Atrial Fibrillation and Flutter

Overview

Epidemiology

• AF is the most common type of arrhythmia, with an estimated prevalence of ~13% in adults in the United States.¹ Atrial flutter (AFL) is a less common arrhythmia associated with AF and other supraventricular arrhythmias.² Intrinsic factors that increase the risk of developing AF include older age, male sex, and European ancestry. Various comorbidities have also been associated with a higher risk of AF and AFL, including heart failure, hyperthyroidism, diabetes, obstructive sleep apnea (OSA), hypertension, and obesity.^2,3
• AF and AFL are important risk factors to consider and manage when identified in the perioperative setting, as AF is associated with increased perioperative mortality and morbidity and a higher risk of heart and renal failure, bleeding, and thromboembolic events, including stroke.^1,3

Signs and Symptoms

• Patients with AF and/or AFL may or may not be symptomatic. These arrhythmias are often detected incidentally in asymptomatic patients during routine check-ups or preoperative evaluations. AF is frequently seen in patients hospitalized for acute illness, especially in patients admitted to intensive care units or patients in the perioperative period.⁴
• Symptomatic patients often present with palpitations, fatigue, lightheadedness, and/or dyspnea on exertion. Less common but more severe symptoms can include presyncope or syncope, severe dyspnea, and anginal chest pain.^2,4 Physical examination findings that may warrant further investigation for possible AF/AFL include irregularly irregular pulse, tachycardia, heart murmurs indicative of mitral or aortic valvular disease, and signs of heart failure.^2,4

Pathophysiology

• The pathophysiology of AF is complex and multifactorial. Contributing factors include: older age, underlying heart disease (congenital, valvular, vascular/ischemic, heart failure, inflammation), hypertension, endocrine disorders, electrolyte abnormalities, OSA, stroke, pulmonary embolism, and alcohol consumption. Inflammation or stress to the heart leading to structural, electrical, and autonomic remodeling in cardiac tissue, particularly in the atria, underlies the majority of these mechanisms.^3,5 These changes result in unsynchronized firing of ectopic foci in the atria, typically in the left atrium around the pulmonary veins. AF produces turbulent blood flow in the left atrial appendage, significantly increasing the risk of intracardiac thrombus formation.⁵ Thrombi which form in the left heart can then travel into the cerebral circulation, resulting in an ischemic cerebrovascular accident.
• AFL is typically caused by a macroentrant circuit traversing the cavotricuspid isthmus (CTI). The CTI is located in the right atrium and bridges the orifice of the inferior vena cava and the tricuspid valve annulus.² AFL that does not involve the CTI is classified as “atypical” AFL and can be caused by scar tissue (due to intrinsic heart disease or surgery/ablation) in any part of the right or left atria.²

Testing and Diagnosis

• In patients in whom AF/AFL is suspected, the first step in diagnosis is to obtain a 12-lead electrocardiogram (ECG). On ECG, AF has an “irregularly irregular” rhythm, variable rate (rapid ventricular response may or may not be present), and no distinguishable p-waves (Figure 1).^4,5 AFL presents with a characteristic pattern of regular, continuous, and rapid atrial activity (typical atrial rate 240-340 beats/min) in a “sawtooth” pattern (Figure 2).² The ventricular rate is typically ½ of the atrial rate (2:1 conduction ratio). Still, different conduction ratios are observed, with even ratios (2:1 or 4:1 atrial-to-ventricular) more common than odd ratios (3:1 or 5:1).² In both AF and AFL, concurrent conditions may be seen, including atrial enlargement, ventricular hypertrophy, bundle branch blocks, prior myocardial infarctions, or preexcitation.²
• AF and AFL are not always captured on ECG, as patients often have intermittent episodes (paroxysmal) of these arrhythmias. If the arrhythmia is not seen on ECG, ambulatory cardiac monitoring using event recorders, external extended time monitors (i.e., holter monitor, Zio patch), or implantable monitors (i.e., loop monitor) may be necessary to detect the arrhythmia.^4,6 Extended monitoring can improve the detection of AF in patients who present with stroke or transient ischemic attack of undetermined cause.⁶ The advent of ECG-capable smart watches has enabled patient detection of arrhythmias at home. While nondiagnostic, AF/AFL events detected on home monitors can provide useful clinical information and trigger additional workup.

• Initial workup of newly diagnosed AF/AFL should include a comprehensive transthoracic echocardiogram (TTE) to rule out structural cardiac disease, and basic laboratory tests (complete blood count, metabolic panel, thyroid function tests, glycated hemoglobin/A1c) to identify common, treatable causes of AF/AFL. Other targeted testing, such as a sleep study, exercise testing, or pulmonary function testing, may be considered based on the clinical examination and review of systems.⁶ Testing for stable coronary artery disease, acute coronary syndrome, and/or pulmonary embolism should not be routinely performed unless other signs/symptoms increase clinical suspicion.^2,4,6

Treatment/Management

• The treatment/management of AF and AFL varies depending on the etiology, clinical presentation, disease severity, and pre-existing comorbidities/risk factors. The primary pillars of management in both AF and AFL include stroke/thromboembolism prevention, risk factor modification, and heart rate and/or rhythm control.⁶
• CHADS₂-VASC₂ is a tool used to assess stroke risk in patients with AF and/or AFL based on the presence or absence of patient-specific risk factors such as congestive heart failure, hypertension, age ≥75 (+2 points), prior thrombotic event, vascular disease, age ≥65-74, and female sex.^3,6 A CHADS₂-VASC₂ score of ≥2 in men or ≥3 in women correlates to an annual risk of stroke or thromboembolism of ≥2%, and patients in this category should receive anticoagulation.^3,6

Management of Asymptomatic Patients

• Pharmacologic Management
  • Anticoagulation:
    • Patients at an increased annual risk of stroke or thromboembolism (≥2%) should be anticoagulated using a direct oral anticoagulant (DOAC) or a vitamin K antagonist (warfarin).^5,6 DOACs have a better side effect profile and are preferred over warfarin (except in patients with moderate-to-severe mitral stenosis or mechanical valve replacements).⁶
    • Anticoagulation may also be considered in patients with an intermediate stroke/thromboembolism risk (1-2% annual risk). An individualized decision is based on bleeding risk and comorbidities.⁶
    • In patients with an elevated stroke risk and a contraindication to anticoagulation, a percutaneous left atrial appendage occlusion (LAAO) may be performed to reduce LV thrombus formation.
  • Rate control:
    • A heart rate of less than 100 beats/min is the target heart rate in patients who are candidates for pharmacologic rate control.^6,11
    • Rate control can be achieved using beta-blockers or nondihydropyridine (non-DHP) calcium channel blockers (CCBs).⁶
  • Rhythm control:
    • Pharmacologic rhythm control is generally not pursued in asymptomatic patients with AF, however procedural rhythm control (catheter ablation, discussed further below) may be beneficial in select patient populations.⁶
• Procedural Management
  • Catheter ablation may be particularly beneficial in select patients, including younger (<70 years old) patients with few comorbidities and moderate-to-high AF/AFL burden or persistent AF/AFL.6 Catheter ablation has also been shown to benefit patients with AF and heart failure with reduced ejection fraction.^5,6
  • Pulmonary vein isolation is the typical catheter ablation strategy used for AF, while ablation of the CTI is used for typical (CTI-dependent) AFL.^2,6
  • In patients with moderate-to-high stroke risk with nonreversible contraindications to anticoagulation, percutaneous LAAO (also known as the Watchman procedure) is a reasonable alternative.⁶
  • In patients with AF and high stroke risk undergoing cardiac surgery, LAAO and continued anticoagulation reduces risk of stroke and systemic embolism.⁶

Management of Hemodynamically Stable, Symptomatic Patients

• Pharmacologic Management
  • Anticoagulation: The indications for anticoagulation described above for asymptomatic patients with AF/AFL are also applicable to symptomatic and hemodynamically stable patients.⁶
  • Rate control:
    • Beta-blockers and non-DHP CCBs are first-line rate-control agents for acute and chronic symptomatic AF/AFL.⁶ Amiodarone, digoxin, and intravenous (IV) magnesium are second-line agents for acute rate control.⁶
    • IV amiodarone is the preferred acute rate control agent for patients with decompensated heart failure.⁶ When using amiodarone for rate control, it is important to keep in mind the risk of inducing cardioversion and subsequent stroke.⁶
  • Rhythm control:
    • Patients who have been in AF for less than 12 hours or less than 48 hours with a CHADS₂-VASC₂ of 0-1 are candidates for direct current electrical cardioversion (DCCV).
    • In patients who do not meet the above criteria, a transesophageal echocardiogram can be performed to exclude thrombus prior to DCCV. If a thrombus is identified, anticoagulation is necessary prior to DCCV to reduce the risk of thromboembolism.
    • Rhythm control is not pursued in patients not on anticoagulation with AF of longer duration.^4,6 Rate control is pursued first until adequate anticoagulation is achieved.
    • Acute pharmacologic treatment of AF/AFL is uncommon but can be considered in patients with a contraindication to DCCV.¹⁰
    • For persistent AF/AFL, long-term rhythm control can be maintained pharmacologically with anti-arrhythmic drugs (AADs) such as flecainide and propafenone (for patients with no history of MI or structural heart disease), or dofetilide and amiodarone (preferred in patients with heart failure).⁶
    • AADs may also be administered as needed for symptomatic, paroxysmal AF/AFL, the so-called “pill-in-pocket” strategy.
• Procedural Management
  • Indications for catheter ablation and LAAO in AF are discussed above. Catheter ablation or surgical ablation may also be considered in patients with refractory AF or patients who desire improved symptom control.¹⁰
  • A 2021 meta-analysis of RCTs comparing the outcomes of an early ablation management strategy to an AAD approach showed better long-term outcomes and a reduction in recurrences and hospitalizations in the catheter ablation group.¹¹

Management of Hemodynamically Unstable Patients

• Hemodynamically unstable AF is defined as AF with rapid ventricular rate (RVR) associated with any of the following: hypotension, acute coronary syndrome, or pulmonary edema.
• Hemodynamic instability secondary to AF with a RVR requires immediate treatment.
• Management of Hemodynamically Unstable AF/AFL is synchronized with DCCV and initiation of anticoagulant therapy.^6,10

Preoperative Recommendations

• As there is scarce literature regarding perioperative management of AFL, the management of AFL in the perioperative period (including anticoagulation, rate control, and rhythm control considerations) is the same as in AF.⁹

Elective Noncardiac Surgeries

• Newly diagnosed AF/AFL
  • A new diagnosis of AF/AFL (often an incidental finding in an asymptomatic or mildly symptomatic patient) should be considered a potentially unstable condition, and most elective surgeries should be delayed until further workup and management of AF/AFL and any underlying triggers/comorbidities.⁹
  • In asymptomatic, hemodynamically stable patients planning for minor surgical procedures (short duration, lower complexity, minimal bleeding risk, minimal sedation requirements), it may be safe to proceed. However, patients should undergo close follow-up and further evaluation after the planned procedure.^1,9
• Known/Existing AF/AFL
  • Periprocedural Anticoagulation Regimen
    • In patients with known AF/AFL on anticoagulation with planned elective noncardiac surgery, periprocedural management decisions should balance the risk of thromboembolism by holding anticoagulants for the shortest possible duration of time while also minimizing periprocedural bleeding risk.^6,9 A wide variety of factors must be considered when developing a perioperative anticoagulation plan, including patient-specific risk factors for bleeding vs. thrombosis, procedure-specific bleeding risk, and pharmacokinetics/pharmacodynamics of the patient’s current anticoagulant.^3,6
  • Rate Control Optimization
    • A preoperative heart rate ranging between 50 and 100 beats per minute is considered reasonably optimized to minimize the risk of rapid ventricular rates and cardiac ischemia in the periprocedural period.⁹
  • Rhythm Control
    • In patients with known paroxysmal AF being managed with rhythm control (pharmacologic or prior ablation) who present in AF, the risks and benefits of further investigation of rhythm control failure vs. proceeding with surgery must be weighed. If the decision is made to proceed with surgery, rhythm control drugs should be continued perioperatively.⁹

Emergency/Urgent Surgeries

• When AF/AFL is newly discovered in a patient needing emergency surgery, anticoagulation is deferred until the postoperative period.^1,9
• Basic laboratory tests should be ordered to identify treatable causes of arrhythmia, including serum electrolytes (magnesium and calcium), thyroid-stimulating hormone, and a complete blood cell count.
• If time allows, a TTE should be obtained to rule out significant structural cardiac disease, which would impact anesthetic planning and management.
• Emergent restoration of sinus rhythm using electrical or chemical cardioversion is only indicated in the hemodynamically unstable patient.⁹
• In stable AF patients with RVR, rate control with beta-blockers or non-DHP CCBs, targeting a heart rate of less than 140 beats/min (ideally 100-110 beats/min if blood pressure permits), is considered beneficial.⁹ Given the fluctuating hemodynamics of an acutely ill patient requiring urgent/emergent surgery, short-acting medications are preferred.⁹
• In patients taking anticoagulants for AF/AFL who require emergent surgeries with high bleeding risk, reversal of anticoagulation should be considered.¹
• Reversal of anticoagulation is typically not indicated for patients receiving anticoagulation who undergo lower-risk procedures (e.g., endoscopic procedures).¹