Download Lecture outline Mechanisms of AF Atrial Fibrillation Coarse - Pri-Med

AF Definitions
Lecture outline
 Definitions and causes of atrial fibrillation
 Rate control
 Prevention of thromboembolism
 Rhythm control
 Rate control vs rhythm control
 When to refer for ablation therapy
 Management of anticoagulation during surgery and
invasive procedures
 Paroxysmal: Episodes of AF usually recurrent, terminating within 7 days  Persistent: continuous AF lasting > 7 days
 Long‐standing persistent: AF lasting > 12 months  Permanent: No attempt to restore sinus rhythm in patient with long standing persistent AF
 Non‐valvular: AF without bio or mechanical valve or rheumatic mitral stenosis or mitral valve repair
 Lone AF: AF in young pts with no underlying cause
2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation
Mechanisms of AF
Atrial Fibrillation
Common arrhythmia, 0.4% of population
4.6% in age 70-79 and 8.8% in 80-89 yrs
Rapid, irregularly irregular rhythm
Some are asymptomatic
Palpitations, dyspnea, dizziness
Worsened angina, heart failure due to rapid
rate, loss of atrial contraction
 Tachycardia induced cardiomyopathy
 Thromboembolism – stroke
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2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation
Coarse Atrial Fibrillation
Fine Atrial Fibrillation
Atrial flutter
AF often missed with paced rhythm AF Rate control
AF Drug of choice for rate control
 Emergency DC cardioversion for patients with rapid ventricular rates and hypotension
 Beta blockers (metoprolol, esmolol) is drug of choice ‐ Avoid in COPD, decompensated HF
 Ca. channel blockers (diltiazem, verapamil) in COPD. Avoid in low EF, HFrEF.  Digoxin – slow acting, second line drug
 IV amiodarone if rate not controlled
 AV nodal ablation with pacemaker implant
 WPW – Cardioversion, procainamide, ibutilide for conversion; ablation, flecainide, propafenone for prevention
2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation
Left atrial appendage LA Appendage thrombus
Risk for systemic embolism
Risk reduction with warfarin
Anticoagualtion–Nonvalvular AF 
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Risk / benefit – shared decision making
Paroxysmal, persistent or permanent A FIB
CHADSVASC score 0: not indicated
CHADSVASC score 1: None or aspirin or AC
CHADSVASC score 2 or more: AC
Warfarin target INR 2.0 -3.0
Warfarin: Narrow therapeutic window, diet and drug
interactions, need for regular monitoring. But
compliance can be documented and reversal agents
available
2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation
New Oral Anticoagulants
 Direct thrombin inhibitor: dabigatran (RELY trial N Eng J Med 2007)
 Xa inhibitors: rivaraxoban (ROCKET AF trial (N Engl J Med 2011) and
apixaban (ARISTOTLE trial N Engl J Med 2011)
 Prevention of stroke and systemic embolism in non
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valvular A Fib, DVT, PE
Rapid onset of action, stable dynamics, few interactions –
no need for coagulation monitoring
Lower dose in renal failure
Do not use in ESRD, Cr clearance < 15 ml, hemodialysis
Do not use in mechanical valves; ? Bioprosthetic valve
New oral anticoagulants
 Superior on non‐inferior to warfarin in prevention of stroke + systemic embolism
 Rate of hemorrhagic strokes lower for all three drugs
 The rates of major bleeding were similar or lower  A small increase in MI with dabigatran
 Rapid onset and offset – no need for heparin bridging. Missing 1‐2 doses could be risky
 Limitations: high cost, lack of lab test to monitor therapy and assure compliance, lack of specific antidotes in the event of serious bleeding, except for dabigatran (Praxbind –
idarucizumab)
 No direct comparison in clinical trials New Oral Anticoagulants Gonsalves Mayo Clin Proc 2013; 88:495
Rate Control vs Rhythm Control
 Rate control: Control ventricular rate using AV blocking
drugs -  blocker, Ca blocker (diltiazem or verapamil) ,
digoxin. Anticoagulation (by risk score)
 Rhythm control: Maintain sinus rhythm with antiarrhythmic drugs, DC cardioversion, ablation, surgery;
Need drugs for rate control + anticoagulation (by risk
score)
 Neither strategy shown to be superior; Both strategies
can fail and patients may cross over
Rate Control vs Rhythm Control
 RCTs and Canadian data base show similar outcomes
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for both strategies – mortality, embolism
If sinus rhythm is successfully maintained, quality of life
and exercise capacity better
More hospitalizations with rhythm control
Rhythm control: episodes of AF common and often
silent. Other factors can cause embolism in sinus
rhythm: poor LAA contraction, aortic plaques, low EF.
Limited efficacy and adverse effects of AA drugs
AFFIRM N Engl J Med 2002; RACE N Eng J Med 2002; Canadian data base Arch Intern Med 2012
Choosing Rate vs Rhythm Control
Drugs for rhythm control
 Rate control: AF well tolerated, minimal symptoms;
elderly; severe LA enlargement, long standing AF,
co-morbidities that precipitate AF.
 Rhythm control: Difficult to control rate; symptoms
despite rate control; young; paroxysmal AF; first
episode of AF; precipitated by acute illness such as
hyperthyroid, pericarditis, PE, surgery; tachycardia
induced cardiomyopathy
2014 ACC AHA HRS Guidelines for management of A Fib
Electrical Cardioversion
Ablation for A Fib
 Contraindications: Digoxin toxicity and severe
 Electrical discharges from pulmonary veins 
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hypokalemia, hypomagnesemia
Anticoagulation 3 weeks before and at least 4 weeks
after. Longer if indicted by risk score
TEE guided cardioversion followed by anticoagulation
– difficult to rate control, symptoms, cardiomyopathy
Increases risk of embolism in the following 3 -10 days
Antiarrhythmic drugs generally not used after
cardioversion of first episode of AF
trigger A Fib, especially paroxysmal A FIB
 Abnormal left atrial substrate maintains A Fib
 Electrical isolation of the pulmonary veins from the left atrium – RF or cryo ablation
Ablation for A Fib
Ablation vs AA drug therapy
 Class I: Symptomatic paroxysmal A Fib, failure of at
 Ablation: procedural complications, PV least 1 anti arrhythmic drug
stenosis, cardiac perforation
 AA drugs: adverse effects, proarrhythmia
 In RCT for paroxysmal AF, freedom from AF was better (MANTR‐PAF) and recurrent atrial arrhythmias less with ablation (RAAFT‐2)  In patients with PAF who failed AA drugs, ablation reduced PAF episodes and improved quality of life compared to AA drugs (ThermoCool
 Class II a: Symptomatic persistent A Fib, failure of at
least 1 anti arrhythmic drug
 Class II a : Recurrent symptomatic paroxysmal A Fib
before trial of anti arrhythmic drug
 Best for younger patients, paroxysmal A fib, no
structural heart disease. Poor for elderly pts with long
standing persistent A fib with structural heart disease
 Inappropriate for pts who cannot be anticoagulated
AF) MANTRA‐PAF N Eng J Med 2012; RAAFT JAMA 2014; Thermocool JAMA 2010
Perioperative Management of warfarin ACCP Guidelines
Bridge with heparin in high risk patients
 Recommendations based on observational studies
 Stop warfarin 5 days pre‐op ‐‐> INR < 1.5
 Resume warfarin 12 – 24 hours post‐op
 Heparin bridge (therapeutic doses) for high or moderate risk patients. LMW Heparin preferred
 Bridging with heparin has not been shown to be effective in randomized controlled trials
Doketis et al Chest 2008
ACCP Guidelines Douketis et al Chest 2008
Stopping new oral anticoagulants for elective surgery
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No need for bridging with heparin Renal clearance – use lower doses with low GFR
Longer hold in renal failure and high risk surgery
Dabigatran ‐ hold 1‐2 days. In renal failure and high risk surgery 3‐4 days
 Rivaroxaban, Apixaban – hold 24 hours. In renal failure and high risk surgery 48 hours
 Restart post‐op after hemostasis is achieved
EHRA Practical Guide for NOAC – Europace 2013: 15:625
Douketis et al. New Engl J Med 2015; 373:823