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Healthcare professional information / Atrial Fibrillation

Atrial Fibrillation

Atria fibrillation (AF) was first described by Sir William Harvey in 17th century who observed chaotic motion of the atria in open chest animals. The ECG findings of AF were described in 1909 by Sir Thomas Lewis as "irregular or fibrillatory waves and irregular ventricular response" or "absent atrial activity with grossly irregular ventricular response".

Frequent questions from patients

If you have diagnosed AF in a patient, there are some questions that this patient may want to ask you.

  • What is the cause of my atrial fibrillation?
  • Will my condition disappear without treatment?
  • What are the risks that my condition will worsen?
  • Am I at increased risk of having a stroke?
  • What are my treatment options?
  • What are the risks/benefits of available treatment options?

Here, you can find the answers to these questions…

Prevalence of AF

2009 – The Heart and Stroke Foundation of Canada estimated that 350,000 Canadians have AF and they are about five times more at risk of having a stroke and twice more likely to die from a stroke than subjects without AF. Its prevalence is estimated to be 0.1% in individuals less than 50% and up to 10%-15% in elderly >80 years old.

Types of Atrial Fibrillation

Paroxysmal AF

Resolves spontaneously within 7 days.

Persistent AF

AF does not stop spontaneously within 7 days and require medications or electrical cardioversion for termination.

Permanent AF

AF persists despite pharmacological or electrical cardioversion or when rate control was selected.

Risk factors for Atrial Fibrillation

Most commonly, there is no apparent cause for AF ("lone" or idiopathic) AF. In other patients, AF may be related to other conditions, such as:

  • Age more than 60 years
  • Diabetes
  • High blood pressure
  • Coronary artery disease
  • Congestive heart failure
  • Structural heart disease (valve problems or congenital defects)
  • Cardiac or thoracic surgery
  • Thyroid disease
  • Chronic or acute lung disease
  • Sleep apnea
  • Obesity
  • Excessive alcohol or stimulant use
  • Serious illness or infection
  • High vagal tone (intensive aerobic exercise)

Clinical manifestations

Patients can be asymptomatic or have some symptoms that can range from

  • Lack of energy or tiredness
  • Palpitations
  • Dyspnea
  • Decreased exercise capacity
  • Dizziness, light headedness or fainting
  • Increased urination (due to increased secretion of atria natriuretic peptides)

More severe symptoms may include angina, hypotension, pre-syncope, syncope and symptoms of left or right-side heart failure.

Diagnostic tests

These tests can be used in the management of AF

  • Electrocardiogram (ECG)
  • The ECG demonstrates the lack organized atria activity (absence of p waves) and irregularly irregular cardiac rhythm.
  • Chest X-Ray to exclude pulmonary edema, associated lung disease or baseline for amiodarone therapy.
  • Holter monitor can be used to document paroxysmal AF and other types of arrhythmia.
  • Stress test to exclude underlying coronary artery disease and/or evaluate heart rate (HR) response to exercise.
  • Event monitor (recorder) that can be inserted under the skin to detect paroxysmal AF with rare episodes.
  • Trans-thoracic echocardiogram:  Ultrasound of the heart to provide detailed information on the functions of the heart and valves.
  • Cardiac computerized tomography (CT) or magnetic resonance imaging (MRI) - Specialized radiological imaging to exclude structural heart diseases.

Management of AF

Management of AF consists of primarily of

  • Prevention of thrombo-emboli
  • Rate/rhythm control
  • Control of heart rate
  • Hospitalisation or referral to emergency room is rarely necessary except for patients with associated unstable angina or heart failure.
  • Referral to arrhythmia specialists for young AF patients (<35 years="" without="" alcohol="" or="" drug="" use="" as="" precipitating="" factors="" ccc-2010="" li="">

Goals

  • Decrease symptoms, improve quality of life
  • Avoid excessive bradycardia/hypotension from rate/rhythm controlling medications
  • Prevent tachycardia-induced cardiomyopathy
  • For rhythm control, goal therapy should be improvement in patient symptoms and clinical outcomes, and not necessarily the elimination of all AF.

Prevention of Arterial Emboli in AF

AF patients are at 3-5 times increased risk of stroke compared to subjects of the same age without AF. Fifteen percent of strokes are due to AF (25% of strokes in elderly >80 years old).  Strokes in AF patients tend to be of greater severity and result in more permanent disability. Most AF patients should be anticoagulated unless they are at particularly high risk of major bleeding. Use of a risk score index for stroke (e.g. CHADS2) and for bleeding (e.g. HAS-BLED) are recommended to guide the decision to anticoagulate.

Systemic embolization of atrial thrombi can occur with any form of AF, either spontaneously or associated with cardioversion. Therefore, long-term anticoagulation is recommended for most of AF patients. Long-term anticoagulation is recommended for patients in whom normal sinus rhythm has been restored, but who remain at risk for CVA.

Prognostication for stroke risk with CHADS2 score

CharacteristicsScores
Congestive Heart Failure1
Hypertension1
Age ≥ 75 years1
Diabetes Mellitus1
Stroke/Transient Ischemic Accident/Thrombo-Embolus2

CHADS2 Scores
Stroke (%/year)
01.9 (1.2 - 3.0)
12.8 (2.0 - 3.8)
24.0 (3.1 - 5.1)
35.9 (4.6 - 7.3)
48.5 (6.3 - 11.7)

CHADS2-VASC has been proposed to improve identification of patients for thrombo-embolic stroke.

CHADS2-VASC

CharacteristicsScores
Congestive Heart Failure1
Hypertension1
Age ≥ 75 years2
Age between 65 and 74 years1
Stroke/Transient Ischemic Accident/Thrombo-Embolus2
Vascular disease (previous MI, peripheral arterial disease or aortic plaque)1
Diabetes Mellitus1
Female1

The score CHADS-VASC has been endorsed by the European Society of Cardiology and anticoagulation is recommended in patients with CHADS-VASC of 2.  The Canadian Cardiovascular Society 2012 recommends a modified use of this score as detailed in the following section.

Canadian Cardiovascular Society Guidelines for Anticoagulation - 2012

WITHOUT Coronary Artery Disease

  • Patients with CHADS2 score of 0 and without any of these clinical factors (woman, vascular disease and ≥65 years) do not need any treatment.
  • Patients with CHADS2 score of 0 and with one of these clinical factors (woman, vascular disease) can receive only aspirin (75 mg-325 mg).
  • Patients with CHADS2 score of 0 and  ≥ 65 years old or female with vascular disease should be anticoagulated (preferably with the new oral anticoagulant than with warfarin).
  • Patients with CHADS2 score of 1 need oral anticoagulants (new oral anticoagulants preferable to warfarin).  Aspirin may be indicated in some patients depending on risk/benefit ratio.
  • Patients with CHADS2 score of ≥ 2 need oral anticoagulants (new oral anticoagulants preferable to warfarin).

WITH STABLE Coronary Artery Disease

  • Patients with CHADS2 score of 0 only need ASA.
  • Patients with CHADS2 score of ≥ 1 need oral anticoagulants (new oral anticoagulants preferable to warfarin).  No need for additional aspirin.

WITH RECENT Percutaneous Coronary Artery Disease or recent Acute Coronary Syndromes

  • Patients with CHADS2 score of ≤1 can receive aspirin+clopidogrel.
  • Patients with CHADS2 score of ≥ 2 should receive aspirin+clopidogrel + oral anticoagulants

Special Considerations

  • The dose of dabigatran 150 mg po bid is generally preferable to a dose of 110 mg po bid, in most patients except elderly (especially ≥80 years old) or creatinine clearance between 30-50ml/min)
  • All patients should have renal function evaluated at least annually.
  • For patients with estimated glomerular filtration of 15-30 ml/min, anticoagulation should be according to the above guidelines (warfarin preferable to novel oral anticoagulants)
  • For patients with estimated glomerular filtration of less than 15 ml/min, anticoagulation may be withheld unless there is strong risk of thrombo-emboli.

Before cardioversion

  • Hemodynamically stable patients with AF or atria flutter of known duration < 48 hours may undergo cardioversion without prior anticoagulation, if there is absence of atria clot on transeosphageal echocardiogram. However, if the patient is at high risk of stroke (such as mechanical valve, rheumatic heart disease, recent stroke or TIA), cardioversion should be delayed and the patient should receive OAC for 3 weeks before and at least 4 weeks following the cardioversion (CCS guidelines 2010).

Following cardioversion

  • FIf AF or atria flutter persists or recurs, antithrombotic therapy should be continued indefinitely with either OAC or aspirin as appropriate.
  • If sinus rhythm is achieved and sustained for 4 weeks, the need for ongoing antithrombotic therapy should be based upon the risk of stroke (CHADS2)

Peri-operative management

  • If there is a very low to moderate risk of stroke (CHADS2 ≤ 2), the patient should have oral anticoagulant (OAC) discontinued before the procedure (aspirin or clopidogrel for 7-10 days, warfarin for 5 days if the INR was in the range 2- 3, and dabigatran for 2 days). Once post-procedure haemostasis is established (about 24 hours), OAC can be reinstated.
  • If there is a particularly high risk of stroke (e.g. prosthetic valve, recent stroke or TIA, rheumatic valve disease, CHADS2 >=3) the patient should have OAC therapy continued perioperatively or have their OAC discontinued before the procedure and be bridged with heparin perioperatively.

Sans Maladie Coronarienne

Anticoagulation in patients with coronary artery disease

Reproduced with permission from www.ccs.org

The following risk score for bleeding has been endorsed by CCS 2012 to identify patients at increased risk of bleeding. If HAS-BLED ≥3 or HAS-BLED greater than CHADS2, patients are at increased risk of bleeding; PRECAUTION with anticoagulation.

HAS-BLED SCORE

CharacteristicsScores
Hypertension (Systolic ≥ 160mmHg)1
Abnormal renal or liver function1 or 2
Previous Stroke1
Bleeding history or predisposition1
Labile INRs1
Elderly ≥ 65 years1
Concomitant Drug or alcohol intake1 or 2

Bleeding risk associated with HAS-BLED score

HAS-BLED Scores Major bleeds (%/year)
01.13
11.02
21.88
33.74
48.70
512.5

Dabigatran, a new oral anticoagulant

Dabigatran is an oral direct anti-thrombin, commercialized under the name of Pradax© and available at 75 mg, 150 mg and 110 mg in Canada. Only the doses of 110 and 150 mg are approved for AF in Canada.

Mechanism of Action

It is a specific and direct thrombin inhibitor that inhibits both free and fibrin-bound thrombin.

Administration

Dabigatran can be taken with foods or on empty stomach. Food does not decrease the bioavailability of dabigatran but delays time-to-peak plasma of 2 hours. The whole capsule should be swallowed. It SHOULD NOT be broken or chewed.

Switch FROM parenteral anticoagulants

Dabigatran should be started 2 hours before the next dose of parenteral anticoagulant.

Switch TO parenteral anticoagulants
Start parenteral anticoagulant 12 hours after the last dose of Dabigatran.
Switch FROM oral vitamin K antagonists
Dabigatran should be started when the INR is <2. br="">
Switch TO oral vitamin K antagonists
Commencer le traitement par l’anticoagulant parentéral 12 heures après la dernière dose de dabigatran, et 24 heures après la dernière dose si la clairance de la créatinine est < 30 ml/min.
  • If creatinine clearance > 50 mL/min, start warfarin 3 days before stopping dabigatran. 
  • If creatinine clearance is between 31-50 mL/min, start warfarin 2 days before stopping dabigatran.
  • If creatinine clearance is between 15-30 mL/min, start warfarin 1 day before stopping dabigatran.
  • If creatinine clearance is less than 15 mL/min, no official recommendation can be made.

Dabigatran can alter INR, so INR only reflects accurately the effect of warfarin only when dabigatran has been stopped for more than 2 days.

Missed dose
The forgotten (missed) dose should be taken as soon as possible on the same day, up to 6 hours prior to the next scheduled dose.  Within 6 hours of the next scheduled dose, a forgotten dose should be omitted. Patients should not take a double dose to make up for missed individual doses.  For optimal effect and safety, dabigatran should be taken at approximately 12 hour intervals.

Overdose or reversal of the effect of dabigatran in case of severe bleeding

  • Activated charcoal can be used when ingestion is ≤2 hours.
  • Consider transfusion of fresh frozen plasma, fresh whole blood, recombinant factor VII or concentrates of II, IX or X such as Octaplex.
  • Dialysis may also be considered (dabigatran may be cleared within 6-8 hours, limited data supporting this approach).
  • Desmopressin 0.3 mcg/kg IV in 30 minutes (Max dose: 20 mcg) if patient is also on antiplatelets

Monitoring Parameters

Dabigatran does not require INR monitoring. In patients with suspected excess activity of dabigatran (either asymptomatic or bleeding), aPTT>80 sec before the next dose reflects increased bleeding risk.

Side effects

  • Major and minor bleeding complications
  • Dyspepsia (4%)
  • GI haemorrhage, gastritis (1%)
  • Abnormal liver function tests (<1%)
  • Thrombocytopenia (<1%)
  • Rare allergic reactions (urticaria, bronchospasm, anaphylaxis)

Contraindications

  • Severe renal impairment (Clcr <30 ml="" minute="" li="">
  • Bleeding diathesis
  • Cerebral infarction or bleeding < 6 months.
  • Concomitant treatment with ketoconazole and other strong P-glycoprotein inhibitors such as itraconazole, tacrolimus, cyclosporine, ritonavir, tipranavir, nelfinavir and saquinavir.
  • Hypersensitivity with dabigatran
  • Peptic ulcer disease with active or previous bleeding

Drug interactions

  • P-glycoprotein inhibitors such as verapamil, quinidine and amiodarone may increase dabigatran concentration.
  • Strong P-glycoprotein inducers such as rifampicin, carbamazepine and St-John wort can reduce dabigatran concentration
  • Antacids may decrease the absorption of dabigatran. Dabigatran should be taken at least 2 hours before an antacid.
  • Other drugs such as proton pump inhibitors may also decrease the absorption of dabigatran by increasing gastric acid.

Peri-Operative Precautions

  • In patients at high risk of bleeding or with major surgery, dabigatran should be stopped 2-4 days and longer in patients with mild or moderate renal insufficiency.  Parenteral peri-operative anticoagulation may be considered for patients at high risk of thrombo-embolic events.
  • For other patients, dabigatran should be hold at least 12-24 hours before any invasive intervention. 
  • For patients who had undergone peri-operative spinal/epidural anaesthesia, the first dose of dabigatran should not be given less than 2 hours after removal of the spinal catheter and only after adequate haemostasis has been obtained.

Special Populations

  • Not recommended in patients younger than 18 years (insufficient data on safety and efficacy)
  • Not recommended in pregnant and nursing women
  • Reduced dose of 110 bid is recommended for patients older ≥80 years and for patients at increased bleeding risk
  • Dabigatran should be used with caution in patients of low body weight (<50 kg="" li="">

Rate/Rhythm control

The choice of rate or rhythm control strategy depends on the severity of the symptoms, impact of AF on quality of life, impact on cardiac function. The following table summarizes the recommendation of CCS 2010 on selection of the appropriate rate/rhythm strategy.

Favors Rate ControlFavors Rhythm Control
Persistent AFParoxysmal AF
Newly Detected AF
Less SymptomaticMore Symptomatic
> 65 years of age< 65 years of age
HypertensionNo Hypertension
No Hystory of Congestive Heart FailureCongestive Heart Failure clearly exacerbated by AF
Previous AntiarrhythmicNo Previous Antiarrhythmic
Drug FailureDrug Failure

www.ccs.ca with permission

Pour le contrôle du rythme, CCS 2012 recommande la stratégie suivante:

Left ventricle ejection fraction <35%: Amiodarone

Left ventricle ejection fraction ≥35% : Amiodarone, Sotalol (to use Sotalol with precaution in patients with left ventricle ejection fraction  35%-40% or with one of the following risk factors for torsade de pointe : woman, age >65 ans, or taking diuretics.

Dronedarone should not be used in patients with heart failure or left ventricular ejection fraction ≤40%.  Dronedarone should be used with caution with digitalis (significant increases in digoxin level).  Dronedarone is a reasonable choice for selected patients (such as patients with paroxysmal AF with minimal structural heart disease).  Monitoring of liver function test is suggested within 6-month of dronedarone initiation.

For rhythm control strategy, CCS 2012 guidelines recommend the following strategies:


www.ccs.ca with permission

Recommendations for catheter ablation- Canadian Cardiovascular Society - 2010

Catheter ablation consists of creating linear "scars" around the foci of the atria fibrillation (near the pulmonary veins), thus preventing AF waves from disseminating across the atria.

Indications

Catheter ablation consists of creating linear "scars" around the foci of the atria fibrillation (near the pulmonary veins), thus preventing AF waves from disseminating across the atria.

In summary, catheter ablation can be considered for AF patients whose heart rate remains sub-optimally despite rate/rhythm control medications or patients with side effects or intolerance to medications.

The long-term efficacy of catheter ablation still requires further study. The majority of patients have 1-year or more freedom from recurrence of AF. However, patients who have undergone catheter ablation were highly selected with the majority of patients having normal size or mildly dilated atria, normal or mildly reduced ventricular function, and absence of severe pulmonary disease.   There is little information on the long-term success in patients with heart failure and other advanced structural heart disease.  These patients may be more likely to have AF recurrence. Therefore, it remains unclear whether the long-term effectiveness of catheter ablation, as shown in previous trials, can be extrapolated to most AF patients.

Following catheter ablation, AF can still recur without symptoms and be unrecognized by the patient or physician. Long-term anticoagulation is still recommended for patients at increased risk for stroke (CHADS2 ≥1) following successful catheter ablation.

Rate Control - CCS 2010 et 2012

  • Aim for resting heart rate of less than 100 per minute.

  • Initial therapy: Beta-blockers or non-dihydropyridine calcium blockers

  • Beta-blockers are recommended for patients with previous myocardial infarction or with heart failure.

  • Calcium-blockers are recommended for patients with hypertension or significant pulmonary diseases.

  • Digitalis should not be used as initial therapy for active patients.

  • Digitalis can be added to other agents in patients with heart failure, inadequate rate control by other agents.

  • Dronedarone should not be used for rate control.

  • Amiodarone use for rate control should be reserved only for exceptional patients with inadequate rate control by other agents.

Selected References

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