B.24 Atrial Fibrillation Flashcards
B.24 Atrial Fibrillation
definition
Atrial fibrillation (Afib) is a common type of supraventricular tachyarrhythmia characterized by uncoordinated atrial activation that results in an irregular ventricular response.
B.24 Atrial Fibrillation
epidemiology
Most common sustained arrhythmia
Incidence: increases with age
The lifetime risk of Afib among individuals > 40 years is 1 in 4. > 95% of individuals with Afib are ≥ 60 years
Prevalence: approx. 1–2% of US population
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Cardiovascular Risk Factors
Advanced age
Hypertension
Diabetes mellitus
Smoking
Obesity
Obstructive sleep apnea (OSA)
B.24 Atrial Fibrillation
Risk Factors cause by intrinsic cardiac disorders
Coronary artery disease (CAD)
Valvular heart disease (especially mitral valve disease)
Heart failure
Preexcitation tachycardia. e.g., Wolff-Parkinson-White (WPW) syndrome
Sick sinus syndrome (tachycardia-bradycardia syndrome)
Cardiomyopathies
Pericarditis
Genetic predisposition (e.g., congenital channelopathies)
Atrial myxoma
B.24 Atrial Fibrillation
Risk factors that are noncardiac disorders
Pulmonary disease: COPD, pulmonary embolism, pneumonia
Hyperthyroidism
Catecholamine release and/or increased sympathetic activity
Stress: sepsis, hypovolemia, post-surgical state (especially following cardiac surgery), hypothermia
Pheochromocytoma
Cocaine, amphetamines
Electrolyte imbalances (hypomagnesemia, hypokalemia)
Drugs: e.g., adenosine, digoxin
Holiday heart syndrome: irregular heartbeat classically triggered by excessive alcohol consumption, but also sometimes by moderate alcohol consumption, stress, dehydration, or lack of sleep
Chronic kidney disease
B.24 Atrial Fibrillation
Pathophys
The new onset of Afib triggers a vicious circle that can ultimately lead to chronic Afib with atrial remodeling:
- Afib is triggered by one or both of the following
Bursts of electrical activity from automatic foci near the pulmonary vein ostia (left atrium) or in diseased, fibrotic atrial tissue
Pre-excitation of the atria as a result of aberrant pathways (e.g., WPW syndrome) - Afib is sustained by re-entry rhythms and/or rapid focal ectopic firing
Re-entry rhythms are more likely to occur with enlarged atria, diseased heart tissue, and/or aberrant pathways (e.g., WPW syndrome). - Atrial remodeling
Electrophysiological changes in the atria occur within a few hours of Afib onset (electrical modeling).
If Afib persists, atrial fibrosis and dilatation (structural remodeling) occur within a few months.
Electrical and structural remodeling increase susceptibility to Afib, resulting in a vicious circle.
Effects of Afib
The atria contract rapidly but ineffectively and in an uncoordinated fashion → stasis of blood within the atria → risk of thromboembolism and stroke
Irregular activation of the ventricles by conduction through the AV node → tachycardia
B.24 Atrial Fibrillation
General features
Irregularly irregular pulse with or without tachycardia
Apex-pulse deficit - The number of cardiac contractions (as auscultated or palpated on the chest) is higher than the peripheral pulse rate. This is due to variability in diastolic intervals, which intermittently leads to a small-volume cardiac contraction that is not strong enough to transmit a pulse wave to the periphery.
B.24 Atrial Fibrillation
Stable A. Fib clinical features
Afib without signs of hemodynamic instability
Most affected individuals are asymptomatic.
Some may present with:
Palpitations
Fatigue
Dyspnea
Lightheadedness
Syncope
Signs of underlying heart disease (e.g., murmurs of mitral stenosis)
B.24 Atrial Fibrillation
Unstable A. Fib clinical features
Afib manifesting with signs of hemodynamic instability
Ischemic chest pain
Altered mental status
Clinical features of pulmonary edema
Clinical features of acute heart failure
Clinical features of cardiogenic shock
B.24 Atrial Fibrillation
Complications
Acute left heart failure → pulmonary edema
Thromboembolic events: stroke/TIA, renal infarct, splenic infarct
, intestinal ischemia
, acute limb ischemia
Tachycardia-induced cardiomyopathy
B.24 Atrial Fibrillation
ECG DX
Clinical Afib
An episode of Afib documented on ECG lasting ≥ 30 seconds May be symptomatic or asymptomatic
Subclinical Afib
Asymptomatic Afib not detected on 12-lead ECG
Detected on implanted cardiac devices and confirmed with intracardiac electrography
Signs of comorbid conditions and/or underlying etiologies
Aberrant conduction: e.g., LBBB, RBBB, ECG findings in WPW
CAD: e.g., rate-dependent ST depressions, ECG findings in STEMI, ECG findings of NSTE-ACS, or evidence of previous myocardial infarction
Others: e.g., ECG findings in pericarditis, ECG signs of LVH
B.24 Atrial Fibrillation
Labs
CBC: assessment for anemia and signs of infection
Serum electrolytes (Na+, K+, Mg2+, and Ca2+): to identify electrolyte imbalances
BUN, serum creatinine, and liver chemistries: to identify abnormal renal or liver function
TFTs: to screen for thyrotoxicosis
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TTE
Goal: to assess cardiac function and rule out underlying structural heart disease (e.g., mitral valve stenosis)
Indications
New Afib diagnosis
Known Afib with clinical deterioration of unclear etiology
Morphological TTE findings may include:
Structurally normal heart (more common in young people)
Left atrial thrombus
Moderate to severe mitral stenosis or presence of a mechanical heart valve (previously known as valvular Afib) is associated with a significantly increased risk of thromboembolic events.
Other valvular heart disease or no valvulopathy (previously known as nonvalvular Afib)
Atrial enlargement
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TEE for Afib
Goals
To evaluate for thrombi and reduce the risk of thromboembolic events prior to cardioversion
Visualize the atria and the left atrial appendage (hotspots for thrombogenesis)
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Initial TX
Evaluate hemodynamic stability using the ABCDE approach.
Establish IV access.
Begin continuous cardiac monitoring and pulse oximetry.
Obtain confirmatory 12-lead ECG and other Afib diagnostics.
Identify and treat reversible causes of Afib.
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TX unstable A Fib
Manage unstable Afib with immediate synchronized electrical cardioversion.
Afib with RVR: 120–200 J biphasic
Atrial flutter with RVR: 50–100 J biphasic
Anticoagulate as soon as possible if indicated, but do not delay emergency electrical cardioversion for preprocedural anticoagulation.
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TX Stable A Fib
Stable Atrial Fibrillation (no urgent cardioversion required): Administer warfarin along with bridging therapy for 3 weeks prior to and up to 4 weeks following cardioversion.
B.24 Atrial Fibrillation
Principles of Rate Control TX
Rate control in acute and chronic Afib is indicated for symptom control and to prevent LV dysfunction.
for elderly patients
CI if AF due to pre-excitation syndrome
B.24 Atrial Fibrillation
Rate Controlled Pharma
First Line
1st Choice: Beta blockers (esmolol, propanolol, metoprolol) OR non-dihydropyridine calcium channel blockers (diltiazem, verapamil)
2nd Choice: Digoxin
3rd Choice: Dronedarone, Amiodarone
2nd Line
AV nodal ablation followed by the implantation of a permanent ventricular pacemaker.
B.24 Atrial Fibrillation
Rhythm control principles
- Terminating atrial fibrillation and restoring sinus rhythm to prevent atrial remodeling.
- In younger patients, there is a failure of rate-control strategies to manage symptoms.
B.24 Atrial Fibrillation
Rhythm control TX
First Line
1. First choice: Elective electrical cardioversion
- Second choice: Pharmacologic cardioversion using antiarrhythmic drugs such as flecainide, propafenone, ibutilide, or dofetilide.
Second Line
Catheter-based radiofrequency ablation of atrial tissue surrounding the openings of the pulmonary veins (pulmonary vein isolation).
B.24 Atrial Fibrillation
Stroke Prevention
Use CHA₂DS₂-VASc score: to asses thromboembolic risk
B.24 Atrial Fibrillation
CHA₂DS₂-VASc score
Congestive heart failure or LV dysfunction
Hypertension
Age ≥ 75 years
Diabetes mellitus
Prior stroke, transient ischemic attack, or thromboembolism
Vascular disease
Age 65–74 years
Sex: female
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Long-term anticoagulation options in atrial fibrillation
First Line Most patients
DOACs (Direct Oral Anticoagulants)
Apixaban
Rivaroxaban
Edoxaban
Dabigatran
Second Line
Vitamin K Antagonist
Warfarin
