Atrial Fibrillation: Symptoms, Causes, ECG & Treatment
Atrial Fibrillation: This lecture reviews atrial fibrillation (a fib) and its definition, meaning, ECG, symptoms, causes, types, pathophysiology, treatment, medications, and more!
Guest Author
Guest Author: Prof. (Dr.) K.V. Sahasranam, MD, DM (Cardio), FACC, FCSI and Retired Senior Consultant Cardiologist
The lecture below was written by guest author Dr. Sahasranam, who is a retired senior consultant cardiologist.
Medical illustrations were created and provided by EZmed.
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Atrial Fibrillation
Welcome to atrial fibrillation made easy!
Everything you need to know about atrial fibrillation all in one spot!
This lecture will review the following about atrial fibrillation:
Definition & Meaning
Signs & Symptoms
Causes
Risk Factors
Types & Classification
Epidemiology
Pathophysiology
ECG Findings
Diagnosis
Treatment
Complications
Prognosis
Bonus: Make sure to check out the treatment mnemonic below and leave a comment at the end if you enjoyed this lecture!
Atrial Fibrillation: Definition, meaning, symptoms, ECG findings, causes, risk factors, pathophysiology, types, diagnosis, treatment, complications, prognosis and more!
What is Atrial Fibrillation?
Let’s start with the basics and review the definition and meaning of atrial fibrillation.
Simple Definition
Atrial Fibrillation (also called AFib, A-fib, or AF) is an irregular heart rhythm (arrhythmia) in which the upper chambers of the heart (atria) quiver or beat extremely fast.
Atrial fibrillation is the most common sustained arrhythmia in clinical practice.
While AFib is manageable (see treatment below), it can cause considerable morbidity and mortality in patients and often requires hospitalization.
Medical Meaning
Atrial fibrillation is a supraventricular tachyarrhythmia with uncoordinated electrical activation of the atria and consequently ineffective atrial contraction (ESC 2020).
Supraventricular = Above the ventricles (in this case the atria)
Tachyarrhythmias = A rapid heart rhythm with a rate greater than 100 beats/min
ECG Findings
Atrial fibrillation is characterized by the absence of P-waves on electrocardiogram (ECG), along with an irregularly irregular ventricular rhythm.
Low amplitude irregular waves called fibrillatory waves (f-waves) may also be present between QRS complexes.
More on ECG findings in the diagnosis section below!
Atrial Fibrillation Definition & Meaning: Atrial fibrillation (AFib) is an irregular heart rhythm (arrhythmia) in which the atria (upper chambers) beat extremely fast
Signs and Symptoms
The signs, symptoms, and clinical features of atrial fibrillation can vary.
Approximately 25% of patients have no symptoms (asymptomatic).
Symptoms may include:
Palpitations
Fatigue
Dyspnea (shortness of breath)
Dizziness
Light headedness
Dyspnea on exertion (DOE)
Chest pain
Syncope
May occur from hypotension (low blood pressure) or low cerebral perfusion
Polyuria
The initial presentation may be a complication such as:
Stroke
Heart failure
Acute (flash) pulmonary edema
Systemic thromboembolic episodes
**See complications section below for more
On examination:
The pulse of the patient is irregular
The heart rate by auscultation is often higher than the pulse rate
Due to the fact that not all the cardiac contractions are felt in the peripheral pulse
This discrepancy between the pulse rate and the heart rate is called the “Pulse Deficit”
The first heart sound is of variable intensity
Heart murmurs will be heard if the AFib is caused by valvular heart disease
Signs of other systemic causes of AFib (heart failure, hyperthyroidism, metabolic syndrome, cardiomyopathy, etc.) may be detected on clinical examination
Atrial Fibrillation Symptoms: Signs and symptoms of atrial fibrillation include palpitations, fatigue, shortness of breath, dizziness, light headedness, chest pain, syncope, etc.
Causes of Atrial Fibrillation
The various cardiovascular and systemic conditions that can cause atrial fibrillation include:
Cardiovascular Causes
Hypertension (high blood pressure)
Coronary artery disease
Myocardial infarction (heart attack)
Valvular heart diseases
Mitral stenosis, mitral regurgitation, aortic stenosis, etc.
Congenital heart diseases
Atrial septal defect (ASD), patent ductus arteriosus (PDA), Ebstein’s anomaly, etc
Heart failure
Cardiomyopathies
Hypertrophic, dilated, or restrictive
Pulmonary artery hypertension
Pericarditis
Acute, chronic, or constrictive
Myocarditis
Other Systemic Diseases
Hyperthyroidism
Obstructive sleep apnea
Obesity
Diabetes
Metabolic syndrome
Chronic kidney disease
Deep vein thrombosis (DVT) and pulmonary embolism (PE)
Systemic infections and inflammation
Sepsis, pneumonia, etc.
Other Causes
Excess alcohol intake
“Holiday Heart Syndrome”
Certain drugs/medications
Theophylline, aminophylline, dobutamine, bisphosphonates, cocaine, methamphetamine, anti-arrhythmic drugs, etc.
Electrolyte imbalances
Hypokalemia (low serum potassium), hypomagnesemia (low serum magnesium), etc.
Atrial Fibrillation Causes: Atrial fibrillation can be caused by hypertension, coronary artery disease, myocardial infarctions (heart attacks), heart failure, thyroid, alcohol, etc.
Risk Factors for Atrial Fibrillation
Risk factors that can lead to atrial fibrillation include:
Age
Risk increases with age, especially over 60
Family history
Common in first degree relatives
Genetic predisposition
Male sex
European ancestry increases risk of AFib
Less in those of African ancestry
Air pollution
Night shift work
Higher incidence in night shift workers
Recurrent supraventricular arrhythmias increases risk of AFib
Smoking
Diabetes mellitus
34% increased risk seen in patients with diabetes
Physical inactivity
Sedentary lifestyle
Atrial Fibrillation Risk Factors: Predisposing factors to atrial fibrillation include increasing age, family history, male sex, smoking, diabetes, sedentary lifestyle, etc.
Types of Atrial Fibrillation
There are different types or classifications of atrial fibrillation.
Depending on the onset and duration, atrial fibrillation can be classified as:
Paroxysmal Atrial Fibrillation
AFib that terminates within 7 days of onset
Usually terminates spontaneously without intervention
Persistent Atrial Fibrillation
AFib that is continuous for more than 7 days
Longstanding Persistent Atrial Fibrillation
AFib that is continuous for more than 1 year
Permanent Atrial Fibrillation
Longstanding AFib which is refractory to cardioversion, or the decision has been made between the patient and provider to stop further attempts to convert to normal sinus rhythm (risk outweighs benefit; low likelihood of success)
Lone Atrial Fibrillation
AFib that occurs in patients younger than 60 years old in the absence of structural heart disease or systemic hypertension
Atrial Fibrillation Types & Classification: Paroxysmal vs persistent vs longstanding vs permanent vs lone atrial fibrillation
Epidemiology of Atrial Fibrillation
The prevalence of atrial fibrillation increases with age.
It is estimated that globally there are 32 million people with AFib, and 5 million are in the United States.
The overall prevalence in the UK is reported to be 0.5% in adults below 60 years, 1% in the 60-64 age group, and 9% in those above the age of 80.
AFib increases the risk of stroke, heart failure, and overall mortality.
Patients with AFib have a two-fold increase in mortality.
Pathophysiology and Mechanism
There are two electrophysiological mechanisms for the development of atrial fibrillation.
They include:
One or more independent foci in the atria that fire at rapid rates causing multiple micro-reentrant circuits leading to fibrillation. These foci are often called the “drivers”.
Multiple simultaneously occurring re-entrant circuits in the atria which perpetuate atrial fibrillation.
Paroxysmal AFib is typically due to multiple ectopic activity.
The most common site for the ectopic activity is where the pulmonary veins join the left atrium.
Re-entry occurs in structurally and electrophysiologically vulnerable atrial muscle.
These atrial changes are abnormalities of atrial myocytes, fibrotic changes, or alterations in the interstitial matrix of the atria.
Atrial Fibrillation Pathophysiology: Normal conduction is affected in atrial fibrillation where multiple disorganized atrial impulses may be sent to the AV node.
Diagnosis of Atrial Fibrillation
There are various diagnostic tests used in atrial fibrillation.
The tests help determine:
The diagnosis or presence of AFib
Electrocardiogram (ECG)
Ambulatory Monitoring
The etiology or cause of AFib
Echocardiogram
Chest X-ray
Treadmill Stress Test
Let’s review each category below.
1. Tests to Diagnose Atrial Fibrillation
There are various tests outlined below that can be used to diagnose atrial fibrillation.
1.1. Electrocardiogram (ECG)
The ECG characteristics in AFib include:
Absence of P waves and presence of an irregular wavy baseline due to the presence of fibrillatory waves (f-waves)
These f-waves occur at a rate of 400-600 per minute
Occasionally the f-waves are of very low amplitude and not perceptible
This is called “Fine AFib”
The totally irregular ventricular rate usually varies from 100-160 beats per minute
When the ventricles beat at a rapid rate from atrial fibrillation, this is known as atrial fibrillation with rapid ventricular response (Afib with RVR)
When the atrioventricular node (AV Node) is normal, the QRS complexes are narrow
The QRS complexes may be wide in AFib under the following circumstances:
Pre-existing bundle branch block
Aberrant conduction
WPW syndrome when the atrial fibrillary waves are conducted through the accessory pathway. In these patients the ventricular rate may be very high – 200-250 beats per minute
When the ventricular rate is very rapid (e.g., 170-180/min), the QRS complexes may apparently seem regular
The QRS complexes may be regular in AFib under the following circumstances:
Permanent pacemaker pacing the ventricles
Atrioventricular block with a junctional or ventricular escape rhythm in the ventricles
1.2. Ambulatory Monitoring
Ambulatory monitoring is used to diagnose atrial fibrillation when it is intermittent or paroxysmal.
Holter Monitoring for 24 or 48 hours may be done.
Extended Monitoring for 2-4 weeks may be needed if the symptoms of AFib are infrequent. In these patients an event monitor or telemetry may be used.
An Implantable Loop Recorder (ILR) may be implanted under the chest wall to record the events in the heart. It can record events up to three years.
2. Tests to Determine the Etiology of Afib
A detailed history and thorough physical examination is essential to diagnose conditions which can lead to AFib.
For example, systemic hypertension, chronic kidney disease, hyperthyroidism, and metabolic syndrome can lead to AFib and clinical diagnostic clues may be present.
Appropriate blood tests such as glucose, thyroid function tests, liver functions tests, and renal function tests are needed to diagnose diabetes, hyperthyroidism, dyslipidemia, and chronic kidney disease respectively.
2.1. Echocardiogram
Echocardiography is performed to diagnose structural diseases such as:
Valvular heart disease
Ischemic heart disease
Cardiomyopathies
Congenital heart disease
Echocardiography also helps detect or assess:
Left atrial size
Left ventricular hypertrophy
Left ventricular function
Presence of a thrombus in the left atrium (LA)
Presence of a thrombus in the left atrial appendage (LAA)
Transthoracic echocardiogram (TTE) is usually performed.
Transesophageal echocardiogram (TEE) is typically performed to detect LA or LAA clots.
2.2. Chest X-ray
Chest X-ray can be used to evaluate the cardiac size and to detect pulmonary disease.
2.3. Treadmill Stress Test
A treadmill stress test is performed to assess the condition of the heart when coronary artery disease is suspected.
Atrial Fibrillation Diagnosis: Diagnostic tests include electrocardiogram (ECG) and ambulatory monitoring. Tests to identify the cause include blood tests, echocardiogram, chest x-ray, stress test, etc.
Treatment of Atrial Fibrillation
The goals of managing AFib are to:
Restore normal sinus rhythm
Eliminate or prevent further episodes of AFib
Re-establish atrioventricular (AV) synchrony
Improve the atrial contribution to stroke volume - “Atrial Kick”
The main methods of management can be remembered as the “ABC of management”
A = Avoiding stroke, Anticoagulants
B = Better symptom management
C = Cardiovascular risk factor & comorbidity management
Important: For an in-depth review of atrial fibrillation treatment options, guidelines and medications, click here!
A = Avoidance of Stroke, Anticoagulants
Atrial fibrillation increases the risk of stroke by five-fold.
Other systemic thromboembolic complications may also occur.
The atria beat fast and “quiver” during atrial fibrillation, which can cause blood to pool in the atria.
This can lead to thrombus (blood clot) formation within the atria.
The blood clots can potentially travel from the heart to other parts of the body (thromboembolism), such as the brain and cause a stroke.
The predictors of stroke and thromboembolic events are:
Age over 70 years
A previous history of stroke or transient ischemic attack (TIA)
Diabetes mellitus
Systemic hypertension
Heart failure
There are 2 main methods for preventing stroke in atrial fibrillation:
Anticoagulants
Left Atrial Appendage Exclusion
1. Anticoagulants in Atrial Fibrillation
Anticoagulants (blood thinners) are medicines that help prevent blood clots.
There are two main types of anticoagulants used in AFib for stroke prevention.
They include:
Vitamin K Antagonists (VKA)
Warfarin (most common)
Phenindione
Acenocoumarol
Non-Vitamin K Oral Anticoagulants (NOACs)
Dabigatran
Rivaroxaban
Apixaban
Edoxaban
**Note: Heparin can be used as an anticoagulant in atrial fibrillation, especially as a bridging therapy, however it is typically not used longterm.
2. Exclusion of Left Atrial Appendage (LAA Exclusion)
Anticoagulation may not be an option for patients with contraindications.
Therefore, another option to reduce the risk of stroke is left atrial appendage exclusion/occlusion (LAAO).
The most common location for a left atrial blood clot to occur in atrial fibrillation is the left atrial appendage (LAA).
The LAA can be isolated or excluded to prevent the thrombus (blood clot) from traveling (embolus) to other parts of the body, such as the brain which could cause a stroke.
Indications for LAA exclusion:
Patients at a high risk of stroke with a contraindication for anticoagulants
Patients on dialysis
Patients with a high HAS-BLED or CHA2DS2-VASC score
Patients with permanent AFib
There are two techniques to achieve this:
Surgical
LAA amputation followed by epicardial closure with sutures is the most effective method.
An exclusion device named Atriclip LAA Exclusion device is applied to the outside of the LAA to clip and occlude the appendage. This can be done as a minimally invasive surgical procedure.
Percutaneous
This is also called Endocardial LAA occlusion.
The devices are introduced percutaneously during cardiac catheterization, and they expand in the appendage to plug them.
The Watchman LAA closure device and the Amplatzer Cardiac Plug are devices used for LAA exclusion.
B = Better Symptom Management
Better symptom management in AFib involves:
Heart rate control
Heart rhythm control
It has been found in recent studies that the rate and rhythm control strategies have the same incidence of total mortality, stroke rate and quality of life.
1. Rate Control in Atrial Fibrillation
An ideal rate control for AFib aims at a resting heart rate of 60-75 beats per minute and a rate of 90 – 110 beats per minute during moderate exercise as assessed by an ambulatory Holter monitor.
Rate control is achieved by pharmacological drugs.
The drugs used in rate control of AFib include:
Beta Blockers
Metoprolol, bisoprolol, atenolol, esmolol, nebivolol, carvedilol
Calcium Channel Blockers (non-dihydropyridines)
Diltiazem, verapamil
Digoxin
Amiodarone
Digitalis is useful in rate control at rest but not during exercise. It is ideal in heart failure.
*Note: Many medications used for rate control are also antiarrhythmics.
Rate control strategy alone is preferable in :
Longstanding, recurrent atrial fibrillation
Patients over the age of 80
Intolerable side effects of antiarrhythmic drug (i.e. proarrhythmias)
Asymptomatic AFib
In poorly controlled, symptomatic AFib, the AV node is ablated, and ventricular pacing done by implanting a permanent pacemaker - “Pace & Ablate Strategy”.
2. Rhythm Control in Atrial Fibrillation
Rhythm control in atrial fibrillation can be achieved by:
Cardioversion
Electrical Cardioversion
Pharmacological Cardioversion
Ablation Procedures
Surgical Rhythm Control
Antiarrhythmic (AA) Medications
Amiodarone
Flecainide
Propafenone
Disopyramide
Sotalol
Ibutilide
Dofetilide
Procainamide
**Note: Many of the antiarrhythmic drugs listed above can be used to terminate AFib as well as for long term maintenance of sinus rhythm after conversion of AFib.
Rhythm control is preferred in the following circumstances:
Newly diagnosed AFib
High cardiovascular risk patients – Those above age 75, prior stroke or TIA, hypertension, diabetes, severe CAD, CKD, etc.
Persistent symptoms
Inadequate Rate control
Heart failure
Tachycardia mediated cardiomyopathy
Younger patients < 65 years of age
C = CV Risk Factor & Comorbidity Management
Adequate management of cardiovascular risk factors and unhealthy lifestyle form the third important aspect of AFib management.
Obesity is managed by an intense weight reduction regimen
High blood pressure should be properly controlled
The blood pressure should be kept ≤ 130/80 mmHg
Diabetes mellitus and dyslipidemia should be optimally controlled
Alcohol excess should be avoided - Abstinence is ideal
Moderate intensity physical exercise and being physically active is encouraged
Heart failure should be optimally treated and controlled
Coronary artery disease should be managed appropriately with medications, angioplasty, or coronary artery bypass graft (CABG)
Obstructive sleep apnea needs continuous positive airway pressure ventilation (CPAP) or other measures to prevent AFib and its recurrences
Atrial Fibrillation Treatment: Guidelines and algorithm for the management of AFib include drugs like anticoagulants, beta blockers, calcium channel blockers, along with possible cardioversion and comorbidity optimization, etc.
Complications of Atrial Fibrillation
Often, a complication may be the first symptom that indicates the presence of atrial fibrillation.
The complications of AFib include:
Thromboembolic Episodes
Clots from the LA and LAA embolize into the cerebral circulation to cause stroke
Thromboembolic complications may occur in the lungs, kidneys, spleen, liver, intestines, or limbs
Heart Failure
Usually occurs due to Tachycardia induced Cardiomyopathy
Heart failure can be both the cause and effect of AFib
Dementia
Seen in chronic AFib
Attributed to the “little strokes” the patient gets due to micro-emboli in the brain
Acute Pulmonary Edema
Can occur in AFib of abrupt onset
Acute Myocardial Infarction (AMI)
Sudden Ventricular Fibrillation
Can lead to cardiac arrest
May occur in AFib with very fast heart rate, especially in WPW syndrome
Atrial Fibrillation Complications: Complications of AFib include stroke, blood clots, heart failure, myocardial infarction, pulmonary edema, dementia, ventricular fibrillation, etc.
Prognosis of Atrial Fibrillation
Progressive atrial abnormality leads to persistent and later permanent atrial fibrillation.
Age is an important prognostic factor.
The risk of AFib and its complications increase with age and are maximum after the age of 65.
The prognosis of AFib is worse in women compared to men, as complications such as stroke are more common in women.
Women have an 11-fold increased risk of developing heart failure and death compared to men, where the risk is 3-fold.
The presence of comorbidities and risk factors worsen the prognosis in AFib.
The presence of a high c-reactive protein (CRP) in AFib increases the chances of stroke, adverse cardiac events, and early death.
The odds of developing a stroke is 5-fold higher in AFib than in normal individuals.
Stroke in turn increases the morbidity and mortality due to AFib.
Post operative AFib after cardiac surgery is associated with a higher long-term mortality.
AFib occurring with myocardial infarction causes a 4-fold increase in death.
Chronic kidney disease (CKD) with AFib is associated with a higher incidence of thromboembolic events.
An increase in mortality was found in AFib patients with renal failure, heart failure, major bleeding, old age and malignancy.
Patients on ACE inhibitors and angiotensin II receptor blockers (ARBs) in AFib have a lower mortality as they have a beneficial effect on heart failure and high blood pressure.
Atrial Fibrillation Prognosis: Prognostic factors related to age, men, women, stroke, heart failure, chronic kidney disease, etc.
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