Atrial fibrillation. Which patients are suitable for ablation' . Atrial fibrillation.. The prevalence of atrial fibrillation in the adult population is 0.5&x00025;, rising to 10&x00025; among people aged over 75 years. 1 It is associated with a 5-6 fold increase in the incidence of stroke. Which patients are suitable for ablation' Electrophysiological mechanisms that cause atrial fibrillation Atrial fibrillation is the result of both substrate and trigger.

Science, medicine, and the future.. . Radiofrequency ablation for atrial fibrillation.. . Neil R Grubb, lecturer in cardiology a and Steve Furniss, consultant electrophysiologist b.. aCardiovascular Research, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH3 9YW, bFreeman Hospital, Newcastle-upon-Tyne  Other Sections? Methods. Atrial fibrillation. Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation.

New non-.pharmacological treatments. Radiofrequency ablation. Which patients are suitable for ablation' References.   Atrial fibrillation is a common arrhythmia, especially among elderly people. Restoration of sinus rhythm by cardioversion or drug treatment improves symptoms, cardiac output, and exercise tolerance. Unfortunately, the recurrence rate in successfully treated patients is high.

Research into the underlying electrophysiological mechanisms that cause atrial fibrillation has fuelled the development of new therapeutic approaches.

Current management of atrial fibrillation. Which patients are suitable for ablation' References. . Atrial fibrillation.. The prevalence of atrial fibrillation in the adult population is 0.5&x00025;, rising to 10&x00025; among people aged over 75 years. 1 It is associated with a 5-6 fold increase in the incidence of stroke. Paroxysmal atrial fibrillation is characterised by repeated, self terminating episodes of arrhythmia.

This can progress to either persistent atrial fibrillation, in which an intervention such as direct current cardioversion may restore sinus rhythm, or permanent atrial fibrillation, which is resistant to cardioversion. Many patients with atrial fibrillation are asymptomatic, especially if their heart rate is not rapid.

Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation. New non-.pharmacological treatments. Which patients are suitable for ablation' References. Electrophysiological mechanisms that cause atrial fibrillation Atrial fibrillation is the result of both substrate and trigger. The substrate is most often a pathology that affects the atria, such as hypertensive heart disease (associated with increased stress on the atrial wall).

5 The trigger often consists of an ectopic atrial electrical focus. 7 Macro re-entry occurs when a continuous loop of atrial depolarisation is set up around an anatomical or functional conduction barrier (such as a vein orifice or zone of diseased atrial tissue). It occurs especially when conduction propagates in only one direction around the barrier (fig &x200B;(fig1). 1 ).

These include shortening of the refractory period of atrial myocytes, which encourages macro re-entry because myocytes are excitable for a greater proportion of each cycle (fig &x200B;(fig1). 1 ). This process is known as electrical remodelling. 8 .. Atrial fibrillation. Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation. New non-.pharmacological treatments.

Radiofrequency ablation. Which patients are suitable for ablation' References. Current management of atrial fibrillation Current management focuses on two issues&x02014;preventing stroke and treating the arrhythmia. Guidelines for preventing stroke are published elsewhere. 9 Arrhythmia is managed by the sinus rhythm strategy or the rate control strategy.

Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation. New non-.pharmacological treatments. Radiofrequency ablation. Which patients are suitable for ablation'. References. New non-pharmacological treatments Atrial fibrillation can be treated with physical as well as pharmacological interventions. Internal cardioversion administered by catheter is effective in three quarters of patients who are resistant to external cardioversion, but it is still associated with a high recurrence rate.

10 Atrial pacing can prevent atrial fibrillation by inhibiting ectopic activity and preventing excessive bradycardia. Trials are in progress to evaluate pacemakers that detect trends in heart rate and ectopy known to be associated with paroxysms of atrial fibrillation and that initiate single site or multisite pacing in response to these changes. 11 , 12 Implantable atrial defibrillators detect episodes of atrial fibrillation at their onset and deliver an internal direct current shock.

13 ..

Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation. New non-.pharmacological treatments. Radiofrequency ablation. Which patients are suitable for ablation' . References. Radiofrequency ablation . Except for atrial surgery, none of the above treatments directly and permanently targets the trigger or substrate for atrial fibrillation.

There is therefore considerable interest in recent developments in catheter ablation, which target these mechanisms and which may offer a cure for selected patients with this condition. . Radiofrequency ablation is the targeted cautery of cardiac tissue by local application of radiofrequency energy. Target zones are identified during an electrophysiological study, in which a series of catheters are placed in the heart (fig &x200B;(fig2).

2 ). Accessory pathways or other critical parts of arrhythmia circuits are identified by recording the cardiac electrical activation sequence. Once a target zone is identified, ablation is performed by heating the interface between catheter and endocardium until cell death occurs, at temperatures over 47&x000b0;C. . Ablation has become the treatment of choice for most patients with supraventricular tachycardia due to accessory pathways or to atrioventricular nodal re-entry, and is becoming widely used for treating atrial flutter.

16 Until recently, ablation has had only a limited role in treating atrial fibrillation itself, but better understanding of the mechanisms causing such arrhythmia has stimulated the development of new ablation techniques that target both substrate and trigger. The role of ablation differs for each of the presentations of atrial fibrillation. .. Paroxysmal atrial fibrillation..

. Some patients with self terminating paroxysms of atrial fibrillation have their arrhythmia initiated by rapid repetitive discharges from foci within one or more of the pulmonary veins or, occasionally, the superior vena cava. 6 , 17 &x02013; 19 These structures contain sleeves of atrial tissue that extend a variable distance from the atria themselves. The culprit foci often lie several centimetres inside the vein, and spontaneous ectopic activity arising therein propagates into the atria, initiating and sometimes maintaining atrial fibrillation.

. It is possible to locate these foci during an electrophysiological study. As they are usually in the pulmonary veins, the interatrial septum has to be punctured to allow catheters to pass into the left atrium and pulmonary veins from the right atrium. Radiofrequency ablation can be used either to destroy the culprit foci or to isolate them electrically from the atria.

Persistent atrial fibrillation usually affects patients with structural or ischaemic heart disease. Atrial disease tends to maintain atrial fibrillation once it occurs. Sinus rhythm can be restored with electrical or pharmacological cardioversion, but fibrillation tends to recur because of the persistence of triggering foci and underlying atrial disease. Focal ablation in this setting is less successful for the above reasons and possibly because of the presence of multiple triggering foci within the atria and pulmonary veins.

Hybrid ablation strategies that target both the trigger, through focal ablation, and the substrate, by linear ablation and compartmentalisation (see below), are under development. 20 .. . Although restoration of sinus rhythm is the goal for these patients, it cannot always be achieved or sustained. In resistant cases ablation can be used to control heart rate in patients who develop an inappropriate tachycardia during exercise or for whom drugs are ineffective or have unacceptable side effects.

The region of the compact atrioventricular node or His bundle is ablated to achieve complete atrioventricular block; a permanent pacemaker is then implanted to control heart rate. 21 &x02013; 23 This is known as the &x0201c;ablate and pace&x0201d; strategy. Modern pacemakers are capable of increasing the ventricular rate appropriately in response to exercise during atrial fibrillation. In patients with paroxysmal atrial fibrillation a mode switching pacemaker is used, which, as well as controlling the heart rate during paroxysms, maintains synchrony of atrial and ventricular contraction during sinus rhythm.

Regularising the ventricular rhythm during atrial fibrillation also improves symptoms and haemodynamic performance. 21 , 22 Concerns have been expressed about an association between total atrioventricular nodal ablation and death due to bradycardia-related torsades de pointes ventricular tachycardia. This risk can be virtually eliminated with pacing at 80-90 beats/min in the month after ablation.

24 .. . Permanent atrial fibrillation.. . For permanent atrial fibrillation, the principal objective, other than effective anticoagulation to prevent stroke, is control of heart rate. This can usually be achieved with atrioventricular node blocking drugs. When drugs are ineffective, poorly tolerated, or cause symptomatic bradycardia, &x0201c;ablate and pace&x0201d; treatment is indicated.

Anticoagulation is required afterwards because the atria continue to fibrillate and the risk of systemic embolism persists. . Recognition that atrial fibrillation is maintained by the presence of macro re-entry circuits, which occupy a critical amount of space in the atria, has prompted the development of treatments that prevent re-entry and thus prevent atrial fibrillation. The aim of these treatments is to create zones that block electrical conduction to prevent the propagation of these circuits.

The surgical maze procedure is one such treatment, and both the rate of successful treatment and the rate of operative complication have driven the development of catheters that can produce contiguous, linear lesions that can compartmentalise the atria without the need for surgery. 14 Early results indicate that linear ablation requires further refinement, but it may have a future role in the management of persistent and permanent atrial fibrillation.

20 ..  Other Sections? .. Methods. Atrial fibrillation. Electrophysiological mechanisms that cause atrial fibrillation.

Atrial fibrillation. Electrophysiological mechanisms that cause atrial fibrillation. Current management of atrial fibrillation.

Electrical remodelling in atrial fibrillation: time course and mechanisms. Circulation. 1996;94 :2968?2974. [ PubMed ] .. . 9. Scottish Intercollegiate Guidelines Network. Antithrombotic therapy. A national clinical guideline. Edinburgh: SIGN; 1999. . 10. Coumel P, Frioucourt P, Mugica J, Attuel P. Long-term prevention of vagal arrhythmias by atrial pacing at 90 beats per minute.

PACE Pacing Clin Electrophysiol. 1983;6 :552?560. [ PubMed ] .. . 11. Delfaut P, Prakash A, Giorgberidze I. The role of pacemaker therapy in the prevention of atrial fibrillation. Semin Intervent Cardiol. 1997;2 :219?225. [ PubMed ] .. . 12. Saksena S, Prakash A, Mangeon L, Varanasi S, Kolettis T, Mathew P, et al. Clinical efficacy and safety of atrial defibrillation using biphasic shocks and current non-thoracotomy endocardial lead configurations.

Am J Cardiol. 1995;76 :913?921. [ PubMed ] .. . 13. Cox JL, Boineau JP, Schuessler RB, Kater KM, Lappas DG. Five year experience with the maze procedure for atrial fibrillation. Ann Thorac Surg. 1993;56 :814?824. [ PubMed ] .. . 14. Cox JL, Ad N, Palazzo T. Impact of the maze procedure on the stroke rate in patients with atrial fibrillation. J Thorac Cardiovasc Surg. 1999;118 :833?840.

[ PubMed ] .. . 15. Cosio FG, Lopez-Gil M, Goicolea A, Arribas F, Barroso JL. Radiofrequency ablation of the inferior vena cava-tricuspid valve isthmus in common atrial flutter. Am J Cardiol. 1993;71 :705?709. [ PubMed ] .. . 16. Nabar A, Rodriguez ML, Timmermans C, Van den Dool A, Smeets JL, Wellens HJ. Effect of right atrial isthmus ablation in the occurrence of atrial fibrillation: observations in four patient groups having type 2 atrial flutter with or without associated atrial fibrillation.

Circulation. 1999;99 :1441?1445. [ PubMed ] .. . 17. Tsai CF, Tai CT, Hseih MH, Lin WS, Yu WC, Ueng KC, et al. Initiation of atrial fibrillation by ectopic beats originating from the superior vena cava. Electrophysiological characteristics and results of radiofrequency ablation. Circulation. 2000;102 :67?74. [ PubMed ] .. . 18. Tsai CF, Chen SA, Tai CT, Chiou CW, Prakash VS, Yu WC, et al. Bezold-Jarisch-like reflex during radiofrequency ablation of the pulmonary vein tissues in patients with paroxysmal focal atrial fibrillation.

J Cardiovasc Electrophysiol. 1999;10 :27?35. [ PubMed ] .. . 19. Robbins IM, Colvin EV, Doyle TP, Kemp EW, Loyd JE, McMahon WS, et al. Pulmonary vein stenosis after catheter ablation of atrial fibrillation. Circulation. 1998;98 :1769?1775. [ PubMed ] .. . 20. Maloney JD, Milner L, Barold S, Czerska B, Markel M. Two-staged biatrial linear and focal ablation to restore sinus rhythm in patients with refractory chronic atrial fibrillation: procedure experience and follow-up beyond 1 year.

PACE Pacing Clin Electrophysiol. 1998;21 :2527?2532. [ PubMed ] .. . 21. Fitzpatrick AS, Kourouyan HD, Siu A, Lee R, Lesh MD, Epstein LM, et al. Quality of life and outcomes after radiofrequency His bundle catheter ablation and permanent pacemaker implantation: impact of treatment in paroxysmal and established atrial fibrillation. Am Heart J. 1996;131 :499?507. [ PubMed ] ..

. 22. Natale A, Zimerman L, Tomassni G, Kearney M, Kent V, Brandon MJ, et al. Impact on ventricular function and quality of life of transcatheter ablation of the atrioventricular junction in chronic atrial fibrillation with a normal ventricular response. Am J Cardiol. 1994;74 :242?246. [ PubMed ] .. . 23. Ha&x000ef;ssaguerre M, Ja&x000ef;s P, Shah DC, Gencel L, Pradeau V, Garrigues S, et al. Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation.

J Cardiovasc Electrophysiol. 1996;7 :1132?1144. [ PubMed ] .. . 24. Wood MA, Brown-Mahoney C, Kay N, Ellenbogen KA. Clinical outcomes after ablation and pacing therapy for atrial fibrillation: a meta-analysis. Circulation. 2000;101 :1138?1144. [ PubMed ] .. . Articles from BMJ : British Medical Journal are provided here courtesy of .. . BMJ Publishing Group..

. Review The epidemiology of atrial fibrillation. . Coron Artery Dis. 1995 Feb; 6(2):95-100. [Coron Artery Dis. 1995]. Epidemiologic assessment of chronic atrial fibrillation and risk of stroke: the Framingham study. . Neurology. 1978 Oct; 28(10):973-7. [Neurology. 1978]. See more articles cited in this paragraph ..

Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter. . J Am Coll Cardiol. 1992 Mar 15; 19(4):851-5. [J Am Coll Cardiol. 1992]. Early recurrences of atrial fibrillation after electrical cardioversion: a result of fibrillation-induced electrical remodeling of the atria' . J Am Coll Cardiol. 1998 Jan; 31(1):167-73.

[J Am Coll Cardiol. 1998]. See more articles cited in this paragraph .. Independent risk factors for atrial fibrillation in a population-based cohort. The Framingham Heart Study. . JAMA. 1994 Mar 16; 271(11):840-4. [JAMA. 1994]. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. . N Engl J Med. 1998 Sep 3; 339(10):659-66.

[N Engl J Med. 1998]. See more articles cited in this paragraph .. Electrical remodeling in atrial fibrillation. Time course and mechanisms. . Circulation. 1996 Dec 1; 94(11):2968-74. [Circulation. 1996]. See more articles cited in this paragraph .. Long-term prevention of vagal atrial arrhythmias by atrial pacing at 90/minute: experience with 6 cases. . Pacing Clin Electrophysiol.

Quality of life and outcomes after radiofrequency His-bundle catheter ablation and permanent pacemaker implantation: impact of treatment in paroxysmal and established atrial fibrillation. Am Heart J. 1996 Mar; 131(3):499-507 [Am Heart J. 1996]. Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation.

Clinical outcomes after ablation and pacing therapy for atrial fibrillation : a meta-analysis. . Circulation. 2000 Mar 14; 101(10):1138-44. [Circulation. 2000]. See more articles cited in this paragraph .. Impact of the maze procedure on the stroke rate in patients with atrial fibrillation. . J Thorac Cardiovasc Surg.