrial lateral strain rate(LALSr).The relevance between AHRE and strain and other clinical features was analyzed.In addition we used Logistics regression analysis to screen risk factors for AHRE.Results:Among the 82 subjects without previous history of atrial fibrillation,the incidence of AHRE within 3 months after CIED implantation was 14%(11 cases).The AHRE-positive group included 11 subjects with 9 females.Sick sinus syndrome was present in 9 patients,atrioventricular block was reported in 4 cases and bundle branch block occurred in 1 case.The AHRE-negative group included 71 subjects with 36 women and with 36 had sick sinus syndromes,41 had atrioventricular block while bundle branch block occurred in 9 cases.E peak velocity was faster in AHRE-positive group than in AHRE-negative group(1.05±0.14 m/s vs 0.81±0.26 m/s,P=0.014<0.05).And compared with the AHRE-negative group,the AHRE-positive group had a lower incidence of E/A ratio being smaller than 1(27.3%vs 63.4%,P=0.045),a lower incidence of left ventricular diastolic dysfunction(27.3%vs 67.6%,P=0.017)and a higher incidence of pulmonary hypertension(36.4%vs 5.6%,P=0.010).The ratio of atrial pacing and ventricular sensing(AP-VS)was higher in AHRE-positive group than in AHRE-negative group(48.17±33.32%vs 25.89±29.47%,P=0.039),and so was the ratio of atrial pacing(AP)(62.48±30.34%vs 35.33±27.84%,P=0.004).As for the CHA2DS2-VASc scores,which means CHA2DS2-VASc system:congestive heart failure,hypertension,age ≥75y(doubled),diabetes mellitus,stroke(doubled),vascular disease,age 65-74 and sex Category(female),the ratio of patients with CHA2DS2-VASc scores greater than 2 in AHRE-postive group was significantly larger(81.8%vs 46.5%,p=0.048).The preoperative STE results were analyzed.First of all,structural remodeling was observed in AHRE,with LAEDVI increasing significantly(79.78±19.56 ml*m-2 vs 62.37± 17.77 ml*m-2).Second,functional remodeling was observed in AHRE.As the global atrial strain reduced,we realized that the booster function and reservoir function decreased in AHRE.As the results told,left atrial GLSa decreased(CH2:-8.80±3.67%vs.12.18±3.98%;CH4:-7.81±3.39%vs-11.77±5.35%),GLSe decreased(APLAX:-8.45±3.68%vs-15.83± 12.90%)and GLSs decreased(APLAX:17.74 ± 5.83%vs 27.78± 12.78%;CH2:17.75± 8.17%vs24.14± 5.49%;CH4:19.17± 5.66%vs24.92±8.32%).Right atrial GLSa also(-9.61 ±4.22%vs-13.52±4.93%),GLSe decreased(-9.85±4.85%vs-13.86±7.61%)decreased with GLSs(19.45±5.90%vs 27.38±8.43%).All of above were statistically significant(P<0.05).In addition,the local strain varibles reduced,demonstrating weaker contraction of atrial segment.Among the strains of the four walls of left atrium,there were LAPSr decreasing(basal:-1.77±0.57%*s-1 vs-2.47±0.72%*s-1;middle:-1.37±0.65%*s-l vs-2.11 ±0.56%*s-1;distal:-1.36±0.69%*s-1 vs-1.97±0.71%*s-1),LAISr decreasing(middle:-1.60±0.43%*s-1 vs-2.09±0.60%*s-1,),LAAS decreasing(basal:-9.77±5.02%vs-14.02±5.00%;middle:-8.36±4.13%vs-12.41±4.15%),LAASr decreasing(basal:-1.41 ± 0.67%*s-1 vs-2.06±0.65%*s-1;middle:-1.16±0.43%*s-1 vs-1.81±0.47%*s-1),and LALSr decreasing(basal:-1.39±0.35%*s-1 vs-2.25±0.73%*s-1;middle:-1.15±0.39%*s-1 vs-1.86±0.62%*s-1;distal:-1.16±0.67%*s-1 vs-1.77±0.75%*s-1),all with statistical significance(P<0.05).According to the postoperative STE results,functional remodeling still exist 3 month after implantation of CIED in AHRE patients.First of all,the global atrial strain reduced and booster function decreased,with left atrial GLSa decreasing(APLAX:-10.50±4.95%vs-15.07±4.65%;CH2:-10.75±4.08%vs-16.27±4.52%)significantly.Second,local strain reduction was observed.As the results told.LAPS decreased(middle:-14.23±4.70%vs-18.06±4.92%;distal:-9.581±7.70%vs-15.06±5.60%),LAPSr decreased(middle:-1.951±0.85%*s-1 vs-2.31±0.64%*s-1;distal:-1.33±0.94%*s-1 vs-2.17±0.83%*s-1),LAAS decreased(basal:-10.28±3.42%vs-17.71 ±6.30%;middle:-9.33±2.55%vs-15.90±7.20%)and LAASr decreased(basal:-0.76±0.87%*s-1 vs-2.34±0.80%*s-1;middle:-0.95±0.33%*s-1 vs-2.19±0.73%*s-1),all having been proved to be statistical significant(P<0.05).In addition,we compared all the patients’ preoperative STE data with their own postoperative one,to find out a smaller left atrium with LAEDV and LAEDVI decreasing significantly.We also find out that all patients’ left atrial GLSa increased and TBS increased,right ventricular GLSa increased,while left atrial GLSe decreased,left atrial GLSs decreased and TRS decreased,all with statistical significance(P<0.05).Besides,local strain and strain rate increased significantly.In more detailed facts,it was recorded that all patients’ LAPS increased and LAPSr increased in the middle segment.LAIS increased in each segment,while LAISr in the middle segment and the distal segment increased.LAAS increased in each segment,while LAASr increases in the middle and distal segments.The increase of LALS in each segment and the increase of LALSr in the distal segment were observed too.All these changes were proved to be statistically significant(P<0.05).A binary logistic regression analysis revealed that greater preoperative left atrium GLSa was associated with lower risk of AHRE(OR=0.764,95%CI:0.592-0.987,P=0.039);What’s more,greater preoperative left atrium GLSe(OR=0.821,95%CI:0.683-0.987,P=0.036)and preoperative GLSs(OR=0.868,95%CI:0.762-0.988,P=0.034)were also associated with lower risk of AHRE.Meanwhile,factor positively associated with AHRE was atrial pacing rate(AP-VS),but P=0.085,which was not statistically significant.Conclusion:1.AHRE was accompanied by atrial structural remodeling and functional remodeling.There was significant difference in both preoperative and postoperative atrial strain results between patients with and without AHRE.2.Implantation of CIED could result in a smaller left atrial,stronger booster function of the atrium,lower conduit function and reservoir function,and enhanced local contraction and deformation of left atrium.3.There were some significant difference between patients with and without AHRE in respects of preoperative E peak flow rate,E/A ratio,left ventricular diastolic restriction,pulmonary arterial pressure elevation,CHA2DS2-VASc score,and the proportion of atrial pacing within first 3 months.4.Left atral GLSa,left atrial GLSe,and right atrial GLSs are the protective factors of AHRE.