Methods

Bi-atrial electroanatomic mapping using a 3-dimensional mapping system (NavX, St. Jude Medical, St. Paul, Minnesota) was performed in 228 consecutive patients (age 52.3 ± 12.6 years, 167 men) with symptomatic drug-refractory paroxysmal AF. An abnormal glucose metabolism was defined as DM or an impaired fasting glucose, which was diagnosed according to the American Diabetes Association criteria. A total of 65 patients (28.5% of the study population) were included in the abnormal glucose metabolism group. Of the abnormal glucose metabolism group, 33 patients (51%) were diagnosed with an impaired fasting glucose, with a fasting glucose level of 109 ± 7 mg/dl, and 32 (49%) were diagnosed with DM with a fasting glucose level of 129 ± 37 mg/dl. The biatrial bipolar peak-to-peak voltage and total activation time were obtained during sinus rhythm. The left atrium diameter and left ventricular ejection fraction were measured using transthoracic echocardiography, according to American Society of Echocardiography criteria.

Each patient underwent an electrophysiologic study and catheter ablation in the fasting, nonsedative state after providing written informed consent. The details have been previously described. In brief, after completing an intact right atrial (RA) and left atrial (LA) geometry reconstruction, a sequential contact voltage map was constructed for all patients during sinus rhythm. For the patients with an AF occurrence during the procedure, external direct current cardioversion was performed to convert the patients to sinus rhythm so mapping could be performed. The recordings from the coronary sinus catheter electrodes were used to provide the timing reference signal during the mapping procedure. A 4-mm-tipped ablation catheter was used to collect the local activation time (relative to the reference signal) and voltages while the catheter came in contact with the atrial wall as it was swiped throughout the atrium during sinus rhythm. After completion of the sequential map, the bipolar mapping points were analyzed using off-line software. Examples of the biatrial voltage map of the patients with and without DM are shown in Figure 1 .

Comparison of RA voltage (A) and LA voltage (B) between patients with and without DM. Voltage of atrium represented by different colors. Gray and purple represent low-voltage zones (<0.5 mV) and normal voltage zones (>2 mV), respectively. Patients with DM had lower biatrial voltage than patients without DM. SVC = superior vena cava; IVC = inferior vena cava; RSPV = right superior pulmonary vein; RIPV = right inferior pulmonary vein; LSPV = left superior pulmonary vein; LIPV = left inferior pulmonary vein; LAA = left atrium appendage; MV = mitral valve; TV = tricuspid valve.

Provocation of AF was performed in each patient before the catheter ablation procedure. Continuous circumferential lesions were created, encircling the ostia of the right and left pulmonary veins (PVs), guided by the NavX system using either a conventional 4-mm-tip or internal irrigated-tip catheter. The intention was to place the radiofrequency lesions ≥1 to 2 cm away from the angiographically defined ostia. Successful circumferential PV isolation was demonstrated by the absence of any PV activity or dissociated PV activity. The requirement of additional ablation was assessed according to AF inducibility.

After completing the PV isolation, the ablation was only applied to the spontaneously initiating focal atrial tachycardias and non-PV ectopy that initiated AF. The methods of identification of the non-PV ectopy have been described in our previous publications. If any non-PV ectopy initiating AF from the superior vena cava were identified, isolation of the superior vena cava was guided by the circular catheter recordings from the superior vena cava–atrial junction.

After discharge, the patients underwent follow-up (2 weeks after catheter ablation and then every 1 to 3 months) at our cardiology clinic or with the referring physicians. Antiarrhythmic drugs were prescribed for 8 weeks to prevent the early recurrence of paroxysmal AF (defined as <1 month after ablation). During each follow-up visit after the ablation, 24-hour Holter monitoring and/or a cardiac event recording with a recording duration of 1 week were performed. AF recurrence was defined as an episode lasting >1 minute and confirmed by electrocardiograms 2 months after ablation (blanking period). If more than one episode of recurrent symptomatic AF or atrial tachycardia/atrial flutter was documented, the patients were encouraged to undergo another ablation procedure, or antiarrhythmic drugs were prescribed to control the recurrent atrial arrhythmias. The long-term efficacy was assessed clinically on the basis of the clinical symptoms, surface 12-lead, at rest, electrocardiogram, and 24-hour Holter monitoring and/or 1-week cardiac event recordings.

The data are presented as the mean ± SD for normally distributed continuous variables and as proportions for the categorical variables. The differences between continuous values were assessed using an unpaired 2-tailed t test or one-way analysis of variance post hoc Bonferroni test for normally distributed continuous variables, the Mann-Whitney rank-sum test for skewed variables, and the chi-square test for nominal variables. Because of significant age differences among the normal and abnormal glucose metabolism groups, the estimated marginal mean values were used to adjust the LA diameter, LA voltage, LA total activation time, RA voltage, and RA total activation time for age. A Bonferroni adjustment was applied for multiple comparisons between these 2 groups. The AF recurrence-free survival curve was plotted using the Kaplan-Meier method, with statistical significance examined using the log-rank test. Statistical significance was set at p <0.05, and all statistical analyses were performed with the Statistical Package for Social Sciences, version 17.0, software (SPSS, Chicago, Illinois).