Atrial Vulnerability In Paroxysmal Supraventricular Tachycardia Patients And Its Influencing Factors

Background:Atrial fibrillation (AF) occurs more frequently in paroxysmal supraventricular tachycardia (PSVT) patients compared with the general population. Even after successful ablation of accessory pathways (APs) or slow pathway of atrioventricular node in patients with atrioventricular reentrant tachycardia (AVRT) or atrioventricular nodal reentrant tachycardia (AVNRT), there remains a high risk of AF recurrence. So "PSVT independent factors" may influence the atrial vulnerability in PSVT patients in addition to APs and/or slow pathway of atrioventricular node. The heart is innervated by both sympathetic and parasympathetic nerves, which are part of the autonomous nervous system. Stimulation of the heart sympathetic nerve can increase calcium entry and the spontaneous release of calcium from the sarcoplasmic reticulum. All of these factors promote the occurrence of AF. However, the relationship between sympathetic stimulation and atrial vulnerability in PSVT patients is currently unknown.Atrial vulnerability was widely defined as the occurrence of spontaneous and inducible AF and maintenance and perpetuation of the arrhythmia in atrial tissues according to the electrophysiological mechanisms underlying AF. The primary indexes of atrial vulnerability include dispersion of atrial effective refractory (dERP) and atrial electromechanical delay. The increases in the dERP and the atrial electromechanical delay are known to be related with an incremental atrial vulnerability, although no critical value can currently be used as a reference. Previous studies have shown that polymorphism of Kir2.1gene and connexin40gene, the pressure and diameter of the atrium, age and neural stimulation can influence atrial vulnerability. However, there is no study for detecting the atrial vulnerability in PSVT patients.Pulmonary veins (PVs) have been demonstrated to be a crucial source of human AF because their electrophysiological properties are strikingly different from those of patients without AF. Previous studies have established that PSVT might trigger remote atrial ectopy, including PVs, in turn initiating AF. Recently, the shortening effect of a history and short-lasting AF on the effective refractory periods of PVs in PSVT patients with APs have been reported by Derejko et al. and Rostock et al. The concept that PSVT begets "PSVT independent AF" in ectopy is widely accepted as an explanation for the high AF recurrence in PSVT patients. Pulmonary vein isolation (PVI) is widely accepted as the cornerstone and most commonly used catheter-based treatment for AF. Approaches to AF recurrence prevention are scarce in PSVT patients with AF episodes before radiofrequency catheter ablation (RFCA). It is unclear that whether PVI procedure can effectively prevent AF recurrence or not. Objectives:This study primarily aimed to:(1), assess whether intra-and interatrialelectromechenical delay could predict AF in PSVT patients after successful treatment by RFCA;(2), determine a predictive dERP value for performing PVI in paroxysmal supraventricular tachycardia patients;(3), determine the relationship between sympathetic stimulation and the atrial vulnerability in PSVT patients with AF. Innovations:The main innovations of this study included:(1), determine atrial electromechanicaldelay cutoff value for predicting AF occurrence in PSVT patients;(2), PSVT patients associated with AF who underwent PSVT ablation plus PVI were followed up to identify the AF prevention effect of PVI procedure;(3), determine whether the residual atrial vulnerability in addition to AP and the slow pathway of atrioventricular node in PSVT patients were associated with sympathetic stimulation or not. Methods:Study population:Part1, Atrial Electromechanical Delay Predicts Atrial Fibrillation in Paroxysmal Supraventricular Tachycardia Patients after Radiofrequency Catheter Ablation524consecutive PSVT patients undergoing electrophysiology examination at Qilu Hospital between January2007and October2009were enrolled in this study.Part2, Effect of Pulmonary Vein Isolation on Atrial Fibrillation Recurrence After Ablation of Paroxysmal Supraventricular Tachycardia in Patients with High Dispersion of Atrial Refractoriness67PSVT patients who had presented to Qilu Hospital between January2007and October2009with any AF documented by ECG or24-hour Holter before successful RFCA,Part3, Sympathetic Stimulation Affects Atrial Vulnerability in Paroxysmal Supraventricular Tachycardia Patients with Atrial Fibrillation768patients were included who were diagnosed as wolff-parkinson-white syndrome (WPW syndrome), AVNRT or AVRT and treated with RFCA at Qilu Hospital between January2009to October2011.All patients provided signed informed consent and the protocol was approved by Research and Ethics Committee of Qilu Hospital. All antiarrhythmic medications (such as beta-blockers, amiodarone and calcium channel blockers), digoxin and other drugs that have an effect on cardiac electrophysiological properties were withdrawn for＞5half-lives prior to operation. For this analysis, we excluded participants with diabetes mellitus, BMI≥25kg/m2, thyroid dysfunction, substance abuse (alcohol, caffeine and nicotine), atrial tachycardia (AT) and hypertension at baseline examination.Atrial electromechanical delay measurement:To establish the atrial electromechanical delay of the atrium, three time intervals were measured based on the echocardiographic indexes.T1:time interval from the beginning of P-wave on surface ECG to the beginning of the late diastolic wave of the lateral mitral annulus. T2:time interval from the beginning of P-wave on surface ECG to the beginning of the late diastolic wave of the septal mitral annulus.T3:time interval from the beginning of P-wave on surface ECG to the beginning of the late diastolic wave of the tricuspid annulus.Interatrial electromechanical delay was the interval from T3to T1, expressed as T1-T3.Intra-atrial electromechanical delay was the interval from T3to T2, expressed as T2-T3.dERP measurement:The atrial effective refractory period (AERP) was determined as the longest delivered coupling interval of atrial extra-stimulation that failed to capture the atrium and was determined at each of the four atrial recording sites, HRA, LRA, distal and proximal CS (respectively CS1,2and CS9,10bipoles). The dERP was defined as the longest ERP minus the shortest ERP of the four sites.Pulmonary vein isolation:Ablation was guided by use of the three-dimensional (3D) mapping system (Carto, Biosense Webster, USA). After reconstruction of the LA, each PV ostium was identified by PV venography and tagged on the3-dimensional electroanatomical map. Irrigated RF energy was delivered at40W and45℃for anterior wall, and at30W and43℃for posterior wall, with30-40s duration for each lesion and saline infusion rate of17-20mL/min. Circumferential ablation lines using a4mm tip irrigated catheter were created at a distance from the PV ostia. The goal of circumferential pulmonary vein (PV) ablation was PV isolation, which was defined as disappearance of all PV potentials or atrium-PV potential dissociation.Follow upAll patients were followed up at the outpatient clinic and whenever patients complained of palpitations or other symptoms. A24-hour Holter recording was performed during the follow-up and whenever patients had symptoms such as palpitations, dizziness, and syncope. Study end point was the occurrence of any type of AF documented by ECG or24-hour Holter. Statistical analysis:Statistical analysis was performed using SPSS13.0software. Continuous variables are reported as mean±SD, and analyzed by Student t test, χ2and Fisher exact tests were used for categorical data. A binary logistic regression analysis was used to identify significant predictors of AF recurrence. Optimal dERP, intra-and interatrial electromechanical delay cut-off levels for AF recurrence prediction was evaluated by receiver operating characteristic (ROC) curve analysis. P＜0.05was considered statistically significant.Results:Part1, Atrial Electromechanical Delay Predicts Atrial Fibrillation in Paroxysmal Supraventricular Tachycardia Patients after Radiofrequency Catheter Ablation:The ROC cure analysis revealed that intra-atrial electromechanical dela≥4.45msec and interatrial electromechanical delay≥20.65msec were the most optimal cutoff value for predicting AF in PSVT patients after RFCA (95%CI,0.632-0.785and0.788-0.909, P＜0.05, respectively).Part2, Effect of Pulmonary Vein Isolation on Atrial Fibrillation Recurrence After Ablation of Paroxysmal Supraventricular Tachycardia in Patients with High Dispersion of Atrial Refractoriness:ROC curve analysis, dERP=74.5msec effectively predicted AF recurrence in PSVT patients (P=0.003). Difference in AF recurrence rate between groups did not reach statistical significance (17.2%,5/29vs.29.4%,10/34, P=0.203). AF recurrence rate was lower in patients with dERP＞74.5msec who underwent AP or slow-pathway ablation with vs. without PVI (18.2%,2/11vs.77.8%,7/9, P=0.012).Part3, Sympathetic Stimulation Affects Atrial Vulnerability in Paroxysmal Supraventricular Tachycardia Patients with Atrial FibrillationThe prevalence of AF was higher in patients sensitive vs. not sensitive to sympathetic nerve stimulation after18months follow-up. Logistic regression analysis showed that age, right and left atrial dimension, and sympathetic stimulation were the significant influencing factors for atrial vulnerability.Conclusions:Our analysis suggested that:(1), The atria-atrial electromechanical delay≥4.45msec and Interatrial electromechanical delay≥20.65msec could effectively predict AF in post-ablation PSVT patients.(2), PVI addition after successful AP or slow-pathway of atrioventricular node ablation significantly reduced AF recurrence in PSVT patients with high atrial vulnerability (dERP＞74.5msec).(3), In PSVT patients, the age and sympathetic stimulation are important factors of atrial vulnerability and the initiation of AF.Further studies will be required to evaluate the potential of targeted anti-adrenergic therapy, such as beta-blockers, for the prevention and treatment of AF in PSVT patients. The AF prevention effect for PVI procedure may be demonstrated convincingly by the PV potential and effective refractory period measurement in PSVT patients.