Baseline characteristics of included study
All enrolled clinical studies were published form 2008 [20] to 2019 [60]. The first enrollment of CBA: CB-1 was found in 2007 [61]; however, records from this study were used later in 2008 in a larger observational registry [22]. The total number of patients in this meta-analysis reached 10,341 with 4164 patients undergoing first generation CBA: CB-1 (23 mm [1164 patients] and 28mm [3328 patients]), 6075 with second generation CBA: CB-2 (23 mm [192 patients] and 28 mm [5765 patients]) and finally 102 patients who had an ablation with the third generation CB-ST procedure, 28 mm. Discrepancies in the number of 23 28 mm and number of procedures could have resulted from the use of two types of diameters in one procedure.
All trials (n = 48) for PNI with relevant baseline information included patients comparable on mean age, gender ratio, body mass index (BMI), atrial fibrillation (AF) duration, comorbidities, left ventricular ejection fraction (LVEF), and left atrium size between the CB generations (Table 1). Each study describes the method of phrenic nerve control and protection (supplemental publication material Table 1), number of PNI (n = 48), and time to recovery (n = 37), if not in days, at least at check-up periods. Intraoperative data was found in 13 studies [8,15,17,23,29,30,36,38,42,47,48,52,62] providing a detailed time to PNI, only eight [15,30,38,42,47,48,52,62] studies delivered information about nadir disruption of temperature to PNI while only five [15,38,42,48,62] detailed time, temperature, and balloon location of the right superior pulmonary vein/right inferior pulmonary vein (RSPV/RIPV) In 20 studies, we found information about diaphragmatic stimulation, 17 described the strength of power to stimulation, 30 studies described the time of freezing as shown in the supplemental publication material.
CMAP was used in 15 studies, four used immediate balloon deflation (IBD; one CMAP + IBD), 30 studies used fluoroscopy control with palpation, and two studies did not use any phrenic nerve protection [20,21]. Detailed information of data included in certain studies are shown in column 13, Table 1. Except for statistical significance of hypertension diagnosis between the CMAP and non-CMAP group, almost all the other demographic characteristics (age, gender, AF duration) and echocardiographic data (left atrium diameter [LAD], left LVEF) were comparable between these two groups. Statistical analyses of the baseline demographic and echocardiographic data are presented in Table 2. The study did not compare the 6-month or 1-year efficacy because of different balloon generations, sizes, and selected techniques. The average success rate ranged from 59.7% in CB-1 [40] to 90.83% in CB-2 [35] with a mean of 75.82% overall.