Minimally invasive surgical ablation of atrial fibrillation: Six-month results

Chronic performance of a novel radiofrequency ablation device on the beating heart: Limitations of conduction delay to assess transmurality

OBJECTIVE

The creation of consistently transmural lesions with epicardial ablation on the beating heart has represented a significant challenge for current technology. This study examined the chronic performance of the AtriCure Coolrail device (AtriCure Inc, West Chester, Ohio), an internally cooled, bipolar radiofrequency ablation device designed for off-pump epicardial ablation. The study also examined the reliability of using acute intraoperative conduction delay to evaluate lesion integrity.

METHODS

Seven swine underwent median sternotomy. The right atrial appendage and inferior vena cava were isolated with a bipolar radiofrequency clamp. Linear ablation lines were created between these structures with the AtriCure Coolrail. Paced activation maps were recorded with epicardial patch electrodes acutely before and after ablation and after keeping the animals alive for 4 weeks. The conduction time across the linear ablation was calculated from these maps. The lesions were histologically evaluated with trichrome staining.

RESULTS

Only 76% of cross-sections of Coolrail lesions were transmural, and only 1 of 12 ablation lines was transmural in every cross-section examined. Mapping data were available in 5 of the animals. Significant conduction delay was present after the creation of each line of ablation acutely; however, after 4 weeks, conduction time returned to preablation values, demonstrating lack of transmurality.

CONCLUSIONS

The AtriCure Coolrail failed to reliably create transmural lesions. Although the Coolrail was able to create acute conduction delay, its failure to transmurally ablate the atrial myocardium left gaps along the length of the lesion, which resulted in neither chronic conduction block nor delay across any line of ablation.

Cox-Maze IV results for patients with lone atrial fibrillation versus concomitant mitral disease

BACKGROUND

This study compared Cox-Maze IV (CMIV) outcomes for the treatment of atrial fibrillation (AF) in patients with lone AF vs those with AF and mitral valve (MV) disease.

METHODS

Since 2002, 200 patients have undergone a CMIV procedure for lone AF (n=101) or concomitantly with MV operations (n=99). Preoperative, perioperative, and late outcomes between these groups were compared. Data were collected prospectively and reported at 3, 6, and 12 months.

RESULTS

Lone AF patients had AF of longer duration; patients with AF and MV disease were older, with larger left atria and worse New York Heart Association classification (p<0.05). Operative mortality (1% vs 4%, p>0.05, respectively) was similar between both groups. Perioperative atrial tachyarrhythmias were more prevalent in patients with concomitant MV operations (57% vs 41%, p=0.03); however, freedom from AF and antiarrhythmics was similar for both groups at 12 months (76% and 77%). The only predictor for atrial tachyarrhythmia recurrence or arrhythmic drug dependence was failure to isolate the posterior left atrium (p<0.01).

CONCLUSIONS

Patients with AF and MV disease have distinct comorbidities compared with patients with lone AF. However, the CMIV is safe and effective in both groups and should be considered for patients with AF undergoing MV operations. Patients with MV disease had more atrial tachyarrhythmias at 3 months, but freedom from AF and antiarrhythmics was similar to patients with lone AF at 1 year. The posterior left atrium should be isolated in every patient, because this was the only predictor for failure of the CMIV for either group.

Importance of evaluating conduction block in radiofrequency ablation for atrial fibrillation

OBJECTIVE

Atrial fibrillation (AF) is the most frequently diagnosed cardiac arrhythmia. Anti-arrhythmic drugs may be used to suppress ectopic foci and interrupt reentry circuits, but are often insufficient to treat recurrent AF and have a number of adverse effects. Alternative therapies, such as catheter and surgical ablation, have been explored. This investigation examines the importance of assessing exit block when performing surgical ablation during beating-heart treatment of AF.

METHODS

This was an evaluation of pooled data from multicenter prospective results obtained in AF patients who received ablation with a new, irrigated, vacuum-integrated device that creates linear lesions during beating-heart/open-chest or minimally invasive, port-access procedures. Electrocardiogram or Holter data were collected intra-operatively and at 1, 3, 6, and 12 months. Outcomes were also evaluated for patients who were or 'were not' tested for exit block following the ablation procedure.

RESULTS

A total of 93 patients were treated (61 open-chest surgeries, 32 port-access procedures). There were no device-related complications and no operative mortality. At 341 days' average follow-up, 71/86 (83%) patients were free from AF, 66/86 (77%) were in sinus rhythm, and 60/86 (70%) were free from AF and off Class I and III anti-arrhythmic drugs (AADs). At 12 months, 23/23 (100%) patients with exit block confirmed were AF free compared with 13/21 (62%) patients with exit block not tested (p≤0.01, Fisher's exact test); 20/23 (87%) were in sinus rhythm compared with 12/21 (57%) patients with exit block not tested (p≤0.05, Fisher's exact test); and 20/23 (87%) were AF free without Class I and III AADs compared with 10/21 (48%) patients with exit block not tested (p≤0.01, Fisher's exact test). Both open-chest and port-access procedures yielded decreases in left-atrial size from baseline to 6 months' follow-up. Patients undergoing port-access procedures also observed an increase in left-ventricular ejection fraction, which was also significant at 6 months.

CONCLUSION

Patients in whom exit block was confirmed following an ablation procedure were more likely to have successful clinical outcomes. Since testing for exit block must be performed on a beating heart, total epicardial beating-heart ablation may provide an important treatment for AF, providing intra-operative feedback indicative of long-term outcomes.

Surgical Treatment of Isolated (Lone) Atrial Fibrillation with Gemini-S Ablation and Left Atrial Appendage Excision (GALAXY Procedure)

Objective

Surgical ablation with radiofrequency is a safe and effective treatment for atrial fibrillation. Recent advances in instrumentation have allowed for the application of bipolar radiofrequency through a minimally invasive approach using small bilateral thoracotomies for pulmonary vein isolation, destruction of autonomic ganglia, and excision of the left atrial appendage (GALAXY procedure).

Methods

Thirty-two patients underwent surgical ablation of atrial fibrillation with the GALAXY procedure over a 43-month period. Data were collected in a prospective manner during hospitalization and at 1-, 3-, 6-, and 12-month intervals for rhythm, medications, and subsequent interventions.

Results

There were no operative mortality, no myocardial infarction, and no stroke. One patient required reexploration for bleeding. Mean follow-up was 28 months (range, 4–43 months). Freedom from atrial fibrillation at 12 and 24 months, respectively, was 90% and 67% for patients with paroxysmal fibrillation and 80% and 63% for patients with persistent atrial fibrillation. Of the patients who were not in sinus rhythm, four reverted to atrial fibrillation and two reverted to atrial flutter.

Conclusions

The GALAXY procedure is a safe and effective, minimally invasive method for treatment of isolated (lone) atrial fibrillation. The operation provides excellent short-term freedom from atrial fibrillation and should be considered in patients with isolated paroxysmal atrial fibrillation.

Surgical Treatment for Isolated Atrial Fibrillation Minimally Invasive vs Classic Cut and Sew Maze

Objective

We sought to compare outcomes after two surgical approaches for the treatment of atrial fibrillation (AF): a minimally invasive, staged hybrid approach combining surgery with catheter ablation, [Hybrid Maze (HM)] and the classic cut and sew Maze (CM).

Methods

From April 2004 to March 2010, 63 stand-alone AF procedures were performed by two surgeons at a single center and followed up for ≥6 months. CM was offered to all patients. After July 2007, patients were also prospectively offered a two-stage HM: stage 1 = a beating heart bipolar radiofrequency pulmonary vein isolation and left atrial appendage ligation; stage 2 = transvenous catheter ablation connecting the pulmonary veins to each other and the mitral annulus when AF was present after stage 1. Outcomes were compared between 25 HM and 38 CM using χ2 or Fisher exact test analysis.

Results

Postoperatively, there was no difference in 30-day mortality (0%), complications (4% HM vs 18% CM), or median length of stay (5 days). At last follow-up, 88% of HM and 95% of CM were free from AF; 80% of HM and 90% of CM were free from AF and antiarrhythmic medication (P ≥ 0.3). Twenty-nine percent of HM required a subsequent catheter ablation (stage 2) when compared with 8% of the CM patients (P = 0.04). Freedom from AF and antiarrhythmic medication at 1 year was 52% for the HM and 87.5% for the CM (P = 0.004).

Conclusions

In AF patients reluctant to undergo a CM but willing to undergo subsequent catheter ablation, a minimally invasive approach is a reasonable strategy. Because pulmonary vein isolation alone may be sufficient in two-thirds of patients and delayed reconnection is common, an interval two-stage hybrid approach may prove preferable over a one-stage combined hybrid approach; however, successful sinus restoration may take longer with this approach.

[Surgical atrial fibrillation ablation therapy and postoperative monitoring]

Atrial fibrillation represents the most common atrial arrhythmia seen in clinical practice. The surgical treatment of atrial fibrillation is recommended in symptomatic patients as well as in asymptomatic patients at low postoperative risk. As a "stand alone" procedure, surgical ablation therapy is indicated after failed catheter ablation therapy, which occurs increasingly due to the high number of catheter-based ablation techniques. In order to gain acceptance among patients as well as referring cardiologists, the surgical ablation procedure ought to be performed in a minimally invasive fashion and with a very high success rate. When applied in an interdisciplinary approach by cardiologists/electrophysiologists and cardiothoracic surgeons, both ablative techniques have the potential to treat atrial fibrillation effectively and in the long-term. In order to document the true heart rhythm after ablation therapy, intermittent "snapshot" ECG documentation ought to be avoided. Small leadless devices that can be implanted subcutaneously enable full heart rhythm disclosure with documentation of atrial arrhythmias. The modern technique of implantable loop recorders permits individualized treatment for each patient.

The golden age of minimally invasive cardiothoracic surgery: current and future perspectives

Over the past decade, minimally invasive cardiothoracic surgery (MICS) has grown in popularity. This growth has been driven, in part, by a desire to translate many of the observed benefits of minimal access surgery, such as decreased pain and reduced surgical trauma, to the cardiac surgical arena. Initial enthusiasm for MICS was tempered by concerns over reduced surgical exposure in highly complex operations and the potential for prolonged operative times and patient safety. With innovations in perfusion techniques, refinement of transthoracic echocardiography and the development of specialized surgical instruments and robotic technology, cardiac surgery was provided with the necessary tools to progress to less invasive approaches. However, much of the early literature on MICS focused on technical reports or small case series. The safety and feasibility of MICS have been demonstrated, yet questions remain regarding the relative efficacy of MICS over traditional sternotomy approaches. Recently, there has been a growth in the body of published literature on MICS long-term outcomes, with most reports suggesting that major cardiac operations that have traditionally been performed through a median sternotomy can be performed through a variety of minimally invasive approaches with equivalent safety and durability. In this article, we examine the technological advancements that have made MICS possible and provide an update on the major areas of cardiac surgery where MICS has demonstrated the most growth, with consideration of current and future directions.

The Cox maze IV procedure: predictors of late recurrence

OBJECTIVES

The Cox maze III procedure achieved high cure rates and became the surgical gold standard for the treatment of atrial fibrillation. Because of its invasiveness, a more simplified ablation-assisted procedure, the Cox maze IV procedure, has been performed at our institution since January 2002. The study examined multiple preoperative and perioperative variables to determine predictors of late recurrence.

METHODS

Data were collected prospectively on 282 patients who underwent the Cox maze IV procedure from January 2002 through December 2009. Forty-two percent of patients had paroxysmal and 58% had either persistent or long-standing persistent atrial fibrillation. All patients were available for follow-up. Follow-up included electrocardiograms in all patients. Since 2006, 24-hour Holter monitoring was obtained in 94% of patients at 3, 6, and 12 months. Data were analyzed by means of logistic regression analysis at 12 months, with 13 preoperative and perioperative variables used as covariates.

RESULTS

Sixty-six percent of patients had a concomitant procedure. After an ablation-assisted Cox maze procedure, the freedom from atrial fibrillation was 89%, 93%, and 89% at 3, 6, and 12 months, respectively. The freedom from both atrial fibrillation and antiarrhythmic drugs was 63%, 79%, and 78% at 3, 6, and 12 months, respectively. The risk factors for atrial fibrillation recurrence at 1 year were enlarged left atrial diameter (P = .027), failure to isolate the entire posterior left atrium (P = .022), and early atrial tachyarrhythmias (P = .010).

CONCLUSIONS

The Cox maze IV procedure has a high success rate at 1 year, even with improved follow-up and stricter definitions of failure. In patients with large left atria, there might be a need for more extensive size reduction or expanded lesion sets.

Selective molecular potassium channel blockade prevents atrial fibrillation

BACKGROUND

Safety and efficacy limit currently available atrial fibrillation (AF) therapies. We hypothesized that atrial gene transfer would allow focal manipulation of atrial electrophysiology and, by eliminating reentry, would prevent AF.

METHODS AND RESULTS

In a porcine AF model, we compared control animals to animals receiving adenovirus that encoded KCNH2-G628S, a dominant negative mutant of the I(Kr) potassium channel alpha-subunit (G628S animals). After epicardial atrial gene transfer and pacemaker implantation for burst atrial pacing, animals were evaluated daily for cardiac rhythm. Electrophysiological and molecular studies were performed at baseline and when animals were euthanized on either postoperative day 7 or 21. By day 10, none of the control animals and all of the G628S animals were in sinus rhythm. After day 10, the percentage of G628S animals in sinus rhythm gradually declined until all animals were in AF by day 21. The relative risk of AF throughout the study was 0.44 (95% confidence interval 0.33 to 0.59, P<0.01) among the G628S group versus controls. Atrial monophasic action potential was considerably longer in G628S animals than in controls at day 7, and KCNH2 protein levels were 61% higher in the G628S group than in control animals (P<0.01). Loss of gene expression at day 21 correlated with loss of action potential prolongation and therapeutic efficacy.

CONCLUSIONS

Gene therapy with KCNH2-G628S eliminated AF by prolonging atrial action potential duration. The effect duration correlated with transgene expression.