Annamalai University

Department of General Medicine

ATRIAL FIBRILLATION

Moderator – Dr S.Sudharshan

Presentor-Dr M.Arun & Dr Varun s (M 5)

Date-2/8/2012

Introduction• An arrhythmia is a problem with the rate or rhythm of the heartbeat.

• Atrial fibrillation (AF) is the most common sustained arrhythmia affecting humans.

• It is marked by disorganized, rapid, and irregular atrial activation

ClassificationParoxysmal - AF that terminates spontaneously within 7 days

Persistent – AF that present continuously for more than 7 days

Longstanding - AF persistent for more than 1 year

Permanent - AF refractory to cardioversion

Lone - AF that occurs in patients younger than 60 years who do not have hypertension or any evidence of structural heart disease

CausesHypertension

Coronary heart disease

Cardiomyopathy Dilated Hypertrophic

Mitral valve disease Stenosis Regurgitation

Thyrotoxicosis

Sick sinus syndrome

Congenital heart disease

Atrial septal defect Ebstein's anomaly

Cardiac surgery

Pericarditis

Tumors

Alcohol

Lung disease

Neurogenic Electric shockLone (idiopathic)

CausesParoxysmal – Pericarditis, Alcohol, Cardiac surgery

Persistent - Coronary heart disease, Cardiomyopathy,

Mitral valve disease, Congenital heart disease

Permanent – Cardiomyopathy, Mitral valve disease, Congenital heart disease

Mechanism of AFInitiating event - a premature atrial or ventricular complex.

Sustaining substrate - one or more Reentrant circuits or Automatic Focus .

The initiating event and sustaining substrate may be all due to automaticity or reentry circuit.

Automatic Focus The drivers appear to originate predominantly from the atrialized musculature that enters the pulmonary veins and represent either focal abnormal automaticity or triggered firing

Microreentry Circuits • Sustained forms of microreentry as drivers also have been documented

around the orifice of pulmonary veins; nonpulmonary vein drivers also have been demonstrated.

Symptoms of Atrial FibrillationThe symptoms of AF vary widely between patients, ranging from none to severe and functionally disabling symptoms

The most common symptoms of AF are palpitations, fatigue, dyspnea, effort intolerance, and lightheadedness. Polyuria can occur because of release of atrial natriuretic hormone.

Syncope is an uncommon symptom of AF, most often caused by a long sinus pause on termination of AF in a patient with the sick sinus syndrome.

Asymptomatic or minimally symptomatic AF patients are not prompted to seek medical care and can present with a complication of AF such as stroke or CCF.

Physical examinationThe hallmark of AF on physical examination is an irregularly irregular pulse.

Short R-R intervals during AF do not allow adequate time for left ventricular diastolic filling, resulting in a low stroke volume and the absence of palpable peripheral pulse. This results in a “pulse deficit,” during which the peripheral pulse is not as rapid as the apical rate.

Other manifestations of AF on the physical examination are irregular jugular venous pulsations and variable intensity of the first heart sound.

Diagnostic Evaluation

• Electrocardiographic Features - Low-amplitude baseline oscillations (fibrillatory or f waves) - The f waves have a rate of 300 to 600 beats/min and are variable in amplitude, shape, and timing. - Irregularly irregular ventricular rhythm

- Atrial flutter (rate of 250 to 350 beats/min and are constant in timing and morphology)

Comparison between the f waves of AF (top panel) and the flutter waves of atrial flutter (bottom panel). f waves are variable in rate, shape, and amplitude, whereas flutter waves are constant in rate and all aspects of morphology.

A recording of AF with a rapid ventricular rate of 160 beats/min. Shown are leads V1, II, and V5. On quick review, there may appear to be a regular rate consistent with paroxysmal supraventricular tachycardia. On closer inspection, it is clear that the rate is irregularly irregular.

• Holter recording Patient who describes rapid palpitations suggestive of paroxysmal AF, ambulatory monitoring is useful to document whether AF is responsible for the symptoms

• Echocardiography Evaluate atrial size and left ventricular function and to look for left ventricular hypertrophy, congenital heart disease & valvular heart disease

• A stress test Appropriate for evaluation of ischemic heart disease in at-risk patients

• Laboratory testing should include thyroid function tests, liver function tests.

Therapy of Atrial Fibrillation: General Principles• Three potential therapeutic goals of treatment

- Restoration and maintenance of sinus rhythm,

- Rate control during AF, - Prevention of thromboembolism

Restore sinus rhythm or Ventricular rate control ?

• Decision should be individual to each patient, based on analysis of the risk benefit ratio for that individual.

• Factors to consider are - Severity of symptoms, - Left atrial size, - Patient age, - Presence of cardiovascular disease or other medical conditions, - Pharmacologic and nonpharmacologic options

• Severity of symptoms

- If patient is hemodynamically unstable or is in severe cardiac failure, immediate DC cardioversion aimed at restoring sinus rhythm must be tried.

• Left atrial size - Patients with dilated left atrium are more prone to AF, and these patients are more likely to remain in AF than those with normal LA dimensions - In these patients rate control is ideal

• Patient age For example, an elderly patient with minimal symptoms and years of persistent AF is an ideal candidate for a rate control and anticoagulation treatment strategy. Alternatively, a young patient with very symptomatic episodes of paroxysmal AF should be considered initially for a rhythm control treatment strategy

• Presence of cardiovascular disease or other medical

conditions

In patients with Permanent AF(Cardiomyopathy, Mitral valve disease, Congenital heart disease) rate control is preferred

AFFIRM TRIAL• The Atrial Fibrillation Follow-Up Investigation of Rhythm

Management (AFFIRM) trial was the largest trial which compared difference in mortality between the rhythm and rate control strategies in AF.

• The mean follow-up in AFFIRM was 3.5 years; thus, only short-term follow-up data are available.

• There was no difference in mortality between the rhythm and rate control strategies.

• Thus, clinicians should individualize their approach and select the treatment strategy that is best for each patient.

• One important observation is that in patients at high risk for stroke, long-term anticoagulation is required regardless of whether a rhythm or rate control strategy is selected.

Two important decisions in acute AF

• If cardioversion is decided on for a hemodynamically stable patient who presents with AF that does not appear to be self-limited, there are two management decisions to be made: early versus delayed cardioversion and pharmacologic versus electrical cardioversion.

Early or Delayed Cardioversion ?

• Duration of AF

Duration < 48 hrs - Less chance of thromboembolism - No need for anticoagulant before cardioversion(chemical or DC) to restore sinus rhythm

Duration > 48 hrs - Transesophagial echocardiography to rule out Atrial thrombus. - If thrombus present- anticoagulant for 3 weeks before Cardioversion (chemical or DC) and 4 weeks following cardioversion.

Chemical cardioversion or DC cardioversion for restoring rhythm ?• Pharmacologic cardioversion has these advantage - Does not requiring general anesthesia or deep sedation. • Disadvantages of pharmacological cardioversion - Associated with the risk of adverse drug effects - Not as effective as electrical cardioversion. - Unlikely to be effective if the duration of AF is longer than 7 days

AF Hemodynamically unstable

DC cardioversionHemodynamically stable

Rhythm control Rate control

< 48 hrs > 48 hrs

Rate control drugs

Cardiovert without

anticoagulant

TEE

Thrombus present

Thromus absent

3 weeks anticoagulation

before cardioversion

Start anticoagulant and cardiovert

Intravenous Agents to Restore Sinus Rhythm• Commonly used drugs are Ibutalide(60-70%), Amiodarone (40-50%), procainamide(30-40%).

• To minimize the risk of QT prolongation and polymorphic ventricular tachycardia (torsades de pointes ), the use of ibutilide should be limited to patients with an ejection fraction >35%

• Other drugs which can be also used are flecainide, propafenone, and sotalol.

Oral Antiarrhythmic Agents for Restoration of sinus rhythm• Acute pharmacologic cardioversion of AF also can be attempted with orally administered drugs in patients without structural heart disease.

• The most commonly used oral agents for acute conversion of AF are propafenone (300 to 600 mg) and flecainide (100 to 200 mg).

Oral agents for Maintenance of Sinus Rhythm• All of the available drugs except amiodarone have similar efficacy and are associated with a 50% to 60% reduction in the odds of recurrent AF during 1 year of treatment

• Lone AF or minimal heart disease - flecainide, propafenone, sotalol, and dronedarone are reasonable first-line drugs, and amiodarone and dofetilide can be considered if the first-line agents are ineffective or not tolerated.

• In patients with substantial left ventricular hypertrophy, the hypertrophy may heighten the risk of ventricular proarrhythmia, and the safest choice for drug therapy is amiodarone.

• In patients with coronary artery disease, the safest first-line options are dofetilide, sotalol, and dronedarone, with amiodarone reserved for use as a second-line agent.

• In patients with heart failure, several antiarrhythmic drugs have been associated with increased mortality, and the only two drugs known to have a neutral effect on survival are amiodarone and dofetilide.

• Drug having higher efficacy than the others is amiodarone. However, because of the risk of organ toxicity, amiodarone is not appropriate first-line drug therapy for most categories of patients with AF.

• Risk factors for proarrhythmia in patients on these drugs include female gender, left ventricular dysfunction, and hypokalemia.

Use of Drug Therapy to Control Ventricular Rate• Drugs used to decrease conduction in the AV node are useful in controlling ventricular rate in patients who have AF

• It is very important to control ventricular rate, not only to decrease symptoms, but also to prevent tachycardia-mediated ventricular cardiomyopathy

• Commenly used drugs are digitalis, beta blockers, calcium channel antagonists, and amiodarone.

• Beta blocker & Calcium channel blocker -The first-line agents for rate control

- Preferred over digoxin for rate control in patients who have not experienced heart failure. - Adrenergic blockers are also recommended in situations in which sympathetic tone is increased, such as thyrotoxicosis

• Digitalis - Adequately control the rate at rest but often does not provide adequate rate control during exertion. - Its use is appropriate in patients with systolic heart failure.

• Amiodarone

- Less frequently used for rate control than the other agents because of the risk of organ toxicity associated with long-term therapy.

- Amiodarone may be an appropriate choice for rate control if the other agents are not tolerated or are ineffective.

Rate control in WPW syndromeUse of agents that depress conduction over the accessory pathway.

In the acute setting, intravenous procainamide and ibutilide are the treatments of choice, unless the patient is unstable and requires urgent electrical cardioversion.

The use of drugs such as digoxin, calcium channel blockers, adrenergic blockers, and adenosine are contraindicated in this situation as they do not block conduction over the accessory pathway and may accelerate the ventricular response

Transthoracic Electrical Cardioversion• Many patient who has AF may be a candidate for transthoracic DC cardioversion.

• Certain characteristics predict poor success in maintenance of sinus rhythm

- Mitral valve disease - Very large left atrium - Patients who have AF of relatively long duration

• Antiarrhythmic drugs are frequently used to maintain sinus rhythm in patients undergoing transthoracic direct current (DC) cardioversion.

• Drug therapy should be considered before use of cardioversion in patients with long-standing AF (e.g., >3 months), to lessen the chance of early recurrence of AF in the first few days after cardioversion

Prevention of Thromboembolism• Prevention of stroke is key to the management of the condition of patients with AF

• warfarin is highly effective in reducing the incidence of ischemic stroke among patients with AF . Overall, a combined risk reduction of 68% is seen.

• Aspirin does not prevent thromboembolic complications as effectively as warfarin in patients with AF

Catheter Ablation• Success rates of more than 95% are attainable when the arrhythmia substrate is well defined, localized, and temporally stable.

• In contrast, the arrhythmia substrate of AF as yet is not well understood, usually is widespread, is variable between patients, and may be progressive.

• AF may recur more than 2 or 3 years after an initially successful ablation procedure.

• Indications for catheter ablation

- Young patients(< 35 yrs) with symptomatic AF that is affecting quality of life and that has not adequately responded to drug therapy. - The ideal candidate has lone AF or only minimal structural heart disease(such as normal left atrial size) - Patients with sinus node dysfunction in whom antiarrhythmic drug therapy is likely to create the need for a permanent pacemaker.

Surgical Approaches to Atrial Fibrillation• The most effective surgical procedure for AF is the “cut-and-sew” maze procedure developed by Cox in 1987.

• This operation involves 12 atrial incisions to isolate the pulmonary veins and to create lines of block in the left atrium and right atrium.

• In addition, the left and right atria are excised.

• Long-term freedom from AF after the Cox maze procedure has been reported to range from 70% to 95%, but 10% to 35% of patients still require antiarrhythmic drug therapy

• The Cox maze procedure has not been widely performed because it requires cardiopulmonary bypass, is technically difficult, and is associated with a mortality risk of approximately 1% to 2%.

References

• Braunwald's Heart Disease, 9th Edition.

• Topol Textbook of Cardiovascular Medicine, 3rd Edition.

• Harrison's Principles of Internal Medicine, 18th Edition.

Annamalai university