ATRIAL FIBRILLATION BACKGROUND. Contributors: Dr Gowri Doraisamy. Advisor: Dr Seow Swee Chong

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1 03 ATRIAL FIBRILLATION Contributors: Dr Simon Lee Dr Gowri Doraisamy BACKGROUND Aetiology Clinical Presentation Clinical Evaluation Diagnosis Investigation Principles of Management INR Targets Stroke Risk Stratification using CHADS2 score Management of Atrial Fibrillation in the Outpatient Setting Anticoagulation Protocol in NHGP Contraindications to Warfarin Drug / Food Interactions Monitoring Using INR Advisor: Dr Seow Swee Chong 33 nhg_guideline_40200_2.indd 33

2 ATRIAL FIBRILLATION Atrial Fibrillation Background 0.5% to % of general population Prevalence increases with age 0.% among those < 55 years old, 5% of those 65 years old and 0% of those 80 years old Associated with increased risk of systemic thrombo-embolism and ischaemic stroke Anti-thrombotic therapy in AF patients significantly decreases the stroke risk Aetiology ) Cardiac Common Hypertension Heart Failure Valvular Heart Disease Sick Sinus Syndrome Lone Atrial Fibrillation Cardiomyopathy Post Cardiac Surgery Less Common Pericarditis & Myocarditis Cor Pulmonale Pre-excitation Syndrome Tachycardia Induced Cardiomyopathy Atrial Septal Defect Acute Pulmonary Embolism 2) Non - Cardiac Alcohol Thyrotoxicosis Sepsis Other intra-thoracic abnormalities Clinical Presentation Asymptomatic up to 25% Palpitations Chest Pain Dyspnoea Fatigue Light-headedness Heart failure Stroke 34 nhg_guideline_40200_2.indd 34

3 Atrial Fibrillation ATRIAL FIBRILLATION Clinical Evaluation Confirm diagnosis of AF Determine if patient has symptomatic AF Determine frequency and duration of AF episodes Determine underlying aetiology or precipitating factors Determine adequacy of ventricular rate control Determine risk of complications from AF. Basic Evaluation History and physical examination Electrocardiogram (ECG) Chest X-ray (CXR) Full blood count (FBC) Serum electrolytes Thyroid function test (TFT) Trans-thoracic 2-D echocardiogram 2. Additional Investigations Holter monitoring Trans-telephonic event recorder Exercise stress testing Trans-oesophageal echocardiogram Electrophysiological study Diagnosis Pulse irregular in both rhythm and rate ECG absence of P waves, irregular undulating baseline (AF waves), variable R-R interval Evidence of pre-excitation (e.g. delta wave) and aberrant conduction (e.g. wide QRS complexes) should also be sought Investigation Stable patients with chronic AF who are not candidates for cardioversion and who have acceptable ventricular rate at rest (eg /min) may be managed in the outpatient setting Apart from an ECG, serum electrolytes and thyroid function tests are recommended for these patients to exclude a correctable underlying cause Many AF patients, however, require referral to the Emergency Department or direct hospital admission for urgent cardiac assessment and monitoring. They include: Patients with serious acute underlying medical conditions, such as suspected myocardial ischaemia or infarction, or heart failure; Patients who are symptomatic or present with impaired haemodynamic status as a result of AF; Patients with a fast ventricular response rate, or in whom pre-excitation through an accessory conduction pathway is suspected; Patients who develop a complication of AF, such as an embolic stroke or a systemic embolic event; and Patients with acute onset of AF within the preceding 48 hours who are judged to be candidates for urgent cardio-version 35 nhg_guideline_40200_2.indd 35

4 ATRIAL FIBRILLATION Atrial Fibrillation Principles of Management The aims of management of AF include: ) Control of Ventricular Rate (recommended strategy for majority of patients with AF) Beta-blockers (e.g. propranolol, metoprolol, atenolol) Calcium antagonists (e.g. diltiazem, verapemil) (Beta blockers and calcium antagonists have faster rate of onset and better control of exertion induced tachycardia than digoxin) Digoxin in patients with LVF or heart failure IV amiodarone for rate control in the acute setting Criteria for rate control: beats/min (at rest) beats/min (during moderate exercise) All three groups of agents are contraindicated in AF associated with pre-excitation in Wolff-Parkinson- White Syndrome 2) Restoration and Maintenance of Sinus Rhythm these aspects of management involve specialist knowledge and skills, and should be performed by cardiologists. Generally, ventricular rate control is adequate for the majority of patients with AF. Maintenance of sinus rhythm is beneficial only in those with symptomatic AF. 3) Stroke Prevention Prophylaxis against thromboembolism is the cornerstone of therapy for AF and should be considered regardless of whether a rate control or rhythm control strategy is chosen. The decision on whether to use warfarin or an antiplatelet agent (eg. aspirin) depends on the individual patient s risk as determined by the CHADS 2 score. INR Targets Paroxysmal AF should be treated as for patients with chronic AF. For patients who are contraindicated for warfarin (e.g. significant bleeding or fall risks, active peptic ulcer disease, or patients unlikely to comply with the diet and monitoring regimens required in warfarin therapy), long-term anti-platelet therapy should be given instead. Stroke Risk Stratification using CHADS 2 Score C H A D S 2 CHADS CONDITIONS Congestive Heart Failure Hypertension (or treated hypertension) Age > 75 years Diabetes Prior stroke or TIA SCORE ANNUAL STROKE RISK POINTS 2 95% CI nhg_guideline_40200_2.indd 36

5 Atrial Fibrillation ATRIAL FIBRILLATION Treatment Recommendations using CHADS 2 Score CHADS 2 Score Risk Anticoagulation Therapy Considerations 0 Low Aspirin 00 mg/day although lower doses may be similarly efficacious Moderate Aspirin or Warfarin Aspirin daily or warfarin at target inr of , depending on factors such as patient preference 2 Moderate or High Warfarin Warfarin at target INR of , unless contraindicated (eg. history of falls, clinically significant GI bleeding, inability to obtain regular I inr screening). Note: - Warfarin is recommended for patients with AF who also have a metallic prosthetic heart valve - In elderly patients >75 years of age, or in those deemed to be at higher bleeding risk, a lower INR target of may be chosen instead, balancing the risks and benefits of anticoagulation 37 nhg_guideline_40200_2.indd 37

6 ATRIAL FIBRILLATION Atrial Fibrillation Management of Atrial Fibrillation in the Out-Patient Setting In the case of any uncertainty, the family physician should contact the cardiologist or the neurologist on-call for further discussion and advice. Irregular Pulse 2 Lead ECG AF Confirmed Not AF Urea & Electrolytes Tyroid Function Test Aspirin 300mg stat, 00mg om Consider Rate Control Unstable CV Status Myocardial Ischaemia Stroke / Embolism Stable Onset < 48 hrs Stable Onset > 48 hrs No Cardiac Assessment Stable Known AF Cardiac Assessment To A&E immediately To A&E or same day Direct Access Clinic Cardiac Referral Manage in Primary Care Finalize Rate Control Medication Assess Stroke Risk using CHADS 2 score CHADS 2 score = 0 CHADS 2 score = CHADS 2 score 2 Aspirin or other antiplatelet agent Aspirin or Warfarin Warfarin at target INR of nhg_guideline_40200_2.indd 38

7 Atrial Fibrillation ATRIAL FIBRILLATION Anticoagulation Protocol in NHGP Initiation of warfarin usually done in hospital setting Re-initiation of warfarin to be performed only by FP or designated FD with 5 years experience Adjustment of dosage needs to be approved / countersigned by FP or designated FD For Anticoagulation Clinic (ACC), FP will work in collaboration with pharmacist in the shared-care follow-up of these patients Contraindications to Warfarin Patients should not continue with warfarin if they present with a history of the following: Aneurysm (cerebral or dissecting) Active bleeding disorder Cerebral vascular haemorrhage (confirmed or suspected) Blood dyscrasias associated with haemorrhage or thrombocytopaenia Severe uncontrolled hypertension Recent (2-3 weeks) trauma (especially to the CNS), or neurosurgery Ulceration or active lesions of the GIT, respiratory or urinary tracts Severe vasculitis Pregnancy (st trimester and before delivery) Other factors making warfarin therapy unsuitable are: Alcohol abuse At high risk of falls Poor family support / inability to return for regular INR monitoring Non-compliance with medication Mentally unstable patient Caution should be exercised in the following conditions which are associated with increased sensitivity to warfarin: Age > 75 years Clinical congestive cardiac failure Drug interactions e.g. drugs which inhibit warfarin metabolism. Elevated baseline INR Hypermetabolic states Liver or renal impairment Malnutrition / low vitamin K intake Thyrotoxicosis 39 nhg_guideline_40200_2.indd 39

8 ATRIAL FIBRILLATION Atrial Fibrillation DRUG / FOOD INTERACTIONS Drugs with Major Interactions with Warfarin INCREASE Effect of Warfarin Antiplatelets Aspirin Clopidogrel Dipyridamole Analgesics NSAIDs COX-2 inhibitors Paracetamol (>2g/day > few days) Tramadol Antibiotics / Antifungals Bactrim Macrolides Quinolones Metronidazole Azole antifungals Isoniazid Cardiac drugs Amiodarone Antilipids (fibrates, statins) Diltiazem Antidepressants SSRIs Tricyclic antidepressants Anticonvulsants Phenytoin (biphasic effect) Others Cimetidine Progestogens Tamoxifen Thyroxine Omeprazole DECREASE Effect of Warfarin Antibiotics / Antifungals Rifampicin Griseofulvin Anticonvulsants Carbamazepine Phenytoin (biphasic effect) Others Antithyroid drugs Azathioprine Barbiturates Cholestyramine Influenza vaccine 40 nhg_guideline_40200_2.indd 40

9 Atrial Fibrillation ATRIAL FIBRILLATION Warfarin-Food Interactions Foods rich in Vitamin K decrease effect of warfarin Green leafy vegetables (e.g. spinach, broccoli, lettuce, brussels sprouts), certain legumes, some vegetable oils (e.g. soybean oil), animal livers, some fermented foods (e.g. cheese), green tea Monitoring Using INR Repeat INR every to 2 weeks for every dose adjustment. When target INR is achieved, next INR may be checked after 4 weeks and subsequently every 8 weeks. Foods with anti-platelet effect Garlic, foods containing salicylates (fruits, vegetables, spices, teas, certain flavoured candies) Others Avocado (decrease effect of warfarin), Vitamin E (potentiate effect of warfarin), dietary supplements (arnica, bilberry, butchers broom, cat s claw, dong quai, feverfew, forskolin, garlic, ginger, ginkgo, horse chestnut, inositol hexaphosphate, licorice, melilot (sweet clover), pau d arco, red clover, St John s wort, sweet woodruff, turmeric, willow bark, wheat grass, alcohol (continuous heavy drinking stiumulates hepatic enzymes, increasing metabolism of warfarin, decrease effect of warfarin) References. Prystowsky EN et at (996): Management of patients with atrial fibrillation. A statement for healthcare professions from the Subcommittee on Electrocardiography, American Heart Association. Circulation 93: Albers GW et al (200): Antithrombotic therapy in atrial fibrillation, Sixth ACCP Consensus Conference on Antithrombotic Therapy. Chest 9: 94s-206S. 3. Gage BF et al (200): Validation of clinical classification schemes for predicting stroke. Results from the national registry of atrial fibrillation. JAMA 285: Management of AF MOH Clinical Practice Guidelines (Aug 2004) 4 nhg_guideline_40200_2.indd 4