Difference Between AFIB and VFIB and SVT

Key Difference – AFIB vs VFIB vs SVT
 

Abnormalities in the heart rate are called arrhythmias. The conditions that are going to be discussed in this article are few varieties of arrhythmias whose pathogenesis is triggered by the defects in the conducting system of the heart. Atrial fibrillation (AFIB) is a common arrhythmia whose incidence is high in the elderly population above 75 years of age. Ventricular fibrillation (VFIB) is the very rapid and irregular ventricular activation with no mechanical effect is called. Sustained ventricular tachycardia (SVT) is typically characterized by the presence of an extremely high pulse rate that is in the 120-220 beats/min range. In fibrillations, the contractions of the cardiac muscles are uncoordinated and irregular, and they occur at a rapid pace. But in tachycardia, although the contractions occur at a rapid rate they are well coordinated. This is the key difference between AFIB and VFIB and SVT.

CONTENTS

1. Overview and Key Difference
2. What is AFIB
3. What is VFIB
4. What is SVT
5. Similarities Between AFIB and VFIB and SVT
6. Side by Side Comparison – AFIB vs VFIB vs SVT in Tabular Form
7. Summary

What is AFIB?

Atrial fibrillation is a common arrhythmia whose incidence is high in the elderly population above 75 years of age. Young adults are more likely to be affected by the paroxysmal form of the disease. P waves are absent in the ECG and there are irregularly irregular QRS complexes.

Causes

Cardiac Causes

• Hypertension
• Congestive heart failure
• Coronary artery diseases
• Valvular heart diseases
• Cardiomyopathies
• Myocarditis and pericarditis

Non- cardiac Causes

• Thyrotoxicosis
• Phaeochromocytoma
• Acute or chronic pulmonary diseases
• Electrolyte disturbances
• Pulmonary vascular diseases

Clinical Features

• Palpitations
• Dyspnea
• Progressive deterioration of the exercise capacity
• Irregular pulse

Clinical Classification

• First detected atrial fibrillation
• Paroxysmal atrial fibrillation – fibrillation stops within seven days from onset
• Persistent atrial fibrillation – requires cardioversion to stop
• Permanent atrial fibrillation – no spontaneous or induced cardioversion

Management

• Use of antiarrhythmic drugs to control the ventricular rate
• Cardioversion with or without the use of anticoagulants

Two main strategies are available for the long-term management of atrial fibrillation.

Rate control strategy uses oral anticoagulants along with AV nodal slowing agents to control the rate at which the heart contracts. Antiarrhythmic drugs together with cardioversion and oral anticoagulants are used in the rhythm control strategy.

What is VFIB?

Very rapid and irregular ventricular activation with no mechanical effect is called ventricular fibrillation (VFIB). The patient becomes pulseless and becomes unconscious. The respiration also ceases in some cases.

In the ECG, well-organized complexes are absent and the waves are shapeless. Rapid oscillations can also be observed in this condition. Ventricular fibrillation is usually provoked by ectopic cardiac beats.

If the fibrillation happens within two days from an acute myocardial infarction, prophylactic treatments are not necessary. But if the fibrillation is not associated with any myocardial infarctions the chance of getting recurrent episodes of atrial fibrillation is extremely high. Most of the patients die because of sudden cardiac arrest.

Management

• Electrical defibrillation
• Basic and advanced cardiac life support
• Transplantation of an implantable cardioverter-defibrilator

What is SVT?

Sustained ventricular tachycardia (SVT) is typically characterized by the presence of an extremely high pulse rate that is in the 120-220 beats/min range.

Clinical Features

• Dizziness
• Hypotension
• Syncope
• Cardiac arrest
• During the auscultation abnormalities in the heart, sounds such as variable intensity of the first heart sound can be observed.

The ECG shows rapid ventricular rhythm with broad QRS complexes. Sometimes it is also possible to observe P waves.

Management

Urgent treatment may be required depending on the hemodynamic status of the patient. In conditions such as pulmonary edema and hypotension where the patient is hemodynamically compromised, DC cardioversion is necessary to stabilize the patient. For patients who are hemodynamically stable, the intravenous infusions of class I drugs or amiodarone are usually used. If the medical therapy fails to achieve the desired outcome, DC conversion has to be used to avoid fatal consequences.

What are the Similarities Between AFIB and VFIB and SVT?

• In all three conditions are characterized by the abnormalities in the heartbeat.

• The defects in the conducting system of the heart are the main reason for these diseases.

What is the Difference Between AFIB and VFIB and SVT?

AFIB vs VFIB vs SVT
AFIB	Atrial fibrillation (AFIB) is a common arrhythmia whose incidence is high in the elderly population above 75 years of age.
VFIB	Ventricular fibrillation (VFIB) is a very rapid and irregular ventricular activation with no mechanical effect.
SVT	Sustained ventricular tachycardia (SVT) is typically characterized by the presence of an extremely high pulse rate that is in the 120-220 beats/min range.
Availability
AFIB	Contractions of the cardiac muscles are well coordinated and take place at a rapid rate.
VFIB	Contractions of the cardiac muscles are well coordinated and take place at a rapid rate.
SVT	Cardiac contractions are fast, irregular and uncoordinated.
Locations
AFIB	This occurs in the atria.
VFIB	This occurs in the ventricles.
SVT	This occurs in the ventricles.
Causes
AFIB	Etiological factors can be categorized into two main categories. Cardiac causes include hypertension, congestive heart failure, coronary artery diseases, valvular heart diseases, cardiomyopathies, myocarditis, and pericarditis.  Noncardiac causes include thyrotoxicosis, phaeochromocytoma, acute or chronic pulmonary diseases, electrolyte disturbances and pulmonary vascular diseases
VFIB	Usually, VFIB is associated with acute myocardial infarctions in the ventricles. Sometimes it can be due to idiopathic causes also.
SVT	Most of the time SVT is due to idiopathic causes.
Symptoms and Signs
AFIB	Palpitations, dyspnea, progressive deterioration of the exercise capacity and irregular pulse are the typical symptoms and signs.
VFIB	The patient becomes pulseless and becomes unconscious. The respiration also ceases in some cases.
SVT	Clinical features of SVT are dizziness, hypotension, syncope and cardiac arrest. During the auscultation abnormalities in the heart sounds such as variable intensity of the first heart sound can be observed.
ECG
AFIB	P waves are absent in the ECG and there are irregularly irregular QRS complexes.
VFIB	In the ECG, well- organized complexes are absent and the waves are shapeless. Rapid oscillations also can be observed in this condition.
SVT	The ECG shows rapid ventricular rhythm with broad QRS complexes. Sometimes it is possible to observe P waves also.
Treatment
AFIB	Treatment is either through the use of antiarrhythmic drugs to control the ventricular rate or cardioversion with or without the use of anticoagulants.
VFIB	The management includes electrical defibrillation, basic and advanced cardiac life support and transplantation of an implantable cardioverter-defibrillator.
SVT	In hemodynamically compromised patients DC cardioversion is necessary to stabilize the heart rate. In patients who are hemodynamically stable, the intravenous infusions of class I drugs or amiodarone are usually used. If the medical therapy fails to achieve the desired outcome, DC conversion has to be used to avoid fatal consequences.

Summary – AFIB vs VFIB vs SVT

Atrial fibrillation is a common arrhythmia whose incidence is high in the elderly population above 75 years of age. Very rapid and irregular ventricular activation with no mechanical effect is called the ventricular fibrillation. SVT or sustained ventricular tachycardia is typically characterized by the presence of an extremely high pulse rate that is in the 120-220 beats/min range. In tachycardias, the contractions are well coordinated but occur at a rapid pace whereas in fibrillations the contractions are fast, irregular, and uncoordinated. This is the basic difference between AFIB and VFIB and SVT.

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References:

1. Kumar, Parveen J., and Michael L. Clark. Kumar & Clark clinical medicine. Edinburgh: W.B. Saunders, 2009. Print.

Image Courtesy:

1. “Afib small (CardioNetworks ECGpedia)” By CardioNetworks: Drj – CardioNetworks: Afib_small.svg (CC BY-SA 3.0) via Commons Wikimedia
2. “De-Rhythm ventricular fibrillation (CardioNetworks ECGpedia)” By CardioNetworks: Googletrans – CardioNetworks: De-Rhythm_ventricular_fibrillation.png (CC BY-SA 3.0) via Commons Wikimedia
3. “E341 (CardioNetworks ECGpedia)” By Michael Rosengarten BEng, MD.McGill – EKG World Encyclopedia (CC BY-SA 3.0) via Commons Wikimedia