Atrial fibrillation

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Diagnosis

Prevalence

A study of routine pulse checks or electrocardiograms during routine office visits, found that the annual rate of detection of atrial fibrillation in elderly patients improved from 1.04% to 1.63%.[1] This implies that the sensitivity of the routine examination is 64% (1.04/1.63).

Routine cardiac monitoring for seven days after ischemic stroke detected atrial fibrillation in 40% of patients.[2]

Electrocardiogram

Regarding the accuracy of the electrocardiogram[3]:

Prognosis

Risk of stroke

The risk of stroke in a patient with atrial fibrillation can be predicted with the CHADS2 score and perhaps better with the CHA2DS2-VASc score.[4][5] CHA2DS2-VASc is:

Interpretation is:

Treatment

Clinical practice guidelines by the American College of Physicians and the American Academy of Family Physicians address treatment.[6][7]

Rate control versus rhythm control

Medications

"Rate control with chronic anticoagulation is the recommended strategy for the majority of patients with atrial fibrillation. ... Rhythm control is appropriate when based on other special considerations, such as patient symptoms, exercise tolerance, and patient preference."[6]

Regarding target heart rate, a recent randomized controlled trial found that resting heart rate <110 beats per minute had similar outcomes to stricter control.[8] Previously, the goal rate is "80 beats per minute during resting ... and of less than 110 beats per minute during a 6-minute walk test."[9]

As compared to rate control, rhythm control was associated with slight, although statistically insignificant, increase in adverse outcomes in randomized controlled trials.[10][9][11] In addition, "the incidence of the components of the primary end point did not differ significantly according to whether the patient had sinus rhythm or atrial fibrillation at the end of follow-up."[10] Whether the index episode was the initial or a recurrent episode did not effect results.[11]

Randomized controlled trials of rhythm versus rate control.[10][11][9]
Study Patients Intervention in rhythm control group Results
Rhythm control group Rate control group
Van Gelder[10]
2002
  • All had prior episode of atrial dysrythmia requiring electrical cardioversion.
  • All had current atrial dysrythmia for median of 32 days.
  • 50% has previous heart failure.
  • Cardioversion followed by sotalol
  • 86% to 99% received anticoagulation.
  • 2.3 years.
  • Sinus rhythm: 39%
  • Cardiovascular death: 6.8%
  • Thromboembolism: 5.5%
  • Sinus rhythm: 10%
  • Cardiovascular death: 7%
  • Thromboembolism: 7.9%
AFFIRM[11]
2002
  • 65% had prior episode of atrial dysrythmia.
  • All had current atrial dysrythmia with 69% lasting 2 or more days.
  • 23% has previous heart failure.
  • "antiarrhythmic drug used was chosen by the treating physician"
  • 70% received anticoagulation.
  • 5 years.
  • Sinus rhythm: 63%
  • Any death: 23.8%
  • Ischemic stroke: 5.5%
  • Sinus rhythm: 35%
  • Any death: 21.3%
  • Ischemic stroke: 7.1%
Roy[9]
2008
  • All had prior episode of atrial dysrythmia.
  • 55% to 60% with current atrial dysrythmia.
  • All with a history of heart failure and systolic dysfunction.
  • Sinus rhythm: 73%
  • Cardiovascular death: 27%
  • Any stroke: 3%
  • Sinus rhythm: 30%
  • Cardiovascular death: 25%
  • Any stroke: 4%

Regarding the choice of medication:
Shown effective in some randomized controlled trials

Shown not effective in some randomized controlled trials

Episodic therapy

Episodic medical therapy has conflicting results with a positive uncontrolled before and after trial of flecainide and propafenone[15] and a negative randomized controlled trial of episodic amiodarone versus continuous amiodarone.[16]

Artificial pacemakers

Regarding artificial pacemakers, "dual-chamber minimal ventricular pacing, as compared with conventional dual-chamber pacing, ...reduces the risk of persistent atrial fibrillation in patients with sinus-node disease" according to a randomized controlled trial.[17]

Dual site, overdrive pacing be effective.[18]

Ablation

Pulmonary-vein isolation

Randomized controlled trial have found that using ablation to cause pulmonary-vein isolation was superior to medical therapy[19][20][21] and to atrioventricular-node ablation[22]. About two thirds of patients remain in sinus rhythm after 9 months.[19]

Anticoagulation

Patients with a CHA2DS2-VASc of two or more may benefit from chronic anticoagulation according to a recent observational study[23] and American clinical practice guidelines[24]. European clinical practice guidelines recommend anticoagulants if the CHA2DS2-VASc is two or more.[25]

Randomized controlled trials of new anticoagulants compared to warfarin for atrial fibrillation.[26] [27] [28]
Trial Patients Intervention Comparison Outcome Results Comments
Intervention Control
ARISTOTLE[26]
2011
18,201 patients Apixaban 5 mg twice daily warfarin (target INR 2.0 to 3.0; time in therapeutic range 62%) stroke or systemic embolism at 1.3 years 1.3% per year 1.6% per year • hazard ratio for primary outcome 0.79
• relative risk for death 0.89 (95% CI: 0.80 to 0.99; P=0.047)
ROCKET AF[27]
2011
14,264 patients Rivaroxaban 20 mg daily
(15 mg daily if creatinine clearance 30 to 49 ml per minute)
warfarin (target INR 2.0 to 3.0; time in therapeutic range 55%) stroke or systemic embolism at 1.6 years 2.1% per year 2.4% per year • hazard ratio for primary outcome 0.79
• relative risk for death 0.92 (95% CI: 0.82 to 1.03; P=0.15)
RE-LY[28]
2009
18,113 patients Dabigatran 150 mg twice daily warfarin (target INR 2.0 to 3.0; time in therapeutic range 64%) stroke or systemic embolism at 1.3 years 1.1% per year 1.5% per year • relative risk for primary outcome 0.66
• relative risk for death 0.88 (95% CI: 0.77 to 1.00; P=0.051)
• Not blinded
Dabigatran versus warfarin for atrial fibrillation[28]
Intervention Outcomes
Stroke or systemic embolism Major bleeding Mortality
Dabigatran 110 mg twice daily 1.53% 2.71% 3.75%
Dabigatran 150 mg twice daily 1.11% 3.11% 3.64%
Warfarin 1.69% 3.36% 4.13%
† p < 0.05 as compared to warfarin group

Anticoagulation can prevent recurrent stroke. Among patients with nonvalvular atrial fibrillation, anticoagulation can reduce stroke by 60% while antiplatelet agents can reduce stroke by 20%. [29]. However, a recent meta-analysis suggests harm from anti-coagulation started early after an embolic stroke.[30]

Anticoagulants is underused for atrial fibrillation.[31] Both doctors[32] and patients[33] are reluctant to use anticoagulants. Patients may avoid warfarin even when they prefer the outcomes of warfarin.[34]

In 2009, dabigatran, a direct thrombin inhibitors, was compared to warfarin in the RE-LY randomized controlled trial.[28]

Antiplatelet therapy

Randomized controlled trials of antiplatelet therapy for atrial fibrillation[35][36][37]
Trial Patients Intervention Comparison Outcome Results
Intervention Control
Copenhagen AFASAK study[35]
1989
1007 patients aspirin 75 mg daily Warfarin stroke, transient ischemic attack, or systemic embolism 6.0% 1.4%
SPAF[36]
1991
1,330 patients aspirin 325 mg daily Warfarin ischemic stroke and systemic embolism 3.6% 2.3%
ACTIVE study[37]
2009
7554 patients:
• All were taking aspirin, usually at 75 to 100 mg per day
•None were taking warfarin
clopidogrel 75 mg daily Placebo stroke, myocardial infarction, systemic embolism, or death from vascular causes 6.8% 7.6%
† This was not a direct comparison as warfarin patients were younger and had to be eligible for warfarin.
‡ However, combination therapy increased major bleeding from 1.3% to 2.0%.

If warfarin is contraindicated, the combination of clopidogrel and aspirin can help, especially in reducing stroke, but increases the risk of major hemorrhage.[37]

Screening

Screening may increase detection according to a systematic review by the Cochrane Collaboration.[38]

References

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  2. Higgins P, MacFarlane PW, Dawson J, McInnes GT, Langhorne P, Lees KR (2013). "Noninvasive cardiac event monitoring to detect atrial fibrillation after ischemic stroke: a randomized, controlled trial.". Stroke 44 (9): 2525-31. DOI:10.1161/STROKEAHA.113.001927. PMID 23899913. Research Blogging.
  3. Mant J, Fitzmaurice DA, Hobbs FD, et al (2007). "Accuracy of diagnosing atrial fibrillation on electrocardiogram by primary care practitioners and interpretative diagnostic software: analysis of data from screening for atrial fibrillation in the elderly (SAFE) trial". DOI:10.1136/bmj.39227.551713.AE. PMID 17604299. Research Blogging.
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