The Short-term Inlfuence Of Low Atrial Septum Pacing On New Onset Atrial Fibrillation After Dual Chamber Paccmakcr In Patients With Sick Sinus Syndrome

Objective Patients with sick sinus syndrome (SSS) were divided to two groupsdepend on whether P wave duration was greater than120ms in lead II or not onsurface electrocardiogram. The atrial leads were randomly implanted to low atrialseptum (LAS) or right atrial appendage (RAA) between the two groups. Thecoronary sinus electrode was inserted to measure the conduction time from P waveto left atrial (P-LA) and left atrioventricular interval (LAVI). The new onset atrialfibrillation (Af) was compared on an average10±5months follow-up period. Wewill evaluate the short-term influence of LAS pacing on the new onset Af onpatients with SSS.Method A total of82consecutive patients (27males and55females; mean age67±10years, range45-86years) with symptomatic SSS who underwent dualchamber pacemaker implantation between March2012and September2013at ourhospital were screened. Af, double node dysfunction, congestive heart failure,valvular heart disease, hyperthyroidism, chronic obstructive pulmonary disease,cardiomyopathy, malignant tumor and contraindication in operation were excludedfrom study. The P wave duration and P wave dispersion were measured on surfaceelectrocardiogram before operation. The patients were divided to interatrialconduction block (IAB) group and non interatrial conduction block (non-IAB)group depended on whether P wave duration in lead II was greater than120ms ornot. The dual chamber pacemaker was implanted to all patients. In all patientscoronary sinus (CS) electrode were embedded to measure the electrophysiologicalparameters. The patients within the two groups were divided into low atrial septal pacing subgroup (LAS subgroup) or right atrial appendage pacing subgroup (RAAsubgroup) according to the randomly implanted sites of atrial leads. The rightventricular lead was placed at the right ventricular apex. The atrial pacing site wasconfirmed by means of X ray imaging and pacing electrocardiogram. P-LA andLAVI were measured on LAS or RAA pacing before and after operation. The Pwave duration and P wave dispersion were measured again after operation. Clinicvisits were scheduled at1,3,6and12months after implantation. The follow upcontents were included symptoms, signs, ECG or Holter, pacemaker program, theoccurence of new onset Af, complication of SSS patients. The occurence of newonset Af and cardiac conduction data were analyzed between groups and subgroups.The short-term effect of LAS pacing on the new onset Af on patients with SSS wereevaluated.Results1.There were no significant differences on complications, pacing andsensing dysfunction, impedance and displacement rate of atrial lead between theLAS pacing group and RAA pacing group on IAB group or non-IAB group（P>0.05）. However, the atrial leads placed time on LAS were longer than RAAbetween the two groups. The difference was statistically significant (P<0.05).2.The P wave duration, P wave dispersion and P-LA of LAS pacing group wereshorter than sinus rhythm of preoperation and RAA pacing on IAB group ornon-IAB group. However, the LAVI was longer on LAS pacing compared to RAApacing. The difference was statistically significant (P<0.05). P-LA and LAVI wereno significant differences when LAS pacing on IAB group compared to non-IABgroup(45±13vs44±11；139±26vs133±28，P>0.05). However, the shortened degreeof P-LA was greater when LAS pacing on IAB group. The difference wasstatistically significant (23±15vs13±10，P<0.05).3. During a mean of10±5months follow-up period,4of patients were lost to follow-up. The occurrence ofnew onset Af between IAB and non-IAB group or LAS and RAA group were no significant differences(20%vs9.4%，6.3%vs22%,P>0.05). However, the newoccurrence of new onset Af was lower while LAS pacing compared to RAA pacingon IAB group in subgroups analysis. The difference was statistically significan（t5%vs30%，P<0.05）. While non-IAB group, there was no statistically significant in theoccurrence of new onset Af between the two subgroups（8.3%vs10%，P>0.05）.Conclusion In patients with SSS and IAB, LAS pacing can obtain loweroccurrence of new onset Af compared to RAA pacing. The mechanism wasprobably associated with shortened interatrial conduction time, decreased P wavedispersion, prolonged LAVI and improved left atrioventricular synchronization.However, the occurrence of new onset Af were no significant differences betweentwo subgroups in patients with SSS and non-IAB.