A b s t r a c t Background and aim:The aim of this study was to examine contemporary results of accessory pathway (AP) ablation in a sizeable number of patients, focusing on periprocedural complications and the learning curve. Methods:We performed a retrospective cohort study of consecutive AP ablation procedures at three centres by the same operator. In total 629 electrophysiological studies and 610 AP ablation procedures were performed in 570 patients (age: 33 ± 18.9 years).Results: There was one (0.16%) serious and there were 14 (2.3%) minor periprocedural complications. Five hundred and ninety APs were successfully ablated: single/multiple procedure success was 93.4%/96.7%, while the average fluoroscopy time was 13.5 min. There was significantly higher success and less fluoroscopy use with increased experience, while periprocedural complications seemed evenly distributed over the years. The learning was most pronounced for the first 120 cases. However, the learning curve fully flattened only after approximately 400 ablations. Conclusions:This study suggests that in the modern era AP ablation is safer than it was in the first two decades after the introduction of catheter ablation of APs. Perhaps, in experienced centres there should be a lower threshold for referring asymptomatic/mildly symptomatic patients with pre-excitation for electrophysiological study.

We report three patients with intermittent loss of the preexcitation pattern in the ECG that had undergone an electrophysiological study. Despite apparently poorly conducting accessory pathway (AP), in each case a fast anterograde conduction, either during spontaneous atrial fibrillation or during incremental atrial pacing (on isoproterenol) was documented; shortest preexcited RR intervals of 200-240 ms were observed. We review the literature and conclude that intermittent preexcitation observed on resting 12-lead ECG lacks sufficient specificity for the diagnosis of an AP with long refractory period and cannot be considered a substitute for electrophysiological study in patients with this electrocardiographical phenomenon.

BACKGROUND The presence of accessory pathways (APs) is a risk factor for sudden cardiac death and other clinical complications. AIMS We aimed to characterize all adverse events likely related to the presence of APs in patients referred for AP ablation and to identify risk factors for malignant arrhythmias. METHODS We performed a retrospective analysis of consecutive patients referred for AP ablation from 2002 to 2017. Electrocardiograms, electrophysiological system records, and hospital discharge notes were reviewed. We collected data concerning symptoms before ablation, occurrence of ventricular fibrillation or malignant atrial fibrillation (AF), as well as other complications related to APs. RESULTS We identified 602 patients with APs. Serious AP-related events were observed in 41 patients, including 14 sudden cardiac arrests (1 death) and 16 pre-cardiac arrest events. Other complications included strokes, pulmonary edema, heart failure, and unnecessary device implantation. The risk of malignant arrhythmias decreased with a longer shortest preexcited RR interval (per 10 ms: odds ratio [OR], 1.3; 95% CI, 1.16-1.47) and increased with age (per 10 years: OR, 1.29; 95% CI, 1.06-1.57). The presence of inducible AF, but not sole atrioventricular reentrant tachycardia, increased the risk for malignant arrhythmias when compared with patients without any inducible arrhythmias. CONCLUSIONS Patients with APs referred for ablation commonly present with various adverse events. The predictive value of clinical risk factors for malignant arrhythmias is too low to prevent devastating consequences. When high safety and efficacy of AP ablation are ensured, even a low risk of sudden death is unacceptable and a lower threshold for prophylactic ablation should be used to prevent AP-related adverse events.

To establish an appropriate treatment strategy and determine if ablation is indicated for patients with narrow QRS complex supraventricular tachycardia (SVT), analysis of a standard 12-lead electrocardiogram (ECG) is required, which can differentiate between the 2 most common mechanisms underlying SVT: atrioventricular nodal reentry tachycardia (AVNRT) and orthodromic atrioventricular reentry tachycardia (OAVRT). Recently, new, highly accurate electrocardiographic criteria for the differential diagnosis of SVT in adults were proposed; however, those criteria have not yet been validated in a pediatric population.All ECGs were recorded during invasive electrophysiology study of pediatric patients (n = 212; age: 13.2 ± 3.5, range: 1–18; girls: 48%). We assessed the diagnostic value of the 2 new and 7 standard criteria for differentiating AVNRT from OAVRT in a pediatric population.Two of the standard criteria were found significantly more often in ECGs from the OAVRT group than from the AVNRT group (retrograde P waves [63% vs 11%, P < 0.001] and ST-segment depression in the II, III, aVF, V1–V6 leads [42% vs 27%; P < 0.05]), whereas 1 standard criterion was found significantly more often in ECGs from the AVNRT group than from the OAVRT group (pseudo r′ wave in V1 lead [39% vs 10%, P < 0.001]). The remaining 6 criteria did not reach statistical significance for differentiating SVT, and the accuracy of prediction did not exceed 70%. Based on these results, a multivariable decision rule to evaluate differential diagnosis of SVT was performed.These results indicate that both the standard and new electrocardiographic criteria for discriminating between AVNRT and OAVRT have lower diagnostic values in children and adolescents than in adults. A decision model based on 5 simple clinical and ECG parameters may predict a final diagnosis with better accuracy.