Difference Between Ventricular Tachycardia and Ventricular Fibrillation

Arrhythmia means irregular cardiac rhythm, and slow arrhythmias are called bradyarrhythmias and fast ones are called tachyarrhythmias. There are various types of arrhythmias. They are atrial tachycardia (monofocal or multifocal), atrial fibrillation, atrial flutter, atrioventricular nodal re-entry tachycardia, atrioventricular re-entry tachycardia, ventricular tachycardia and ventricular fibrillation. Ventricular tachycardia and ventricular fibrillation are both major arrhythmias. Both originate in the ventricles below the atrioventricular node (which is the secondary natural pacemaker of the heart). Myocardial infarction, inflammation of myocardium, cardiomyopathies, electrolyte imbalances and other metabolic abnormalities may cause ventricular tachycardia and fibrillation. The symptoms of both ventricular tachycardia and ventricular fibrillation are palpitations, chest pain, and difficulty in breathing. They are very dangerous because in some patients with ventricular tachycardia and ventricular fibrillation both are manifestations of a cardiac arrest. Therefore, it is very important to understand that both these conditions are life threatening and need immediate admission to the emergency room.

Ventricular Tachycardia

Ventricular tachycardia is an abnormal ventricular rhythm with a pulse rate above 100 beats per minute. Ventricular tachycardia presents with palpitations, chest pain, and difficulty in breathing. They may also come in a state of cardiac arrest. Electrocardiogram (ECG) shows regular R waves in the absence of atrial rhythm. All R waves are similar and regular. Ventricular tachycardia can be broad complex or narrow complex. Normally the QRS complex in ECG which marks the ventricular contraction is three small squares long. If this complex is broader than three small square, it is called a broad complex ventricular tachycardia and, if narrow, it is called a narrow complex ventricular tachycardia. It is important to differentiate between the two in a clinical standpoint because the management protocols differ greatly.

Ventricular tachycardia can be pulseless or with pulse. Narrow complex ventricular tachycardia usually has pulse while broad complex may or may not. Pulseless ventricular tachycardia is cardiac arrest and immediate cardiopulmonary resuscitation procedures should be implemented to save the patient’s life. For a brief overview of cardiopulmonary resuscitation procedures see below under ventricular fibrillation.

In all tachycardias the patient should be admitted to emergency room, put to a bed flat, IV access secured, oxygen given with a high flow rate, cardiac monitor attached, and an ECG should be taken. Ventricular arrhythmias are easily seen on ECG. In broad complex tachycardia, absence of pulse should trigger CPR while presence should trigger assessment to find out if the blood pressure is below 90mmHg, heart rate is above 150, chest pain is there, and heart failure features are there. If these danger signs are there, the patient needs immediate DC cardioversion followed by medical cardioversion. If no danger signs, medical cardioversion can go ahead. Potassium and magnesium levels should be checked and corrected because they both are arrthymogenic. Narrow complex ventricular tachycardia needs vagal maneuvers, IV adenosine in addition to cardioversion. After stabilization, oral antiarrhythmic drugs should be started and continued.

Ventricular Fibrillation

In ventricular fibrillation, there are no regular QRS complexes. There is no pulse, and the patient is in cardiac arrest. IV line, oxygen high flow, and cardiac monitor should be immediate. After two rescue breaths, CPR can start. If the cardiac monitor shows ventricular tachycardia or ventricular fibrillation (only two shockable rhythms), defibrillation should be done at 360j. This should be followed by 1 minute of CPR. 1mg of adrenaline should be administered IV while CPR goes on to jump start the heart. If the cardiac monitor shows some other rhythm, no shock is indicated. The cause for the arrest should be sought. Low blood oxygen, high blood carbon dioxide, low core temperature, low blood pressure, low blood volume, tension pneumothorax, cardiac tamponade, toxins, and pulmonary embolism are the major preventable causes.

What is the difference between Ventricular Tachycardia and Ventricular Fibrillation?

• Ventricular tachycardia has regular QRS complexes in ECG while fibrillation doesn’t.

• Ventricular tachycardia may be narrow or broad complex while fibrillation cannot be subdivided.

• Ventricular fibrillation always is an arrest rhythm while pulseless ventricular tachycardia is the arrest rhythm.


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