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Atrial Fibrillation

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Atrial Fibrillation

  1. 1. Atrial Fibrillation
  2. 2. A Fib • Atrial fibrillation (AF) is the most common cardiac arrhythmia • Prevalence increases with age - 1 in 5 people over the age of 85 years having the condition, compared to <1% of people younger than 60 years • Spontaneous discharge by ectopic pacemaker cells in large pulmonary veins @ point where they join LA
  3. 3. Pathophysiology • Chaotic electrical discharge in the atria of the heart from ectopic foci • Cause an irregular, rapid atrial contraction • Leads to rapid ventricular conduction via AV nodal conduction
  4. 4. Features • RR intervals follow no repetitive pattern— they have been labeled as “irregularly irregular.” • While electrical activity suggestive of P waves is seen in some leads, there are no distinct P waves • ”cherche la P!”
  5. 5. Causes • IHD • Valvular Disease (MS/MR/Mitral Prolapse) • HTN • CCF/LV Failure C2H5OH COPD Idiopathic Thyrotoxicosis OSA Infection – Pneumonia HOCM PE
  6. 6. Sx • Asymptomatic! • Palpitations • Irreg Irreg Pulse • Heart Failure • Syncope • Dizziness • Lethargy • SOBOE • ACS/Angina • Systemic emboli – CVA, – Mesenteric ischaemia, – PVD/Leg ischaemia
  7. 7. Main complications : Systemic emboli Heart failure • Systemic emboli are mainly to the cerebrum are due to irregular haemodynamic flow through the left atrium. • Predisposes to thrombus formation • Assoc with 16% of all strokes
  8. 8. • Atrial fibrillation also leads to loss of atrial contraction at the end of diastole, which in elderly people with reduced ventricular compliance, can lead to reduced stroke volume and thus reduced cardiac output, predisposing to the development of heart failure • Atrial fibrillation is present in up to 50% of patients with heart failure
  9. 9. Classification • Paroxysmal: Terminates spontaneously in less than 7 days (usually <24h) • Persistent: Sustained greater than 7 days and rarely terminates spontaneously • Permanent: Cardioversion has failed or the restoration of sinus rhythm is no longer possible
  10. 10. Ix • Hx & Examination – CVS Risk Factors • Apical Pulse Rate > Radial Pulse Rate • Bloods – FBC, SMAC, CRP, BNP, TFTs, TropTs • ECG – Absent P waves, Irreg QRS, Irreg Baseline, QT interval, LVH, LBBB/RBBB • Echo – Valve, Atrium Size • TOE – Look for Thrombus • Holter - Paroxysmal
  11. 11. ESC, AHA & NICE Acutely unwell with rapid ventricular rate and acute symptoms need: i) urgent rate control treatment via oral or IV pharmacological intervention and/or i) emergency DC (electrical) cardioversion to restore normal sinus rhythm (NSR)
  12. 12. OPD Setting • Outpatient initiation of antiarrhythmic drug therapy with the following agents may be considered: • Flecainide or propafenone in patients in sinus rhythm who have no underlying structural heart disease, normal baseline QT intervals, and no profound bradycardia or suspected sinus or AV node dysfunction. • Amiodarone or dronedarone in selected patients who have no other risk factors for torsades de pointes (eg, hypokalemia, hypomagnesemia) or sinus node dysfunction or AV conduction disease. Dronedarone and amiodarone are the only two drugs that can be initiated in outpatients while in atrial fibrillation.
  13. 13. Decision for Inpatient • The decision to hospitalize depends upon several factors: i. The presence and severity of structural heart disease. ii. The indication for treatment (eg, etiology of the arrhythmia and type and severity of associated symptoms). Treatment for ventricular tachycardia is usually started in the hospital. iii.The drug used. For example, the labeling information for dofetilide and sotalol specify inpatient initiation, while flecainide, propafenone, dronedarone, and amiodarone can generally be initiated outside the hospital in appropriate patients.
  14. 14. New onset atrial fibrillation
  15. 15. Reasons to not cardiovert Circumstances in which it is reasonable to avoid cardioversion attempts in patients with new onset AF include: •Patients who are minimally symptomatic, particularly those with multiple comorbidities or poor overall prognosis, where the risks of undergoing cardioversion and/or pharmacologic rhythm control may outweigh the benefits of restoring sinus rhythm. There is no age cut-off for the restoration of sinus rhythm, but the benefit from cardioversion begins to decline as age increases after 80.Patients with a low likelihood of maintenance of sustained SR (see below). •Patients with paroxysmal AF are usually not cardioverted, as the AF is often of short duration, resolves spontaneously, and almost always. The following factors decrease the likelihood of success of immediate conversion as well as long-term maintenance of SR; they should be considered when deciding whether to perform a cardioversion: •AF has been present continuously for more than one year [1-8] •The left atrium is markedly enlarged (atrial dimension >5.0 cm) [9-13] •Elderly (>80 years of age) [2] •Associated cardiovascular conditions (eg, left ventricular dysfunction) [2] •Patients who had recurrence while taking adequate doses of appropriate antiarrhythmic drug therapy. Drug refractory patients may be able to be converted to SR but are less likely to maintain SR long term. •Cardioversion with maintenance of SR is likely to be unsuccessful if the cause (thyrotoxicosis, pericarditis, and mitral stenosis) for the AF has not been corrected prior to attempted cardioversion.
  16. 16. If haemodynamically stable and few symptoms: • slow heart to a normal range using rate control • use adequate anticoagulation therapy to prevent emboli forming • Then long term management strategy is chosen depending on the patient’s circumstances
  17. 17. • 1st episode atrial fibrillation of <48 hours onset in well patients with mild symptoms, can be treated with pharmacological or DC cardioversion, with IV heparin prophylaxis for thrombus formation. • Once NSR is restored, 4 weeks of OAC may be necessary in a patient with an increased risk of thrombus formation. • This may be extended to long term OAC if risk is significantly high.
  18. 18. • If it cannot be determined that onset is <48 hours, a transoesophageal echocardiograph may be performed to detect the presence of a LA thrombus. • If none is present, immediate cardioversion may be carried out, or 3 weeks of therapeutic OAC to give an INR 2-3 may be carried out first before cardioverting. • If a thrombus is detected on TOE and is still present after 3 weeks OAC therapy, rate control and long term OAC is deemed to be the most suitable treatment
  19. 19. Management of persistent/permanent atrial fibrillation • Traditionally been one of either rate or rhythm management • NICE, ESC and AHA guidelines recommendation are for 1st line management are:
  20. 20. Examples of rhythm controls (according to efficacy of cardioversion): a) Emergency cardioversion Flecainide (most efficient for emergency cardioversion). Propafenone (2nd most efficient for em. cardioversion) *Ibutilide. (b) Maintenance of NSR Amiodarone (use if structural heart disease. Delayed pro-arrhythmic hence least efficient for emergency cardioversion but most efficient for maintenance of NSR, and rapid ventricular rate control). Dofetilide (rarely used for cardioversion but maintenance of NSR) . Less effective for cardioversion and maintenance: Sotalol Dronedarone Newer agents: *Vernakalant. Examples of rate controls: Beta blockers (acute: metoprolol, propanolol, esmolol, chronic: also **atenolol, **nadolol). Calcium blockers (Verapamil, diltiazem). Digoxin (use if sedentary. Controls HR at rest, can be used in combination with BB or ?CB). Amiodarone (best avoided due to severe side effects, rapid ventricular control but can promote cardioversion, consider if all the above fails). MgSO4 (little evidence, under trials). *IV only ** long half life so can be given OD
  21. 21. OAC & A Fib • AFFIRM and RACE trial data of rate vs rhythm control of A Fib regarding ischaemic stroke emphasizes the need for OAC therapy in patients being treated for atrial fibrillation. • In AFFIRM & RACE a trend towards reduction in ischaemic strokes in the rate control branch of both studies was due to maintained OAC and an INR therapeutic range of 2-3 in those on rate therapies
  22. 22. CHADS2 Score
  23. 23. CHADS2 • Aspirin is recommended for patients scoring 1 on the CHADS2 score, or those in whom warfarin is contraindicated. • Patients scoring > 1 are recommended for anticoagulation using warfarin • Usually anticoagulation is recommended as long term treatment. • Warfarin treatment with an INR = 2-3,has been shown to reduce the risk of stroke by 65-68% when compared to placebo, and 32-47% when compared to aspirin
  24. 24. • Aspirin in turn resulted in a 21% reduction in strokes when compared to placebo. • Warfarin & aspirin combined therapy should not be used as it increases haemorrhage risk significantly • Warfarin vs combined therapy or low dose aspirin + clopidogrel (75mg/75mg) in patients with atrial fibrillationshowed warfarin to have a significantly lower annual rate of mortality & morbidity [RR 0.69 (95% C.I 0.57-0.85)].
  25. 25. • Aspirin monotherapy vs combined Aspirin/Clopidogrel in atrial fibrillation patients when warfarin is contraindicated showed a significant decrease in mortality and morbidity in the combination group [RR 0.72 (95% C.I. 0.81-0.98)] but a significant increased risk in incidence of major bleed (2% vs 1.3%) [RR 1.57 (95% C.I. 1.29-1.92)] • Therefore it is reasonable to say that dual therapy of aspirin and clopidogrel is a suitable alternative to aspirin monotherapy in patients with atrial fibrillation who are at high risk of stroke and in whom warfarin is contraindicated
  26. 26. ESC Guidelines • ESC guidelines, while acknowledging the benefit of CHADS2 scoring system, prefer not to classify stroke risk as “low”, “moderate” and “high”, as risk is seen as something which is a continuum • CHADS2 does not include many stroke risk factors, and other ‘stroke risk modifiers’ which must also be considered when starting OAC, such as vascular disease and sex. • CHA2DS2VASc!
  27. 27. Bleed Risk assessment before start of OAC • HAS-BLED score assesses bleeding risk in AF patients, with a score of ≥3 indicates ‘high risk’. • Cautious initial dosing and regular review of the patient is needed following the initiation of antithrombotic therapy, whether with warfarin or aspirin.
  28. 28. HAS BLED
  29. 29. Drug-resistant AF • Some patients are refractory to individual antiarrhythmic agents plus an AV nodal blocker or develop side effects on doses necessary for arrhythmia prevention. Although some have suggested that combination antiarrhythmic drug therapy (eg, a class IC agent with sotalol or amiodarone, often in lower doses) may be an alternative, there are limited data to support such an approach and the patient may be exposed to a greater risk of proarrhythmia and other side effects. • As a result, combination antiarrhythmic drug therapy is not recommended. Such patients can be treated with a rate control strategy or referred for nonpharmacologic therapy to prevent recurrent AF including surgery (such as the maze operation), radiofrequency ablation (such as pulmonary vein isolation), or an implantable atrial defibrillator. • Surgical approaches that are available include the maze and corridor operations as well as radiofrequency or cryoablation. These procedures appear effective in a high percentage of patients. However, the follow-up for many of these studies was limited in scope and did not employ very rigorous arrhythmia surveillance. • Long-term anticoagulant therapy is required in many patients after successful treatment of AF with these surgical approaches. • Patients with recurrent AF after one of these procedures may be candidates for electrophysiology study and catheter ablation.
  30. 30. Future A Fib Mx and OACs • Current anti-arrhythmics show no superiority to rate control therapies due to their pro- arrhythmic and tissue toxic side effects. • Dronedarone is an anti-arrhythmic similar to amiodarone but doesn’t have Iodine moiety
  31. 31. Dronedarone (Multaq) • Dronedarone is less toxic to the body, especially to the thyroid and pleural tissue, • Benefit over amiodarone in people requiring long term treatment. Dronedarone has been shown to be better than placebo at maintaining NSR and has reduced rate of hospital admissions • However trials have shown that dronedarone has an increased mortality rate in NYHA Class III/IV heart failure when compared to amiodarone. • Thus dronedarone is not recommended for use in patients with severe heart failure and atrial fibrillation.
  32. 32. Future OAC therapies • Warfarin is the anti-coagulant of choice in management of systemic emboli risk reduction in atrial fibrillation • Acts by inhibiting vitamin K end-glycosylation of Factor II, VII, IX and X. • However patients on warfarin require careful INR monitoring through frequent venepuncture and altering of dosing. • Warfarin also interacts with a large variety of medications, thus altering the INR profile and increasing risk of clot formation or haemorrhage. • However: – Cheap as chips! – Long term use & hx known and S/Es – Reversible (Octaplex Prothombin Complex) – Reduced blled risk in elderly compared with newer OACs.
  33. 33. Future? • Direct thrombin and Factor X inhibitors remove the need for continued INR sampling. • Dabigatran (Pradaxa) is a direct thrombin inhibitor, • Requires no INR monitoring or dose adjustments. • Therapeutic in 4 hrs • 2 recent large scale RCTs [26] have shown the non-inferiority of dabigatran vs warfarin in prevention of thromboembolus formation, with a significantly lower rate of haemorrhagic stroke and major bleeding with dabigatran. • However increased GI bleed risk • Dabigatran received FDA licensing for the prevention of embolic events in atrial fibrillation in October 2010 • However BD dosing • Not reversible/No antidote currently • More suited to younger patients?
  34. 34. • Direct factor Xa inhibitors ('xabans') are a class of OAC which act directly upon Factor X in the coag cascade, without using antithrombin as a mediator • Rivaroxaban (Xarelto) • Max inhibition of factor Xa occurs four hours after a dose. • Effects last 8–12 hours, but factor Xa activity does not return to normal within 24 hours • Once-daily dosing is possible. • Similar qs as Dabigatran
  35. 35. A few trials • RACE trial, AFFIRM trial – rhythm control not superior to rate control. • RELY trial – Dabigatran. • ROCKET AF trial – Rivaroxaban. • ARISTOTLE trial – Epixaban.

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