ABC | Volume 110, Nº5, May 2018

Original Article Chen et al PV anatomy and cryo kinetics Arq Bras Cardiol. 2018; 110(5):440-448 PV Anatomy Assessment Image acquisition Prior to the procedure, MDCT studies were performed on a MDCT scanner (SOMATOM Definition Flash, Siemens). Scanning parameters were the following: tube voltage 100 - 120 kV, 3D automatic tube current modulation, thickness / increment of reconstruction 0.625 / 0.625 mm. ECG-gating was not used, and patient breath holding was required during image acquisition. A bolus tracking protocol with 50 ~ 70 mL i.v. contrast agent (Ultravist 370, Bayer Schering) and 3 ~ 5 mL/s flow rate was applied. Image analysis MDCT images were reconstructed and analyzed using CartoMerge software (Biosense Webster, Diamond Bar, CA, USA) right before the procedure. PV ostia were defined anatomically at the parietal pericardium point of reflection 10 and were depicted semi-automatically (Figure 1A), together with ostia perimeters calculated automatically by computerized image analysis. Long (D long ) and short (D short ) ostia diameters were then measured. Corrected ostial diameters (D corrected ) were calculated using the formula D corrected = perimeter / π. The ratio between D short and D long (D short / D long ) was also calculated for analysis. Taking consideration of D short / D long values, PV ostium shapes were divided into 4 types: type I (round), ostia with value between 0.90 ~ 1.00; type II (oval), value between 0.60 ~ 0.90 and a smoothly curved edge; type III (triangular), value between 0.60 ~ 0.90 and an obviously straight part at the edge; and type IV (narrow), value less than 0.60. (Figure 1B-E). Five PV drainage patterns were defined for the targeted superior/inferior PVs based on the definition by Marom et al. 11 When the superior and inferior PVs on the same side joined together to form a common trunk vein and drained into LA through a common ostium, the superior and inferior PV were defined as “with common trunk”. If the superior and inferior PVs on the same side drained into LA through two independently trunk but drained into LA through ostia hardly separated by LA wall (the minimum distance between the two ostia was less than 2 mm on MDCT images), the two PVs were then defined as “with common antrum”. PV “with ostial branch” was defined as a PV branch joining within 10 mm from the ostium. PV “with supernumerary vein” was defined as the superior or inferior PV with neighboring additional vein(s), when a middle PV existed, both the superior and inferior PV on the same side were defined as “with supernumerary vein”. PV “with typical drainage” was defined as a superior or inferior PVdrained into LA independently, through neither a common trunk nor antrum, and that did not have an ostial branch or supernumerary vein. (Figure 1F-J) Anatomical assessment reproducibility In order to assess evaluating methods reproducibility of diameters described above, 40 PVs ostial diameter of first 10 patients were measured on CT images by two blind experienced observers at the beginning of the study. One observer measured two times in different moments to study the inter-observer reproducibility. The other observer measured one time, and the intra-observer reproducibility between the two observers was studied. The ostium shapes and drainage patterns were also assessed by two experienced observers in consensus during the study. Ablation procedure The ablation procedures were carried out as previously reported. 12 Briefly, an octapolar electrode catheter was placed into the coronary sinus and a phrenic nerve (PN) pacing electrode catheter into the superior vein cava (SVC). After a single transseptal puncture, selective PV angiography was carried out and a CB catheter (Arctic Front, Medtronic, Quebec, Canada) was inserted into LA together with a spiral catheter (SC) (Achieve, Medtronic, CA, USA). There are currently two sizes of balloon catheters (23 or 28 mm) and two sizes of SCs (15 or 20 mm) available. PV ostia diameters were determined from MDCT images; CB and SC size were selected accordingly: If long diameters of three or four PVs were < 22 mm, 23-mm CB a 15-mm SC were selected; If that ≥ 22 mm, a 28-mm CB and a 20-mm SC were preferred; otherwise the choice would be made by the operator temporaly. As soon as good contact of balloon to PV ostium indicated by the contrast retention in PV was obtained, freezing cycle was started with two to three applications per vein. Generally each freeze lasted 240s, and ideal freezing temperature was between -45°C and -55°C. If exists a common PV, freezing was analyzed separately as in superior or inferior PV based on location of balloon distal end during freezing. Supernumerary PVs were not taken as targeted PV as there are usually too small in dimension. PN was constantly paced (10 mA, 2 ms, 50/min) with PN pacing catheter in SVC when freezing at right PVs. After each freeze, PV conduction was re-evaluated by adjusting SC position within the PV. In all patients, PVI of all targeted PVs with primary use of CB only was the procedural endpoint. If PVI was not achieved for a particular vein following a minimum of two freezing, either further cryoablation would be performed or conventional RF ablation would be undertaken, depending on the initial contrast-guided occlusion and the minimum temperature achieved. Cryo kinetics Three parameters of cryo kinetics 5 were introduced: balloon freezing time from 0 to -30°C (BFT), balloon nadir temperature (BNT) and balloon warming time from -30 to +15°C (BWT). Freezing cycles with a BNT lower than -30°Cwere taken into analysis. Statistical analysis After being tested for normality distribution and variances equality using One-Sample Kolmogorov-Smirnov test and Levene’s test, continuous variables were presented as mean ± standard deviation (SD) or median (interquartile range), and were compared using the unpaired Student’s t-test or nonparametric variables Mann-Whitney U test as appropriate. Categorical variables were expressed as number (percentage) and were compared by means of χ 2 analysis or Fisher exact test. Measuring reproducibility of PV ostial diameters was assessed using intra-class correlation coefficient (ICC). Pearson or Spearman correlation was used to evaluate the 441