Catheter ablation of paroxysmal atrial fibrillation using a 3D mapping system

Pulmonary vein antrum isolation for treatment of atrial fibrillation in patients with valvular heart disease or prior open heart surgery

OBJECTIVES

The goal of this study was to assess the safety and efficacy of pulmonary vein antrum isolation in patients with moderate valvular heart disease or open-heart surgery and atrial fibrillation (AF).

BACKGROUND

Valvular heart disease and open-heart surgery are commonly associated with AF and increase the risk of adverse events in AF patients.

METHODS

A total of 391 consecutive patients who had pulmonary vein antrum isolation performed between December 2000 and December 2002 were screened. A total of 142 of these patients had clinically significant valvular disease or prior cardiac surgery. End points included AF recurrence and pulmonary vein antrum isolation complication rates.

RESULTS

Patients with valvular heart disease or prior open-heart surgery were older, had larger left atria and a more advanced New York Heart Association class. They did not differ significantly with respect to gender, but had a longer history of AF. Procedure times were similar between patients with and without valvular heart disease or prior open-heart surgery. After 18 +/- 7 months in the lone AF patients, 11 +/- 5 months in patients with valvular heart disease, and 10 +/- 5 months in patients with prior open heart surgery, there was a trend toward lower recurrence of AF in patients with lone AF who enjoyed a 98% overall cure rate after up to 2 pulmonary vein antrum isolations versus 93% among patients with valvular heart disease (P = .04) and prior open heart surgery (P = .07). Complication rates were comparable between groups.

CONCLUSIONS

Pulmonary vein antrum isolation is safe and effective in patients with moderate valvular heart disease and the patients who developed AF after open-heart surgery. These results have implications for our understanding of the pathophysiology of AF in patients with moderate valvular heart disease or past cardiac surgery and should be considered when discussing treatment options in these patients.

Acute Effects of Left Atrial Radiofrequency Ablation on Atrial Fibrillation

INTRODUCTION

Acutely, when left atrial ablation is performed during atrial fibrillation (AF), the AF may persist and require cardioversion, or it may convert to sinus rhythm or to atrial tachycardia/flutter. The prevalence of these acute outcomes has not been described.

METHODS AND RESULTS

Left atrial ablation, usually including encirclement of the pulmonary veins, was performed during AF in 144 patients with drug-refractory AF. Conversion to sinus rhythm occurred in 19 patients (13%), to left atrial tachycardia in 6 (4%), and to atrial flutter in 6 (4%). In the 6 patients with a focal atrial tachycardia, the mean cycle length was 294 +/- 45 ms. The tachycardia arose in the left atrial roof in 3 patients, the left atrial appendage in 2, and the anterior left atrium in 1. In 3 of 6 patients, the focal atrial tachycardia originated in an area that displayed a relatively short cycle length during AF. In 6 patients, AF converted to macroreentrant atrial flutter with a mean cycle length of 253 +/- 47 ms, involving the mitral isthmus in 5 patients and the septum in 1 patient. All atrial tachycardias and flutters were successfully ablated with 1 to 15 applications of radiofrequency energy.

CONCLUSION

When left atrial ablation is performed during AF, the AF may convert to atrial tachycardia or flutter in approximately 10% of patients. Focal atrial tachycardias that occur during ablation of AF may be attributable to driving mechanisms that persist after AF has been eliminated, whereas atrial flutter results from incomplete ablation lines.

Pulmonary vein isolation for the treatment of atrial fibrillation in patients with impaired systolic function

OBJECTIVES

We aimed to determine the safety and efficacy of pulmonary vein isolation (PVI) in atrial fibrillation (AF) patients with impaired left ventricular (LV) systolic function.

BACKGROUND

To date, PVI has been performed primarily in patients with normal LV function. Yet, many AF patients have impaired LV systolic function. The outcomes of PVI in patients with impaired LV systolic function are unknown.

METHODS

We included 377 consecutive patients undergoing PVI between December 2000 and January 2003. Ninety-four patients had impaired LV function (ejection fraction [EF] <40%), and they comprised the study group. The control group was the remaining 283 patients who had a normal EF. End points included AF recurrence and changes in EF and quality of life (QoL).

RESULTS

Mean EF was 36% in our study group, compared with 54% in controls. After initial PVI, 73% of patients with impaired EF and 87% of patients with normal EF were free of AF recurrence at 14 +/- 6 months (p = 0.03). In the study group, there was a nonsignificant increase in EF of 4.6% and significant improvement in QoL. Complication rates were low and included a 1% risk of pulmonary vein stenosis.

CONCLUSIONS

Although the AF recurrence rate after initial PVI in impaired EF patients was higher than in normal EF subjects, nearly three-fourths of patients with impaired EF remained AF-free. Although our sample size was nonrandomized, our results suggest PVI may be a feasible therapeutic option in AF patients with impaired EF. Randomized studies with more patients and longer follow-up are warranted.

Catheter ablation therapy for atrial fibrillation

The past several years have witnessed a significant growth in the number of institutions offering catheter ablation for atrial fibrillation (AF). This growth has been a result of a better understanding of pathophysiology of AF and use of instruments and approaches that made catheter ablation of AF a safe and an effective alternative to the drug therapy. The procedure increasingly is becoming a therapy of choice for a select group of symptomatic, drug-refractory patients without structural heart disease, and it is being offered to a rapidly widening patient pool. This article reviews the procedural aspects and clinical evidence supporting this wider use of AF ablation. In addition, new techniques and technologies for AF ablation and new avenues of research in this area are explored.

Long-Term Follow-Up of Right Atrial Ablation in Patients with Atrial Fibrillation:

INTRODUCTION

The aim of this study was to evaluate the efficacy and the impact on quality of life of a new ablative approach to the right atrium in patients with atrial fibrillation (AF).

METHODS AND RESULTS

Seventy-four symptomatic patients with paroxysmal (n = 49) or permanent (n = 25) refractory AF underwent radiofrequency ablation. A nonfluoroscopic electroanatomic mapping system was used to perform the following lesions: (1) an isthmus line between the tricuspid annulus and the inferior vena cava; (2) a posterior intercaval line from the superior vena cava and the inferior vena cava; (3) a septal line from the superior vena cava to the fossa ovalis, proceeding to the coronary sinus ostium where a circumferential line around the ostium was performed, and then on to the inferior vena cava; and (4) a transversal lesion connecting the posterior intercaval and the septal lesions. In addition, electrical disconnection of the superior vena cava was performed. There were no complications. Postablation remapping showed the absence of discrete electrical activity inside and just around the ablation lines. Electrical disconnection of the superior vena cava was obtained in all patients. After 21 +/- 6 months, 49 patients (66%) had stable sinus rhythm with continuation of the previous antiarrhythmic drug therapy, 13 patients (18%) were considered improved, and 12 (16%) received no benefit (unsuccessful procedure). After ablation, quality of life was significantly improved, reaching the levels of the general Italian population. Ejection fraction and the extent of the low-voltage area were found by multivariate analysis to be independent predictors of AF recurrence.

CONCLUSION

The results of the present study suggest that this ablative approach in combination with antiarrhythmic drugs is safe and effective in treating AF, leading to a marked increase in quality of life in patients with refractory AF.

Role of the Coronary Sinus in Maintenance of Atrial Fibrillation

INTRODUCTION

Bursts of tachycardia arising in the pulmonary veins may play an important role in perpetuating atrial fibrillation (AF). However, the role of the coronary sinus (CS) in the perpetuation of AF has been unclear. The aim of this study was to determine whether the CS plays a role in perpetuation of AF.

METHODS AND RESULTS

Pulmonary vein isolation was performed by segmental ostial ablation with radiofrequency energy in 22 consecutive patients with paroxysmal AF. Bipolar and unipolar electrograms recorded in the left atrium and CS were analyzed during atrial pacing from the mitral annulus and during AF. There was a mean of 2.5 +/- 0.5 electrical connections between the CS and the left atrium. The electrical connections between the left atrium and CS were ablated with a mean of 6.2 +/- 2.7 minutes of radiofrequency energy applied along the atrial side of the inferior mitral annulus. During AF, episodes of intermittent tachycardia alternated between the left atrium and the CS. Among the 22 patients, sustained AF was still inducible in 9 after pulmonary vein isolation. After electrical disconnection of the CS from the left atrium, sustained AF was inducible in only 3 of these 9 patients.

CONCLUSION

The CS may be a source of rapid repetitive electrical activity during AF. The lower probability of inducible sustained AF after electrical disconnection of the CS from the left atrium suggests that the CS may play a role in perpetuating AF.

Clinical results with catheter ablation: AV junction, atrial fibrillation and ventricular tachycardia

With the limitations of pharmacologic and device therapies for atrial fibrillation and ventricular tachycardia, catheter ablation is assuming a larger role in the management of patients with these common arrhythmias. Multiple case series and clinical trials have helped to define the evolving role of these techniques for ablation of the atrioventricular node, atrial fibrillation, and ischemic ventricular tachycardia. Based on very low complication rates, excellent efficacy and proven outcomes with radiofrequency ablation of the atrioventricular node, this approach with permanent pacing should play a larger role in the treatment of symptomatic patients with permanent atrial fibrillation. While linear ablation of atrial fibrillation has limited clinical utility for the treatment of this common arrhythmia, the results of multiple case series of focal atrial fibrillation ablation indicate the potential for an expanding role of this curative technique. Catheter ablation techniques for ventricular tachycardia in the setting of coronary artery disease have a role as supplemental therapy to the implantable cardioverter defibrillator in patients with recurrent pharmacologically refractory ventricular arrhythmias requiring frequent device interventions.

A model for in vivo validation of linear lesions in the right atrium

Linear lesions have been proposed for treatment of complex atrial arrhythmias including atrial macroreentry tachycardia and compartmentalization in atrial fibrillation.

AIM

To judge the effectiveness of a given lesion design, definite endpoints are necessary to ascertain the completeness of the line of block produced.

METHODS AND RESULTS

We report validation criteria for long linear lesions in the right atrium in 42 pts, that combine both conventional and 3D mapping information (CARTO). Transferring from the validation of bi-directional block of the cavotricuspid isthmus line for atrial flutter, we validated 2 additional long linear lesions in the right atrium (anterior line and intercaval line). In addition to a complete isthmus line in all 42 pts, in 28 pts a complete anterior line was achieved and validated by both conventional and CARTO criteria. A complete intercaval line was deployed in 11 pts with complete anterior and isthmus lines (with a characteristic shift for the intercaval line) and in 5 pts without a complete anterior line (without characteristic shift).

CONCLUSIONS

Conventional catheters placed at strategic locations on opposite sides of the intended ablation line, can depict a sudden characteristic change in the activation sequence. Using a combination of both techniques, deployment and validation of long linear lesion can be facilitated.

Atrial fibrillation: what are the targets for intervention?

Atrial fibrillation (AF) is a difficult and growing problem in the population. While medical therapy controls symptoms in many patients, a proportion of individuals with this common arrhythmia cannot be optimally managed with drugs alone. However, truly curative therapy for AF has always been one of the "holy grails" of electrophysiology. The surgical maze procedure was the first to offer permanent maintenance of sinus rhythm in patients with AF but subjected the patient to open heart surgery; a catheter-based translation of the maze procedure served as proof of concept that a catheterization technique could be used to treat AF. Subsequent experience has narrowed the electrophysiologist's attention to ablation of triggers of AF, most often residing in the pulmonary veins, rather than requiring more extensive ablation lines to control the arrhythmia. The following discussion deals with the development and current status of techniques for catheter ablation of atrial fibrillation, focusing on determination of appropriate target sites for ablation.

Atrial Excitation Assuming Uniform Propagation

INTRODUCTION

We investigated the spread of the excitation wave over the atria following initiation in a given focus in an atrial model containing its overall geometry only, i.e., without atrial bundles.

METHODS AND RESULTS

The propagation velocity of the excitation wave was taken to be uniform, and the wall thickness was discarded. The timing of excitation of any point on the atrium thus becomes directly proportional to its shortest distance over the atrial wall to the focus. Despite these gross simplifications, the general nature of the excitation sequence found corresponded closely to clinical data reported in the literature. This suggests that the complex overall geometry of the atria dominates the timing of the excitation. A highly intriguing observation from this study was that, when looking at the pathways from the sinus node to all other points on the atrium, prominent routes became visible even though no such pathways formed part of the model of the atrial geometry used. The locations of these prominent routes coincide with those of various distinct bundles in the atria. Possible inferences of these observations are discussed.

CONCLUSION

Based upon comparison with data from other studies, it is concluded that, during stable heart rhythms, propagation of the atrial excitation wave is well approximated by an assumption of uniform velocity, even though no atrial bundles were included in the model. The overall geometry seems to be the dominant factor in the spread of excitation.

Catheter-induced linear lesions in theleft atrium in patients with atrial fibrillation

OBJECTIVES

In this study using radiofrequency current and the electroanatomic mapping system CARTO, four line designs were tested in 84 patients suffering from drug-refractory atrial fibrillation (AFib).

BACKGROUND

Prevention of AFib by trigger elimination within the pulmonary veins (PVs) has been recently reported, but the success may be lesser in patients with chronic AFib or large atria requiring linear lesion deployment.

METHODS

Type A encircled the ostia of all four PVs with a connection to the mitral annulus (MA). In type B, three lines connected anatomic barriers. Type C encircled both septal and lateral PVs with connections between PVs and to the MA. Type D encircled PVs only. In the initial 12 patients (type D/1), line validation was performed without, and in 23 patients (type D/2) with, an additional catheter inside the encircled PVs.

RESULTS

The ability to achieve completeness of all intended lines was 5% in type A, 21% in type B, 29% in C, 66% in type D/1, and 61% in type D/2. This resulted in stable sinus rhythm in 19% (4/21 patients) in type A, 32% (6/19 patients) in type B, 50% (7/14 patients) in type C, 58% (7/12 patients) in type D/1, and 65% (15/23 patients) in type D/2, respectively, over a mean follow-up of 620 +/- 376 days. Besides thromboembolic events (one stroke and one transient ischemic attack), total occlusion of a PV was a major complication in one patient, and acute tamponade in two patients.

CONCLUSIONS

Complete lesions in the left atrium were difficult to achieve using conventional radiofrequency current technology, but were associated with sinus rhythm in 74% of patients during long-term follow-up, whereas incomplete lesions led mostly to recurrences of AFib or gap-related atrial tachycardia.

Paroxysmal atrial fibrillation: ectopic atrial activity and prevalence of severely symptomatic patients

Catheter ablation is a promising approach in severely symptomatic patients with paroxysmal atrial fibrillation (PAF). Until this time it has only been performed in highly selected patients with weekly episodes and frequent premature atrial contractions (PACs). The aim of the present study was to estimate the prevalence of severely symptomatic patients with PAF and to evaluate the significance of PACs. The files of 7,447 consecutive patients were screened and 1,357 PAF patients identified. Holter recordings were performed in 108 patients with >/=2 spontaneous AF episodes. Despite antiarrhythmic treatment, 6.5% (1.8-11.1%) had a history of weekly PAF episodes. 29.2% of patients and 10% of healthy, age-matched controls had more than 700 PACs. The number of PACs was inversely related to the reported numbers of previous episodes and directly related to age and size of left atrium. We estimate that about 6.5% of patients with PAF are severely symptomatic and might benefit from catheter ablation. Our data suggest that the number of PACs should not be used as a selection criterion for catheter ablation. Frequent PACs are seen in a substantial proportion of elderly healthy individuals.

Mortality, morbidity, and quality of life after circumferential pulmonary vein ablation for atrial fibrillation: outcomes from a controlled nonrandomized long-term study

OBJECTIVES

This study was designed to investigate the potential of circumferential pulmonary vein (PV) ablation for atrial fibrillation (AF) to maintain sinus rhythm (SR) over time, thus reducing mortality and morbidity while enhancing quality of life (QoL).

BACKGROUND

Circumferential PV ablation is safe and effective, but the long-term outcomes and its impact on QoL have not been assessed or compared with those for medical therapy.

METHODS

We examined the clinical course of 1,171 consecutive patients with symptomatic AF who were referred to us between January 1998 and March 2001. The 589 ablated patients were compared with the 582 who received antiarrhythmic medications for SR control. The QoL of 109 ablated and 102 medically treated patients was measured with the SF-36 survey.

RESULTS

Median follow-up was 900 days (range 161 to 1,508 days). Kaplan-Meier analysis showed observed survival for ablated patients was longer than among patients treated medically (p < 0.001), and not different from that expected for healthy persons of the same gender and calendar year of birth (p = 0.55). Cox proportional-hazards model revealed in the ablation group hazard ratios of 0.46 (95% confidence interval [CI], 0.31 to 0.68; p < 0.001) for all-cause mortality, of 0.45 (95% CI, 0.31 to 0.64; p < 0.001) for morbidities mainly due to heart failure and ischemic cerebrovascular events, and of 0.30 (95% CI, 0.24 to 0.37; p < 0.001) for AF recurrence. Ablated patients' QoL, different from patients treated medically, reached normative levels at six months and remained unchanged at one year.

CONCLUSIONS

Pulmonary vein ablation improves mortality, morbidity, and QoL as compared with medical therapy. Our findings pave the way for randomized trials to prospect a wider application of ablation therapy for AF.

Prevention of paroxysmal atrial fibrillation in patients with sinus bradycardia: role of right atrial linear ablation and pacing site

INTRODUCTION

Right atrial linear lesions (RALL), either alone or in combination with antiarrhythmic drug therapy, may modify the substrate for maintenance of atrial fibrillation (AF). The aim of this prospective randomized study was to determine whether RALL provides additional benefit to right atrial appendage pacing (RAAP) and/or interatrial septum pacing (IASP) and drug therapy in patients with symptomatic paroxysmal AF and sinus bradycardia requiring permanent atrial pacing.

METHODS AND RESULTS

Sixty-four patients (33 men and 31 women, mean age 73 +/- 10 years) completed the 6-month follow-up. Patients were randomized to either RALL (n = 33) or non-right atrial linear lesions (NRALL), and then to either IASP (n = 32) or RAAP (n = 32). Fifteen RALL patients were paced at the IAS and 18 at the RAA. Seventeen NRALL patients were paced at the IAS and 14 at the RAA. No statistical difference was observed with regard to the mean atrial tachyarrhythmia (AT) burden between NRALL (84 +/- 169 min/day) and RALL patients (202 +/- 219 min/day). Mean AT burden was significantly lower in the IASP group (70 +/- 150 min/day) than in RAAP group (219 +/- 317 min/day; P < 0.016). In the RALL group, the mean AT burden was 99 +/- 180 min/day in the IASP patients and 288 +/- 372 min/day in the RAAP patients (P < 0.046). In the NRALL group, no statistical difference in the mean AT burden was observed between IASP patients (46 +/- 117 min/day) and RAAP patients (130 +/- 211 min/day).

CONCLUSION

The results of the present study indicate that RALL did not provide any additional therapeutic benefit to combined antiarrhythmic drug therapy and septal or nonseptal atrial pacing in patients with sinus bradycardia and paroxysmal AF.

Anatomic characteristics of extensions of atrial myocardium into the pulmonary veins in subjects with and without atrial fibrillation

Myocardial extensions around pulmonary veins (PVs) have been recognized as the most important sites of origin for arrhythmogenic foci that trigger atrial fibrillation. The aim of this study was to evaluate the characteristics of atrial myocardium in pulmonary veins from subjects with and without a history of atrial fibrillation. A total number of 43 human hearts obtained at autopsy were studied (27 men, 16 women, mean age 67 +/- 8 years). Sixteen subjects (group 1) had a history of atrial fibrillation (11 men, mean age 66 +/- 10 years). The remaining 27 subjects (group 2) were without arrhythmia (16 men, mean age 68 +/- 8 years). The presence and morphology of the myocardial extensions were studied microscopically. Of the total number of 172 PVs evaluated, myocardial extensions were revealed in 117 (68%) cases. Myocardial fibers were arranged in a variable manner with the most prevailing circular pattern. Continuous extensions were present in 74, while a discontinuous pattern was revealed in 29 PVs. Maximum extension of the sleeves reached 48 mm (mean 7.7-10 mm) and their maximum thickness was 5 mm. Myocardial extensions were longer and thicker in the upper PVs from subjects with previous atrial fibrillation. In conclusion, a significant interindividual variability in the presence, arrangement, and thickness of atrial myocardial sleeves into PVs was revealed. Patients with a history of atrial fibrillation were found to have longer and thicker myocardial extensions into the upper PVs, and this finding may have implications for the catheter ablation technique.

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.

Initial experience with a novel focused ultrasound ablation system for ring ablation outside the pulmonary vein

INTRODUCTION

Atrial fibrillation has been shown to initiate from triggers within pulmonary veins. Several studies have documented that electrical isolation of those triggers can lead to maintenance of sinus rhythm. The complication of pulmonary vein stenosis has limited the utility of delivering ablation energy within the pulmonary vein. We utilize a focused ultrasound catheter ablation system for delivery of transmural ablation lines proximal to the pulmonary vein ostium.

METHODS

Nine dogs (weight 30-39 kg) were anesthetized and ventilated. Through a transseptal approach, pulmonary veins were engaged with the focused balloon ultrasound catheter. Ultrasound power was delivered at 40 acoustic watts outside the pulmonary vein ostium, focused 2 mm off the balloon surface, with a depth of approximately 6 mm, for 30-120 seconds. Following ablation, lesions were histopathologically analyzed.

RESULTS

Of nine animals studied, fourteen pulmonary veins were ablated. We found successful delivery of near circumferential and transmural ablation lines in 6/14 pulmonary veins. In each of the six circumferential ablations, successful alignment of the ultrasound transducer along the longitudinal axis of the parabolic balloon occurred. The final four ablations were conducted with an enhanced catheter design that assured axial alignment. Of these ablations, all four were circumferential. The remaining 8 pulmonary veins had incomplete delivery of lesions. In each of these veins the ultrasound transducer was misaligned with the balloon axis when therapy was delivered.

CONCLUSION

Focused ultrasound ablation is a new means of performing pulmonary vein isolation. This method provides delivery of lesions outside the vein, limiting the risk of pulmonary vein stenosis for the treatment of atrial fibrillation.

Catheter ablation of chronic atrial fibrillation with noncontact mapping: are continuous linear lesions associated with ablation success?

Catheter-based, right and left atrial compartmentalization procedure was evaluated using a noncontact mapping (NCM) system. Its usefulness to identify and close discontinuities in linear lesions in both atria was evaluated. The impact of linear lesion continuity on ablation success of chronic AF was also investigated. Nineteen patients with symptomatic, drug refractory chronic AF were studied. Right atrial ablation with three predefined lines was attempted in all patients. In 18 patients, left atrial ablation was performed with four linear lesions. During a follow-up of 12 +/- 3 months, 6 of 19 patients remained in sinus rhythm (SR) without antiarrhythmic agents (AAs). In addition, four patients were maintained in SR with AA. Thirteen of 14 patients with gaps identified during off-line analysis had recurrence of AF. Only one patient with a gap was free of recurrence without AAs. In the remaining five patients without recurrence of AF, no gap was observed during off-line analysis. In all four patients who were free of AF with additional treatment of AAs, two gaps had been identified. In the remaining nine patients with chronic AF recurrence, a mean of 4.9 gaps were identified. Excluding the initial learning period (first five patients) the success rate increased to 43% (6/14 patients) without and to 71% (10/14 patients) with AA. NCM identifies discontinuities in lines of ablation. Successful ablation of chronic AF is associated with continuity of linear lesions and good clinical technique demands a vigilant search for and closure of every gap.

Atrial fibrillation in the elderly: facts and management

Although atrial fibrillation is not widely known by the general public, in developed countries it is the most common arrhythmia. The incidence increases markedly with advancing age. Thus, with the growing proportion of elderly individuals, atrial fibrillation will come to represent a significant medical and socioeconomic problem. The consequences of atrial fibrillation have the greatest impact. The risk of thromboembolism is well known; other outcomes of atrial fibrillation are less well recognised, such as its relationship with dementia, depression and death. Such consequences are responsible for diminished quality of life and considerable economic cost. Atrial fibrillation is characterised by rapid and disorganised atrial activity, with a frequency between 300 and 600 beats/minute. The ventricles react irregularly, and may contract rapidly or slowly depending on the health of the conduction system. Clinical symptoms are varied, including palpitations, syncope, dizziness or embolic events. Atrial fibrillation may be paroxysmal, persistent or chronic, and a number of attacks are asymptomatic. Suspicion or confirmation of atrial fibrillation necessitates investigation and, as far as possible, appropriate treatment of underlying causes such as hypertension, diabetes mellitus, hypoxia, hyperthyroidism and congestive heart failure. In the evaluation of atrial fibrillation, cardiac exploration is invaluable, including electrocardiogram (ECG) and echocardiography, with the aim of detecting cardiac abnormalities and directing management. In elderly patients (arbitrarily defined as aged >75 years), the management of atrial fibrillation varies; it requires an individual approach, which largely depends on comorbid conditions, underlying cardiac disease, and patient and physician preferences. This management is essentially based on pharmacological treatment, but there are also nonpharmacological options. Two alternatives are possible: restoration and maintenance of sinus rhythm, or control of ventricular rate, leaving the atria in arrhythmia. Pharmacological options include antiarrhythmic drugs, such as class III agents, beta-blockers and class IC agents. These drugs have some adverse effects, and careful monitoring is necessary. The nonpharmacological approach to atrial fibrillation includes external or internal direct-current cardioversion and new methods, such as catheter ablation of specific foci, an evolving science that has been shown to be successful in a very select group of atrial fibrillation patients. Another serious challenge in the management of chronic atrial fibrillation in older individuals is the prevention of stroke, its primary outcome, by choosing an appropriate antithrombotic treatment (aspirin or warfarin). Several risk-stratification schemes have been validated and may be helpful to determine the best antithrombotic choice in individual patients.

Feasibility of pulmonary vein ostia radiofrequency ablation in patients with atrial fibrillation: a multicenter study (CACAF pilot study)

Radiofrequency (RF) catheter ablation has been proposed as a treatment of atrial fibrillation (AF). Several approaches have been reported and success rates have been dependent on procedural volume and operator's experience. This is the first report of a multicenter study of RF ablation of AF. We treated 44 men and 25 women with paroxysmal (n = 40) or persistent (n = 29), drug refractory AF. Circular pulmonary vein (PV) ostial lesions were deployed transseptally, during sinus rhythm (n = 42) or AF (n = 26), under three-dimensional electroanatomic guidance. Cavo-tricuspid isthmus ablation was performed in 27 (40%) patients. The mean procedure time was 215 +/- 76 minutes (93-530), mean fluoroscopic exposure 32 +/- 14 minutes (12-79), and mean number of RF pulses per patient 56 +/- 29 (18-166). The mean numbers of separate PV ostia mapped and isolated per patient were 3.9 +/- 0.5, and 3.8 +/- 0.7, respectively. Major complications were observed in 3 (4%) patients, including pericardial effusion, transient ischemic attack, and tamponade. At 1-month follow-up, 21 of 68 (31%) patients had had AF recurrences, of whom 8 required electrical cardioversion. After the first month, over a mean period of 9 +/- 3 (5-14) months, 57 (84%) patients remained free of atrial arrhythmias. RF ablation of AF by circumferential PV ostial ablation is feasible with a high short-term success rate. While the procedure and fluoroscopic exposure duration were short, the incidence of major cardiac complications was not negligible.

Pulmonary vein ablation: role in preventing atrial fibrillation

Several investigators have identified the pulmonary vein as the most common initiator of atrial fibrillation, and isolation of the pulmonary vein from atrial tissue can cure approximately 70% of patients with paroxysmal atrial fibrillation. Ongoing trials of a new device may increase the success rate and decrease the complication rate during the pulmonary vein isolation procedure.

Pulmonary vein bigeminy: electrophysiological characteristics and results of catheter ablation

Pulmonary vein bigeminy is the pair of a second, late and ectopic pulmonary vein potential following atrial far-field activation and a first passive pulmonary vein potential during sinus rhythm. The aim of this study was to determine the electrophysiological characteristics of pulmonary vein bigeminy and to evaluate its relevance as a trigger for paroxysmal atrial fibrillation.

METHODS AND RESULTS

Pulmonary vein bigeminy was recorded in 8 of 45 patients (18%) who underwent mapping of pulmonary veins for ablation of focal atrial fibrillation. The premature ectopic pulmonary vein potentials were conducted to the atria in 5 patients and were not conducted (concealed bigeminy) in 3 patients. The coupling interval of the ectopic pulmonary vein potential to the preceding atrial signal during sinus rhythm was significantly longer in patients with conducted bigeminy (375 +/- 25 ms) than with concealed bigeminy (230 +/- 17 ms). The pulmonary vein bigeminy was driven by coronary sinus pacing with the pacing cycle length at lower stimulation rates and was suppressed by overdrive pacing. Coronary sinus pacing led to a separation of the first pulmonary vein potential from the atrial signal but the interval between the atrial signal and the second pulmonary vein potential remained unchanged. Focal ablation at the site of earliest ectopic pulmonary vein activity in 5 patients induced rapid repetitive firing before elimination of the pulmonary vein bigeminy. Ostial disconnection of the arrhythmogenic pulmonary vein in 3 patients was associated with elimination of the pulmonary vein bigeminy. During the follow-up of 9 +/- 5 months after ablation of the pulmonary vein bigeminy, 5 of the 8 patients (63%) were free of atrial fibrillation without antiarrhythmic medication.

CONCLUSIONS

The response of pulmonary vein bigeminy to atrial pacing and ostial ablation suggests that pulmonary vein bigeminy depends on an intact electrophysiological breakthrough between the left atrium and the pulmonary vein. Ablation targeting the pulmonary vein bigeminy is a possible limited approach for this subgroup of patients with paroxysmal atrial fibrillation.

Specific linear left atrial lesions in atrial fibrillation: intraoperative radiofrequency ablation using minimally invasive surgical techniques

OBJECTIVES

A specific left atrial (LA) linear lesion concept for treatment of paroxysmal and permanent atrial fibrillation (AF) was tested using intraoperative ablation with minimally invasive surgical techniques.

BACKGROUND

Curative treatment for patients with chronic AF is among the main challenges of interventional electrophysiology.

METHODS

Seventy patients (mean age 53 +/- 10 years) with drug-refractory persistent (n = 28) or paroxysmal (n = 42) AF underwent intraoperative radiofrequency (RF) ablation using video-assisted minimally invasive techniques via a right anterolateral minithoracotomy. Contiguous lesion lines involving the mitral annulus and the orifices of the pulmonary veins were placed with RF energy application under direct vision to prevent anatomically defined LA re-entrant circuits.

RESULTS

Mean follow-up was 18 +/- 7 months in patients with permanent AF and 18 +/- 5 months in patients with paroxysmal AF. Antiarrhythmic drug treatment was instituted in patients with postoperative atrial arrhythmias to allow "reverse electrical remodeling" and was discontinued after three months. Six months following ablation, 93% of the patients were in sinus rhythm in both groups, and after 12 months, 95% and 97%, respectively. As major complications, one esophagus perforation and one circumflex coronary artery stenosis were observed.

CONCLUSIONS

A pure linear lesion line concept confined to the left atrium targeting specifically at elimination of anatomically defined LA "anchor" re-entrant circuits eliminated AF in >90% of the patients treated with intraoperative ablation using minimally invasive surgical techniques over a mean follow-up of 1.5 years.

Curative treatment of atrial fibrillation with intraoperative radiofrequency ablation: short-term and midterm results

OBJECTIVE

This report describes the early and midterm results after intraoperative radiofrequency ablation of atrial fibrillation for patients with isolated chronic atrial fibrillation or atrial fibrillation in combination with additional valvular and nonvalvular cardiac diseases.

METHODS

From August 1998 to March 2001, a total of 234 patients with chronic atrial fibrillation underwent isolated intraoperative radiofrequency ablation alone (n = 74, 31.6%) or in combination with other cardiac procedures, such as mitral valve reconstruction (n = 57, 24.4%), mitral valve replacement (n = 38, 16.2%), aortic valve replacement (n = 11, 5.1%), coronary artery bypass grafting (n = 8, 5.0%), or a combination of the last with other cardiac procedures (n = 46, 19.7%). In all cases anatomic reentrant circuits confined within the left atrium were eliminated by placing contiguous lesion lines involving the mitral anulus and the orifices of the pulmonary veins through the use of radiofrequency energy application (exposure time, 20 seconds). A median sternotomy was used in 101 cases (43.2%), and video assistance through a right lateral minithoracotomy was used in 133 cases (56.8%).

RESULTS

A total of 188 patients (83.9%) were discharged in sinus rhythm, 17 patients (7.6%) had atrial fibrillation, and 19 patients (8.5%) had atypical flutter. Pacemakers were implanted in 23 patients (9.8%). There were 10 in-hospital deaths (4.2%), and 30-day mortality was 5 patients (2.1%). In 3 cases (1.3%) an atrioesophageal fistula developed, necessitating surgical repair. Six months' follow-up was complete for 122 (61.0%) of 200 patients, with 99 patients still in stable sinus rhythm (81.1%, 95% confidence interval 73.1%-89.9%). Twelve months' follow-up was complete for 80 (90.9%) of 88 patients, with 58 patients still in sinus rhythm (72.5%, 95% confidence interval 61.3%-83.2%).

CONCLUSIONS

Intraoperative radiofrequency ablation is a curative procedure for chronic atrial fibrillation. It is technically less challenging than the maze procedure and can be applied through a minimally invasive approach. Protection of the esophagus seems mandatory to avoid the deleterious complication of a left atrioesophageal fistula, such as was observed in 3 cases.

A new radiofrequency thermal balloon catheter for pulmonary vein isolation

OBJECTIVES

We sought to evaluate whether porcine pulmonary vein (PV) isolation (PVI) can be produced by ablation using our novel radiofrequency (RF) thermal balloon catheter (RBC).

BACKGROUND

It has been proposed that PVI can prevent focal atrial fibrillation (AF) originating in or close to the PV.

METHODS

The RBC is composed of a 12F main shaft, a 4F inner tube and a balloon. Inside the balloon, there is a unipolar coil electrode with a thermocouple sensor mounted along the tube, the former to deliver RF energy (13.56 MHz) and the latter to monitor the temperature. After the presence of a PV potential was confirmed, the RBC was safely inserted into the left atrium (LA) by the trans-septal approach. Once the balloon was inflated and optimally wedged at the junction between the PV and LA, RF energy was applied for 5 min. Radiofrequency catheter ablation (RFA) was repeated up to three times, until elimination of the PV potential or dissociation between the LA and PV was observed. Finally, each heart was examined histologically.

RESULTS

In 18 PVs that had PV potentials, PVI was performed, resulting in success in 15 (success rate 83%, 95% confidence interval [CI] 58.0% to 96.3%; failure rate 17%, 95% CI 3.7% to 42.0%). After successful PVI, the PV potentials completely disappeared and the histologic examination revealed circumferential, transmural necrosis around the PV trunks. No major complications, such as PV stenosis or macroscopic thrombosis, were observed.

CONCLUSIONS

The RBC was useful for PVI.

Advances in cardiac electrophysiology and pacing

Significant advances have been made in the management of cardiac arrhythmias. New technology has enhanced the ability to understand and treat a variety of tachycardias. Excitement and caution surround ablative approaches for atrial fibrillation. The role of ICDs and class III antiarrhythmic drugs in the management of patients at risk for sudden cardiac death has been clarified. A new indication for cardiac pacing is evolving as a supplemental treatment for patients with refractory congestive heart failure. These and other advances provide numerous exciting options for management of cardiac patients.

Linear ablation using an irrigated electrode electrophysiologic and histologic lesion evolution comparison with ablation utilizing a non-irrigated electrode

OBJECTIVES

To characterize the electrophysiologic and histologic sequelae of linear atrial ablation utilizing an irrigated electrode. To compare "irrigated" lesions with lesions deployed using the same electrode in a non-irrigated mode.

BACKGROUND

Previous reports of radiofrequency catheter ablation using an irrigated electrode have emphasized its favorable effect on lesion depth. We hypothesized that electrode irrigation would also benefit linear ablation of smooth atrial myocardium, a relatively superficial target.

METHODS

In healthy pigs, lesions were deployed in the right and left atria. Acutely, lesions resulting from ablation using an irrigated electrode, with radiofrequency energy titration guided by electrogram amplitude reduction, were compared to lesions using the same electrode without irrigation, with energy titration guided by electrode thermometry. Irrigated lesions were also assessed serially.

RESULTS

Acutely, irrigated lesions formed complete conduction barriers and were uncomplicated. In contrast, non-irrigated lesions formed complete conduction barriers but were frequently complicated, exhibiting endocardial charring, barotrauma, and pericardial damage. The rate and pattern of histologic evolution of irrigated lesions were uniform throughout each lesion; right and left atrial lesions healed similarly. During healing, 90 % of lesions remained complete conduction barriers and 10 % manifested single discrete conduction gaps where viable appearing myocytes bridged the lesion.

CONCLUSIONS

Complete, uncomplicated linear lesions could be reliably deployed in either atrium with an irrigated electrode. Not all lesions remained complete barriers to conduction during their histologic evolution. Lesions deployed with the same electrode in a non-irrigated mode were complete but frequently complicated.

Homogeneity and diameter of linear lesions induced with multipolar ablation catheters: in vitro and in vivo comparison of pulsed versus continuous radiofrequency energy delivery

BACKGROUND

For invasive treatment of atrial fibrillation, linear lesions induced with multipolar ablation catheters (MAC) are needed to prevent recurrence. The aim of the study was to compare the efficacy of pulsed versus continuous radiofrequency (RF)-energy delivery using MAC.

METHODS

In vitro tests were performed using endomyocardial preparations of fresh pig hearts in a 10-liter-bath of physiologic saline solution (37 degrees C) at constant flow conditions (1.5 l/min). The MAC were placed with a constant pressure of 20 ponds onto the endocardium. The energy (generator: Osypka HAT 200 S) was delivered either pulsed (4 electrodes simultaneously, 5ms duty-cycle) or continuously (each electrode separately). In vivo experiments were performed in 6 anesthetized pigs using fluoroscopic positioning of MAC at 40 different intracardial positions and with similar conditions as in vitro experiments. Lesion volume (LV) was calculated after measuring lesion diameter with a microcaliper. The homogeneity of the lesions (LH) was classified from 1-4; with 1 as highest homogeneity.

RESULTS

Pulsed energy delivery produced more homogeneous linear lesions in significantly less time. There was no difference in electrode temperature values (50.2 +/- 0.8 and 51.3 +/- 1.4 degrees C) in vitro and in vivo. In the in vivo experiments, lesion depth and calculated lesion volume were less in both modes of energy delivery but pulsed energy delivery was superior regarding lesion depth and homogeneity.

CONCLUSION

With pulsed energy delivery it is possible to create linear lesions of significantly greater homogeneity. Moreover, larger lesions are induced in less time by pulsed energy delivery in vitro and in vivo.

[Characteristics of atrial electrograms recorded in radiofrequency induced block lines in an experimental model]

AIM

To analyze and quantify atrial electrogram modifications following the induction of linear lesions in the atrial wall using radiofrequency ablation procedures.

METHODS

An epicardial multiple electrode (221 unipolar electrodes) was used in 12 Langendorff perfused rabbit hearts to analyze atrial activation before and after radiofrequency induction of a linear lesion in the left atrial wall. After confirming the existence of conduction blockade in the lesion zone by epicardial mapping and propagation vector analysis, six electrodes each were selected in the lesioned and non-lesioned zones in all experiments, comparing the amplitude, maximum negative slope and morphology of the electrograms in both zones, before (control) and after radiofrequency delivery.

RESULTS

Analysis of the reproducibility of the measurements in two consecutive cycles showed a variation of 1 +/- 5% for amplitude (NS) and 1 +/- 9% for maximum negative slope (NS). In the non-damaged zone, amplitude (105 +/- 22%) and slope (92 +/- 16%) (values normalized with respect to those recorded before radiofrequency) did not vary significantly following radiofrequency, and simple electrograms were the most frequent recordings (82 vs 83% in control; NS). Amplitude (19 +/- 7%, p < 0.001) and slope (24 +/- 11%; p < 0.001) decreased significantly in the lesion zone, as did the percentage of simple electrograms (6 vs 86% in control; p < 0,001). In this same zone the morphology could not be determined in 12% of the recordings, while multiple electrograms were obtained in 15% (vs 2% in control; p < 0.01), and the most frequent type corresponded to double electrograms (67 vs 12% in control, p < 0.001), with both components coinciding in time with atrial activation in the zones proximal and distal to the lesion line.

CONCLUSIONS

Electrograms recorded directly in radiofrequency induce block lines show a significant decrease in amplitude and maximum negative slope. Double electrograms predominate in these recordings, both components of which represent activation on either side of the lesion. In a small proportion of cases simple and multiple electrograms can also be recorded in the block line.

Mapping-guided ablation of pulmonary veins to cure atrial fibrillation

Catheter ablation of triggers inducing paroxysms of atrial fibrillation (AF) is an emerging therapy for this common arrhythmia. In a series of 225 consecutive patients with AF resistant to multiple drugs, 96% presented with triggering foci originating from 1 or multiple pulmonary veins (PV), independently of whether or not the patient had ectopy or structural heart disease. The present article describes the mapping and ablation techniques applicable to individual patients: (1) criteria to define an arrhythmogenic PV; (2) use of provocative maneuvers; and (3) the role of circumferential mapping catheters to provide extent, distribution, and activation of PV muscle as well as monitoring distal PV potentials (PVP) during ablation. Radiofrequency ablation can be performed by targeting the PVP during sinus rhythm (right PV) or left atrial pacing (left PV) with the procedural endpoint of PVP elimination, which is more effective in predicting a successful outcome than suppression of acute ectopy. Complete elimination of AF is presently obtained in 70% of patients, allowing interruption of arrhythmias and in use anticoagulants. It is anticipated that continued technologic improvements will improve and facilitate this technique of curative treatment of AF.

Catheter ablation of atrial fibrillation: challenges and promise

Although atrial fibrillation is the most common sustained arrhythmia that requires medical attention, it remains a challenge to treat. Nevertheless, considerable progress has been made toward developing curative, catheter-based treatments for selected patients with atrial fibrillation. The most significant clinical observation during electrophysiologic testing in patients with atrial fibrillation has been a recognition of the importance of the pulmonary veins for the initiation of this arrhythmia. In addition to being the most common site of arrhythmogenic foci that trigger the onset of atrial fibrillation, the unique electrophysiologic characteristics of the pulmonary veins may serve to perpetuate established atrial fibrillation. Because of the very short-duration refractory periods that are measured within the pulmonary veins, these structures may serve as a site of high frequency activation due to reentrant activation with small wavelengths. Catheter ablation strategies that are designed to ablate the site of triggering foci with the pulmonary veins have been very successful in selected patients with paroxysmal atrial fibrillation, although the risk of recurrent arrhythmias remains relatively high. In addition, ablation strategies that are designed to electrically isolate the pulmonary veins from the bulk of the left atrium are likely to lead to improvements in the long-term outcome of ablation. For patients with permanent atrial fibrillation, considerable progress has been made in the restoration of sinus rhythm by linear ablation strategies in the left atrium. It is likely that a comprehensive nonpharmacologic treatment for atrial fibrillation will incorporate the lessons learned from each of these approaches and lead to a genuine cure of this vexing arrhythmia.

Noncontact system-guided simplified right atrial linear lesions using radiofrequency transcatheter ablation for treatment of refractory atrial fibrillation

This article describes our experience with a staged "hybrid" approach to the treatment of drug resistant AF, in which the completeness of a single linear lesion in the RA was verified with a noncontact mapping system. Inferior vena cava-tricuspid annulus ablation was performed and followed by the creation of a single intercaval lesion. The study population consisted of 24 patients with a 3.4 +/- 1.6-year history of drug resistant, severely symptomatic, lone paroxysmal (n = 19), or persistent (n = 5) AF. During a follow-up of 8 +/- 2.6 months, 12 (50%) patients remained asymptomatic and 6 (25%) had a significant decrease in AF episodes, while the arrhythmia was unchanged in 5 (21%) patients and aggravated in 1 (4%) patient. Overall, a favorable clinical result was achieved in 18 (75%) patients.

Acute electrophysiologic effects and antifibrillatory actions of the long linear lesions in the right atrium in a sheep model

Linear lesions (LL) represent an option for curing of atrial fibrillation (AF) with ablation techniques.

METHODS AND RESULTS

In 11 sheep (w. 72+/-16 kg), LL were created with radiofrequency ablation in the lateral, posterior and septal walls of the right atrium (RA). AF was induced before and after LL with burst pacing. Mapping of the AF was performed with a 64-electrode basket catheter deployed in the RA. Quantitative analysis was performed with a custom-made software program. LL were confirmed histologically 7 to 10 days after the procedure. LL were transmural in 78% of their length. Stimulation thresholds and right atrial activation times were increased after LL compared to preablation values. Effective refractory periods of the RA were prolonged significantly in 7 out of 12 regions after generation of LL. Conduction velocities in the RA segments between LL were reduced in lateral, posterior and septal walls. During paced rhythms double potentials were recorded in all animals. AF could be induced in all animals of this model despite the presence of LL in the RA. AF episodes were significantly more regular after LL throughout the RA due to a significant reduction of the number of the wave fronts in the RA. During AF episodes, in the presence of LL, the RA was driven by wave fronts of left atrial origin entering the right side of the septum through interatrial connections.

CONCLUSIONS

1) LL profoundly affect electrophysiologic parameters of RA. 2) In the presence of LL, AF manifest a higher degree of regularity as compared to preablation episodes. 3) Dissociation between wave fronts of left atrial origin entering the RA through the interatrial connections is an important mechanism of the antifibrillatory action of the septal LL.

Prevention of atrial fibrillation by complete compartmentalization of the left atrium using a catheter technique

INTRODUCTION

Right atrial compartmentalization has been demonstrated to only reduce the number of atrial fibrillation (AF) episodes; left atrial (LA) fibrillation still occurs.

METHODS AND RESULTS

We report successful LA compartmentalization resulting in isolation of all four pulmonary veins in a 51-year-old woman suffering from paroxysmal AF. Deployment of a complete encircling line resulted in dissociation of electrical activation within the isolated area from the remaining LA. Despite attempts at reinduction by pacing maneuvers inside and outside the isolated area, AF was no longer inducible. During 21-week follow-up, the patient remained in stable sinus rhythm with rare atrial extrasystoles.

CONCLUSION

If reproducible, this ablation strategy could allow treatment of AF independent of suppression of any triggering event.