Atrial fibrillation (AF) is the most frequent cardiac rhythm disorder with an increasing prevalence and is responsible for substantial morbidity, mortality, and use of health care resources.1 Currently, the first choice for treating AF is pharmacological therapy with antiarrhythmic drugs (AADs), which has shown to be effective in less than 40% of patients.2 Unfortunately, AADs have considerable adverse effects.3 Rhythm-control therapy for using transcatheter pulmonary vein isolation (PVI) has gained strong popularity in younger patients in recent years, especially those with paroxysmal AF.4,5 Success rates of transcatheter PVI vary widely, worsening with the progression of the disease to more persistent presentations. The technical difficulty of achieving transmural electrical isolation hampers the results of transcatheter PVI, especially long-term success, and in one third of the patients, more than one procedure is required to obtain stable sinus rhythm.6 Minimally invasive surgical PVI (SMI-PVI) was introduced in 2005 as an alternative to transcatheter PVI.7 The SMI-PVI has the advantage of being less technically demanding than a conventional full Maze open-chest operation, delivering a continuous lesion with bipolar radiofrequency in the setting of epicardial, off-pump ablation. Previous studies with SMI-PVI have described promising short-term follow-up success rates with freedom from AF without AADs in 64% to 73% of patients.8–11 However, clinical outcome data beyond 1 year are largely unavailable. The aim of this article was to report midterm results of SMI-PVI, by analyzing both procedural efficacy and safety in patients with mostly paroxysmal AF.
This observational, retrospective study examined a series of 86 consecutive patients treated with SMI-PVI between July 2005 and November 2011 in three centers. In two centers, the patients were treated by the same surgeon. Inclusion criteria were symptomatic paroxysmal or persistent AF, without concomitant cardiac structural disease, refractory to class I and/or class III AADs or failed transcatheter PVI. The exclusion criteria for SMI-PVI were left atrial (LA) size of greater than 55 mm (parasternal echocardiographic view), prior heart or lung surgery, significant coronary disease or previous myocardial infarction, left ventricle hypertrophy of greater than 12 mm, previous hospitalization for heart failure, left ventricular dysfunction (ejection fraction <50%), moderate or severe mitral or aortic valve disease, and lung disease (prior tuberculosis or chronic obstructive pulmonary disease Gold class III-IV). Definitions of paroxysmal and persistent AF, success and failure of ablation, adverse events, and follow-up monitoring were based on the Heart Rhythm Society Consensus Statement for the catheter and surgical ablation of AF.5
When the technique was first introduced (2005), pulmonary veins (PVs) were targeted via bilateral video-assisted minithoracotomy. Since 2007, a switch was made to a totally thoracoscopic approach. All patients were operated on in the supine decubitus position, with general anesthesia and double-lumen endotracheal intubation. After lung deflation, the pericardium was divided 2 cm anterior to the phrenic nerve from the superior vena cava to the inferior vena cava. Blunt dissection was used to access the oblique sinus between the right inferior PV and the inferior vena cava, and both right PVs were surrounded with the help of an articulated lighted dissector (Lumitip; AtriCure, Inc, Cincinnati, OH USA). A rubber tube (Glidepath; AtriCure, Inc, Cincinnati, OH USA) was placed around the PVs. A 5-cm–long bipolar radiofrequency clamp (Isolator; AtriCure, Inc, Cincinnati, OH USA) was advanced with the Glidepath attached to the tip of the lower jaw to guide it through the oblique sinus, until its tip could be visualized cephalic to the superior PV. Bipolar ablation was performed by closing the bipolar clamp along the LA cuff adjacent to the ostium of the PVs, taking care not to ablate the PVs themselves. This clamp produces a linear thermal lesion by radiofrequency energy (Fig. 1). After ablation, the measurement of effective conduction block was performed by pacing within the PVs (exit block). After testing the conduction block, the lung was reinflated. Then, from the left side, the left PVs and the LA appendage (LAA) were addressed. The placement of thoracoscopic ports on the left side was similar to the right. After division of the ligament of Marshall, both left PVs were surrounded by a Glidepath with the aid of the articulated lighted dissector, as described for the right PVs. The ablation lesions were repeated at least three to five times on each side before testing of exit block. In the last 33 patients, ganglionic plexi (GP) were tested for inducibility by means of high-rate pacing.12 Whenever active GP were found, these were additionally ablated using the monopolar Isolator Pen (Atricure). No additional linear ablations (ablation lines) were applied on the atria. All patients in AF were cardioverted to sinus rhythm for these measurements. Concerning LAA management, the LAA was excised by stapling or excluded with the Atriclip device in all patients of the center 1 series. The LAA was intentionally not addressed in the center 3 series and a subgroup of the center 2 series.
During postoperative hospitalization, the patients were treated with full-dose low–molecular-weight heparin. Oral anticoagulation was restarted 1 month after surgery, and low–molecular-weight heparin was not stopped until international normalized ratio of greater than 2.0 was reached. Oral anticoagulation treatment was determined on the basis of the CHADS2VA2Sc score for stroke.4,13 Antiarrhythmic drugs were continued during the first 3 months, and when atrial arrhythmias occurred in this period, they were not treated with electrical cardioversion because spontaneous conversion is known to occur frequently.
All patients visited the outpatient clinic and received standard care for patients treated for AF and underwent 24-hour or 96-hour Holter monitoring at 3, 6, and 12 months. Because of the observational nature of this study, no further specific investigation was requested for the patients. After the first year, follow-up was conducted annually or on indication, consisting of 24-hour Holter monitoring and physical examination during outpatient visits. In case of early recurrence of atrial tachyarrhythmias (before 3-month follow-up visit), the patients underwent cardioversion.
The primary efficacy endpoint was defined as freedom from atrial arrhythmias, that is, no evidence of AF, atrial flutter, or other atrial arrhythmias with a duration of greater than 30 seconds, as documented by Holter monitoring, or implantable cardioverter defibrillator and pacemaker interrogation, without the use of class I or III AADs,5 in accordance with the definitions as described in the 2012 expert consensus statement on AF ablation.5
The secondary efficacy endpoints were freedom from atrial arrhythmias with the use of AADs, freedom from atrial arrhythmias after SMI-PVI as first-line invasive treatment (without previous transcatheter PVI), and freedom from atrial arrhythmias after SMI-PVI with additional GP ablation.
The safety endpoint was the occurrence of procedural and postprocedural adverse events. Adverse events were defined as an event that resulted in death or permanent injury or in temporary injury that required intervention or specific treatment (eg, stroke, transient ischemic attack, major bleeding requiring surgery or blood transfusion or cardiac tamponade and/or perforation, significant/symptomatic PV stenosis >70%, pericarditis and/or pericardial effusion, acute coronary syndrome, myocardial infarction, nervus phrenicus lesion, pneumothorax, wound infections, empyema, pneumonia, periprocedural conversion to thoracotomy, and other nonpredefined events).
Baseline descriptive statistics are presented as mean ± SD or median (range) for continuous variables, as appropriate, and counts with percentages for categorical variables. Differences between subgroups, in terms of patient characteristics at baseline, different follow-up times, and end of study were evaluated by the Student t test or the Mann-Whitney U test, depending on normality of the data. The χ2 or Fisher exact test was used for comparison of categorical variables. Follow-up data were censored for the patients who had a first recurrence of AF or had been followed through February 1, 2012. The observation time was calculated as the time from ablation until either the occurrence of AF or the moment of censoring. The statistical software package Statistical Package for the Social Sciences 20 was used for analysis.
A total of 86 patients were treated with SMI-PVI in three centers, by two surgeons. The number of patients was 28, 25, and 33. The mean ± SD age was 54 ± 11 years, and 67 patients (78%) were men. There were 74 patients (86%) with paroxysmal AF and 12 patients (14%) with persistent AF. Atrial fibrillation was present for a median of 30 months (2-200) before the SMI-PVI procedure. Previous transcatheter PVI had been performed in 15 patients (17%). Preoperatively, four patients (5%) had a pacemaker and two patients (2%) had an implantable cardioverter defibrillator. Patient baseline characteristics of the three groups are illustrated in detail in Table 1.
The procedure was performed successfully in all patients. More specifically, 13 patients (15%) were treated via bilateral video-assisted minithoracotomy and 73 (85%) underwent a total thoracoscopic approach. No additional ablation lines were applied, and additional ablation of the GP was performed in 25 patients (29%). The mean ± SD procedural time was 180 ± 61 minutes. The LAA was excised in 31 patients (36%) by stapling and was excluded in 10 patients (12%) using the Atriclip device (AtriCure, Inc, Cincinnati, OH USA). In 45 patients (52%), the LAA was intentionally left unaddressed. The mean ± SD postoperative hospitalization was 7 ± 3 days.
After a median follow-up of 24 months (6–78), 62 (72%) of all patients were free from atrial arrhythmias without the use of AADs. Success was higher when AADs were taken into account, with 71 patients (83%) free from atrial arrhythmias.
Over time, the percentage of the patients free from atrial arrhythmias without use of AADs was 71% at 12 months, 72% at 24 months, and 69% at 36 months (Fig. 2). With the use of AADs, freedom from atrial arrhythmias was 81%, 77%, and 74% at 12, 24, and 36 months, respectively.
Among failures, which occurred mostly during the first year, 50% (12/24 patients) received an additional transcatheter PVI. This resulted in a combined success of 80% freedom from arrhythmia at midterm follow-up without AADs and 91% with AADs. In two patients, a pacemaker was implanted because of sick sinus syndrome after SMI-PVI.
The overall freedom from oral anticoagulants at midterm follow-up was 72%; in the group with LAA exclusion, 93%; and in the group without LAA exclusion, 53% (P > 0.001).
Periprocedural major adverse events occurred in seven patients (8%). During the procedure, two patients required conversion to sternotomy, one because of bleeding of the LAA and one because of laceration of the right pulmonary artery. One patient required unilateral (left-side) conversion to minithoracotomy for adhesions of the left side of the chest. During hospitalization, two patients had late tamponade (after 2 and 5 days) and one patient had pericardial effusion. These patients required evacuation through video-assisted thoracoscopic surgery (VATS) and recovered completely. In one case, pericardial effusion was not treated, and the patient recovered completely. One patient had right-sided homonymous anopsia; magnetic resonance imaging showed signs of posterior cerebral ischemia but was inconclusive; therefore, there was a clinical diagnosis of stroke, confirmed by a neurologist. At 1-year follow-up, the patient had recovered partially. No 30-day or in-hospital mortality was recorded. As described, one patient had a laceration of the right pulmonary artery and required conversion to sternotomy. Postoperatively, pulmonary artery angioplasty was performed by the interventional cardiologist. This patient died 7 months after surgery because of a pulmonary embolism. Furthermore, minor adverse events occurred in seven patients (8%). We report four cases of pneumothorax, which were treated with chest drainage. Two transient phrenic nerve lesions were observed; at 3-month follow-up, the patients had completely recovered. In one case, pericardial effusion was not treated, and the patient recovered completely. All individual adverse events are listed in Table 2.
Of all patients, 71 (83%) underwent SMI-PVI as a first-line invasive treatment. In this subgroup, freedom from arrhythmia without AADs was obtained in 73%. These results do not differ significantly when compared with patients with previous transcatheter PVI (P = 0.608).
When comparing results of SMI-PVI between paroxysmal and persistent AF patients, the paroxysmal AF group shows 72% freedom from arrhythmia, compared with 70% in the persistent group (P = 0.876).
In our study, additional GP ablation resulted in freedom from arrhythmia in 75% of the patients; this was 72% in the group without additional GP ablation (P = 0.810).
Comparing the patients with and without LAA exclusion, adverse events occurred in 20% and 13%, respectively (P = 0.438).
This study reports on a multicenter clinical experience with SMI-PVI, as a stand-alone procedure for the treatment of refractory AF. Our results show that SMI-PVI is effective for the treatment of mostly paroxysmal AF and that benefits are maintained at midterm follow-up. Perioperative adverse events do remain a point of caution.
In recent years, several publications have reported on short-term outcomes of SMI-PVI, showing promising results, with success rates without AADs ranging from 64% to 73%.8–11 However, almost no clinical results beyond 1 year are available. The recently published atrial fibrillation catheter ablation versus surgical ablation treatment (FAST) trial, which compared SMI-PVI with transcatheter PVI at 1-year follow-up, without AADs, documented a 66% freedom from arrhythmias after SMI-PVI against 37% after transcatheter PVI.8 Compared with the FAST trial, our data show a slightly higher success percentage with longer follow-up. This might be explained by the higher rateof persistent AF in the FAST population (33%). Nevertheless, the population of the FAST trial differed from ours in that it enrolled patients less amenable to percutaneous treatment, with prior failed transcatheter PVI, LA diameter of 40 to 44 mm with hypertension, or LA diameter of greater than 44 mm.
Two recently published studies, reporting on outcome of SMI-PVI as a stand-alone procedure, show 80% success at a mean follow-up of 17 months14 and 90% success at a mean of 24 months.15 Our study found slightly lower success rates compared with these reports but in a larger patient population with prolonged follow-up and an extensive description of adverse events. In addition, no additional ablation lines were applied in our series. Most of the patients in this study underwent SMI-PVI as first-line invasive treatment. In our subanalysis, there was no significant difference compared with the patients who underwent previous transcatheter PVI.
Surgical isolation of the PVs offers potential benefits.
First, thanks to the use of bipolar radiofrequency with an automatic transmurality algorithm with impedance feedback, and systematical verification of exit block, SMI-PVI offers certainty regarding objective isolation of the PVs, via a total thoracoscopic approach. In approximately 90% of all cases, the trigger for paroxysmal AF originates from the region of the PVs.16 Addressing the PVs is essential and in most cases sufficient to control the arrhythmia. Lone SMI-PVI has proven to be a relatively safe and reproducible technique. However, using this lesion set, triggers in non-PV sites may lead to AF recurrence. In our study, SMI-PVI was performed without any additional linear ablations, although the literature reports a large variety of lesion sets.17–19
Second, although not performed in all patients of our series, the surgical approach may offer the possibility of excluding the LAA to reduce the future risk for stroke.20 These potential advantages notwithstanding, the LAA was not routinely addressed in the patients treated in center 3 and in a subgroup of the patients treated in center 2 to maintain LA contractility and prevent possible hydroelectrolytic unbalances.21 This policy did not influence the primary endpoint or incidence of adverse events, although it resulted in a higher percentage of patients on oral anticoagulants. When regarding future cardiac interventions, thoracoscopically entering the pericardium may leave some adhesions, but it does not exclude the possibility for later cardiac interventions through median sternotomy.
Finally, SMI-PVI via VATS offers the possibility to achieve autonomic nervous system denervation of the atria because the GP are located on the epicardial surface of the atrial myocardium. Ganglionic plexi ablation remains controversial because the additional benefits compared with lone SMI-PVI have never been investigated in a randomized clinical trial.22 Nonetheless, the combination of techniques has shown good clinical results.23
Our study shows that, when both AADs and additional transcatheter PVI are considered, 91% of our population is free from atrial arrhythmia. In our experience, the feasibility and the encouraging results of repeated percutaneous ablation after failed SMI-PVI suggest that the two procedures may perform well in a sequential multidisciplinary context.
Unfortunately, because of the invasive nature of the VATS approach, the higher efficacy of SMI-PVI was accompanied by a higher adverse event rate and longer hospitalization than for transcatheter PVI. In the presented patient group, fewer adverse events occurred than reported in other studies, although the reported incidence of adverse events remains high.8 Most adverse events in the preliminary phase occurred in the very first patients, indicating lower complication rates as a surgeon’s experience increases. No perioperative mortality was registered. One perioperative cerebrovascular accident with visual disorders and partial recovery was reported. In this 49-year-old patient, the LAA was intentionally not excluded.
Minimally invasive surgical PVI is an effective treatment of mostly paroxysmal AF at midterm follow-up. If combined with a progressive abatement of operative risk, midterm results of SMI-PVI show potential for a solid and durable first-line nonpharmacological treatment of paroxysmal and persistent AF.
Although all patients in our study underwent the same SMI-PVI procedure, the population was heterogeneous when prior transcatheter ablation, additional GP ablation, and LAA amputation are considered. The retrospective nature of this study means that no definite conclusions may be drawn regarding SMI-PVI efficacy. The extensive follow-up may counterbalance this. Furthermore, 24- and 96-hour Holter monitoring may underestimate the recurrence of AF. As observed in the transcatheter PVI results, success is very likely to decrease over time. From this perspective, it will be interesting to report on long-term results (>36 months) when available.
This retrospective multicenter observational study shows that SMI-PVI was effective at a median follow-up of 24 months for the treatment of mostly paroxysmal drug-refractory AF. Adverse events do remain a point of caution.
The authors thank Bart Mulder and Mattia Valente for their contribution to the figures and text.
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This is a retrospective, multi-center observational study of 86 patients who underwent minimally invasive surgical pulmonary vein isolation between 2005 and 2011. Fifteen percent of patients had a mini-thoracotomy approach, while 85% of patients had a thoracoscopic procedure. The left atrial appendage was either excised or excluded in just under 50% of the patients. Eighty six percent of the patients had paroxysmal atrial fibrillation. Follow-up was performed with either 24-hour or 96-hour Holter monitoring. Periprocedural adverse events occurred in 8% of patients with 2 conversions to sternotomy for bleeding and one conversion to mini-thoracotomy for adhesions. There was one stroke. There was no operative mortality. The overall freedom from atrial arrhythmias without the use of anti-arrhythmia drugs was 71% at 12 months and remained stable at 2 years.
This report, like others in the literature, showed that surgical minimally invasive pulmonary vein isolation was an effective treatment for paroxysmal atrial fibrillation. However, therewas a relatively high rate of perioperative adverse events even in the words of these expert surgeons. As a single procedure, the success rate reported in this series was higher than has been reported after a single catheter-based pulmonary vein isolation. These results and others suggest that surgical pulmonary vein isolation is an effective treatment strategy for paroxysmal atrial fibrillation and should be considered in patients who either have failed catheter ablation or are not considered good candidates for a catheter-based approach.