The surgical management of atrial fibrillation

Cost-effectiveness of catheter ablation for rhythm control of atrial fibrillation

Objective. The objective of this study is to evaluate the cost-effectiveness of catheter ablation for rhythm control compared to antiarrhythmic drug (AAD) therapy in patients with atrial fibrillation (AF) who have previously failed on an AAD. Methods. An economic model was developed to compare (1) catheter ablation and (2) AAD (amiodarone 200 mg/day). At the end of the initial 12 month phase of the model, patients are classified as being in normal sinus rhythm or with AF, based on data from a meta-analysis. In the 5-year Markov phase of the model, patients are at risk of ischemic stroke each 3-month model cycle. Results. The model estimated that, compared to the AAD strategy, ablation had $8,539 higher costs, 0.033 fewer strokes, and 0.144 more QALYS over the 5-year time horizon. The incremental cost per QALY of ablation compared to AAD was estimated to be $59,194. The probability of ablation being cost-effective for willingness to pay thresholds of $50,000 and $100,000 was estimated to be 0.89 and 0.90, respectively. Conclusion. Based on current evidence, pulmonary vein ablation for treatment of AF is cost-effective if decision makers willingness to pay for a QALY is $59,194 or higher.

Cost of atrial fibrillation: invasive vs non-invasive management in 2012

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It places an enormous burden on the patients, caregivers and the society at large. As a chronic illness, AF accrues significant costs related to clinical presentation, complications and loss of productivity. Novel invasive approaches to AF promise a cure in some patients and a significant reduction in AF burden in others, but are very expensive. This paper will address the cost of conventional and invasive strategies in AF care and will review the evidence on the comparative cost effectiveness of these approaches.

The ambiguous pulmonary venoatrial junction: a new perspective

PURPOSE

The pulmonary venoatrial junction (PVAJ) has recently received attention due to the widespread use of catheter ablation for atrial fibrillation. However, the literature lacks a consensus in the definition of the PVAJ. We aim to review the inconsistent definitions for the PVAJ and related implications in imaging and catheter ablation for atrial fibrillation.

RESULTS

The PVAJ as described by embryology, gross anatomy, histology and imaging is ambiguous, leading to disparities in its definition. Because of differing definitions of the PVAJ, there is a broad range in the prevalence of anatomic variations, including (1) percentage of common pulmonary veins (10-79% on the left), (2) supernumerary pulmonary veins (10-42%) and (3) ostial diameter and shape. We postulate several reasons for this broad range in the described prevalence of anatomic variation of the PV as follows: (1) different definitions of the PVAJ, (2) different vantage points, (3) different imaging modalities, and (4) different prevalence of anatomic variants among different study populations.

CONCLUSIONS

The ambiguous PVAJ with its gradual transition from the left atrium to the pulmonary veins defies precise definition even though it plays an important role in the management of atrial fibrillation. Physicians should be aware of variability in the language used to describe the PVAJ and resultant discrepancy in reported anatomical information.

Ten-year Experience With the Cox-Maze Procedure for Atrial Fibrillation: How Do We Define Success?

BACKGROUND

The Cox-maze procedure is the standard to which other surgical treatments of atrial fibrillation (AF) are compared. However, evaluation of new devices and lesion sets is difficult because of variable methods of reporting success in eliminating AF. We analyzed 10-year outcome with the "cut and sew" Cox-maze procedure and present rhythm at last follow-up, interval contact, and actuarial AF freedom.

METHODS

Between March 1993 and December 2002, 335 patients (211 men) underwent the Cox-maze procedure (age, 22 to 83 years; median, 62 years). Atrial fibrillation was chronic (CAF) in 175 patients and paroxysmal (PAF) in 160.

RESULTS

Concomitant mitral valve procedures were performed in 59%, coronary artery bypass grafting in 19%, and tricuspid valve repairs in 7%. Early mortality was 0.9%. During hospitalization, transient AF occurred in 29% of patients and 10% required implantation of a new permanent pacemaker (PPM). Dismissal electrocardiogram was normal sinus rhythm in 64%, junctional rhythm in 18%, AF in 11%, and PPM in 7%. At last follow-up (mean 42 +/- 6 months), 88% of patients were free of AF. However, when analyzed by the Kaplan-Meier method, freedom from AF was lower for patients with preoperative lone PAF (5 years, 90%; 10 years, 64%), preoperative lone CAF (5 years, 80%; 10 years, 62%), and patients undergoing combined maze-mitral valve surgery (5 years, 68%; 10 years, 41%).

CONCLUSIONS

Ten-year results with the standard Cox-maze procedure confirm high effectiveness, but reporting methods should be standardized to account for patients who have transient atrial arrhythmias during long-term follow-up.

Catheter ablation of atrial fibrillation

Following the advent of the surgical maze procedure, several catheter techniques have been developed to provide permanent prophylaxis against atrial fibrillation. These noninvasive techniques work by compartmentalizing the atria, by ablating the arrhythmogenic foci, or by isolating the atria from these foci. Although still at an early stage of development, preliminary results using focal ablation and circumferential ablation show extreme promise.

Dose response curves for microwave ablation in the cardioplegia-arrested porcine heart

INTRODUCTION

Microwave ablation has been used clinically for the surgical treatment of atrial fibrillation, particularly during valve procedures. However, dose- response curves have not been established for this surgical environment. The purpose of this study was to examine dosimetry curves for the Flex 4 and Flex 10 microwave devices in an acute cardioplegia-arrested porcine model.

METHODS

Twelve domestic pigs (40-45 kg) were acutely subjected to Flex 4 (n = 6) and Flex 10 (n = 6) ablations. On a cardioplegically arrested heart maintained at 10-15(o)C, six endocardial atrial and seven epicardial ventricular lesions were created in each animal. Ablations were performed for 15 s, 30 s, 45 s, 60 s, 90 s, 120 s, and 150 s (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride and lesions were sectioned at 5 mm intervals. Lesion depth and width were determined from digital photomicrographs of each lesion (resolution +/- .03 mm).

RESULTS

Average atrial thickness was 2.88 +/- .4 mm (range 1.0 to 8.0 mm). 94% of ablated atrial sections created by the FLEX 4 (n = 16) and the FLEX 10 (n = 16) were transmural at 45 seconds. 100% of atrial sections were transmural at 90 seconds with the FLEX 10 (n = 14) and at 60 seconds with the Flex 4 device (n = 15). Lesion width and depth increased with duration of application.

CONCLUSION

Both devices were capable of producing transmural lesions on the cardioplegically arrested heart at 65 W. These curves will allow surgeons to ensure transmural ablation by tailoring energy delivery to the specific atrial geometry.

Microwave ablation for atrial fibrillation: dose-response curves in the cardioplegia-arrested and beating heart

BACKGROUND

Microwave ablation has been used to replace the traditional incisions used in the surgical treatment of atrial fibrillation. However, dose-response curves have not been established in surgically relevant models. The purpose of this study was to develop dose-response curves for the Flex 10 (Guidant, Inc) microwave device in both the acute cardioplegia-arrested heart and on the beating heart.

METHODS

Twelve domestic pigs (40 to 45 kg) were subjected to microwave ablation in either the arrested (n = 6) or beating heart (n = 6). The cardioplegia-arrested heart was maintained at 10 degrees to 15 degrees C while six atrial endocardial and seven right ventricular epicardial lesions were created in each animal. On the beating heart, six right atrial and seven ventricular epicardial lesions were created. Ablations were performed for 15, 30, 45, 60, 90, 120, and 150 seconds (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride, and sectioned at 5-mm intervals. Lesion depth and width were determined from digital micrographs.

RESULTS

Mean atrial wall thickness was 2.8 mm (range, 1 to 8 mm). In the arrested heart, 94% of atrial lesions were transmural at 45 seconds and 100% were transmural at 90 seconds. In the beating heart, only 20% of atrial lesions were transmural despite prolonged ablation times (90 seconds). Ventricular lesion width and depth increased with duration of application, and were similar on the arrested and beating hearts.

CONCLUSIONS

Microwave ablation produces linear dose-response curves. Transmural lesions can be reliably produced on the arrested heart, but not consistently on the beating heart.

C-reactive protein is a risk indicator for atrial fibrillation after myocardial revascularization

BACKGROUND

Activation of the complement system after coronary artery bypass graft surgery involves C-reactive protein (CRP). This inflammatory response is related to baseline CRP levels and associated with postoperative arrhythmia, in particular atrial fibrillation (AF). We investigated whether baseline CRP levels are a risk indicator for the occurrence of AF and whether this phenomenon is cardiopulmonary bypass dependent.

METHODS

C-reactive protein was measured in perioperative blood samples of patients of the Octopus Study (coronary artery bypass graft surgery with [n = 73] or without cardiopulmonary bypass [n = 79]). Baseline CRP was dichotomized into a low and a high baseline group, using a cutoff value of 3.0 mg/L.

RESULTS

After coronary artery bypass graft surgery with cardiopulmonary bypass 11 of 53 patients (21%) with low preoperative CRP levels had AF versus 11 of 20 patients (55%) with high baseline CRP levels (p = 0.01). In the off-pump group AF occurred in 4 of 52 patients (8%) who had low baseline CRP levels, versus 8 of 27 patients (30%) with high preoperative CRP levels (p = 0.002). After adjusting for age, the odds ratio (95% confidence interval) was 4.6 (1.4 to 15.3) with cardiopulmonary bypass, 3.7 (0.93 to 14.7) in the off-pump group, and 3.3 (1.4 to 7.6) for both groups together. Continuous baseline CRP was an independent predictor for AF in a multivariate logistic regression model (p = 0.02).

CONCLUSIONS

Patients with high baseline CRP levels are at higher risk of having postoperative AF in both on-pump and off-pump surgery.

Left Ventricular Dysfunction in Atrial Fibrillation: Restoration of Sinus Rhythm by the Cox-Maze Procedure Significantly Improves Systolic Function and Functional Status

BACKGROUND

Atrial flutter or fibrillation with rapid, uncontrolled ventricular response may lead to left ventricular dysfunction, and conversion to sinus rhythm with control of heart rate can improve left ventricular ejection fraction. Little is known about the effects of the Cox-maze procedure on this form of tachycardia-induced cardiomyopathy.

METHODS

Four hundred forty-three patients underwent the Cox-maze procedure from 1993 to 2002. Ninety-nine had atrial flutter or fibrillation without associated valvular or congenital heart disease, and 37 (37%) had decreased left ventricular function (ejection fraction < 0.35 in 11 [severe], ejection fraction 0.36 to 0.45 in 8 [moderate], and ejection fraction 0.46 to 0.55 in 18 [mild]). Ages of these 37 patients (34 male) ranged from 35 to 74 years (median, 55 years).

RESULTS

Atrial flutter or fibrillation was present for 3 months to 19 years (median, 48 months) preoperatively, and 24 patients (65%) exhibited symptoms of heart failure. Preoperative ejection fraction ranged from 0.25 to 0.55 (median, 0.45). At last follow-up (median, 63 months), the Cox-maze procedure eliminated atrial flutter or fibrillation in all but 1 patient, and the greatest improvement was observed in patients with severe preoperative impairment (0.31 to 0.53; p = 0.01, preoperative versus follow-up), and patients with preoperative chronic atrial flutter or fibrillation (0.43 to 0.55; p < 0.05 preoperative versus follow-up). This improvement was observed immediately postoperatively and was sustained at last follow-up. Further, improvement in left ventricular function correlated with enhancement of functional status.

CONCLUSIONS

In some patients, atrial flutter or fibrillation may be the cause rather than the consequence of left ventricular dysfunction. Importantly, systolic function and functional status can be significantly improved with the restoration of sinus rhythm by the Cox-maze procedure.

A new minimally invasive heart surgery instrument for atrial fibrillation treatment: firstin vitro and animal tests

BACKGROUND

The paper presents a new robotic system for beating heart surgery. The final goal of this project is to develop a tele-operated system for the thoracoscopic treatment of patients with atrial fibrillation. The system consists of a robot that moves an innovative end-effector used to perform lines as in the Cox-Maze technique.

METHODS

The device is an electrode mesh that is introduced in the thorax through a trocar and is deployed inside the left atrium, where it can create selective ablation lines at any atrial region, using radio frequency. The current version of the umbrella has 22 electrodes. Using visual feedback from an ultrasound based navigation system, the surgeon can choose which electrodes on the mesh to activate. Once the umbrella is in contact with the endocardium of the left atrium, at the expected position, the surgeon activates the chosen electrodes sequentially. The umbrella can then be moved to another position.

RESULTS

In vitro and in vivo animal tests have been carried out in order to test and improve the instrument, the robotic system and the operative procedure.

CONCLUSIONS

The performed trials proved the ability of the system to treat atrial fibrillation. More in vivo tests are currently being performed to make the robot and its device ready for clinical use.

New antiarrhythmic agents for atrial fibrillation and atrial flutter

Atrial fibrillation is the most common sustained cardiac arrhythmia and is a frequent reason for antiarrhythmic therapy. Existing antiarrhythmic drugs have important side effects and presently the therapy to maintain sinus rhythm is not superior to a strategy of controlling excessive heart rate. This review summarises current strategies to improve antiarrhythmic therapy for atrial fibrillation. The most important strategies are: i) to develop drugs without proarrhythmic effects--development of drugs devoid of QT prolonging potential is the main strategy; ii) multiple channel-blocking drugs--inspired by the efficacy of amiodarone, several drugs are being developed that have similar electrophysiological properties as amiodarone, but without the extracardiac side effects; iii) drugs that act exclusively in the atria--the atria contain specific potassium channels, and several drugs that act only on these channels are in development; and iv) antiarrhythmic therapy without effects on ion channels--inhibition of the renin-angiotensin system and steroid therapy has been shown to have some effect in the treatment of atrial fibrillation. Many drugs are in development and the therapeutic scenario for treatment of atrial fibrillation may change quickly.

Pulmonary vein ablation of atrial fibrillation: beyond the traditional

The present review aims at giving a synthesis on the evolution in the last decade of the catheter-based ablative treatments for atrial fibrillation (AF). We report the rationale of current pulmonary vein (PV) ablation techniques: segmental PV isolation and circumferential PV ablation. The endpoint is the electrical isolation of the PVs from the left atrium, as they house foci triggering AF in 80% to 95% of cases and seem to play a key role in arrhythmia maintenance. Recurrence rates of AF after these PV ablation strategies are very encouraging. Two recent randomized trials, AFFIRM and RACE, showed no significant difference in outcomes between a strategy of pharmacological heart rate control and that of restoration and maintenance of sinus rhythm with antiarrhythmic drugs. However, multicenter randomized trials comparing PV ablation with drug therapy are required. Future refinements in catheter technology and navigation systems should provide simpler and faster procedures and render PV ablation more widespread and accepted from the scientific and medical communities.

Radiofrequency ablation for atrial fibrillation: different approaches

The existing literature regarding radiofrequency ablation for the surgical treatment of atrial fibrillation was reviewed, analyzing the early and late results. A MEDLINE search supplemented with a manual bibliographic review was performed for all peer-reviewed English language articles regarding the use of radiofrequency ablation for the treatment of atrial fibrillation. Six studies were identified, with a total of 451 patients. None of the studies was completely randomized. All patients underwent radiofrequency ablation as an adjunct to a variety of cardiac surgical procedures. The hospital mortality rate was 2.7%. The overall survival rate was 97.1%, and freedom from atrial fibrillation was 76.3% +/- 5.1% after a mean follow-up period of 13.8 +/- 1.9 months. It was concluded that radiofrequency ablation should be considered a safe and effective means to cure atrial fibrillation in patients undergoing open heart surgery.

A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation

OBJECTIVE

The Cox maze III procedure has excellent long-term efficacy in curing atrial fibrillation. It has not been widely practiced because it is technically challenging and requires prolonged cardiopulmonary bypass. The aim of this study was to examine a simplified Cox maze III procedure that uses bipolar radiofrequency energy as an ablative source.

METHODS

Beginning January 2002, a total of 40 consecutive patients underwent a modified Cox maze III procedure with bipolar radiofrequency energy. Nineteen had a lone maze procedure and 21 had a maze procedure plus a concomitant operation. One month after the operation, the first 8 patients were investigated with high-resolution magnetic resonance imaging. Patients were followed up monthly with clinical examination and electrocardiography.

RESULTS

There was no operative deaths. The crossclamp times were 47 +/- 26 minutes for the modified lone Cox maze III procedure and 92 +/- 37 minutes for the Cox maze III procedure plus concomitant procedures. These were significantly shorter than our previous times for the traditional Cox maze III procedure (93 +/- 34 minutes and 122 +/- 37 minutes, respectively, P <.05). Follow-up magnetic resonance imaging showed no evidence of pulmonary vein stenosis, and atrial contractility was preserved in all patients. There were no late strokes. At 6-month follow-up, 91% of patients (21/23) were in sinus rhythm.

CONCLUSIONS

Bipolar radiofrequency ablation can be used to replace the surgical incisions of the Cox maze procedure. This energy source did not result in pulmonary vein stenosis. The modification of the Cox maze III procedure to use bipolar radiofrequency ablation simplified and shortened this procedure without sacrificing short-term efficacy.

Successful Performance of Cox-Maze Procedure on Beating Heart Using Bipolar Radiofrequency Ablation: A Feasibility Study in Animals

BACKGROUND

The Cox-Maze procedure is the gold standard for the surgical treatment of atrial fibrillation with proven long-term efficacy. However, its application has been limited by its complexity and significant morbidity. The purpose of this study was to test the feasibility and safety of performing the Cox-Maze procedure using bipolar radiofrequency ablation on the beating heart without cardiopulmonary bypass.

METHODS

After median sternotomy, 6 Hanford mini-pigs underwent a modified Cox-Maze procedure using bipolar radiofrequency energy. The animals survived for 30 days. Atrial function, coronary artery, pulmonary vein anatomy, and valve function were assessed by magnetic resonance imaging. At reoperation, pacing documented electrical isolation of the pulmonary veins. Induction of atrial fibrillation was attempted by burst pacing with cholinergic stimulation. Histologic assessment was performed after sacrifice.

RESULTS

There were no perioperative mortalities or neurologic events. At 30 days, atrial fibrillation was unable to be induced, and pulmonary vein isolation was confirmed by pacing. Magnetic resonance imaging assessment revealed no coronary artery or pulmonary vein stenoses. Although atrial ejection fraction decreased slightly from 0.344 +/- 0.0114 to 0.300 +/- 0.055 (p = 0.18), atrial contractility was preserved in every animal. Histologic assessment showed all lesions to be transmural, and there were no significant stenoses of the coronary vessels or injuries to the valves.

CONCLUSIONS

Virtually all of the lesions of the Cox-Maze procedure can be performed without cardiopulmonary bypass using bipolar radiofrequency energy. There were no late stenoses of the pulmonary veins. Clinical trials of this new technology on the beating heart are warranted.

Pulmonary vein isolation using transvenous catheter cryoablation for treatment of atrial fibrillation without risk of pulmonary vein stenosis

OBJECTIVES

We sought to evaluate the efficacy and safety of pulmonary vein (PV) isolation using transvenous cryoablation for the treatment of atrial fibrillation (AF).

BACKGROUND

Although electrical isolation of PVs with radiofrequency energy for the treatment of AF is feasible, it is associated with a significant risk of PV stenosis. Cryoablation is a new alternative therapy allowing ablation of tissue while preserving its underlying architecture.

METHODS

In 52 patients with paroxysmal (n = 45) or persistent (n = 7) AF, PV isolation using the CryoCor cryoablation system (CyroCor Inc., San Diego, California) with a 10F deflectable transvenous catheter was performed as guided by ostial PV potentials. Cryoablation was applied twice at each targeted site (2.5 to 5 min/application). Computed tomography (CT) of the thorax was performed at baseline and at 3 and 12 months to evaluate for PV stenosis.

RESULTS

All targeted PVs were completely isolated in 49 (94%) of 52 of patients. Of 152 PVs targeted, 147 (97%) were successfully isolated (mean 3.0 PVs isolated per patient). After a mean period of 12.4 +/- 5.5 months of follow-up, 37 (71%) of 52 patients had no recurrence of AF or were clinically improved, including 29 patients (56%) who had no recurrence of AF with (n = 11) or without the use of anti-arrhythmic drugs. At 3 and 12 months, the CT scan showed no evidence of PV stenosis associated with cryoablation in any patients.

CONCLUSIONS

Transvenous catheter cryoablation is an effective method to create PV electrical isolation for the treatment of AF. A clinically satisfactory result can be achieved in 71% of patients with AF, without the risk of PV stenosis.

Evolution of non-pharmacological curative therapy for atrial fibrillation. Where do we stand today?

The present review aims at giving a comprehensive synthesis regarding not only the epidemiological aspects but also the evolution, over the last decades, of the curative surgical and catheter-based ablative treatments for atrial fibrillation (AF), with particular emphasis on the experience of Milan working group which has always been committed to the on-going and fascinating therapeutic challenges inherent in this type of cardiac arrhythmia. After discussing the surgical treatment of AF we report the rationale basis of current pulmonary vein (PV) ablation techniques. In particular, we report on circumferential PV ablation, an intellectually appealing strategy, aimed at creation of RF lesions around each PV ostia using a non-fluoroscopic electro-geometric mapping system to reconstruct the anatomy of venous-atrial junction, allowing to tailor number and size of lesions to the complex morphology of the PV-LA junction in each patient. This purely anatomic approach not only disconnects PVs (as demonstrated by elimination of PV ostial potentials and absence of discrete electrical activity inside the lesion during pacing outside the ablation line), but also, like surgery, reduces the "electrically active" atrial tissue, involving substantial parts of the posterior LA wall, with a profound atrial electroanatomic remodeling, as expressed by voltage abatement (<0.1 mV) inside and around the encircled areas.

Atrial fibrillation complicating the course of degenerative mitral regurgitation: determinants and long-term outcome

OBJECTIVES

The study was done to define the incidence, determinants and prognostic implications of onset of atrial fibrillation (AF) during follow-up of mitral regurgitation (MR) initially in sinus rhythm.

BACKGROUND

The rates and clinical implications of AF in MR are undefined.

METHODS

We analyzed the occurrence of AF under conservative management in two populations of patients with degenerative MR in sinus rhythm at diagnosis: 1) 360 patients (65 +/- 13 years, 74% men) with MR due to flail leaflets; and 2) 89 residents of Olmsted County, Minnesota (67 +/- 17 years, 56% men) with grade 3 or 4 MR due to simple mitral valve prolapse (MVP) diagnosed echocardiographically.

RESULTS

In patients with MR due to flail leaflets, AF rates at 5 and 10 years were 18 +/- 3% and 48 +/- 6%, respectively, and the linearized rate was 5.0 +/- 0.7% per year. Development of AF during follow-up was independently associated with high risk of cardiac death or heart failure (adjusted risk ratio 2.23, p = 0.025). The AF rate at 10 years was higher in patients >or=65 years (75 +/- 10% vs. 24 +/- 6%, p < 0.0001) and in those with baseline left atrial (LA) dimension >or=50 mm (67 +/- 8% vs. 37 +/- 9%, p < 0.001). In multivariate analysis, independent baseline predictors of AF were age and LA diameter (both p < 0.01). In patients with MR due to MVP, similar rates of AF (41 +/- 7% vs. 44 +/- 6% at nine years, p > 0.50) and predictors of AF (age and LA dimension, both p < 0.006) were noted.

CONCLUSIONS

In patients with degenerative MR in sinus rhythm at diagnosis, the incidence of AF occurring under conservative management is high and similar whether the cause of MR is flail leaflet or simple MVP. After onset of AF, an increased cardiac mortality and morbidity are both observed under conservative management. The risk of AF increases with advancing age and larger LA dimension. These data suggest that the clinical management of MR should take into account the high incidence, excess risk, and predictors of AF.

The technology in use for the surgical ablation of atrial fibrillation

The purpose of this article is to present and evaluate the various technologies recently developed for the surgical treatment of atrial fibrillation as alternatives or adjuncts to the traditional Maze III procedure and other "cut and sew" techniques. The discussion contains a detailed consideration of the biophysical background of the most common ablation techniques, their mode of tissue injury, the methods of use, and the related complications through a review of the existing literature and analysis of experimental results. All of the current technologies presented are still being tested to augment the success rates and reduce the incidence of complications, although all are not available for clinical use. Radiofrequency and cryoablation have been used clinically on large numbers of patients with varying results. Microwave technology has been used in small groups of patients, and the results are to be evaluated. Laser technology is still in an experimental phase, and the clinical results are forthcoming. True transmurality, reduction of operative time, friendly use of ablation devices, and substantial reduction of complications appear to be the key factors for broad adoption of alternative energy sources for surgical ablation.

Atrial Fibrillation

The conversion of atrial fibrillation (AF) to normal sinus rhythm should be attempted in patients who present with this condition, as long as the cure is not worse than the disease itself. In young patients with normal hearts, AF has a small impact on morbidity and mortality. The primary indication for conversion in this population is often symptoms. In contrast, in patients with diseased hearts or who are older than 65 years, maintaining sinus rhythm may have a favorable impact on stroke risk, ventricular function, and symptoms. In the absence of normal sinus rhythm, these patients should receive anticoagulants. Rate control is the preferred first-line strategy for asymptomatic patients and patients presenting with a history of long-standing, persistent AF, making conversion and maintenance of sinus rhythm unlikely. Rate control may be used in patients who develop AF during an acute systemic illness, which will likely terminate with time or therapy. Conversion to sinus rhythm should be considered in patients with a first episode of AF, as unconverted AF tends to perpetuate itself. Conversion can be attempted if the duration of AF is less than 48 hours or if the patient has received anticoagulants when the duration is not known. Other indications for cardioversion are prolonged episodes in patients with otherwise infrequent episodes of paroxysmal AF, and in patients who refuse to take anticoagulants or in whom anticoagulation is contraindicated. After the patient is converted to sinus rhythm, the decision to initiate chronic drug therapy should be based on the presence of other cardiac and medical diseases that increase the risk of recurrence and serious symptoms in case of recurrence (such as hypertrophic cardiomyopathy or mitral stenosis). It is acceptable to manage patients with new-onset AF and normal cardiac function with cardioversion alone and not initiate chronic antiarrhythmic therapy afterwards. However, in patients with abnormal hearts (coronary artery disease, hypertensive or mitral valvular heart disease, and cardiomyopathy) AF is likely to recur, and such patients should be placed on antiarrhythmic medication.

Catheter-ablative techniques for the treatment of atrial fibrillation

Atrial fibrillation is the most commonly encountered arrhythmia in clinical practice and is associated with significant morbidity and mortality. Pharmacologic therapy, although useful for rate control, has proven much less effective in the long term maintenance of sinus rhythm. The utility of implantable atrial defibrillators or pacing to prevent atrial fibrillation remains largely untested. This article describes four catheter-based therapies for atrial fibrillation: His ablation, atrioventricular nodal modification, the Maze procedure, and the ablation of pulmonary vein foci which initiate the arrhythmia. Whereas the first two procedures are largely palliative and recommended for patients with symptomatic, drug-refractory atrial fibrillation, the latter two offer the potential for a curative intervention.

Cryothermal ablation: mechanism of tissue injury and current experience in the treatment of tachyarrhythmias

Cryosurgery has been an integral part of the surgical management of cardiac arrhythmias since the late 1970s. With the recent development of intravenous cryocatheters, the use of cryothermy in the treatment of cardiac arrhythmias will increase in the near future. The following discussion includes a detailed consideration of the mode of tissue injury associated with cryothermy and a comprehensive review of cryosurgery in the management of a variety of cardiac arrhythmias. Cryosurgical management of supraventricular and ventricular tachycardias has proven to be both safe and effective. Cryothermal tissue injury is distinguished from hyperthermic injury by the preservation of basic underlying tissue architecture and minimal thrombus formation. Such differences will be particularly important in settings requiring extensive lesion formation, such as catheter-based maze procedures for the treatment of atrial fibrillation.

A new system for catheter ablation of atrial fibrillation

Increased attention is now being focused on developing new technologies to cure atrial fibrillation using catheter ablation techniques. The performance of a MAZE-type procedure using standard catheter ablation technologies is arduous and is associated with an unacceptable risk of complications. The Guidant Heart Rhythm Technologies Linear Ablation System was developed to create long transmural linear lesions. Unique features of this system include the availability of different preshaped multi-electrode steerable ablation catheters, the use of phased radiofrequency (RF) energy, and the control of RF output by varying the duty cycle. A prospective multicenter clinical trial to evaluate the safety and efficacy of a right atrial ablation procedure using this technology to treat atrial fibrillation is currently underway. To date, 15 patients have been enrolled and the procedure was acutely effective in 14 of 15 patients with no complications. Atrial fibrillation has recurred during short-term follow-up in 12 of 15 patients, a not surprising result, because this initial phase of testing involved only right-sided ablation. The early results of the phase I clinical trial confirm the findings of others that successful ablation of chronic atrial fibrillation is likely to require a left atrial approach. This clinical trial, as well as others that are currently underway, will be invaluable in the continuing development of catheter ablation of atrial fibrillation and, ultimately, in determining if the routine use of this therapeutic tool can become a reality.