Hatim Al Lawati, MD, FRCPC, Cardiology Resident, Division of Cardiology, Faculty of Medicine, University of Toronto, Toronto, ON.
Fatemeh Akbarian, MD, Dermatologist, Research Fellow, University of Toronto, Toronto, ON.
Mohammad Ali Shafiee, MD, FRCPC, General Internist, Nephrologist, Department of Medicine, Toronto General Hospital, University Health Network; Clinician Teacher, University of Toronto, Toronto, ON.

Atrial fibrillation (AF) is by the far the most common cardiac rhythm disturbance encountered in clinical practice. It is associated with significant morbidity and mortality and has potentially lifelong implications in terms of therapy and complications. This disease is more commonly seen now given the increased life expectancy and the remarkable advances made in health care. The already at-risk older adult population is particularly vulnerable to complications from AF, especially embolic cerebrovascular events. This article reviews the evidence-based management of AF with a particular focus on the older adult population.
Key words: atrial fibrillation, older adults, stroke, rate control, rhythm control, stroke prophylaxis, anticoagulation.

Nikolai Steffenhagen MD, Calgary Stroke Program, University of Calgary, Calgary, AB.
Michael D. Hill, MD, MSc, FRCPC, Calgary Stroke Program, University of Calgary, Calgary, AB.

The majority of strokes occur among the older adult population. Typically, ischemic stroke can be classified by mechanism, and this is the most practical way to think about stroke since it has a direct bearing on the approach to prevention. It is not enough to simply consider that a past stroke implies a need for antiplatelet therapy or anticoagulant therapy without consideration of cause. In this article, we discuss the use of preventive strategies within the context of antithrombotics and according to stroke mechanism.
Key Words: stroke prevention, geriatric, octogenerian, vascular risk factors, carotid stenosis, atrial fibrillation.

Sarah E. Wilson, MSc, MD, PGY1, Internal Medicine, University of Toronto, Toronto, ON.
Mark A. Crowther, MD, MSc, Associate Professor of Medicine, Department of Medicine, McMaster University, Hamilton, ON.

Warfarin reduces the risk of thrombotic complications in a wide range of patients and appears to be particularly effective in older adults. Warfarin initiation should be undertaken with care in the older adults because they are likely to require smaller maintenance doses to achieve the same target international normalized ratio (INR). Inappropriate prescribing of medications among older adults increases the risk of drug interactions that may alter warfarin anticoagulation. Such interactions should be anticipated and monitored to ensure that over- or under-anticoagulation do not persist. A range of strategies are available to follow warfarin therapy in the outpatient setting to ensure safe and effective anticoagulation.
Key words: warfarin, anticoagulation, vitamin K, atrial fibrillation.

Rajneesh Calton, MD, FACC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.
Vijay Chauhan, MD, FRCPC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.
Kumaraswamy Nanthakumar, MD, FRCPC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.

Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia worldwide, with an estimated prevalence of 0.4% in the general population. Despite recent advances in our understanding of the mechanism and consequences of AF, effective therapy for patients with AF remains difficult in many patients. Antiarrhythmic drug therapy includes control of ventricular rate as well as restoration and maintenance of sinus rhythm. The risks and benefits of each treatment modality must be assessed according to each individual patient’s circumstances. Anticoagulation for stroke prevention is a critical component of AF management that is currently underprescribed. Anticoagulation with vitamin K antagonists, such as warfarin, remains the treatment of choice for preventing stroke and cardio embolism. The oral direct thrombin inhibitor ximelagatran has the potential to favourably influence the management of patients with AF by maximizing the potential of anticoagulation for stroke prevention.
Key words: atrial fibrillation, anticoagulation, rate control, warfarin, ximelagatran, antiarrhythmic.

Rajneesh Calton, MD, FACC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.
Vijay Chauhan, MD, FRCPC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.
Kumaraswamy Nanthakumar, MD, FRCPC, Division of Cardiac Electrophysiology, University Health Network, Toronto General Hospital, Toronto, ON.

Atrial fibrillation (AF) is the most common sustained cardiac rhythm disturbance for which patients seek medical attention. AF has a heterogeneous clinical presentation, occurring in the presence or absence of detectable heart disease or related symptoms. Depending upon the duration and response to pharmacological and electrical cardioversion, AF can be classified as paroxysmal, persistent, or permanent. AF can be isolated or associated with other arrhythmias, often atrial flutter or atrial tachycardia. Minimum clinical evaluation of a patient with AF includes history, physical examination, and ECG documentation by at least single-lead ECG recording during the dysrhythmia. Additional investigation may include Holter monitoring, exercise testing, transesophageal echocardiography, and/or electrophysiological study.
Key words: arrhythmia, atrial fibrillation, Holter monitoring, atrial tachycardia.

Findings of a Provocative New Meta-Analysis

Jason M. Burstein, MD
Internal Medicine Resident,
University of Toronto,
Toronto, ON.

Shabbir M.H. Alibhai, MD, MSc, FRCP(C)
Clinical Assistant, Internal
Medicine & Geriatrics,
University Health Network, Toronto, ON.

Introduction
Atrial fibrillation is a common cardiac condition that challenges many physicians, including primary care and emergency doctors, general internists, geriatricians and cardiologists. One of the best-understood and most studied complications is cardio-embolic stroke. While management of atrial fibrillation may seem straightforward, it is interesting to note that there are still large variations in practice patterns, and a recent meta-analysis was contradictory to many previous studies and guidelines. This paper will focus on the epidemiology and treatment of atrial fibrillation in the older population and will examine both the reasons for variations in practice pattern and the conflicting evidence in major medical journals.

Epidemiology and Causes of Atrial Fibrillation
Age is perhaps the most important influence on the incidence and prevalence of disease. The prevalence rate of atrial fibrillation is 2-3% at age 60 to 65 and 8-10% at age 80. Up to 70% of all affected patients are at least 65 years old. The incidence of atrial fibrillation before age 50 is 0.

Rubina Sunderji, Pharm.D., FCSHP
Pharmacotherapeutic Specialist&emdash;Cardiology,
Pharmaceutical Sciences CSU,
Vancouver General Hospital,
Clinical Assistant Professor,
Faculty of Pharmaceutical Sciences,
University of British Columbia,
Vancouver, BC.

Kenneth Gin, MD, FRCPC
Director, Post Graduate Cardiology,
Training Program, and Clinical Assistant, Professor, Faculty of Medicine,
University of British Columbia,
Director, Coronary Care Unit, and Assistant, Director, Echocardiography Laboratory,
Vancouver General Hospital,
Vancouver, BC.

Amiodarone is a class III antiarrhythmic agent with a unique and complex pharmacological profile. The drug was originally used as an antianginal agent due to its potent coronary vasodilating activity.¹ It has subsequently been shown to be effective for both supraventricular and ventricular arrhythmias. The risk of inducing proarrhythmia is lower than with other antiarrhythmics and, unlike the class I antiarrhythmic agents, it has not been associated with increased mortality.² However, amiodarone can cause a variety of side effects and close monitoring of the patient is necessary.

Pharmacology
Amiodarone is a di-iodinated benzofuran compound containing 37.3% iodine by weight.

D'Arcy Little, MD, CCFP
Director of Medical Education,
York Community Services, Toronto, ON. 

Introduction
Atrial fibrillation (AF) is the most common, chronic arrhythmia seen in clinical practice,^1,2 and is a common cause of morbidity, mortality and health care expenditure. The prevalence of the arrhythmia increases dramatically with age; it is estimated to have a prevalence of 5% in individuals aged 60 to 70 and of 22% in persons aged 91 to 103 years.^2,3 AF commonly causes symptoms in elderly patients, including palpitations, shortness of breath, fatigue and exercise intolerance.⁴ In addition, the presence of AF is an independent risk factor for stroke, especially in older persons.⁴ The risk of stroke is increased six-fold in patients with AF, even those without coexistent rheumatic heart disease. Further, it is estimated that over one-third of all strokes in the elderly are a consequence of AF.^2,4,5,6

Approach to Treatment with Electrical Cardioversion
The goals of therapy in patients with AF are to control the patient's symptoms and to reduce the risk of complications from thrombo-embolism.¹ Conversion of AF back to normal sinus rhythm will accomplish the first goal immediately and the second goal, theoretically, over the long term if sinus rhythm can be maintained post conversion. These results are thought to be due to the return and maintenance of atrial mechanical function.¹

Atrial fibrillation (AF) is characterized by the irregular and very rapid beating of the heart's atrial chambers. It results from a malfunction of the electrical conduction system of the atria, leading to chaotic electrical signals. The regular pumping action of the atria is replaced by irregular and disorganized spasms of atrial tissue, leading to reduced blood flow, blood clots (thrombi), stroke and even death.

Considerations Prior to Electrical Cardioversion

Spontaneous Cardioversion
In up to 48% of cases of recent-onset AF, spontaneous reversion to sinus rhythm occurs. The most important factor in determining whether spontaneous reversion can occur is the duration of the AF. AF of less than 72 hours duration has a spontaneous conversion rate of approximately 40%.¹

Emergent Cardioversion
Immediate, direct current (DC) cardioversion should be performed in patients who are unstable with serious signs or symptoms. This can be the case in atrial fibrillation with a very rapid ventricular rate (greater than 150 bpm) contributing to acute myocardial infarction, angina, congestive heart failure, hypotension or syncope.²

Elective Cardioversion:

Contraindications
The treatment or elimination of any reversible, predisposing conditions should be undertaken prior to elective cardioversion. Such precipitating causes include hyperthyroidism, pneumonia, acute myocardial infarction, pulmonary embolism and pericarditis. Conditions that are relatively unfavourable for elective DC cardioversion, or where elective DC cardioversion is contraindicated, should also be investigated. These conditions are listed in Table 1. However, a recent study suggested that the duration of AF may have less of an influence on the ability of AF to be cardioverted to, and maintained in normal sinus rhythm in the absence of coexisting significant heart disease.⁷ Appropriate initial blood work includes complete blood count, creatinine, electrolytes and thyroid function (sTSH).¹ Age does not influence the success of cardioversion. Congestive heart failure, poor LV function and increased left atrial size have been found by some but not all investigators to decrease success.⁸

TABLE 1 Unfavourable Conditions for Elective Cardioversion of Chronic Atrial Fibrillation

Duration of atrial fibrillation of more than 1 year (see text) Moderate to severe cardiomegaly Echocardiographic left atrial dimension >45 mm Digitalis toxicity (contraindication) Slow ventricular rate (contraindication) Sick sinus syndrome (contraindication) Mitral valve disease Congestive heart failure COPD Recurrent atrial fibrillation despite anti-arrhythmic drugs Inability to tolerate anti-arrhythmic drugs

Modified from: Aronow WS. Management of atrial fibrillation, ventricular arrhythmias and pacemakers in older persons: Management of the older person with atrial fibrillation. JAGS 1999;47(6):740-8.

Anticoagulation
Patients with AF have an increased risk of thrombo-embolism. Cardioversion from AF to sinus rhythm in a patient with prolonged AF who is not anticoagulated is associated with a 5-7% risk of stroke.⁸ While there are no randomized trials evaluating the efficacy of anticoagulation with warfarin, several large studies suggest that, with prior anticoagulation, systemic embolism associated with cardioversion is reduced to 0-1.1%.^1,8 As a result, it is recommended that in patients with AF of longer than 48 hours, oral anticoagulant therapy with warfarin should be administered (goal for INR of 2.0 to 3.0) for a minimum of three weeks before cardioversion. In addition, because the return of atrial mechanical activity may be delayed for several weeks after the restoration of sinus rhythm, it is recommended that anticoagulation be continued for a minimum of four weeks after cardioversion. This will also decrease the chances of embolism if AF recurs.¹

Transesophageal echocardiography (TEE) has been advocated by some as a screening tool to identify patients with AF of greater than 48 hours duration where there is no evidence of left atrial clot, allowing these patients to be cardioverted without prophylactic anticoagulation. However, studies have revealed that this technique is associated with a significant incidence of thromboembolic complications, resulting in current recommendations for anticoagulation in these patients.^1,9,10 In addition, prior to cardioversion, even patients whose AF has lasted less than 48 hours should be anticoagulated with intravenous heparin, in order to cover the delays that may be encountered during medical treatment.¹

Cardioversion Technique
Elective DC cardioversion has a higher rate of success in converting AF to sinus rhythm than does medical cardioversion,^2,6 making it the most reliable means to restore sinus rhythm.¹ The technique works by delivering an R-wave synchronized shock between two thoracic electrode paddles in an anesthetized patient. The paddles can be oriented anterolaterally or anteroposteriorly. A success rate of over 90% is achieved with either configuration.¹ However, some data suggest that with regards to technical success, an anteroposterior defibrillator paddle position is superior to an anterolateral position and permits lower energy usage.¹¹ Digoxin is usually stopped 24h before cardioversion, or at least a level is checked prior to cardioversion, since digitalis toxicity increases the risk of malignant ventricular arrhythmias.¹ Generally, energy requirements depend on the duration of the AF (for instance, recent AF has coarser fibrillatory waves and requires lower energy). The first attempt at cardioversion is made with 200J. Increments of 100J are used if preceding shocks are not successful.¹ Some studies have suggested that phamacologic agents, such as ibutilide, facilitate successful cardioversion of AF in patients who failed conventional external cardioversion. The medication is administered and cardioversion is attempted again.¹² Internal cardioversion (beyond the scope of this article) is an option if external cardioversion has not been successful, and some studies indicate that this technique may work for AF of duration greater than one year but less than three years.¹³

Complications
A variety of short-lived arrhythmias can follow cardioversion, including premature atrial and ventricular beats, sinus pauses and junctional escape rhythms. These usually do not require treatment. There is a small risk of ventricular fibrillation, especially if there is poor synchronization of the DC shock and the native QRS complex. Pulmonary edema can also be a rare complication in the context of severely depressed left ventricular function.¹⁴ Thrombo-embolic complications are discussed above.¹

Clinical Decisions
The decision to cardiovert a patient from atrial fibrillation to sinus rhythm is a clinical one. The most symptomatic patients will gain the most relief.1 Patients who have had atrial fibrillation for a shorter period will likely have less left atrial dilatation; therefore they have a greater probability of being maintained in sinus rhythm.

A reasonable approach is to attempt to cardiovert patients with AF of recent onset. Patients with chronic AF have two broad therapeutic options: 1) rate control and anticoagulation; and 2) cardioversion and maintenance of sinus rhythm. The comparative value of these approaches is still under investigation,⁸ although it might be reasonable to attempt to convert symptomatic patients to sinus rhythm. Conversion to sinus rhythm improves a patient's hemodynamic status and, as a result, his or her exercise tolerance. The left ventricular stroke volume and ejection fraction increase immediately after cardioversion, while the cardiac contractility remains unchanged. This implies that the improvement in hemodynamics is secondary to enhanced left ventricular diastolic filling, due to an increased cycle length and to the return of left atrial mechanical function (atrial "kick").¹⁵ This could be very important for patients with reduced left ventricular function.⁷ Other studies have demonstrated that changes in atrial electrophysiology and the atrial dilatation associated with chronic AF are reversible after cardioversion.^16,17

Maintenance of Sinus Rhythm
While electrical cardioversion of AF to normal sinus rhythm is successful in more than 80% of cases, without antiarrythmic therapy, only 25% of patients will remain in sinus rhythm after one year.18 A cost-benefit analysis in the Annals of Internal Medicine suggests that cardioversion alone should be the initial management strategy for persistent, non-valvular atrial fibrillation. For a relapse of the arrhythmia, repeated cardioversion plus low-dose amiodarone was found to be cost-effective for patients at moderate to high risk for ischemic stroke.¹⁹ Another study has demonstrated that amiodarone is more effective than sotalol and propafenone for the prevention of recurrences of atrial fibrillation²⁰ (see article).

Conclusions
Atrial fibrillation is a common, significant arrhythmia in the elderly. DC cardioversion is used in unstable cases, and as an elective procedure in cases of recent onset, to convert the patient to normal sinus rhythm. To avoid thromboembolic complications, patients with AF of greater than 48 hours duration should be anticoagulated with warfarin for three weeks prior to, and four weeks after cardioversion. Repeat cardioversion can be used for recurrent atrial fibrillation, and antiarrhythmic therapy, such as amiodarone, can be initiated to help maintain sinus rhythm. Cardioversion can also be used in symptomatic cases of AF of long duration, as duration has been shown to be less important than underlying heart disease in the success of conversion and maintenance of sinus rhythm.

References

1. Beamish RE. (Ed.) Canadian Cardiovascular Society Consensus Conference on Atrial Fibrillation. Can J Cardiol 1996;12A:1A-61A.
2. Aronow WS. Management of atrial fibrillation, ventricular arrhythmias and pacemakers in older persons: Management of the older person with atrial fibrillation. JAGS 1999;47(6): 740-8.
3. Aronow WS, Ahn C, Gutstein H. Prevalence of atrial fibrillation and association of atrial fibrillation with prior and new thromboembolic stroke in older patients. J Am Geriatr Soc 1996;44:521-3.
4. English KM, Channer KS. Managing atrial fibrillation in elderly people: Active management of atrial fibrillation should include elderly people. BMJ 1999;318:1088-9.
5. Hampton JR. The management of atrial fibrillation in elderly patients. Age and Ageing 1999;28:249-50.
6. Morris JJ Jr, Peter RH, McIntosh HD. Electrical conversion of atrial fibrillation: Immediate and long-term results and selection of patients. Ann Intern Med 1966;65:216-31.
7. Nakazawa H, et al. Is there a place for late cardioversion of atrial fibrillation? Eur Heart J 2000;21:327-33.
8. Lampert R, Ezekowitz MD. Management of arrhythmias. Clin in Ger Med 2000;16(3):593-618.
9. Warren J, et al. Cardioversion from atrial fibrillation without prolonged anticoagulation with use of transesophageal echocardiography to exclude the presence of atrial thrombi NEJM 1993;328(11):750-5.
10. Black IW, et al. Exclusion of atrial thrombus by transesophageal echocardiography does not preclude embolism after cardioversion of atrial fibrillation. A multicentre study. Circ 1994;89:2509-13.
11. Botto GL, Politi A, Bonini W, Broffoni, T, Bonatti R. External cardioversion of atrial fibrillation: role of paddle position on technical efficacy and energy requirements. Heart 1999;82:726-30.
12. Li H, et al. Usefulness of ibutilide in facilitating successful external cardioversion of refractory atrial fibrillation. Am J Cardiol. 1999;84:1096-8.
13. Tse HF, et al. Long-term outcome in patients with chronic atrial fibrillation after successful internal cardioversion. Am J Cardiol. 1999;83:607-9.
14. Levy S, et al. Atrial fibrillation: current knowledge and recommendations for management. Eur Heart J. 1998;19:1294-1320.
15. Raymond RJ, et al. Cardiac performance early after cardioversion from atrial fibrillation. Am Heart J 1998;136(3):435-42.
16. Hobbs WJC, et al. Reversal of atrial electrical remodeling after cardioversion of persistent atrial fibrillation in humans. Circ 2000:101;1145-51.
17. Mattioli AV, et al. Serial evaluation of left atrial dimension after cardioversion for atrial fibrillation and relation to atrial function. Am J Cardiol. 2000;85:832-36.
18. Coumel P, Thomas O, Leenhardt A. Drug therapy for prevention of atrial fibrillation. Am J Cardiol 1996;77(3):3A-9A.
19. Catherwood E, et al. Cost-effectiveness of cardioversion and antiarrhythmic therapy in non-valvular atrial fibrillation. 1999;130(8):625-36.
20. Roy D, et al. Amiodarone to prevent recurrence of atrial fibrillation. N Engl J Med 2000;342:913-20.

Christopher B. Overgaard, MSc, MD

Atrial Fibrillation and Elderly Patients
Atrial fibrillation (AF) is by far the most common cardiac arrhythmia, and is most prevalent among the elderly. One large study found that 70% of all patients with AF were between 65 and 85 years of age.¹ Many underlying conditions have been associated with the development of AF, including diabetes, hypertension, pulmonary disease, thyrotoxicosis, cardiomyopathy, and nonspecific conduction defects; the AF patient population is, therefore, a heterogeneous one.² Regardless of underlying cardiac pathology, this arrhythmia is associated with a doubling of mortality and is a very significant health issue for elderly patients.

AF occurs through the propagation of random waves of intra-atrial reentry, with many macroreentrant circuits moving throughout the atrial muscle.³ This chaotic pattern results in a random irregular rhythm, a significant decrease in stroke volume and cardiac output, and the risk of thrombus formation due to atrial stasis. Systemic embolization from an atrial clot is considered to be the most devastating, albeit potentially preventable, consequence of this disease process.²

Atrial Fibrillation, Stroke, and Bleeding Risk
Elderly patients with atrial fibrillation are at a fourfold higher risk of suffering a stroke than the age-matched general population.

Andrea Sotirakopoulos, BSc

Atrial fibrillation (AF) is one of the most common sustained arrhythmias encountered by clinicians. Its incidence increases with age and the presence of structural heart disease, although it may also be present in patients without identifiable heart disease. When healthy, the atria contract at a rate that is coordinated with the contractions in the ventricles. In AF instead of beating effectively, the atria produce numerous chaotic electrical impulses that result in a non-organized, quivering movement of the heart muscle called fibrillation. As a result, the ventricles then beat too quickly, generating a rapid pulse rate and possibly allowing the blood to pool and clot. If a piece of the blood clot in the atria becomes lodged in an artery in the brain, a stroke occurs. A rapid or irregular heart rate during AF can cause symptoms such as palpitations, exertional breathlessness, fatigue, or hypotension. AF may be classified as Paroxysmal, defined as recurrent episodes reverting spontaneously or following treatment to sinus rhythm or Chronic, referring to persistent arrhythmia.

Treatment of AF should be of special interest to doctors treating the elderly. The prevalence of AF is 0.5% for the group aged 50 to 59 years and rises to 8.8% in the group aged 80 to 89 years.