1. Study population
We enrolled 186 consecutive patients who underwent radiofrequency catheter ablation for AVNRT or Aflu at the Heart and Vascular Center of Semmelweis University, Budapest, Hungary, between July 2018 and July 2020 in the study. Inclusion criteria were documented, symptomatic Aflu or AVNRT. Patients without ECG documentation and patients who were previously enrolled in other clinical trials were excluded. Participants were assigned to either the ZF or CF group according to the operator's preference. EAMS were not used in the CF group. However, the use of fluoroscopy was allowed in the ZF group whenever it was necessary. Anthropometric characteristics, relevant medical history, and current medical therapy of the patients were collected. Structural heart disease was defined as the presence of ischemic or valvular heart disease or heart failure. The efficacy endpoint was acute success, defined as non-inducibility in case of the AVNRT (which was inducible before the ablation) and bidirectional cavo-tricuspid isthmus (CTI) block in case of the Aflu. The safety endpoint was the occurrence of periprocedural complications. Fluoroscopy dose was calculated using the internationally used formula: ED (mSv)= KAP (Gycm2) x 0.2 (mSv/Gycm2) . All patients provided written informed consent to the ablation procedure, data retrieval, and analysis. The study protocol was reviewed and approved by the Regional and Institutional Committee of Science and Research Ethics of Semmelweis University (No: 179/2020), and was in accordance with the Declarations of Helsinki.
2. Catheter ablation procedure
Femoral venous access was used for all procedures. In AVNRT patients, quadripolar catheters were placed in the high right atrium (HRA), the right ventricular apex (RVA), and a decapolar catheter was inserted into the coronary sinus. After the electrophysiological diagnostic maneuvers, the HRA catheter was replaced by a non-irrigated 4 mm tip ablation catheter. Radiofrequency ablations in the slow pathway region were applied in temperature control mode (65°C temperature limit, 40 W power).
In Aflu patients, a decapolar catheter was inserted into the coronary sinus, and a Halo catheter was placed in the right atrium (around the tricuspid annulus). An irrigated 4 mm tip ablation catheter was introduced to the cavo-tricuspid isthmus region, where radiofrequency energy was applied in temperature control mode (43°C temperature limit, 40 W power).
In the CF group, diagnostic catheters were introduced under X-ray guidance into the heart and positioned in the above-described positions. Ablation was performed under fluoroscopy guidance as well.
During the ZF procedures performed with the EnSite NavX system, a decapolar diagnostic catheter was introduced as the first step, and an anatomical map of the venous route was created. After respiration compensation, mapping of the right atrium, the right ventricle, and the coronary sinus were performed. Two diagnostic quadripolar catheters were introduced and positioned in their specific positions; meanwhile, the map was further created. Catheter ablation was guided by the EnSite NavX EAMS without fluoroscopy. In AVNRT patients, His region was tagged before slow pathway ablation (Figure 1).
In the case of procedures performed with Carto3 (Figure 2) or Rhythmia (Figure 3) systems, the ablation catheter was introduced first, and an electroanatomical map of the right atrium, the right ventricle, and the coronary sinus were created. Further diagnostic catheters were positioned using the previously created map. The following steps of the procedure were similar to the EnSite NavX procedures.
3. Statistical analysis
The majority of the variables showed non-parametric distributions after performing the Shapiro-Wilk test. The continuous variables were expressed as medians and interquartile ranges. Categorical variables were expressed as percentages with event numbers. Continuous variables were compared with the Mann-Whitney test and the Kruskal-Wallis test, respectively. Fisher's exact test was applied for categorical data comparisons.
A two-tailed p-value of <0.05 was considered statistically significant. Statistical analyses were performed using IBM SPSS 25 (Apache Software Foundation, USA) and GraphPad Prism 8.01 (GraphPad Software, Inc., USA) software products.