To the best of our knowledge, this is the first study that presented and used semi-quantitative assessment for PVI success which we called Pulmonary Vein Isolation Outcome Degree. PVIOD 1 stands for patients with the best result of catheter ablation while PVIOP 4 refers to the worst outcome of patients. Until now the trials usually used a qualitative measure of PVI success with 2 possible outcomes: effective or unsuccessful procedure [2, 5, 7].
After a 7-year follow-up, a single PVI had a modest success of 32.5% in our study group, with the best result of 40.2% in patients with paroxysmal AF, 20.8% in persistent AF and as low as 12.5% in longstanding persistent AF. Numerous trials detected long-term success after single catheter ablation from 29–57% [2, 4, 5, 7]. Repeated ablations without ASM, after the 7-year follow-up, increased cumulative success in our study to 57.3%. Additional substrate strategies with an efficacy rate of 4.3% made very small benefit to procedural success which increased to 61.6%. In the study by Teunissen et al., the efficacy of additional substrate ablations was 4.2%, which magnified procedural success to 62.5% [2]. The work of Ouyang et al. showed that patients with paroxysmal AF and normal left ventricular ejection fraction after single PVI (4.8-year follow-up) had a success rate of 46.6%, after the second procedure 73.9% and after the third ablation the efficacy was 79.5% [4]. Our results were satisfactory in patients with paroxysmal AF; after the first PVI and the 7-year follow-up, the success rate was 40.2%, and after the last ablation success was 69.4%.
In our patients, long-term clinical success was reported in 14.5% of subjects which increased cumulative success to 76.1% with excellent result in paroxysmal AF (85%), good outcome in persistent AF (70.8%) and modest efficacy in longstanding persistent AF (43.7%). These data show the importance of clinical improvement and the role of AAD therapy in AF management. Therefore, long-term clinical success (on top of procedural success) is a very significant outcome. Teunissen et al. found that clinical improvement on or off AAD was 25% and increased cumulative success to 87.5% in the total population of 509 study patients [2].
The most challenging issue in managing patients with AF is identifying those predictors for unsuccessful ablation. A large number of studies determined the risk factors for poor outcome following PVI as non-paroxysmal AF (particularly longstanding persistent AF), LA dilatation and higher CHA2DS2-VASc score, which was confirmed in our trial [2, 8, 9, 12]. In our study, MV ordinal logistic regression analysis found an independent association between PVIOD and LA diameter, CHA2DS2-VASc score and AF type. LA diameter > 41mm was a high predictor of procedural failure (AUC 0.726) and procedural with clinical failure (AUC 0.741) in our patients. LA enlargement is a well-known risk factor for AF, associated with atrial electroanatomical remodeling, which plays the main role in the perpetuation and progression of AF [11]. The computational model confirmed that a critical LA effective conducting size > 40mm was required for sustained multiple wavelet reentry [11]. A meta-analysis of D'Ascenzo et al. showed that persistent AF, LA diameter > 50mm and arrhythmia recurrences within the first month after catheter ablation are the most powerful predictors of procedural failure [12]. PVI success is highly dependent on atrial disease stage and enlarged LA is widely accepted as a predictor of AF recidivism.
Our study determined that CHA2DS2-VASc score ≥ 2 was a predictor of poor PVI outcome. Patients with CHA2DS2-VASc scores 0 and 1 displayed successful ablations, but those with other scores showed high predictive value for procedural failure (AUC 0.711) and procedural with clinical failure (AUC 0.718). A score of ≥ 2 for both CHADS2 and CHA2DS2-VASc scores had the highest predictive value for AF recurrence after single catheter ablation for paroxysmal AF in the study of Letsas et al. [13]. In a relatively small cohort of patients with longstanding persistent AF, it was shown that CHA2DS2-VASc score ≥ 3 and renal dysfunction were significantly associated with ablation failure within 31 months [14]. Other scores, like APPLE, DR-FLASH and MB-LATER predicted electro-anatomical substrate and arrhythmia recurrences in patients with AF who underwent catheter ablation [15]. The identification of specific markers before PVI in patients with AF defines the best candidates for the procedure and future ablation responders. Prediction of arrhythmia recurrences is complex because of the influence of disease stage, patients' comorbidities, operators' experience, equipment for ablation, etc.
In the current study, UV ordinal logistic regression analysis showed an association of PVIOD with structural heart disease and diabetes mellitus, but not in the MV model. Structural heart disease is a well-known predictor of early and very late recurrence of AF after RF ablation [9]. Cardiac risk factors such as hypertension and diabetes mellitus are closely correlated with inflammation and consequently with atrial fibrosis and remodeling [16]. Although in our MV analysis it does not reach significance, the importance of diabetes mellitus prevention and treatment in AF patients is obvious.
In our study nomograms presented a seven-year probability for procedural failure and for procedural with clinical failure, which were predicted with 3 risk factors: LA diameter, CHA2DS2-VASc score and type of AF. Determination of AF type, CHA2DS2-VASc score and measurement of LA diameter could provide an easy and available way of predicting catheter ablation outcome.
PVIOD is a new PV ablation outcome scoring system. This classification considers the number and efficacy of PVI, clinical success, optional additional substrate modification and antiarrhythmic therapy. The scoring of PVIOD is a novel way of assessing PVI success since other studies with standard instruments rate PVI efficacy by procedural success or failure. The novelty of our results is an independent association between PVIOD and 3 clinical parameters: LA diameter, CHA2DS2-VASc score and type of AF, after a 7-year follow-up. These risk factors are very convenient to predict future PVI outcomes and easy to be measured already at baseline with cardiac echocardiography and clinical evaluation of patients. By using nomograms we can calculate both long-term procedural failure and procedural with clinical failure for patients with AF who will be treated with PVI.
This study showed significant major ablation complications in 3.3% of procedures, which is acceptable and can compare with the result (2.5-8%) from other eminent electrophysiology laboratories [17, 18]. There were no deaths connected to catheter ablations in our patients which are the excellent results.