Cardiology

Diagnosis and Management of Atrial Fibrillation

SUMMARY:

Atrial fibrillation, the most common cardiac arrhythmia, increases stroke risk and can exacerbate underlying heart disease. The 2014 ACC/AHA/HRS Guideline for the Management of Patients with Atrial Fibrillation offers a comprehensive approach to treating this condition. A focused update released in 2019 includes new evidence in support of novel drugs and devices to prevent thromboembolism, as well as other clinical considerations. Of note, these recommendations apply to atrial fibrillation (AF) and atrial flutter, regardless of the pattern of arrhythmia (i.e. paroxysmal, persistent, or permanent).

Diagnosis and Workup
Treatment Highlights
Risk stratification
Anticoagulation
Alternatives to Anticoagulation
Rate Control
Rhythm Control

Diagnosis and Workup

Diagnosed by EKG or cardiac monitoring: Characteristic irregular rhythm without discrete p-waves
Workup at time of diagnosis should include
- TTE | Thyroid function tests | CBC | Renal function and electrolytes | LFTs | CXR (if suspicion for heart failure or pulmonary disease) | Sleep study (if suspicion for sleep apnea)
Outpatient management appropriate for hemodynamically stable patients without evidence of severe volume overload or acute coronary syndrome

Note: Routine screening for AF in the general population is not currently recommended by the USPSTF | The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for AF (I statement)

Treatment Highlights

Mainstays of treatment for most patients are anticoagulation and rate control (typically beta blocker or nondihydropyridine calcium channel blocker)
For some patients, attempted cardioversion to sinus rhythm may be preferred initially
Invasive procedures to ablate AF or occlude the LAA are appropriate for select patients

KEY POINTS:

Valvular vs. non-valvular AF
- Valvular: AF associated with moderate to severe mitral stenosis or mechanical heart valve
- Non-valvular: All other AF (much more common)

Risk stratification

CHA₂DS₂-VASc: Estimates annual stroke risk for non-valvular AF, based on various demographic and comorbid factors
- Anticoagulation is recommended for score ≥2 in men, ≥3 in women
- Anticoagulation “may be considered” for score 1 in men, 2 in women; aspirin is also an option
Stroke risk can be weighed against bleeding risk using clinical calculators such as HAS-BLED
- However per ACC/AHA “their clinical utility is insufficient for use as evidence”
- Higher bleeding risk may warrant closer monitoring of anticoagulated patients, but should not necessarily preclude anticoagulation

Anticoagulation

Choosing an anticoagulant

Goal is to prevent thromboembolic events
Decision to start anticoagulation should always involve discussion of risks vs benefits

Medications

Warfarin
- Indicated for all valvular AF
- Goal INR 2-3
Non–vitamin K oral anticoagulants (NOACs) also known as direct-acting oral anticoagulants (DOACs)
- Dabigatran (Pradaxa) | Rivaroxaban (Xarelto) | Apixaban (Eliquis) | Edoxaban (Savaysa)
- Recommended over warfarin for non-valvular AF in absence of contraindications
- All either superior or non-inferior to warfarin | Do not require INR monitoring | Have lower risk of major bleeding
- All have reduced dose options for CKD

ESRD
- Use warfarin or apixaban (limited data to support this)
Bridging
- For patients with mechanical heart valves undergoing surgery or other invasive procedure, bridge with unfractionated or low molecular weight heparin to provide uninterrupted anticoagulation
- For all others, a brief interruption of therapy without bridging is considered safe

Anticoagulation with antiplatelet therapy
- Patients with AF and recent coronary stenting who are on triple therapy (oral anticoagulant + aspirin + P2Y₁₂ inhibitor) may be narrowed to double therapy (warfarin, dabigatran, or rivaroxaban + P2Y₁₂ inhibitor) to reduce bleeding risk

Dosing

Apixaban (Eliquis)
- Usual dose: 5 mg twice a day
- Adjusted dose: 2.5 mg twice a day if ≥2 of the following
  - Age: ≥80 years
  - Body weight: ≤60 kg
  - Serum creatinine: ≥1.5 mg/dL

Note: Caution with use of apixaban and the following

Other medications that can interfere with hemostasis: May increase risk of bleeding
- Aspirin and antiplatelet agents | Other anticoagulants | Heparin | Thrombolytic agents | SSRIs | SNRIs | NSAIDs (chronic use) | Fibrinolytics
Combined P-gp and strong CYP3A4 inhibitors
- Ketoconazole | Itraconazole | Ritonavir
- Reduce dose by 50% in usual dosing regimen and do not use with 2.5 mg reduced dose | Dose does not need to be altered with clarithromycin
Combined P-gp and strong CYP3A4 inducers: Avoid concomitant use
- Rifampin | Carbamazepine | Phenytoin | St. John’s wort

Dabigatran (Pradaxa)
- CrCl >30 mL/min: 150 mg orally, twice daily
- CrCl 15 to 30 mL/min: 75 mg orally, twice daily

Note: Exercise caution with use of dabigatran and the following

P-gp inducers rifampin: Avoid coadministration
P-gp inhibitors in patients with CrCl 30-50 mL/min: Reduce dose or avoid
P-gp inhibitors in patients with CrCl <30 mL/min: Not recommended

Rivaroxaban (Xarelto)
- 15 or 20 mg, once daily with food

Note: Exercise caution with use of rivaroxaban and the following

Avoid combined P-gp and strong CYP3A inhibitors and inducers
Anticoagulants: Avoid concomitant use
Renal impairment: Avoid or adjust dose
Hepatic impairment: Avoid use in Child-Pugh B and C hepatic impairment or with any degree of hepatic disease associated with coagulopathy

Alternatives to Anticoagulation

Since thromboemboli tend to develop in the left atrial appendage (LAA), non-pharmacologic strategies for minimizing stroke risk involve occluding or removing the LAA
- Percutaneous LAA occlusion (Watchman device): For patients with a contraindication to long-term anticoagulation (however, must be able to receive periprocedural anticoagulation)
- Surgical LAA occlusion/excision: Only for patients already undergoing cardiac surgery for another indication

Rate Control

Goal: To reduce symptoms, improve intra-cardiac hemodynamics and perfusion, and prevent tachycardia-induced cardiomyopathy
Choosing a rate control strategy
- Beta blockers (e.g., metoprolol, carvedilol, atenolol) or nondihydropyridine calcium channel blockers (e.g., diltiazem, verapamil) are first-line
- Avoid CCBs in heart failure with reduced EF
- Second-line options include digoxin (possibly associated with increased mortality) and amiodarone (not for long-term use due to toxicities)
Strict (<80 bpm) vs. lenient (<110 bpm) rate control
- Lenient approach acceptable as long as patient is asymptomatic and with preserved EF

Rhythm Control

Not superior to rate control and associated with increase in hospitalizations
May be indicated for new-onset AF, persistent symptoms, difficulty achieving rate control, young age, or tachycardia-induced cardiomyopathy
- These approaches generally require expert consultation
Electrical cardioversion
- In non-emergent setting, requires anticoagulation three weeks pre- and four weeks post-procedure (if duration of AF >48 hours or unknown)
- Often preceded by TEE to exclude LA thrombus
Maintaining sinus rhythm
- Typically achieved with antiarrhythmics (e.g., amiodarone, dofetilide, flecainide)
- Caution: These drugs have significant side effects and toxicities
Catheter ablation
- For symptomatic paroxysmal AF not responding to antiarrhythmic therapy