Thoracoscopic microwave ablation of atrial fibrillation

The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation

EXECUTIVE SUMMARY

Surgical ablation for atrial fibrillation (AF) can be performed without additional risk of operative mortality or major morbidity, and is recommended at the time of concomitant mitral operations to restore sinus rhythm. (Class I, Level A) Surgical ablation for AF can be performed without additional operative risk of mortality or major morbidity, and is recommended at the time of concomitant isolated aortic valve replacement, isolated coronary artery bypass graft surgery, and aortic valve replacement plus coronary artery bypass graft operations to restore sinus rhythm. (Class I, Level B nonrandomized) Surgical ablation for symptomatic AF in the absence of structural heart disease that is refractory to class I/III antiarrhythmic drugs or catheter-based therapy or both is reasonable as a primary stand-alone procedure, to restore sinus rhythm. (Class IIA, Level B randomized) Surgical ablation for symptomatic persistent or longstanding persistent AF in the absence of structural heart disease is reasonable, as a stand-alone procedure using the Cox-Maze III/IV lesion set compared with pulmonary vein isolation alone. (Class IIA, Level B nonrandomized) Surgical ablation for symptomatic AF in the setting of left atrial enlargement (≥4.5 cm) or more than moderate mitral regurgitation by pulmonary vein isolation alone is not recommended. (Class III no benefit, Level C expert opinion) It is reasonable to perform left atrial appendage excision or exclusion in conjunction with surgical ablation for AF for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C limited data) At the time of concomitant cardiac operations in patients with AF, it is reasonable to surgically manage the left atrial appendage for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C expert opinion) In the treatment of AF, multidisciplinary heart team assessment, treatment planning, and long-term follow-up can be useful and beneficial to optimize patient outcomes. (Class I, Level C expert opinion).

Surgical Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common chronic arrhythmia in the adult population. Ablation lines have largely replaced the historical and challenging cut and sew techniques. Surgical ablation of AF is commonly performed in cases with other indications for cardiac surgery and less commonly as a stand-alone therapy. Pulmonary vein isolation is the cornerstone of this procedure. Extended left atrial ablation lines may increase efficacy in cases with longstanding persistent or permanent AF. Additional efficacy by adding right atrial ablation is controversial but is often performed in cases undergoing right atrial or atrial septal surgery. Left atrial volume reduction is recommended in cases with large left atria and AF undergoing another cardiac surgery. Arrhythmia recurrence is not uncommon after surgical ablation of AF and varies among studies due to heterogeneity in patient population, lesion set and endpoints. Freedom from AF recurrence was 65-87% at 12 months and 58-70% at 2 years follow-up. Long-term monitoring is recommended due to an increased prevalence of asymptomatic recurrences. The strongest predictors of AF recurrence are longstanding or persistent AF and a large left atrium. The most common mechanisms of recurrence are pulmonary vein reconnection, nonpulmonary vein triggers, and gaps in the ablation lines. About 20% of atrial tachyarrhythmia recurrences are atrial flutter or atrial tachycardia. There are not enough data in the surgical literature to support withdrawal of anticoagulation after surgical AF ablation. Patients selected for stand-alone surgical ablation usually have low risk profiles and low postoperative mortality rates (0.2%).

Positioning of the ablation catheter in total endoscopic ablation

Minimally invasive ablation of atrial fibrillation is an option in patients not suitable for or refractory to catheter ablation. Total endoscopic ablation can be performed via a monolateral approach, whereby a left atrial box lesion is created. If the ablation is introduced from the right side, the positioning of the ablation catheter on the partly hidden left pulmonary veins is of vital importance. Using thoracoscopy in combination with multiplane transoesophageal echocardiography, the anatomical position of the ablation catheter can be established. Our experience in over 60 procedures has confirmed this to be a safe technique of total endoscopic ablation.

A Step toward Nonrobotic Total Endoscopic Coronary Bypass Grafting: 40 Coronary Anastomoses in a Biomechanical Beating Heart Model

Objective

Nonrobotic total endoscopic coronary bypass grafting is commonly considered as technically too difficult. After endoscopic practicing in a simple box model, we questioned this statement in a more sophisticated training model.

Methods

In a handmade chest model containing a mechanically actuated porcine heart, anastomoses between homologous vein and shunted anterior coronary artery were performed using Prolene 7–0 sutures or U-clips in 20 anastomoses each. Commercially available endoscopic instruments and exclusive two-dimensional endoscopic vision were used. As quality control, the procedures were recorded, flow was measured, indocyanine green dye angiograms were performed, vinylpolysiloxane endocasts were produced, and finally the anastomoses were assessed from the endothelial side. Three-dimensional computed tomographic reconstruction was explored for cast measuring.

Results

All anastomoses were completed successfully in a time of 51 ± 14 minutes (Prolene) and 48 ± 10 minutes (U-clips). Despite suboptimal equipment, a reproducible sequence of the procedure was established and documented. Improving surgical performance was reflected in a reduction in anastomotic leakage and time requirement. The quality assessment protocol showed a learning curve and problems itself, which are briefly discussed.

Conclusions

A beating heart model is an adamant requirement of training for the technically demanding procedure of nonrobotic total endoscopic coronary bypass grafting. Refinement of the model and quality assessment as well as expansion of training to other regions of the heart should prepare for a cost-effective, broad-based clinical application of nonrobotic endoscopic techniques in coronary surgery. Available high-definition three-dimensional vision systems and the development of appropriate (articulating) instruments will make the procedure safer and quicker and will cut the learning curve.

Strategies in the surgical management of atrial fibrillation

Atrial fibrillation (AF) is associated with substantial morbidity, mortality, and economic burden and confers a lifetime risk of up to 25%. Current medical management involves thromboembolism prevention, rate, and rhythm control. An increased understanding of AF pathophysiology has led to enhanced pharmacological and medical therapies; however this is often limited by toxicity, variable symptom control, and inability to modulate the atrial substrate. Surgical AF ablation has been available since the original description of the Cox Maze procedure, either as a standalone or concomitant intervention. Advances in novel energy delivery systems have allowed the development of less technically demanding procedures potentially eliminating the need for median sternotomy and cardiopulmonary bypass. Variations in the definition, duration, and reporting of AF have produced methodological limitations impacting on the validity of interstudy comparisons. Standardization of these parameters may, in future, allow us to further evaluate clinical endpoints and establish the efficacy of these techniques.

Surgical treatment of lone atrial fibrillation

Currently, off-pump video-assisted thoracoscopic epicardial pulmonary vein isolation offers an attractive alternative to on-pump Maze procedures for surgical treatment of lone atrial fibrillation. Nevertheless, on-pump Maze procedures through a mid-sternotomy approach still play an important role in patients with lone atrial fibrillation on many occasions, especially in patients with failed percutaneous pulmonary vein alone. The aim of this article was to give a brief review of the surgical strategies for treating lone atrial fibrillation, and present the possible indications for on-pump Maze procedures through a mid-sternotomy approach.

A new instrument of suction support adapter system for epicardial radiofrequency ablation

OBJECTIVE

Recently, epicardial ablation on a beating heart has been conducted as a minimally invasive surgical procedure for atrial fibrillation. We have developed a suction support adapter with the aim of ensuring contact between the ablation probe and the atrial wall to obtain transmural coagulation, and we evaluated the effectiveness of the adapter in electrophysiologic and histopathologic procedures.

METHODS

To ensure contact between the radiofrequency ablation probe and the atrial wall, we designed and fabricated a suction support adapter. Twelve pigs were used in this study. A comparison was made between a group in which the ablation probe alone was used (group C, n = 6) and a group in which the ablation probe was used with the adapter (group S, n = 6). In both groups, epicardial ablation was conducted on a beating heart. An electrophysiologic evaluation was conducted to determine whether there was electrical isolation. Histopathologic evaluations were performed to identify the range of coagulation in the resected atrial wall specimens.

RESULTS

The coagulation range was significantly deeper in group S than in group C, and the breadth was significantly narrower. Transmural coagulation and electrical isolation of the atrial wall were seen in 1 case in group C and in all cases in group S.

CONCLUSIONS

Using the suction support adapter, we were able to maintain good contact between the ablation probe and the atrial wall. This device is thus thought to be useful for the safe and reliable performance of epicardial ablation on a beating heart.

Video-assisted thoracoscopic surgical treatment of lone atrial fibrillation

A modified Maze procedure is a successful treatment for patients with chronic atrial fibrillation undergoing open cardiac surgery. We present our method and mid-term results of modified minimally invasive Maze procedure for patients with lone atrial fibrillation. Fifty-four patients (41 male patients; average age 58 years) with chronic lone atrial fibrillation underwent surgical treatment by video-assisted operation. All patients had unsuccessful drug therapy and 15 previous unsuccessful catheter ablations. The method includes bilateral pulmonary vein isolation, creation of a left atrial posterior wall line and exclusion of the left atrial appendage. We used one 10-mm camera port and a 5-cm working port on each chest side. Pulmonary vein isolation was achieved using a bipolar radiofrequency device. The left atrial appendage was excluded with a purse-string suture. Performance of the procedure was technically successful in all patients. There was no conversion to sternotomy or thora-cotomy. All patients were extubated in the operation room and all patients were in sinus rhythm at the end of the operation. In 15 patients intraoperative cardioversion was necessary. Echocardiography showed contractions of the left atrium and electrophysiological examination complete exit bloc across the ablation lines. Follow-up was complete at 3 months postoperatively for 48 patients (40 in sinus rhythm, 83%), at 6 months for 44 patients (37 in sinus rhythm, 84%) and at 1 year for 38 patients (32 in sinus rhythm, 84%). Bilateral video-assisted pulmonary vein isolation and creation of a left atrial posterior wall line is an effective treatment with stable functional mid-term results for patients with lone atrial fibrillation.

Preliminary results with a training program for thoracoscopic atrial fibrillation therapy

BACKGROUND

Novel devices have been designed for the treatment of atrial fibrillation (AF) using minimally invasive approaches. This study aimed to determine the usefulness of a sheep model for training in cardiac surgical ablation using a minimally invasive approach in an experimental hands-on training course.

METHODS

After initial training using a laparoscopic pelvic trainer, 15 sheep were subjected to surgery by six thoracic surgeons attending a hands-on thoracoscopic course. Dissection to the posterior wall of the pulmonary veins was followed by insertion of a microwave device around both the caudal cava vein and the pulmonary veins. The complications were recorded, and the effectiveness of the surgery was evaluated by complete deployment of the microwave device. The animals were killed after completion of the procedure.

RESULTS

Isolation of the cava vein and the pulmonary veins and placement of the microwave probe were performed successfully for 10 animals using a complete thoracoscopic approach. Two animals died during the procedure. The main complications of the procedure were hemorrhage and difficulty isolating the blood vessels using a minimally invasive procedure. After the training period, the thoracoscopic surgical maneuvers were accurate and reliable.

CONCLUSION

The technical feasibility of performing safe and efficient thoracoscopic placement of a microwave device in a sheep model was demonstrated in this study, suggesting that the results of this study are a useful contribution to the development of an animal model for surgical training and experimental cardiac surgeries.