Pulmonary vein isolation by microwave energy ablation in patients with permanent atrial fibrillation

Impact of epicardial ablation of concomitant atrial fibrillation on atrial natriuretic peptide levels and atrial function in 6 months follow-up: does preoperative ANP level predict outcome of ablation?

Background

Epicardial ablation concomitant to cardiac surgery is an easy and safe approach to treat atrial fibrillation (AF), but its efficacy in longstanding persistent (LsPe) AF remains intermediate. Although larger left atrial size has been associated with worse outcome after ablation, biochemical predictors of success are not well established. The aim of this study was to evaluate relationship between biochemical marker, echo-characteristic and cardiac rhythm in 6 months follow-up after epicardial ultrasound (HIFU) ablation.

Methods

We included 78 consecutive patients, who underwent elective cardiac surgery. 42 patients with AF (11.9% paroxysmal, 23.8% persistent, 64.3% LsPeAF) underwent concomitant HIFU ablation (AF ablation group), 16 with AF underwent cardiac surgery without ablation (AF control) and 20 had preoperatively normal sinus rhythm (SR control). We measured plasma ANP secretion before, on postoperative day (POD) 1, POD 7 as well as 3 and 6 months after surgery. Moreover, we estimated cardiac rhythm and atrial mechanical function by Atrial Filling Fraction (AFF) and A-wave velocity in follow-up.

Results

Baseline ANP levels were higher in patients with LsPeAF, as compared to the paroxysmal and permanent AF and to the SR control group. Patients with LsPeAF (n = 27) who converted to SR had preoperatively smaller left atrial diameter (LAD) and LA area (p < 0.05) and higher ANP level (p = 0.009) than those who remained in AF at 6 months after ablation. Multivariate regression analysis revealed that only preoperative ANP level was an independent predictor of cardiac rhythm after ablation. Patients with LsPeAF and preoperative ANP >7.5 nmol/l presented with SR in 80%, in contrast to those with ANP <7.5 nmol/l who converted to SR in 20%. We detected gradual increase of AFF and A-velocity at 6 months after ablation (p < 0.05) solely in AF ablation group. ANP levels were increased on POD 1 in ablation group (p < 0.05), without changes in further follow-up.

Conclusion

Our results indicate that preoperative ANP levels may be a new biochemical predictor of successful epicardial ablation in patients with concomitant LsPeAF. HIFU ablation caused a significant improvement of atrial mechanical function and gradual increase of AFF and did not associate with alteration of atrial endocrine secretion at 6 months follow-up.

A minimally invasive cox-maze procedure: operative technique and results

OBJECTIVE

The Cox-Maze procedure (CMP) for the surgical treatment of atrial fibrillation (AF) traditionally has required a median sternotomy and cardiopulmonary bypass. This study describes a method using ablation technologies to create the full Cox-Maze lesion set through a 5- to 6-cm right minithoracotomy.

METHODS

Twenty-two consecutive patients underwent a CMP through a right mini-thoracotomy and cardiopulmonary bypass. All patients were followed prospectively with electrocardiogram and 24-hour Holter monitoring at 3, 6, and 12 months. The CMP lesion set was created using bipolar radiofrequency energy and cryotherapy.

RESULTS

There was no operative mortality or major complications.Two patients required a permanent pacemaker. Five patients (23%) had early atrial tachyarrhythmias. At last follow-up(mean, 18 ± 12 months), all the patients (n=22) were free from atrial dysrhythmias. At 3 months (n=19), 84% of patients were off antiarrhythmic drugs. At 6 months (n=18), 94% of patients were free from AF and off antiarrhythmic medications. At 12 months (n=16), 81% of patients were free from AF and off antiarrhythmic drugs and three patients remained on warfarin for a mechanical mitral valve.

CONCLUSIONS

A full CMP can be performed through a right mini-thoracotomy with outstanding short-term results. This less invasive procedure can be offered to patients without compromising efficacy.

How effective is microwave ablation for atrial fibrillation during concomitant cardiac surgery?

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was whether performing microwave ablative procedures during concomitant cardiac surgical procedures is effective for the treatment of atrial fibrillation (AF). In total, 200 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Major exclusion criteria included studies exclusively using bipolar ablation, ambiguous or unspecified ablation technique, other energy modalities and studies with highly variable or undisclosed follow-up time. One study reported that 66% of patients were in sinus rhythm (SR) with follow-ups ranging from 1 to 14 months and suggested that the risk of AF recurrence was significantly increased with a larger left atrial diameter (OR = 1.21, P = 0.02) and an increased duration of preoperative AF (OR = 2.14, P = 0.03). A separate study found no significant difference in the success rate on the basis of the concomitant procedure (coronary artery bypass grafting or mitral valve surgery, P > 0.5). In the only randomized trial identified, microwave ablation delivered significantly inferior SR restoration rates to radiofrequency (RF) ablation at all time points from discharge to 24 months. There is a large degree of heterogeneity in the studies, with patients' characteristics, for example type of AF, and patient management postoperatively, for example administration of anti-arrhythmias, being inconsistent. Of the 12 studies, nine assessed SR at a mean of 6-12 months and found postoperative success rates between 62 and 87%. One study looked at the medium range follow-up of 24 months with SR restoration at 71%. Two studies looked at the long-term follow-up (5 and 5.37 years) with SR restoration at 39 and 61%, respectively. We conclude that microwave ablation, as an intervention for the treatment of AF during concomitant surgery, is not currently recommended on the limited available evidence. This is because the success rates in the longer term are less clear and the only randomized study to date has found inferior outcomes compared with RF-based ablation.

Surgical Ablation for Atrial Fibrillation in Cardiac Surgery a Consensus Statement of the International Society of Minimally Invasive Cardiothoracic Surgery (ISMICS) 2009

Objective

This purpose of this consensus conference was to determine whether surgical atrial fibrillation (AF) ablation during cardiac surgery improves clinical and resource outcomes compared with cardiac surgery alone in adults undergoing cardiac surgery for valve or coronary artery bypass grafting.

Methods

Before the consensus conference, the consensus panel reviewed the best available evidence, whereby systematic reviews, randomized trials, and nonrandomized trials were considered in descending order of validity and importance. Evidence-based statements were created, and consensus processes were used to determine the ensuing recommendations. The American Heart Association/American College of Cardiology system was used to label the level of evidence and class of recommendation.

Results

The consensus panel agreed on the following statements in patients with AF undergoing cardiac surgery concomitant surgical ablation: 1. Improves the achievement of sinus rhythm at discharge and 1 year (level A); this effect is sustained up to 5 years (level B). Does not reduce the use of antiarrhythmic drugs at 12 months after surgery (level A; 36.0% vs. 45.4%), although trials were not designed to answer this question. 2. Does not increase the requirement for permanent pacemaker implantation (4.4% vs. 4.8%; level A). 3. Does not increase the risk of perioperative mortality (level A), stroke (level A), myocardial infarction (level B), cardiac tamponade (level A), reoperative bleeding (level A), esophageal injury (level B), low cardiac output (level A), intraaortic balloon (level B), congestive heart failure (level B), ejection fraction (EF; level B), pleural effusion (level A), pneumonia (level A), renal dysfunction (level B), and mediastinitis (level A). The incidence of esophageal injury remains to be low (level B). 4. Does not reduce mortality at 1 year (level A). There is a possible reduction in mortality beyond 1 year (level B), but no difference in stroke (level A), myocardial infarction (level A), and heart failure (level B). EF is increased (+4.1% more than control; level A). 5. Has been shown to improve exercise tolerance at 1 year (level A), but no impact on quality of life at 3 months and 1 year (level A); however, the methodology used and the number of trials studying these outcomes are insufficient. 6. Increases cardiopulmonary bypass and cross-clamp times (level A), with no difference in intensive care unit and hospital length of stay (level A). Overall costs were not reported.

Conclusions

Given these evidence-based statements, the consensus panel stated that, in patients with persistent and permanent AF undergoing cardiac surgery, concomitant surgical ablation is recommended to increase incidence of sinus rhythm at short- and long-term follow-up (class 1, level A); to reduce the risk of stroke and thromboembolic events (class 2a, level B); to improve EF (class 2a, level A); and to exercise tolerance (class 2a, level A) and long-term survival (class 2a, level B).

Surgical Ablation for Atrial Fibrillation in Cardiac Surgery a Meta-Analysis and Systematic Review

Objectives

This meta-analysis sought to determine whether surgical ablation improves clinical outcomes and resource utilization compared with no ablation in adult patients with persistent and permanent atrial fibrillation (AF) undergoing cardiac surgery.

Methods

A comprehensive search was undertaken to identify all randomized (RCT) and nonrandomized (non-RCT) controlled trials of surgical ablation versus no ablation in patients with AF undergoing cardiac surgery up to April 2009. The primary outcome was sinus rhythm. Secondary outcomes included survival and any other reported clinically relevant outcome or indicator of resource utilization. Odds ratios (OR) and weighted mean differences (WMD) and their 95% confidence intervals (95% CI) were analyzed as appropriate using the random effects model. Heterogeneity was measured using the I2 statistic. Meta-regression was performed to explore the relationship between the benefit from surgical AF and duration of follow-up.

Results

Thirty-three studies met the inclusion criteria (10 RCTs and 23 non-RCTs) for a total of 4647 patients. The number of patients in sinus rhythm was significantly improved at discharge in the surgical AF ablation group versus (68.6%) the surgery alone group (23.0%) in RCTs (OR 10.1, 95% CI 4.5–22.5) and non-RCTs (OR 7.15, 95% CI 3.42–14.95). This effect on sinus rhythm (74.6% vs. 18.4%) remained at follow-up of 1 to 5 years (OR 6.7, 95% CI 2.8–15.7 for RCT, and OR 15.5, 95% CI 6.6–36.7 for non-RCT). The risk of all-cause mortality at 30 days was not different between the groups in RCT (OR 1.20, 95% CI 0.52–3.16) or non-RCT studies (OR 0.99, 95% CI 0.52–1.87). In studies reporting all-cause mortality at 1 year or more (up to 5 years), mortality did not differ in RCT studies (OR 1.21, 95% CI 0.59–2.51) but was significantly reduced in non-RCT studies (OR 0.54, 95% CI 0.31–0.96). Stroke incidence was not reduced significantly; however, in meta-regression, the risk of stroke decreased significantly with longer follow-up. Other clinical outcomes were similar between groups. Operation time was significantly increased with surgical AF ablation; however, overall impact on length of stay was variable.

Conclusions

In patients with persistent or permanent AF who present for cardiac surgery, the addition of surgical AF ablation led to a significantly higher rate of sinus rhythm in RCT and non-RCT studies compared with cardiac surgery alone, and this effect remains robust over the longer term (1–5 years). Although non-RCT studies suggest the possibility of reduced risk of stroke and death, this remains to be proven in prospective RCTs with adequate power and follow-up.

Determinants of lesion dimensions during transcatheter microwave ablation

BACKGROUND

Transcatheter microwave ablation is a novel technique for treating cardiac arrhythmias.

METHODS

We investigated the effects of catheter temperature, application duration, and antenna length on lesion dimensions during catheter-based microwave ablation. In a swine thigh muscle preparation, microwave was delivered at targeted temperatures of 60 degrees C (n = 18), 70 degrees C (n = 27), 80 degrees C (n = 43), or 90 degrees C (n = 18) for 120 seconds with 10-mm antenna; and at targeted temperatures of 80 degrees C for 120 seconds (n = 22), 150 seconds (n = 18), 180 seconds (n = 18), 210 seconds (n = 18), and 240 seconds (n = 17) with 20-mm antenna using 10 F catheter (MedWaves, San Diego, CA, USA) during parallel orientation. Conventional radiofrequency ablation (RF) using a 4-mm tip electrode was performed as control.

RESULTS

With 120-second energy applications, lesion length and depth were significantly larger with targeted temperatures of 80 degrees C and 90 degrees C than 60 degrees C (P< 0.05). Furthermore, lesion depth and width, but not length, were significantly increased by prolonging energy application duration from 120 to 240 seconds at targeted temperature of 80 degrees C (P< 0.05). Compared to RF, microwave lesions were significantly longer but had comparable depth and width. A 20-mm microwave antenna produced longer lesions than either a 10-mm antenna or RF ablation catheter. Multivariate analysis demonstrated that targeted temperature >or=80 degrees C, application duration >or=150 seconds, and use of 20-mm antenna were independent predictors for lesion depth and width (P< 0.05). Surface dessication was observed in 4/18 (22%) lesions at 90 degrees C, as compared with 1/136 (0.7%) at 80 degrees C targeted tip temperature (P < 0.05).

CONCLUSIONS

This study demonstrated that lesions size with transcatheter microwave ablation can be controlled by adjusting targeted temperature, energy application duration, and antenna length. A targeted temperature of 80 degrees C for more than 150 seconds should provide optimal lesion dimensions and lower risk of surface dessication or charring.

Surgical Treatment of Atrial Fibrillation: A Look into the Future

The surgical treatment of atrial fibrillation began in 1987, when Dr. James Cox introduced the maze procedure. This operation proved to be extremely effective in curing atrial fibrillation and preventing its most dreaded complication, stroke. However, many surgeons found the operation to be too difficult and invasive. Over the last 5 to 10 years, various groups have tried to develop less invasive approaches using a number of different energy sources to create linear lines of ablation to replace the surgical incisions. This has led to a plethora of new operations for this arrhythmia. There is significant confusion in the literature at the present time as to what is the best lesion pattern and what is the best energy source. It is our feeling that a great deal of this confusion is due to our lack of understanding of the mechanisms of atrial fibrillation and the effect of ablation technology on atrial hemodynamics and electrophysiology. Future progress will require a better understanding of this arrhythmia and continued research into the safety and efficacy of ablation devices.

Preliminary Results with Percutaneous Transcatheter Microwave Ablation of Typical Atrial Flutter

BACKGROUND

Linear microwave ablation has been shown to be effective for treatment of atrial fibrillation during open-heart surgery by producing transmural lesions in the atrium to isolate the pulmonary veins. However, the safety and efficacy of percutaneous, transcatheter, linear microwave ablation for atrial arrhythmias, while demonstrated in animal models, is unknown in humans. Therefore, we studied the safety and efficacy of linear microwave ablation of the cavotricuspid isthmus (CTI) in humans with typical atrial flutter, utilizing a 2-cm long microwave antenna mounted on a steerable 9-French catheter.

METHODS AND RESULTS

In seven consecutive patients, multielectrode catheters were positioned at the His bundle (quadripolar) and around the TV annulus (duo-decapolar) for pacing and recording atrial activation sequence before and after ablation. The microwave antenna was withdrawn gradually from tricuspid annulus towards inferior vena cava to ablate the CTI. Intracardiac ultrasound was used to ensure adequate endocardial contact of the microwave ablation catheter with the CTI. Microwave energy was applied at a power of 18 to 21 W at each ablation point for 120 seconds. Ablation was repeated until bidirectional CTI block was confirmed by demonstrating a descending activation wavefront in the contralateral atrial wall during pacing from the coronary sinus ostium or low lateral right atrium, respectively. Bidirectional isthmus block was achieved in all patients, after a mean number of 27.4 +/- 14.7 energy applications per patients. There were no acute procedural complications.

CONCLUSIONS

Percutaneous, transcatheter microwave ablation of CTI dependent atrial flutter was demonstrated to be safe and effective in this preliminary feasibility study.

Minimally Invasive Surgery for Atrial Fibrillation

Although the surgical treatment of atrial fibrillation has become technically simpler and faster with the advent of new ablative technologies, the ultimate goal of treating large numbers of patients for lone AF remains elusive. The ideal procedure would be performed epicardially, on the beating heart, with minimal risk to and impact on the patient, a rapid recovery and high cure rates. As minimal access techniques improve along with device designs and our understanding of pathophysiology, the field continues to move toward this objective. This article provides a brief overview of the progress made, questions yet unanswered and possible future directions.

Surgical and minimally invasive ablation for atrial fibrillation

The Cox-Maze procedure, first introduced in 1987, has been the gold standard for the surgical treatment of atrial fibrillation. At 10 years, over 90% of patients remain free from atrial fibrillation. The procedure has been shown to be effective at eliminating the incidence of late stroke in this high-risk population. The development of new ablation technologies has greatly simplified and shortened the Cox-Maze procedure without sacrificing efficacy. These technologies have spurred interest in the development of new, simpler operations for the surgical treatment of atrial fibrillation that can be performed through minimal access and, in some instances, off of cardiopulmonary bypass. The early results with these more limited procedures on the whole have not been as good as with the Cox-Maze procedure, but they are promising. There are many problems with the development of a truly minimally invasive procedure with high efficacy. When patients are referred for surgery, there is no information available regarding the mechanisms of their atrial fibrillation. Thus, it is impossible to tailor the ablation to the individual patient. Future progress will require better understanding of the mechanisms of atrial fibrillation, and the development and refinement of clinical diagnostic technology that will allow for better preoperative diagnosis.

Surgical ablation as treatment for the elimination of atrial fibrillation: A meta-analysis

OBJECTIVE

The maze procedure is recognized as the most effective surgical treatment of atrial fibrillation. In the last few years, new surgical ablation techniques were developed involving the left atrium only and modifications of the maze procedure in ablating both atria. For this study, we evaluated the evidence regarding the effectiveness of the surgical ablation procedures (biatrial and left atrial) in reducing postoperative atrial fibrillation and subsequent survival.

METHODS

MEDLINE was searched for English-language studies using the terms "maze," "atrial fibrillation," and "surgical treatment" for 1995 through August 2005. Primary outcomes of interest were postoperative survival and postoperative freedom from atrial fibrillation. Survival data were collected at 1-, 2-, and 3-year intervals. Freedom from atrial fibrillation was collected at 3 months and at 1-, 2-, and 3-year intervals.

RESULTS

Sixty-nine studies were included in this analysis. Five thousand eight hundred eighty-five total patients were involved. Patients undergoing surgical ablation (range, 90.4-85.4) demonstrated significantly greater rates of freedom from atrial fibrillation compared with those seen in control patients (range, 47.2-60.9). Survival rates among patients with biatrial surgical procedures (range, 94.9-92.8) were similar to those who had left atrial procedures only (range, 93.9-89.4). However, patients undergoing biatrial ablation (range, 92.0-87.1 vs 86.1-73.4) demonstrated superior freedom from atrial fibrillation at all time points.

CONCLUSION

Biatrial ablation surgical procedures were more effective in controlling atrial fibrillation than procedures confined to the left atrium. To encourage the use of future meta-analysis within the surgical literature, we suggest the more frequent reporting of either through Kaplan-Meier survival analyses and the reporting of rates for specific time intervals.

Can we ablate permanent atrial fibrillation?

There is growing evidence of the benefit of ablation in the treatment of drug refractory atrial fibrillation.

The Need of a Hybrid Approach for the Treatment of Atrial Fibrillation

Atrial fibrillation represents nowadays one of the most important burdens in the field of arrhythmia. Albeit often inadequate, medical treatment is still considered the "first-step" approach. Non-pharmacological strategies, either surgical or interventional, recently gained an increasing interest among both cardiac surgeons and electrophysiologists. From the surgical standpoint, the introduction of different energy sources and the development of minimally invasive techniques as an alternative to the original "cut-and-sew" technique allowed a new dawn in the surgical treatment of atrial fibrillation. In the meanwhile, electrophysiologists developed more complex ablation systems that allowed the creation of linear lesions, similar to the surgical ones, while mapping the atria with three-dimensional (3D) navigation systems. Nevertheless, the success rate in terms of sinus rhythm restoration was around 80%-85% in both fields. We foresee that the combination of the two approaches (i.e., surgical and percutaneous approach), in common hybrid approach, will allow a substantial reform for the definitive cure of atrial fibrillation, either paroxysmal or permanent, providing the highest success rates along with the best care for patients' health.

Surgical Treatment of Lone Atrial Fibrillation in an Awake Patient

Surgical treatment of atrial fibrillation recently gained new popularity since the introduction of different energy sources and the development of minimally invasive techniques as an alternative to the original "cut-and-sew" technique. However, closed-chest ablation procedures are not feasible in presence of pericardial or pleural adhesions. To our knowledge, this is the first report of surgical treatment of atrial fibrillation in a conscious patient by means of a high epidural anesthesia. Since evidence of fibrothorax was found, a conscious patient suffering from lone atrial fibrillation underwent a beating-heart pulmonary veins isolation with a microwave device through a standard sternotomic approach. At 6 months follow-up, the patient is in stable sinus rhythm, without any palpitation nor electrocardiographic evidence (Holter monitoring) of recurrent atrial fibrillation.