Initial experience with a novel pulsed field ablation catheter for ablation of atrial fibrillation: procedural findings and acute safety

Funding Acknowledgements

Type of funding sources: None.

Background

Currently employed catheters for treatment of symptomatic atrial fibrillation (AF) leverage thermal energy to ablate the myocardium. Despite excellent acute success rates, the non-selective nature of thermal injury has been associated with frequent AF recurrences and complications such as pulmonary vein stenosis and thermal damage to adjacent structures. Recently, a novel, non-thermal ablative modality has been introduced for the treatment of AF: pulsed field ablation (PFA). The selective nature of PFA translates in the ability to perform full transmural lesions whilst sparing adjacent tissues and structures, making PFA an attractive solution to limitations faced with thermal energy sources. Although several pre-clinical studies investigated the safety and feasibility of PFA, limited reports have been published so far describing the clinical application of this novel catheter technology.

Purpose

In this study we present our initial experience with a pulsed field ablation catheter and describe procedural findings and acute safety of the first 68 patients treated at our center.

Methods

We investigated the first 68 patients treated for symptomatic AF at our center using pulsed field ablation between July 2021 and January 2022. Procedural findings at the time of ablation are presented. Procedure-related complications are reported. Qualitative analysis of electrograms and electrophysiological maps before and after ablation are also provided. Lastly, learning curves of operators who performed more than 10 procedures are described.

Results

Mean age of patients was 63.1±9.2 years, and most were men (57.4%). Most patients suffered from paroxysmal AF (79.4%). The median CHA2DS2-VASc score was 2.0 (1.0; 3.0) and mean left-atrium (LA) volume index was 33.0±8.3 ml/m2. All procedures were performed using conscious sedation. In 63/68 patients ablation of the PVI was performed and in 5/68 patients additional ablation of the left atrial posterior wall was performed. 3D electroanatomic mapping was performed during 10/68 procedures which lasted on average 107.3±15.5 min. Procedures where no mapping was performed lasted on average 48.5±20.7 min. Mean LA time was 39.9±19.0 min. Mean number of applications per pulmonary vein (PV) were 8.6±1.1. In all patients (100%) PVs were confirmed to be isolated. Four different operators performed the ablations: operator 1 performed 25/58 procedures (36.8%), operator 2 28/58 (41.2%), operator 3 9/58 (13.2%), and operator 4 6/58 (8.8%). The learning curves of both operator 1 and operator 2 showed negligible variation of performance over time (R2: Operator 1 = 0.181; Operator 2 = 0.078). The only complications reported were two cases of bleeding at the percutaneous access site of the femoral vein.

Conclusions

Our initial experience with a PFA catheter in 68 patients shows that PFA is a safe, quick, easy-to-learn, and effective ablation technique for the treatment of symptomatic AF.

Heart rate increase and inappropriate sinus tachycardia after cryoballoon pulmonary vein isolation for atrial fibrillation

BACKGROUND

Cryoballoon pulmonary vein isolation (PVI) is a common therapy for atrial fibrillation (AF). While moderately increased sinus rhythm heart rate (HR) after PVI has been observed, inappropriate sinus tachycardia (IST) is a rare phenomenon. We aimed to investigate the prevalence and natural history of an abnormal sinus HR response after cryoballoon PVI.

METHODS

We included 169/646 (26.2%) patients with AF undergoing PVI with available Holter recordings before and 3, 6 and 12 months after the procedure. Patients with AF on Holter monitoring were excluded. Mean HR increase ≥ 20 bpm or an IST-like pattern (mean HR > 90 bpm or > 80 bpm when beta-blocking agents were used) following PVI was categorised as abnormal sinus HR response.

RESULTS

Following PVI, mean HR ± standard deviation increased in the entire group from 63.5 ± 8.4 to 69.1 ± 9.9 bpm at 3 months (p < 0.001), and to 71.9 ± 9.4 bpm at 6 months (p < 0.001). At 12 months, mean HR was 71.2 ± 10.1 bpm (p < 0.001). Only 7/169 patients (4.1%) met criteria for abnormal sinus HR response: mean HR was 61.9 ± 10.6 bpm (pre-ablation), 84.6 ± 9.8 bpm (3 months), 80.1 ± 6.5 bpm (6 months) and 76.3 ± 10.1 bpm (12 months). Even at 12 months, mean HR was significantly different from that pre-ablation in this group (p = 0.033). However, in patients meeting IST-like pattern criteria, mean HR at 12 months was no longer significantly different from that pre-ablation.

CONCLUSION

Few patients had an abnormal sinus HR response after PVI. Peak HR was observed 3 months after PVI, but HR was still significantly increased 12 months post-ablation compared with pre-ablation. An IST-like pattern was rarely observed. In these patients, HR decreased to pre-ablation values within a year.

[Cardiogenetics: the importance of identifying patients with hereditary heart disease]

During the past decade, developments in the field of DNA diagnostics have resulted in the confirmation of the genetic nature of several cardiac diseases. In a cardiogenetics outpatient clinic, a cardiologist and a clinical geneticist together evaluate persons with a (possible) hereditary cardiac disease. It is of utmost importance that patients with hereditary cardiac diseases be recognised and subsequently referred for genetic counselling as several preventive and therapeutic options are available.

[Life-threatening ventricular tachycardia during flecainide treatment for symptomatic atrial fibrillation in a patient with a structural cardiac disorder]

A 37-year-old man with symptomatic acute atrial fibrillation and a low-voltage electrocardiogram was treated with flecainide intravenously. Instead of conversion to sinus rhythm, he developed a wide-complex tachycardia suggestive of ventricular tachycardia. The patient recovered following electric cardioversion. First-choice therapy for symptomatic atrial fibrillation of recent onset (duration < 48 hours) is chemical conversion with a class IC antiarrhythmic drug (e.g. flecainide, propafenone). However, in patients with structural heart disorders, these drugs may induce ventricular tachycardia. A low-voltage electrocardiogram is suggestive of left ventricular damage. For these patients, electric cardioversion is a better alternative.

[Arrhythmogenic right-ventricular cardiomyopathy: different manifestations as precursors of sudden death which might be prevented]

Two men aged 47 and 56 and one woman aged 21 presented at our cardiology department with presyncope, heart failure and exercise induced palpitations, respectively. Using the criteria of McKenna et al., a diagnosis of arrhythmogenic right-ventricular cardiomyopathy (ARVC) was made. Following implantation of a defibrillator, one of the men experienced seven appropriate interventions within six months and also developed psychological problems. The other man was problem-free and the woman recovered reasonably well, having only one appropriate intervention from the defibrillator one year after implantation. Indications of ARVC were also found in her mother but not in any other family members. Because ARVC manifests itself in various different ways it is difficult to diagnose. It is important to consider ARVC in patients with exercise-induced palpitations, presyncope, and unexplained cardiomyopathies or arrhythmias, especially if there is a family history of unexpected deaths. ARVC is a potentially life-threatening disease, that may require implantation of a cardioverter defibrillator. Furthermore, since genetics play an important role and ARVC can be asymptomatic, evaluation of close relatives for preclinical symptoms is important.

Radiofrequency ablation of atrial fibrillation

Twenty-five patients (16 males, mean age 46 years) underwent radiofrequency ablation because of either paroxysmal (13 patients) or persistent atrial fibrillation (12 patients). Ablation aimed at earliest activation of spontaneous and catheter-induced repetitive ectopy in left and right atria and appendages, and pulmonary veins. Catheter-induced repetitive ectopy was defined as acute onset of a burst of rapid atrial premature beats on touching the wall, sustained irritability while at the spot and acute termination of rapid activity upon release of the catheter. Post-ablation patients received antiarrhythmic drugs to prevent tachycardias, thereby allowing reversal of atrial remodeling.

RESULTS

Lone atrial fibrillation was present in 19 patients, 4 patients had hypertension and 2 patients coronary artery disease with preserved left ventricular function. The median duration of the history of atrial fibrillation was 4 years (range 1-14 years) and the median number of antiarrhythmic drug failures 5 (range 1-6). Ablation was successful, i.e. no recurrences of atrial fibrillation with or without antiarrhythmic drugs in eight patients (32%) during a median follow-up of 28 months (range 18-52). The median number of foci was 3 (range 2-6) and 2 (range 1-7) in the successfully and unsuccessfully treated patients, respectively. Minor complications occurred in three patients.

CONCLUSIONS

Radiofrequency ablation of atrial fibrillation aiming at spontaneous and catheter-induced repetitive ectopy is a safe procedure. However, it is only successful in one third of the patients. Further investigations are warranted to identify the ideal patient, as well as to develop better ablation strategies.