Twenty Questions (And Answers) About Atrial Fibrillation (AF)

Michael B. Weinstock, MD

Brought to you by EM RAP and UC MAX

How Common Is Atrial Fibrillation?

Atrial fibrillation is the most common dysrhythmia in adults, present in 37% of those over the age of 55. Incidence increases with age.

What Are Risk Factors for Atrial Fibrillation?

Risk factors include older age, coronary artery disease, male, European ancestry, hypertension, obesity, smoking, diabetes, obstructive sleep apnea, and a family history of atrial fibrillation in a first-degree relative.

Of Patients Newly Diagnosed With Atrial Fibrillation, How Many Had an Acute Precipitant?

Wang et al. looked at more than 10,000 patients over 14 years and found that 19% had an acute precipitant such as cardiac surgery (22%), pneumonia (20%), and non-cardiothoracic surgery (15%). 

Does an Acute Precipitant Predict Recurrence?

Interestingly, those with an acute precipitant had less chance of recurrence (41% compared to 52%). This was also demonstrated by Lubitz et al, with the finding that of patients with new onset atrial fibrillation 31% had an acute precipitant including cardiothoracic surgery (30%), infection (23%), other surgery (20%) and acute MI (18%)

What Are Causes of Atrial Fibrillation?

One way to break down causes are cardiac and noncardiac.

  1. Cardiac
  2. Valvular
  3. Post-surgical (cardiothoracic surgery)
  4. Heart failure
  5. Hypertension
  6. Myocardial ischemia/infarction
  7. Pericarditis/myocarditis
  8. Infiltrative (amyloid, sarcoidosis)
  9. Congenital
  10. Non-cardiac
  1. Pulmonary – Pulmonary embolism (PE), pneumonia, sleep apnea, cor pulmonale
  2. Alcohol
  3. Medications – Sympathomimetics, antidepressants, digoxin, theophylline
  4. Electrolyte abnormalities
  5. Fever/hypothermia
  6. Thyrotoxicosis

What Is the Pathophysiology of Atrial Fibrillation?

Changes in the electrophysiology of the atrial myocytes including fibrosis (though this is debated).

What Are the Risks of Atrial Fibrillation?

Interestingly, patients don’t usually get into trouble from the rate or the rhythm; the main risk is associated with increased risk of stroke (men risk by factor of 4 and women factor of almost 6), heart failure (men factor 3 and women factor 11), and dementia (increased by a factor of 1.4). Death is increased by factor 2.4 in men and 3.5 in women. The dementia associated with AF is likely from strokes and cerebral hypoperfusion.

What Symptoms May Be Present in Patients With Atrial Fibrillation?

Atrial fibrillation patients may experience fatigue, palpitations, or decreased ability to exercise. When AF is present with tachycardia, there may be syncope, hypotension, chest pain from angina, or acute pulmonary edema.

When Do We Need To Use Caution?

Patients with Wolff-Parkinson-White Syndrome (WPW) and AF will display an irregularly irregular wide complex but with polymorphic QRS complexes (complexes are not of uniform morphology) that do not demonstrate right or left BBB morphology AND will have a short PR interval. The rate is often very elevated at 250-300 beats per minute.

Atrial flutter is often interpreted by the ECG machine as sinus tachycardia.

What Rate Risks Are There With AF?

Atrial fibrillation with rapid ventricular response (RVR).

Atrial fibrillation with an elevated heart rate/rapid ventricular response (RVR) is often not the etiology behind the patient’s decompensation. AF that is chronic or refractory may not convert to sinus rhythm. Synchronized cardioversion is also the preferred treatment for AF with RVR in the setting of pre-excitation (such as WPW).

Which Patients with AF Need to be Transferred From the UC to the ED?

Patients that need to be transferred are those:

  • Who are hemodynamically unstable or with suspected acute congestive heart failure (CHF) or acute coronary syndrome (ACS).
  • Who require treatment of their underlying etiology (such as PE or valvular problems).
  • With a rapid ventricular response (caveat that if rate is greater than 100 but due to an underlying problem in patients with chronic AF, they would not necessarily need to be transferred).
  • Who are unable to be safely discharged for other reasons (i.e., social, support) require admission to the hospital.

Which Acute or Chronic Rate Control Medications Are Recommended for Management of AF?

Calcium channel blockers, beta blockers, digoxin. 

When Should a Patient Be Emergently Cardioverted?

Unstable, hypotensive, altered level of consciousness if there is associated WPW.

Why Aren’t All Patients Cardioverted?

There is an increased risk of stroke especially for patients with AF which has been present for longer than 48 hours.

What Is More Effective for Chronic Management of AF, Meds or Catheter Ablation?

Catheter ablation (especially for paroxysmal atrial fibrillation).

What Is Atrial Flutter and Is It Managed Differently?

Atrial flutter is produced by a macro-reentrant loop in the right atrium just above the AV node. The atrial rate in atrial flutter ranges from 240 to 360bpm, and the resulting ventricular rate is determined by the AV node, which may have fixed (producing a regular ventricular rate at a multiple of the atrial rate) or variable conduction (producing a regularly irregular rhythm with R-R intervals at varying multiples of the atrial rate).

In most physiologic states, the AV node conducts the atrial circuit in a 2:1 fashion, resulting in a regular rhythm around 150bpm without rate variation. The atrial flutter circuit usually produces a continuous sawtooth pattern best visualized in leads II and V1, but occasionally appears only as small narrow spikes with the false appearance of a return to baseline between them.

The sawtooth baseline of atrial flutter may simulate or hide ST-segment changes. 

What Is the Risk of Stroke in Patients With AF?

Risk of stroke ranges from 1% to nearly 20%. It is estimated that one-sixth of strokes are the result of AF.

How Do We Calculate Recommendations for Anticoagulation in Patients With AF?

The most common way is by using the CHA₂DS₂-VASc score. Calculators are available in apps such as MDCalc or CorePendium. The elements involved include:

  • A history or CHF or known LV dysfunction
  • Hypertension
  • Age
  • History of diabetes
  • History of prior stroke, TIA, or thromboembolic event
  • History of vascular disease
  • Gender

 

Patients with a score of 0 do not need anticoagulation.

Patients with a score of 1 should be considered for a daily aspirin or anticoagulation.

Patients with a score >1 require anticoagulation

What Are the Best Anticoagulants To Use?

Direct oral anticoagulants (DOACs) are now recommended as the agents of choice by the 2019 American College of Cardiology (ACC) and American Heart Association (AHA) guidelines for patients with AF. However, patients with severe valvular disease or mechanical valves require anticoagulation (AC) with warfarin and not DOACs.

  • Anticoagulation can reduce the risk of a stroke by up to 80%.
  • There is also some evidence that the early initiation of AC can prevent vascular dementia in patients with AF.

 

How Can We Gauge the Risk of Bleeding?

  • The decision to initiate AC must be balanced with the risk of bleeding.
  • Calculate the bleeding risk rather than citing clinical concern alone. Clinician estimates of bleeding risk do not correlate with calculated risks, with fall risk being the most cited reason for withholding AC.
  • The HAS-BLED Score demonstrated superior performance compared with others. This can be estimated with the risk calculator in CorePendium
  • Patients with a score >2 are at an increased risk of bleeding, and the decision to initiate AC must be taken with caution.

 

 References:

  1. Michaud GF, Stevenson WG. Atrial Fibrillation. N Engl J Med. 2021 Jan 28;384(4):353-361. doi: 10.1056/NEJMcp2023658. PMID: 33503344.
  2. Wang EY, Hulme OL, Khurshid S, et al. Initial Precipitants and Recurrence of Atrial Fibrillation. Circ Arrhythm Electrophysiol. 2020 Mar;13(3):e007716. doi: 10.1161/CIRCEP.119.007716. Epub 2020 Feb 12. PMID: 32078361; PMCID: PMC7141776.
  3. Lubitz SA, Yin X, Rienstra M, Schnabel RB, et al. Long-term outcomes of secondary atrial fibrillation in the community: the Framingham Heart Study. Circulation. 2015 May 12;131(19):1648-55. doi: 10.1161/CIRCULATIONAHA.114.014058. Epub 2015 Mar 13. PMID: 25769640; PMCID: PMC4430386.

 

You can reach Michael B. Weinstock, MD at:

mweinstock@mweinstock.com

www.embouncebacks.com

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