Abstract
Aims
Advanced atrial fibrillation (AF) is currently a dilemma for electrophysiologists when choosing a minimally invasive treatment strategy. Previous studies have demonstrated the outcome of either catheter ablation or thoracoscopic surgical ablation (SA) is unsatisfactory in these patients. Whether hybrid ablation (HA) could improve outcomes in these patients is unknown. The purpose of this study was to evaluate the clinical efficacy of HA for the treatment of advanced AF.
Methods and results
A randomized controlled trial was designed to enrol patients with persistent AF (PerAF) and enlarged left atrium or long-standing persistent AF (LSPAF) who were randomized to HA or thoracoscopic SA at a 1:1 ratio. The primary endpoint was freedom from any recurrence of AF off antiarrhythmic drugs (AADs) 12 months after operation. The primary endpoint was monitored by 7-day electrocardiogram monitoring devices. One hundred patients were enrolled. The mean age was 58.5 ± 7.6 years, and the mean left atrial diameter (LAD) was 50.1 ± 6.1 mm. At 12 months, freedom from AF off AADs was recorded in 71.4% (35/49) of patients in HA group and 45.8% (22/48) in SA group [odds ratio 2.955, 95% confidence interval (1.275–6.848), P = 0.014]. HA significantly reduced patients’ AF burden (30.2% in SA group and 14.8% in HA group, P = 0.048) and the LAD (mean differences: −5.53 ± 4.97 mm in HA group and −3.27 ± 5.20 mm in SA group, P = 0.037) at 12 months after operation.
Conclusion
In patients with PerAF and enlarged left atrium or LSPAF, HA achieved better freedom from AF after 1 year of follow-up compared with thoracoscopic SA.
Keywords: Atrial fibrillation, Simultaneous hybrid ablation, Thoracoscopic surgical ablation
Graphical Abstract
Graphical Abstract.
What’s new?
This single-centre, prospective, randomized controlled trial was the first study to compare the efficacy between hybrid ablation and thoracoscopic surgical ablation in patients with advanced atrial fibrillation (persistent atrial fibrillation with enlarged left atrium or long-standing persistent atrial fibrillation).
In patients with advanced atrial fibrillation, hybrid ablation achieved better freedom from atrial fibrillation after 1 year of follow-up compared with thoracoscopic surgical ablation.
These encouraging results with 1-year follow-up would provide evidence for clinicians to make decisions for patients with advanced atrial fibrillation.
Introduction
Atrial fibrillation (AF) is the most common type of atrial tachyarrhythmia (ATA) and increases the risk of ischaemic stroke, systemic thromboembolism, dementia, heart failure exacerbation, and mortality.1–4 Catheter ablation (CA) is recommended for rhythm control after failure or intolerance of antiarrhythmic drugs (AADs) in patients with AF.5 Thoracoscopic surgical ablation (SA) should be considered in patients who have symptomatic paroxysmal or persistent AF (PerAF) refractory to AAD therapy and have failed CA, or with evident risk factors for catheter failure, to maintain long-term sinus rhythm (SR).6 However, for patients with advanced AF [PerAF with enlarged left atrium or long-standing PerAF (LSPAF)], the mechanisms that generate and maintain AF are more complex.7 Whether CA or thoracoscopic SA, SR maintenance is challenging in these patients.8–10
To improve the efficacy for patients with AF, hybrid ablation (HA) has been employed with additional endocardial mapping and electrophysiologically (EP) guided endocardial ablation after thoracoscopic SA.11,12 Several observational studies demonstrated widely varying success rates, from 63 to 94%, which were associated with the type of AF, left atrial diameter (LAD), previous failed CA, and different lesion sets.12–20 It remains unknown whether HA can achieve superior efficacy of SR restoration with additional EP mapping and touch-up CA for patients with advanced AF. We designed this study to answer this question.
Methods
Study design
This study was a prospective, single-centre RCT (randomized controlled trial) designed to compare the efficacy of simultaneous HA (intervention group) with that of thoracoscopic SA (control group) among patients with PerAF with LAD > 50 mm or LSPAF.7 The ethics approval for this study was obtained from the Fuwai Hospital Research Ethics Committee (October 2016, no. 2016-828). The trial was registered at www.clinicaltrials.gov (NCT03127423).
Patient selection
Patients with PerAF and LAD > 50 mm or LSPAF (with no restriction on LAD) were eligible. PerAF means AF that lasts longer than 7 days, including episodes that are terminated by cardioversion, either with drugs or by direct current cardioversion, after 7 days or more, and LSPAF means continuous AF lasting for ≥1 year when it is decided to adopt a rhythm control strategy.21 Exclusion criteria included presence of significant structural heart diseases and previous percutaneous CA or thoracoscopic SA for AF. Detailed inclusion and exclusion criteria are shown in Supplementary material online, Table S1. All participants provided written informed consent.
Randomization and allocation concealment
Patients were randomly assigned to SA group or one-stage HA group by computer-generated sequence in a 1:1 ratio using simple randomization. The page containing the random number and group information of each participant was printed and conserved in a single sealed envelope whose cover was marked with the sequence number. After informed consent forms were signed by eligible participants, the unique random number for the participant was confirmed with the corresponding envelope being opened and the planned procedure being determined. Allocation was concealed, but blinding was not possible in this trial. However, the trial statistician and research staff were blinded to the treatment arms.
Interventions
Simultaneous hybrid ablation
In this arm, thoracoscopic SA was performed first. The detailed procedure had been introduced in our previous study,22,23 as described briefly in the following. General anaesthesia was induced and patient intubated with a double-lumen endotracheal tube allowing for deflation of the lungs. Preoperative transoesophageal echocardiography was always used to exclude intracardiac thrombi. Heparin was not used during thoracoscopic SA procedure. One camera port and the other two working ports were established to perform the ablation procedure. Generally, left-side ablation was performed first. The right-side approach was similar to the left-side approach with three ports but positioned more anteriorly. The left-side ablation included left atrial (LA) appendage excision with a stapling device (EZ60, Ethicon Endosurgery Inc., USA), Marshall ligament division with an ultrasonic scalpel, left pulmonary vein isolation (PVI) and partial ganglion ablation with bipolar radiofrequency clamps (Isolator AtriCure Inc., USA), and linear ablation in the left atrium completed with bipolar clamps and pens (Isolator AtriCure Inc., USA). The right-sided lesion sets included right PVI, a linear lesion connecting the vena cava, right atrial free wall, and right atrial appendage (RAA), which were completed with bipolar clamps and pens (see Supplementary material online, Figure S1). Generally, lesions were completed by clamping six times or ablating with pen for 80 s in one place.
Endocardial CA was immediately performed after thoracoscopic SA. Two multiple-polar catheters were always be positioned within the coronary sinus (Bard, Dynamic or IBI, St. Jude Medical, USA) at the right ventricle (IBI, St. Jude Medical, USA). Two long Swartz sheaths (8F, SR0, St. Jude Medical, USA) were introduced into the left atrium via transseptal puncture. After transseptal puncture, 70–100 IU/kg heparin was administered intravenous (i.v.), and the activated clotting time was maintained at 200–300 s. And then, an overall LA voltage profile was then acquired based on a semiquantitative description of the severity of LA substrate remodelling with the help of an EnSite NavX™ mapping system. Guided by the colour-coded voltage map of the LA anatomy, a 4.0 mm TactiCath™ quartz ablation catheter (Abbott, USA) was used to confirm whether the surgical lesions were transmural. The normal voltage areas were defined as voltage > 0.5 mV, transmural areas were defined as < 0.1 mV, and low-voltage areas were defined as 0.1–0.5 mV. The full length of the surgical linear lesion and the length of the normal voltage areas were tagged and measured, and the ratio of the two was calculated. A touch-up endocardial ablation was applied to the residual conduction gaps or non-transmural area along the previous surgical lesions. Irrigated radiofrequency ablation was applied with an upper temperature limit of 43°C, power of 30–40 W, and flow rate of 17 mL/min. Linear lesions of the coronary sinus, mitral and tricuspid isthmus were completed routinely after the aforementioned steps. Complete PVI, conduction block over the mitral isthmus, and tricuspid isthmus lesions were later confirmed. Intensive pacing at each lesion (output 10 mA, pulse width 2 ms) was applied to confirm transmurality with contact force monitoring (10–20 g); further ablation was delivered at lesions that could be captured until loss of capture. If AF continued, i.v. ibutilide (maximum: 1 mg) was administered, followed by elimination of atrial tachycardia under activation and voltage mapping if atrial tachycardia occurred; if AF still continued, direct current cardioversion would be applied.
Stand-alone thoracoscopic surgical ablation
In this arm, thoracoscopic SA procedure was performed, which has been described above.
Criteria for discontinuing or modifying allocated interventions
During simultaneous HA or stand-alone thoracoscopic SA procedure, thoracoscopic SA was converted to median sternotomy when there was diffused pleural adhesion or severe bleeding. If cardiopulmonary bypass was established and the heart was arrested, Cox-maze procedure was performed. And further planned EP mapping and CA were cancelled when the patient was assigned to simultaneous HA. After randomization, when the participants changed the decision, patient’s desire was respected, including withdrawn from the trial or crossover between one-stage HA and SA groups.
Postoperative anticoagulation and antiarrhythmic drug treatment
After the operation, low molecular weight heparin was started as soon as bleeding risk allowed, then bridged to warfarin or new oral anticoagulant and continued for 3 months after the procedure. In HA group, anticoagulation strategies were more aggressive, including dose and frequency. After the index procedure, oral amiodarone or sotalol was routinely administered until 3 months after procedure. Patients were discharged with stable haemodynamics and heart rate/rhythm (SR if possible, including amiodarone/sotalol or direct current cardioversion), 24 h Holter without severe bradycardia, and other examinations such as echocardiography and chest X-ray. At 3-month follow-up, if patients underwent AF or atrial flutter recurrence, continuous AAD treatment was recommended; if patients converted to SR, AADs could be discontinued.
Study endpoints
The primary endpoint was freedom from any recurrence of AF off AADs 12 months after operation. Recurrent AF was defined as AF of at least 30-s duration that was documented by electrocardiogram, 24 h Holter, or 7-day electrocardiogram continuous monitoring device after the post-ablation 3-month blanking period.
The secondary endpoints were procedure-associated adverse events, freedom from any recurrence of ATAs, the AF burden (total duration of AF as a proportion of 7-day electrocardiogram continuous monitoring), quality of life score by AF Effect on Quality-Of-Life (AFEQT) questionnaire, cardiac function, and major adverse cardiovascular and cerebral events (including major adverse cardiovascular events, major bleeding events, and major thromboembolic events) 12 months after operation. All endpoints are listed in Supplementary material online, Table S2.
Follow-up schedule
Follow-up visits were performed at 3, 6, and 12 months postoperatively, and patients were requested to undergo a 7-day electrocardiogram monitoring (unwearable Tele-ECG-Card) examination at each follow-up visit. All of the 12-lead electrocardiograms or 24 h Holter during each follow-up visit were also analysed. Patients who underwent CA because of recurrent ATAs during follow-up were considered as study termination. A follow-up questionnaire including medications, adverse events, and clinical examinations was completed at each visit. Cardiac echocardiography was performed to evaluate cardiac function at 12 months. The postoperative quality of life questionnaire was completed at the 12-month follow-up visit.
Statistical analysis
The calculation of the sample size was based on the primary endpoint according to previously published data and our own clinical experience. We assumed the probability of 47% without any recurrence of AF in SA group24 and 75% in HA group.25 A total of 94 patients randomly allocated to each group provided 80% power for detecting an absolute increase of 28% (47% vs. 75%) in the proportion of patients free from AF based on a two-tailed 0.05 level Fisher exact test. To compensate for the drop-out rate and a loss ratio of 5% during follow-up, ∼50 cases were ultimately enrolled in each trial arm.
The primary, secondary, and prespecified subgroup analyses were based on modified intention-to-treat (mITT) principle. Categorical data were analysed by either χ2 tests or Fisher’s exact tests, and continuous data were analysed by either Student’s t-test or Mann–Whitney test and presented as mean [±standard deviation (SD)] or median [interquartile range (IQR)] depending upon distribution of obtained data. The prespecified subgroup analyses of primary endpoint [by age, sex, hypertension, diabetes, type of AF, years since AF diagnosis, PerAF duration, LAD, and left ventricular ejection fraction (LVEF)] were presented as a Forest plot depicting odds ratios (OR) with 95% confidence intervals (CIs). Secondary endpoints were only exploratory analyses.
We conducted sensitivity analyses to validate the reliability of the primary endpoint including per-protocol analysis and as-treated analysis. The per-protocol analysis was performed in all participants treated according to the prespecified protocol. The as-treated analysis was performed according to the actual treatments given to the participants rather than according to the treatments intended for the participants when they were assigned to their arm of the study. All tests of significance were two tailed, with an α of 0.05. The statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).
Results
Patients
From December 2016 to December 2021, 969 patients with non-paroxysmal AF were assessed for eligibility (Figure 1). One hundred patients were enrolled (HA = 50, SA = 50), and one patient in HA group and two patients in SA group withdrew consent post-randomization. Two patients in HA group received thoracoscopic SA procedure, and two patients in HA group received open-chest Cox-maze ablation procedure. The reasons for withdrawal and protocol deviation are listed in Supplementary material online, Table S3.
Figure 1.
Study flow diagram depicting the participant enrolment. HA, hybrid ablation; mITT, modified intention to treat; LAD, left atrial diameter; SA, surgical ablation.
The mean age was 58.5 ± 7.6 years; 81 (81%) patients were male and 19 (19%) patients were female. Seventeen (17%) and 83 (83%) patients were diagnosed persistent and LSPAF, respectively. The mean LAD was 50.1 ± 6.1 mm. Baseline characteristics are shown in Table 1.
Table 1.
Baseline characteristics
| Overall (N = 100) |
HA group (n = 50) |
SA group (n = 50) |
P value | |
|---|---|---|---|---|
| Age, years, mean (SD) | 58.5 (7.6) | 59.9 (7.0) | 57.2 (8.0) | 0.078 |
| Male, n (%) | 81 (81.0) | 40(80.0) | 41 (82.0) | 1.000 |
| BMI, kg/m2, mean (SD) | 26.9 (2.7) | 27.3 (2.8) | 26.6 (2.6) | 0.197 |
| Diabetes mellitus, n (%) | 19 (19.0) | 12 (24.0) | 7 (14.0) | 0.308 |
| Coronary artery disease, n (%) | 17 (17.0) | 10 (20.0) | 7 (14.0) | 0.595 |
| Previous stroke, n (%) | 33 (33.0) | 20 (40.0) | 13 (26.0) | 0.202 |
| Hyperlipidaemia, n (%) | 36 (36.0) | 18 (36.0) | 18 (36.0) | 1.000 |
| Hypertension, n (%) | 58 (58.0) | 31 (62.0) | 27 (54.0) | 0.544 |
| Years since AF diagnosis, median (IQR) | 4.0 (2.0–7.8) | 5.0 (2.0–8.0) | 4.0 (2.0–7.3) | 0.317 |
| Persistent AF duration, years, median (IQR) | 2.0 (1.0–4.0) | 2.0 (1.0–4.0) | 2.0 (1.0–4.3) | 0.685 |
| Type of AF, n (%) | 1.000 | |||
| Persistent AF | 17 (17.0) | 9 (18.0) | 8 (16.0) | |
| Long-standing persistent AF | 83 (83.0) | 41 (82.0) | 42 (84.0) | |
| CHA2DS2-VASc score, n (%) | 0.220 | |||
| 0 | 17 (17.0) | 6 (12.0) | 11 (22.0) | |
| 1 | 29 (29.0) | 11 (22.0) | 18 (36.0) | |
| 2 | 22 (22.0) | 15 (30.0) | 7 (14.0) | |
| ≥3 | 32 (32.0) | 18 (36.0) | 14 (28.0) | |
| LAD, mm, mean (SD) | 50.1 (6.1) | 50.8 (5.8) | 49.4 (6.4) | 0.240 |
| LVEDD, mm, mean (SD) | 48.3 (4.2) | 48.2 (4.0) | 48.4 (4.4) | 0.831 |
| LVEF, %, mean (SD) | 61.4 (4.3) | 61.4 (4.5) | 61.4 (4.1) | 1.000 |
AF, atrial fibrillation; BMI, body mass index; HA, hybrid ablation; IQR, interquartile range; LAD, left atrial diameter; LVEF, left ventricular ejection fraction; SA, surgical ablation; SD, standard deviation.
Procedural characteristics
In SA group, 48 patients underwent thoracoscopic epicardial ablation procedure. After procedure, 6 patients (12.5%) converted to SR, 6 patients (12.5%) converted to atrial flutter, and 36 patients (75.0%) still maintained AF, and electrical cardioversion was required.
In HA group, 45 patients underwent electrophysiological mapping and endocardial CA procedure. After initial thoracoscopic SA, 8 patients (17.8%) converted to SR, 5 patients (11.1%) converted to atrial flutter, and 32 patients (71.1%) still maintained AF. Endocardial electrophysiological mapping and checking at the left atrium were analysed in 45 patients. Left pulmonary vein (PV) entrance–exit block was confirmed in 44 patients (97.8%), and right PV entrance–exit block was confirmed in 45 patients (100%). Persisting normal potentials were present in the linear lesion connecting the left inferior PV to the great cardiac vein in 33 patients (73.3%). After CA procedure, 30 patients (66.7%) converted to SR, and 15 patients (33.3%) remained in AF or atrial flutter requiring medication or electrical cardioversion to SR. Lesions of CA are described in Table 2. Endocardial 3D voltage mapping and CA after initial thoracoscopic SA in a patient are shown in Supplementary material online, Figure S2.
Table 2.
Electrophysiological voltage mapping and procedural characteristics of CA in patients after thoracoscopic epicardial ablation in HA group
| Parameter | Persisting normal potentials, n (%) | Ratio of normal voltage, %, mean ± SD | Reinforced or touch-up CA, n (%) |
|---|---|---|---|
| Left atrial mapping (n = 45) | |||
| Left PV isolation loop | 1 (2.2) | – | 30 (66.7) |
| Right PV isolation loop | 0 | – | 29 (64.4) |
| Roof line | 15 (33.3) | 5.0 ± 16.4 | 40 (88.9) |
| Inferior line | 17 (37.8) | 4.5 ± 10.9 | 28 (62.2) |
| Left fibrous trigone line | 19 (42.2) | 6.0 ± 11.4 | 27 (60.0) |
| Left inferior PV to GCV/MI | 33 (73.3) | 13.1 ± 20.7 | 42 (93.3) |
CA, catheter ablation; GCV, great cardiac vein; HA, hybrid ablation; MI; mitral isthmus; PV, pulmonary vein; SD, standard deviation.
Perioperative parameters
Postoperative atrial flutter occurred in 14 patients (28.6%) in HA group and 20 patients (41.7%) in SA group (P = 0.206). Two patients (4.1%) in HA group received postoperative electrical cardioversion and six patients (12.5%) in SA group (P = 0.159), and the remainder received only medication therapy. Both pleural drainage volume on the first postoperative day and total pleural drainage volume were higher in HA group compared with SA group (all P < 0.001) (Table 3).
Table 3.
Perioperative parameters and complications
| HA group (n = 49) | SA group (n = 48) | P value | |
|---|---|---|---|
| Perioperative parameters | |||
| Procedure time (min), median (IQR) | 290 (264–323) | 164.5 (154–180.5) | <0.001 |
| Perioperative atrial flutter, n (%) | 14 (28.6) | 20 (41.7) | 0.206 |
| Perioperative electrical cardioversion, n (%) | 2 (4.1) | 6 (12.5) | 0.159 |
| Volume of pleural drainage (the first day after procedure) (mL), median (IQR) | 260 (155–475) | 145 (70–220) | <0.001 |
| Total volume of pleural drainage (mL), median (IQR) | 880 (535–1285) | 340 (215–650) | <0.001 |
| ICU time (days), median (IQR) | 2 (1–3) | 1 (1–2.75) | 0.464 |
| Hospital length of stay after procedure (days), median (IQR) | 8 (7–12) | 8 (6–10) | 0.291 |
| Perioperative complications, n (%) | 4 | 1 | 0.362 |
| Stroke | 0 | 0 | |
| Conversion to sternotomy due to bleeding | 2a | 0 | |
| Phrenic nerve injury | 0 | 0 | |
| Encapsulated haemothorax requiring thoracotomy | 1 | 0 | |
| Persistent pacemaker implantation | 1 | 1 | |
| Pulmonary vein stenosis | 0 | 0 | |
| Femoral arteriovenous fistula/pseudoaneurysm | 0 | 0 | |
| Left atrial-oesophageal fistula | 0 | 0 | |
| Peripheral vascular thrombosis | 0 | 0 |
HA, hybrid ablation, ICU, intensive care unit; IQR, interquartile range; SA, surgical ablation.
aReceived open-chest ablation procedure.
Primary endpoint
Two patients in SA group and one patient in HA group withdrew consent post-randomization. Therefore, 49 patients in HA group and 48 patients in SA group were analysed of the primary endpoint on the basis of mITT principle. At 3-month follow-up, 95.9% (93/97) of patients completed 7-day electrocardiogram monitoring examinations; at 6-month follow-up, 92.8% (90/97) of patients completed; and at 12-month follow-up, 97.9% (95/97) of patients completed. Patients who did not complete 7-day electrocardiogram monitoring examinations had 24 h Holter or 12-lead electrocardiograms. Freedom from AF off AADs was 71.4% (35/49) in HA group and 45.8% (22/48) in SA group at 12 months after operation, respectively [OR 2.955, 95% CI (1.275–6.848), P = 0.014] (Figure 2). Freedom from AF on AADs was 75.5% (37/49) in HA group and 52.1% (25/48) in SA group at 12 months after operation, respectively (P = 0.021) (see Supplementary material online, Figure S3).
Figure 2.
Freedom from atrial fibrillation off antiarrhythmic drugs at 3, 6, and 12 months after operation between HA and SA groups based on modified intention-to-treat principle. HA, hybrid ablation; SA, surgical ablation.
Sensitivity analyses including per-protocol analysis (45 patients in HA group, 48 patients in SA group) and as-treated analysis (45 patients in HA group, 50 patients in SA group) were also performed. Freedom from AF was higher in HA group than that in SA group in both per-protocol analysis and as-treated analysis (all P < 0.05) (see Supplementary material online, Figure S4, Figure S5).
Secondary endpoints
Freedom from atrial tachyarrhythmias
Freedom from ATAs was 61.2% (30/49) in HA group and 50.0% (24/48) in SA group on AADs (P = 0.310), and 55.1% (27/49) in HA group and 39.6% (19/48) in SA group off AADs (P = 0.156) (see Supplementary material online, Figure S6). During 12-month follow-up, three patients in SA group underwent CA procedure, and one patient converted to SR.
Atrial fibrillation burden
One patient in SA group did not have 7-day electrocardiogram monitoring data due to non-compliance. Therefore, 49 patients in HA group and 47 patients in SA group were analysed for AF burden. Patients in SA group had higher AF burden (30.2%) than patients in HA group (14.8%) at 12 months after operation (P = 0.048) (Figure 3).
Figure 3.
Atrial fibrillation burden at 3, 6, and 12 months after operation between HA and SA groups. HA, hybrid ablation; SA, surgical ablation.
Cardiac function
Forty-five patients in both groups were available for the analysis of cardiac function. The postoperative 12-month echocardiogram demonstrated that LAD was significantly reduced in patients in both HA group and SA group compared with the preoperative echocardiogram. The mean differences were higher in HA group (−5.53 ± 4.97 mm) than that in SA group (−3.27 ± 5.20 mm) (P = 0.037) (Figure 4A). Left ventricular ejection fraction was elevated at 12 months postoperatively in both groups; however, the mean differences were similar between the two groups (P = 0.556) (Figure 4B).
Figure 4.
Cardiac function from baseline to 12 months after operation between HA and SA groups. (A) LAD. (B) LVEF. HA, hybrid ablation; LAD, left atrial diameter; LVEF, left ventricular ejection fraction; SA, surgical ablation.
Quality of life
Improvements in quality of life measured by AFEQT were seen at 12 months after operation compared with preoperative quality of life in both groups (all P < 0.05). The overall AFEQT scores were changed from 70.46 to 79.81 in SA group and from 72.28 to 80.68 in HA group (P = 0.845) (see Supplementary material online, Figure S7).
Procedural complications and follow-up adverse events
There was no significant difference regarding procedural complications between the two groups in our study [four patients (8.2%) in HA group and one patient (2.1%) in SA group, P = 0.362] (Table 3). Two patients (4.1%) in HA group received open-chest ablation due to bleeding, which was required to convert to median sternotomy all occurred during the thoracoscopic ablation. In addition, one patient with postoperative haemothorax needed to remove the clots with thoracotomy in HA group during the early term of the study, and no patient occurred again when we paid attention to haemostasis at ports in the chest wall. One patient in each group underwent permanent pacemaker implantation in hospital after ablation procedure. There was no major complication directly related to the endocardial part of the HA procedure. During 12-month follow-up, no deaths, strokes, and major bleeding events occurred. Visceral artery embolism occurred in one patient in SA group during follow-up (see Supplementary material online, Table S4).
Subgroup analyses
Figure 5 shows the Forest plot for the subgroup analyses of the primary endpoint. For patients with LAD ≤ 50 mm, HA was superior to thoracoscopic SA, and for patients with LAD > 50 mm, there was no difference between the two groups (P interaction = 0.015). There was no significant difference in other subgroup analyses.
Figure 5.
Forest plot of the prespecified subgroup analyses of primary endpoint. AF, atrial fibrillation; CI, confidence interval; HA, hybrid ablation; LAD, left atrial diameter; LVEF, left ventricular ejection fraction. OR, odds ratio; SA, surgical ablation.
Discussion
This study demonstrated that HA procedure combining thoracoscopic SA with catheter mapping and ablation significantly improved clinical outcomes in patients with advanced AF compared with thoracoscopic SA. As recommended by the latest expert consensus statement, HA is reasonable in symptomatic patients with PerAF who are intolerant or refractory to AAD therapy and prefer a hybrid approach, after careful consideration of relative safety and efficacy of treatment options.26 HA procedure might be another treatment option for patients with PerAF or LSPAF.
Patient selection
AF occurs by complex mechanisms, including structural and electrical remodelling, especially in patients with advanced AF (PerAF with enlarged left atrium or LSPAF). The management of AF remains a topic of ongoing debate in current literature. Previous studies have shown that CA and thoracoscopic SA as the first choice have unsatisfactory outcomes in these patients.27,28 The emergence of HA technology might improve the efficacy. Therefore, we wanted to explore whether HA procedure was the best option for patients with advanced AF.
Efficacy
In this study, we applied 7-day electrocardiogram monitoring examinations at 3, 6, and 12 months, which would greatly reduce the rate of missed diagnosis of paroxysmal AF and paroxysmal atrial flutter. This study suggested that additional electrophysiological mapping and CA procedure could improve freedom from AF and reduce AF burden during HA procedure for advanced AF. This superiority may be attributed to additional CA mapping and lesions. Previous studies have reported that PVs could be isolated successfully by bipolar clamp in thoracoscopic SA for AF, but non-transmural linear lesion created by transpolar pen was not uncommon due to the heat sink effect of intracardiac blood flow.29 We advocate epicardial mapping during surgery, which is helpful to judge and improve the transmurality effect of the lesion sets. However, due to the technical limitations of transpolar pen, with the increase of LA wall thickness, transmurality effect of transpolar pen ablation is pessimistic. At present, to solve the technical limitation of transpolar pen and improve the transmurality of ablation on beating heart is the major issue. Therefore, we used the bipolar clamp to create ablation lines as much as possible during SA procedure.
The results of electrophysiological mapping in HA group in this study showed that percentage of persisting normal potentials was 33–73% in the LA linear ablation after thoracoscopic SA (Table 2, Supplementary material online, Figure S2). Persisting normal potentials were present in the linear lesion connecting the left inferior PV to the great cardiac vein created by transpolar pen in 33 patients (73.3%), which might be due to epicardial fat and the heat sink effect of intracardiac blood flow. Furthermore, patients with advanced AF might have severe atrial fibrosis, which affected the conduction of radiofrequency energy. Despite the high rate of PVI, conduction recovery at linear lesions on the roof or the floor of LA might be an important factor of AF recurrence in SA group. Therefore, to improve the efficacy, we advocate SA procedure combining with endocardial mapping and CA for patients with advanced AF. In HA group, electrophysiological mapping after SA procedure could identify the lesion and evaluate whether the lesion was transmural. Additional CA ablation could be safely performed at the conduction gaps or non-transmural area in line with the previous surgical lesions. Furthermore, coronary sinus, tricuspid and mitral isthmus lesions could be performed during endocardial CA, which were difficult to be performed during thoracoscopic SA.
Recently, in a prospective study, Magni et al.30 reported that first-line single-stage HA achieved a success rate with 67% for patients with PerAF and LSPAF after 2-year follow-up. In this study, we achieved similar results. In another RCT, the HA procedure was confirmed with superior effectiveness compared to CA for the treatment of PerAF and LSPAF.31 Previous studies had also demonstrated that HA had satisfactory mid-term and long-term results.19,20 Based on the results of these clinical trials, HA might be a more recommendable treatment than CA or thoracoscopic SA alone for advanced AF. However, the clinical efficacy of HA is still challenging when comparing with conventional Cox-maze IV procedure. The possible gaps of supplemental ablation via endocardial CA after SA procedure including mitral isthmus as well as tricuspid isthmus ablation might be the reasons. These lead to a high incidence of postoperative atrial flutter as this study shown. Ablation energy with better tissue transmurality and continuity (such as pulsed field ablation) might further improve the clinical efficacy of HA.32,33
We also evaluated freedom from ATAs as a secondary endpoint in our study. Although the incidence of postoperative ATAs in HA group had a decreasing tendency compared with SA group, it was not statistically significant. As the primary endpoint of this study is freedom from AF, the difference in freedom from ATAs between the two groups is limited by sample size and needs to be confirmed by studies with a larger sample in the future. However, our study displayed that new onset atrial flutter was more common in HA group (8 patients without AADs) compared to SA group (3 patients without AADs) at 12 months after operation. During simultaneous HA procedure, the immediate subendocardial EP mapping might lead to false negative due to tissue oedema after thoracoscopic SA, which would influence the subsequent subendocardial CA.25 Staged HA procedure might decrease the incidence of postoperative atrial flutter, which needs further confirmation with perspective RCTs. As mentioned above, the point-to-point linear CA in enlarged left atrium might increase the risk of conduction gaps.34 Subgroup analysis revealed that the advantage of efficacy in HA group in patients with LAD >50 mm was not significant. Overall, new onset atrial flutter needs to be taken into account after the simultaneous HA procedure for the treatment of patients with PerAF and dilated left atrium.
The postoperative 12-month echocardiography demonstrated that LAD was significantly reduced in patients in both HA group and SA group compared with the preoperative echocardiography and was reduced more significantly in HA group, which implied that the reduction of AF burden had a positive effect on the remodelling of left atrium. At the same time, the quality of life in both groups was improved postoperatively, but there was no significant difference, which might imply that postoperative atrial tachycardia in HA group still had an impact on the quality of life of patients. However, further confirmation by larger studies is needed.
Safety
This study showed that in terms of perioperative complications, HA group was numerically higher than SA group, but there was no statistical difference. Two patients (4.1%) in HA group received open-chest ablation due to bleeding, which was required to convert to median sternotomy all occurred during the thoracoscopic SA, not during subsequent CA. However, postoperative drainage was higher in HA group than that in SA group due to the use of anticoagulants during endocardial CA and more aggressive anticoagulant use in the early postoperative period in HA group. One patient in each group underwent permanent pacemaker implantation in hospital after ablation procedure. Cox et al.35 demonstrated several factors that could lead to a dysfunctional sinoatrial node preoperatively in patients with AF. For example, some patients had underlying sinus node dysfunction prior to ablation procedures; after operations, a pre-existing sick sinus syndrome was unmasked. How to avoid permanent pacemaker implantation after ablation has been an important topic that needs to be explored in more future studies. There were no serious adverse events in either group during the 1-year follow-up period after procedures, which might be associated with a short follow-up period.
The two RCTs, CEASE-AF and HARTCAP-AF, both demonstrated that HA had superior effectiveness compared to CA for the treatment of PerAF and LSPAF, without increasing perioperative adverse events.36–38 However, in recent years, CA has improved a lot with contact force, steerable sheaths, high-power short-duration ablation, and pulsed field ablation. Whether HA still improves success rates compared to CA with the application of these newer technologies needs to be explored in subsequent studies. Furthermore, whether HA increases the incidence of perioperative adverse events compared with thoracoscopic SA as well as CA still needs to be confirmed by studies with large sample sizes.
Limitations
Though the Cox-maze lesion set was applied during the HA procedure, the clinical efficacy of the HA procedure was less satisfactory compared to full Cox-maze IV procedure. Radiofrequency energy producing the transmural lesion in a beating heart is somewhat limited, and more effective energies are expected to improve the efficacy in the future. Simultaneous HA does have the advantage of simplifying hospitalization for patients, but our study showed that this strategy had non-negligible incidence of postoperative atrial flutter, and we look forward to further studies to show the advantages of staged HA. Additionally, asymptomatic recurrence might be under-detected with 7-day electrocardiogram monitoring. However, postoperative restoration of SR was evaluated by 7-day electrocardiogram monitoring at 3, 6, and 12 months after operation and all of the 12-lead electrocardiograms during each follow-up visit were also analysed, which might decrease the under-detected asymptomatic recurrence. As non-invasive long-term monitoring devices become available in the future, they will have a more positive impact on research. Furthermore, patients who had previously undergone CA were excluded from this study. In addition, endocardial mapping during HA procedure was performed with an ablation catheter and not with a high-density mapping catheter. Finally, the results from a single-centre and small-sample trial may not be extrapolated into general practice because our hospital has highly trained surgeons and electrophysiologists, and both teams are well experienced.
Conclusions
In patients with PerAF and enlarged left atrium or LSPAF, HA combining thoracoscopic SA with catheter mapping and ablation achieved better freedom from AF after 1 year of follow-up compared with thoracoscopic SA. The results of this study might provide new evidence for the treatment of this rhythm disorder in clinical practice.
Supplementary Material
Acknowledgements
The authors would like to thank all the patients that participated in the study.
Contributor Information
Zhe Zheng, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Cardiovascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Yan Yao, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Arrhythmia, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Haojie Li, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Cardiovascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Chunyu Yu, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Cardiovascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Lihui Zheng, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Arrhythmia, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Ligang Ding, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Arrhythmia, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Lingmin Wu, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Arrhythmia, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Sipeng Chen, Department of Information Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, People’s Republic of China.
Hengqiang Lin, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Cardiovascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Ying Meng, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China; Department of Cardiovascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 167 Beilishi Rd, Xicheng District, Beijing 100037, People’s Republic of China.
Supplementary material
Supplementary material is available at Europace online.
Authors’ contributions
Z.Z.: conceptualization, methodology, project administration, supervision, and writing—review & editing. Y.Y.: conceptualization, methodology, project administration, supervision and writing—review & editing. H.L.: data curation, formal analysis, and investigation. C.Y.: data curation, formal analysis, and investigation. L.Z.: validation and resources. L.D.: validation and resources. L.W.: validation and resources. S.C.: formal analysis and investigation. H.L.: validation and resources. Y.M.: validation and resources.
Funding
This study was supported by the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (CIFMS, 2021-I2M-1-063). The funder had no role in study design, data collection, data analysis, data interpretation, or writing of the manuscript.
Data availability
The data underlying this article cannot be shared publicly due to privacy of the individuals that participated in the study.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The data underlying this article cannot be shared publicly due to privacy of the individuals that participated in the study.