A Review article on “Concept of the five ‘A’s in the treatment of Cardiac Arrhythmia”


Debashis Mohapatra*, Sunita Mishra, Asish Kumar Dash

College of Pharmaceutical Sciences, Marine drive Road, Baliguali, Puri, Odisha-752002

*Corresponding Author E-mail: dmohapatra911@gmail.com



Cardiac arrhythmic disorders are defined as bradycardia or tachycardia on the basis of ventricular response that is less than 60 beats/minute for bradyarrhythmias and more than 100 beats/minute for tachyarrhythmias. Arrhythmias are a common cause of syncope and must be considered in all patients in whom syncope occurs, particularly when cardiac disease is present. Either extreme of ventricular rate, bradycardia or tachycardia, can depress cardiac output to the point of critical hypotension and syncope. Pulse rates outside this range may reduce cerebral circulation. The most common arrhythmias producing syncope or presyncope are profound sinus bradycardia, high-grade atrioventricular (AV) block, supraventricular tachycardia (SVTs), ventricular tachycardia, pacemaker malfunction, pacemaker induced arrhythmias, and pacemaker syndrome. The supraventricular tachycardias (SVTs) are sinus tachycardia, atrial tachycardia, AV-nodal re-entrant tachycardia, and tachycardia due to accessory pathways. It is essential to evaluate the arrhythmia history, to perform a good physical examination, and to accurately analyze the 12-lead electrocardiogram. In ventricular tachycardia there are broad QRS complexes (QRS width > 0.12 s). For acute management of arrhythmia there may be a new concept of the five 'A' strategy, which refers to “Adenosine, Adrenaline, Ajmaline, Amiodarone, and Atropine”. The five 'A' concept may revolutionise the treatment and effective management of all bradycardias, tachycardias, SVT, VT.


KEYWORDS: Bradycardia; bradyarrhythmias; five ‘A’ concept; supraventricular arrhythmias; tachycardia; ventricular arrhythmias.




Rapid diagnosis, emergency medicines and intervention are required in specific situations, such as- in cardiac emergencies. It is highly necessary to differentiate accurately between ventricular and supraventricular tachyarrhythmia[1]. This is essential for appropriate management of the clinical condition of the patient[2].


It becomes necessary to use the clues from various physical examination as well as ECG. although there may be underlying reasons for arrhythmia[3],[4]. Still the treatment of cardiac arrhythmia in intensive care is sometimes difficult, in spite of the clinical findings. The purpose of the present manuscript is to present a new concept for the treatment of patients with bradycardia and supraventricular or ventricular tachyarrhythmias in intensive care or cardiac emergencies: the concept of the five 'A's.



Better known as Bradycardia, is defined as a heart rate lower than 50 beats/min, may be caused by different mechanisms and has various reasons.



Incidence %





Acute Coronary Syndrome (ACS)








Pacemaker Failure


Other Reasons



Sinoatrial (SA) block is a conduction disorder in which impulses generated in the sinus node are intermittently conducted or not conducted to the atrial myocardium. SA conduction abnormalities can be manifested as second-degree block or complete SA block. Second-degree SA block may be type 1, type 2, or a 2-to-1 SA block (which looks Sick Sinus Syndrome is a dysfunction of the sinus node or SA conduction. Atrioventricular (AV) block is traditionally divided into first-degree, second-degree, and third-degree blocks. In first degree AV block, every P wave is conducted to the ventricles but the PR interval is prolonged. Second-degree AV block P waves are not conducted to the ventricles. This category is divided into type 1 & type 2, and second-degree AV block with 2-to-1 conduction. Third-degree AV block is characterized by complete blockade of electrical impulses from Atria to Ventricles. [Figure 1].






Narrow-QRS Complex Tachycardia:

Narrow-QRS complex tachycardia is a type of arrhythmia with a heart rate faster than 100 beats per minute and a QRS duration of less than 0.12 s[6],[7]. The patient suffering from narrow-QRS tachycardia usually complains about symptoms like palpitations, light-headedness, shortness of breath, or anxiety. The heart rate in many cases usually becomes very high (180-240 beats per min) and therefore the patient must be admitted in an intensive care unit for further treatment. The mechanism of this type of arrhythmia is usually diagnosed from ECG. and proper treatment can be sorted out for the patient. Causes of narrow QRS tachycardia are Sinus tachycardia, Atrial tachycardia, Atrial flutter, Atrial fibrillation, AV Nodal Re-entry Tachycardia (AVNRT).


Wide -QRS Complex Tachycardia:

Any Wide QRS complex tachycardia is assumed to be Wide-QRS complex tachycardia (QRS duration > 0.12 s) which is difficult to diagnose and fix the treatment pattern. It may be sustained or non-sustained.


Ventricular Fibrillation and Cardiac Arrest:

In USA the common cardiac ailments are acute myocardial infarction[8] with accompanying ventricular fibrillation (VF) or unstable VT. American Heart Association (AHA) reported about  the 'chain of survival' concept, with the four links-early access, cardiopulmonary resuscitation (CPR),[9]  defibrillation, and advanced care It is advisable to stick to  the following treatment pattern for higher degree of survival and faster recovery: (a) recognition of early warning signs, (b) activation of the emergency medical services system, (c) institution of basic cardiopulmonary resuscitation, (d) defibrillation, (e) management of the airway and ventilation, and (f) administration of intravenous medications.


Concept of the Five 'A's as an Emergency Approach in Bradyarrhythmia and Tachyarrhythmia

In emergencies the treatment of bradyarrhythmias, tachyarrhythmias, ventricular flutter, or ventricular fibrillation can be done by a concept that involves five drugs[10], all beginning with 'A' − Adenosine, Ajmaline, Amiodarone, Adrenaline, and Atropine − the five 'A' concept.



In regular narrow-QRS complex tachycardia, vagus nerve stimulation should be initiated to arrest the arrhythmia or even to modify AV conduction. If this fails, IV. anti-arrhythmic drugs should be administered for recovery from arrhythmia in hemodynamically stable patients. The patient can be administered with Adenosine,[11], calcium channel blockers, or beta-blocking agents are the drugs of first choice. Adenosine which was approved by the Food and Drug Administration in 1990 and is used today as the drug of choice for acute therapy of SVT. Adenosine is a naturally occurring substance. It binds to nodal A1 receptors in the SA and AV nodes. Adenosine has negative chronotropic effects in the SA node, hence it depresses conduction, and increases refractoriness in the AV node. Adenosine has a half-life of approximately 10 s. The drug does not have clinically significant negative inotropic effects. Adenosine[12] can cause flushing due to peripheral vasodilatation. Some patients may also develop non-cardiac chest pain.



The initial approach of using IV drugs in patients with wide-QRS complex tachycardia depends on the hemodynamic stability and the symptoms associated with the tachycardia. When the patient is hemodynamically unstable or has pulmonary oedema, the tachycardia should be promptly converted with a direct current (DC), synchronized shock. Ajmaline has advantages in the termination of both VT and SVT. Ajmaline prolongs the refractory period of the ventricles as well as that of any accessory pathway and the retrograde fast AV nodal pathway. Ajmaline may therefore terminate VT, SVT by an accessory pathway, and the common form of AVNRT.



Amiodarone is currently regarded as the most effective antiarrhythmic drug available for the treatment of patients with both supraventricular (SVT) and ventricular tachyarrhythmias (VT). It is considered to be particularly useful in case of ventricular tachyarrhythmias. The most relevant antiarrhythmic effect of amiodarone is due to its prolongation of cardiac repolarization. Amiodarone has been classified as a class-III anti-arrhythmic drug. In patients with sustained (duration> 30 s), hemodynamically stable, monomorphic VT, amiodarone should be administered as bolus dose -initially (150−300 mg in 5 min IV), followed by an infusion of 1050 mg/day. It is also used as a drug of choice for the treatment of polymorphic VT.



Pressor drugs such as Catecholamines have been used to treat cardiac arrest as well as certain types of cardiac arrhythmia since decades. The most common agent has been the catecholamines which induce adrenergic receptor stimulation. Adrenaline is supposed to be one of  the best studied and most widely administered adrenergic agonist used in the treatment of cardiac arrest. Adrenaline stimulates both α-1and α-2 receptors almost in a ratio of approximately 1: 4. The American Heart Association and the European Resuscitation Council continue to recommend repeated administration of adrenaline (with doses of 1 mg IV) during advanced cardiopulmonary resuscitation.



It is a competitive antagonist for the muscarinic acetylcholine receptor and is an anticholinergic drug. Atropine increases firing of the SA node and conduction through the AV node, opposes the actions of the vagus nerve, blocks acetylcholine receptors, and decreases bronchiole secretions. In general, atropine lowers the parasympathetic activity of all muscles and glands regulated by the parasympathetic nervous system. This occurs because atropine is a competitive antagonist of the muscarinic acetylcholine receptors. Acetylcholine is the main neurotransmitter used by the parasympathetic nervous system. Atropine may cause swallowing difficulties and reduced secretions. Atropine works because the main action of the vagus nerve of the parasympathetic system on the heart is to decrease the heart rate. Atropine blocks this action and, therefore, may increase the heart rate. Indications for atropine administration are vagus-mediated sinus bradycardia, blocks in the AV node, and vagus-mediated asystole. For symptomatic bradycardia or when there is asystole, the usual dosage of atropine is 0.5-1.0 mg IV every 3-5 min, up to a maximum dose of 0.04 mg/kg (3 mg.).



It is well known fact that evaluation of mechanism of arrhythmia plays the key role in the survival and treatment of all patients with tachyarrhythmias. For acute therapy, there is the new concept of the five 'A's, which refers to adenosine, adrenaline, ajmaline, amiodarone, and atropine. The five 'A's concept will enable survival as well as safe and effective treatment of all bradycardias, tachycardias, SVTs, VT, ventricular flutter, ventricular fibrillation, and of asystole patients.



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Received on 18.06.2020            Modified on 08.07.2020

Accepted on 29.07.2020     ©AandV Publications All right reserved

Res.  J. Pharmacology and Pharmacodynamics.2020; 12(3):133-136.

DOI: 10.5958/2321-5836.2020.00024.5