Premature ventricular complexes (PVC) are common arrythmias in clinical practice, occurring in 75% of the cases in the absence of structural heart disease, most of them originating from the right ventricular OT (RVOT).1–3 Triggered activity or abnormal automaticity, usually from a focal source, are the mechanisms underlying these arrhythmias.4 Many patients present with symptoms (mainly palpitations, but also chest pain and pre-syncope/syncope) associated with exercise, stress or the use of stimulants.1,3 Although symptoms can affect quality of life, idiopathic VA tends to have a benign prognosis. However, a high VA burden can result in left ventricular (LV) systolic dysfunction and cardiomyopathy and, rarely, OT VA can trigger idiopathic ventricular fibrillation.4,5 PVC may also derive from subclinical cardiomyopathy. Sometimes it is even impossible to determine whether the PVC or the cardiomyopathy is the cause or the consequence.2 The standard therapy to provide symptom relief is antiarrhythmic drugs. Beta blockers or verapamil usually show limited effectiveness.1,3,5 Other antiarrhythmic drugs, such as propafenone, flecainide, and specially amiodarone, have better outcomes, but are associated with adverse side effects.6 Several studies have demonstrated that radiofrequency (RF) ablation is more efficient than pharmacological therapy for eliminating PVC, especially for refractory symptoms and very frequent PVC.1–3,5 The number of patients being referred for ablation of OT VA continues to increase, especially earlier in their disease course, due to its efficacy (ranging between 83% and 100%) and safety (overall complication rate: 3.1-5.2%).2,7 However, RF ablation may be of limited use if PVCs are scarce, even with adrenergic and electrical stimulation in the electrophysiology laboratory, since activation mapping becomes more difficult. Also, pacemapping has a low spatial resolution.3,5,8 Noncontact mapping permits ablation guided by a single PVC analysis, which may facilitate ablation of these difficult cases.8 Due to technical challenges, including difficulty in handling and stabilizing the catheter inside the heart chambers, the non-contact balloon system has never been widely used.

In this study we describe our center's experience using the Ensite Array NCM system (St. Jude Medical, St. Paul, Minnesota, United States) for ablation of OT VA. To localize the focal arrythmia, this system uses a multielectrode array catheter with a 7.5 ml balloon and 64 microelectrodes. It is a method that can record endocardial electrograms from more than 3000 sites simultaneously from one single premature beat, to create a three-dimensional map of electrical activation.5,8–10

Clinical characteristics are presented in Table 1. The population comprised 58 patients, mean age 43.9±17.6 years, mostly female (79.3%), without any associated disease or comorbidity in 63.8% of the cases. Structural heart disease was excluded by echocardiography and/or cardiac magnetic resonance in 88% of the patients. In 85.7% of the patients left ventricle ejection fraction (LVEF) was preserved (LVEF≥50%), 8.6% had mild systolic dysfunction (LVEF 40-49%) and 5.7% had moderate systolic dysfunction (LVEF 30-39%).

All patients were symptomatic. Most cases (74.1%) presented with palpitations, 13.8% with fatigue and 12.1% with presyncope/syncope. Twenty-four hour Holter recordings documented sustained VA episodes in 12.1%, non-sustained VA in 31.0%, and >10 000 PVC in 56.9%. The 12-lead ECG suggested an OT origin in all cases.

A large majority (77.6%) of patients were refractory to antiarrhythmic drugs: beta blockers 48.3%, amiodarone 8.6%, calcium channel antagonists 6.9%, flecainide 3.4% and sotalol 3.4%. In 7%, antiarrhythmic drugs were combined.

The origin of the arrhythmia was in the RVOT in 84.5% (n=49) and in the LVOT in 15.5% (n=9). The average number of RF energy deliveries to achieve success was 13±8. The earliest activation RVOT sites were: posteroseptal (31.5%), posterolateral (16.7%), posterior (13%), anterolateral (11.1%), and other locations (12.2%). In the LVOT, the earliest activation points were: anterior (5.3%), posterolateral (3.4%), posterolateral (3.4%), posterior (1.7%) and inferior (1.7%) (Figures 3 and 4).

Figure 3.

Three-dimensional electroanatomic mapping using the noncontact EnSite 3000. The acquisition of maps during sinus rhythm and ventricular premature complexes (PVC) identifies the early activation points. A: Surface twelve-lead ECG showing isolated monomorphic PVC originating from RVOT (left bundle branch block with an inferior axis pattern). B: Three-dimensional reconstruction of right ventricle outflow tract (left anterior oblique projection) and virtual electrograms at the site of earliest activation (note the QS pattern).

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Figure 4.

An example of successful ablation. Three-dimensional reconstruction of right ventricle anatomy (left anterior oblique projection) and identification of early activation points, marked in white/red (made possible by the acquisition of maps during sinus rhythm and premature ventricular complexes). Red dots (L1 to L9) indicate the sites of ablation therapy. The early activation point was seen to have moved away from the original site, where the first application was performed. Further ablation at the new site successfully abolished the ectopies.

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Noncontact balloon guided ablation was acutely successful with total elimination of PVC in 87.9% patients (89.9% in RVOT origin and 100% in the LVOT cases). 3.4% patients achieved a >90% reduction of PVC. In 8.7% the ablation was non-successful. In 4 cases (6.9%), the procedure was complicated by small pericardial effusion (n=1), cardiac tamponade (n=2) and a pseudo-aneurysm of the femoral artery solved by ultrasound-guided compression (n=1). Peri-procedural complications were observed in patients with VA originating from the LVOT in three out of four cases; one patient with VA from the RVOT presented mild pericardial effusion.

Echocardiographic reevaluation between six months and one year after the procedure showed that 6.3% patients maintained mild systolic dysfunction, while 8% recovered systolic function to normal values. Patients with a previous preserved LVEF maintained within that range.

During a mean follow-up of 5.5 years, 87.9% of the patients achieved a reduction of >90% in total PVC burden on the Holter recordings and remained asymptomatic in the absence of antiarrhythmic drugs after the first ablation. 12.1% underwent re-ablation due to symptomatic PVC recurrence, and two cases underwent a third successful intervention.

Our study confirms that OT VA in symptomatic patients or with very frequent PVC activity refractory to medical therapy can be safely eliminated based on tridimensional geometry and activation maps using NCM-guided multielectrode balloon catheter. NCM-based ablation was acutely successful in 87.9% of our population. Although mostly a young and healthy population, it reflected a challenging ablation group: 12% with structural cardiopathy and more than 80% with no sustained arrythmias to guide the electrophysiological mapping. Despite the fact that other authors have shown the usefulness of NCM-base ablatio in OT VA,6 its use is not widespread. In fact, the technical challenges and the long learning curve of this system, combined with the development of new catheters and mapping platforms from different manufacturers, have contributed to the recent discontinuation of the 64-pole NCM-guided Ensite Array Balloon. In our experience, acute success in mapping OT VA based on a single beat was high, with a low rate of recurrence during long-term follow-up.

Expert consensus statements on VA recommend catheter ablation for PVC in patients who remain symptomatic despite conservative treatment or who have probable reversible LV dysfunction.11,12 According to the recommendations, in our population, all patients were symptomatic before the first ablation procedure. The commonest symptom of OT arrhythmias is palpitations, also demonstrated in our study. In our experience, most patients remained asymptomatic after the first ablation, even in the absence of antiarrhythmic drugs. Lauck et al. demonstrated, through invasive continuous monitoring, a 50% reduction of cardiac output during ventricular bigeminism.13 The same reduction in cardiac output can be demonstrated with OT Doppler with transthoracic echocardiography, justifying the phenomenon of tachycardiomyopathy associated with frequent PVC, as demonstrated by Yarlagadda et al.14 Improvement in LVEF is other benefit after VA disappearance. In a meta-analysis performed by Lamba et al.,15 RF catheter ablation significantly improved LVEF by a mean of 10.36% (confidence interval 8.75-11.97, p<0.00001) in patients with frequent PVC originating from the RVOT.6 In our study, most patients had preserved LVEF prior to the ablation procedure. Of the 14.3% patients with LV systolic dysfunction, 8% recovered it to normal values after the ablation procedure.

In 8.7% of the cases, ablation was not successful. One of the cases could be attributed to the limitation imposed by the patient's anatomy, since it maintained an activation focus on an anterior position, not accessible to the ablation catheter due to the presence of the multielectrode balloon that was not possible to overcome. In the other cases, the failure was probably related to the difficulty with the substrate location, presumably with an intramyocardial or epicardial origin. These are considered the common mechanisms justifying procedure failure.8 Another aspect to be taken into account is that RF lesions usually have a diameter of 5 mm.16 The precise positioning of the ablation catheter in the arrhythmogenic tissue can be critical for the success of the ablation.8 Wen et al. described as factors associated with the failure of ablative therapy a delta wave-like QRS onset (suggesting epicardial origin) and short endocardial activation to QRS onset times, both suggesting distancing of the ablation catheter from the target.17 However, cases cataloged as immediate failure may not require re-ablation, since the simple modification of the automatic focus of ventricular ectopic activity seems to be sufficient to alter the refractoriness to antiarrhythmic therapy, was the case with a patient in our series. Although the procedure was acutely complicated in four cases due to pericardial effusion and a femoral pseudo-aneurysm, these conditions were all successfully resolved. Most importantly, our long-term success rate was high, with almost 90% of the patients remaining asymptomatic in the absence of antiarrhythmic drugs.

The study's main limitation was the fact that it is a retrospective, single center, observational study. The reported results were not compared with conventional ablation techniques nor with the use of other three-dimensional mapping systems.

Despite the efficacy of this technique, there are some inherent limitations. The progression of the guidewire and the positioning of the inflated balloon in the OT can be difficult and may require a significant fluoroscopy time.6 Another limitation is when the distance between the central axis of the balloon catheter and the focus of the arrhythmia is greater than 4.0 cm. In this situation, the confidence of the activation map is impaired and there is a risk of applying RF in an inadequate site. This is particularly important in arrhythmias originating in sites other than the RVOT, which was the case in almost 15% of patients. Another limitation of the method is the contact of the balloon catheter with the endocardium in certain circumstances, especially when using isoproterenol, possibly generating ectopic activity different from the clinical one.6 All these limitations led to the discontinuation of this system more than one year ago. This is therefore can be considered as a “historical evaluation” since the 64-pole NCM-guided Ensite Array Balloon is no longer available on the market.

Non-contact mapping-guided multi-electrode balloon catheter OT VA ablation in symptomatic patients or with very frequent PVC activity, refractory to medical therapy, is a highly effective and safe procedure, with a low rate of long-term recurrence.

The authors have no conflicts of interest to declare.