We do not give a second thought to our heartbeats when the heart works normally. Nevertheless, the heart beats over 100,000 times per day and its rhythm is extremely accurate allowing the efficient distribution of blood through our whole body.

If the heart's rhythm is either too quick, too slow or is not regular, it is called arrhythmia. Arrhythmia does not necessarily indicate any problem with the heart. Sometimes arrhythmia is totally harmless, and sometimes it is quite dangerous and may result in heart attack under certain circumstances.

Mechanism Of The Heart's Electrical System

The heart's rhythm is controlled by the heart's electrical conduction system. The electrical impulse originates in the sinus node (also SA node) that is located in the upper right chamber of the heart (right atrium). The sinus node acts as the natural pacemaker of the heart.

The electrical impulse will then pass from the atria to the atrioventricular (AV) node before passing on to the ventricles via the conduction system. The electrical activity results in a heartbeat that is effective and regular.

In cases where there are irregular impulses being generated by the electrical system or cases where the generation of the impulses is either too slow or too fast, there will be abnormal passage of the impulses through the heart resulting in arrhythmia.

An arrhythmia can be categorised depending on whether the heart is beating too fast, too slowly or abnormally.

1. Supraventricular Tachycardia (SVT)

This is a condition that results in rapid heartbeats originating from above the ventricles, specifically the atrium and the area around the AV node. During an attack, the heart rate might suddenly increase to 150-180 or more beats per minute before suddenly falling back to normal again.

A patient will experience a sudden feeling of a pounding or racing heart beat (palpitations). Other symptoms include:

  • Chest pain
  • Difficulty breathing
  • Lightheadedness
  • Dizziness
  • Fainting

Even though SVT might be a frightful experience, it is still usually treatable in patients who suffer from it repeatedly through definite treatments like catheter ablation depending upon the nature of their SVT and personal circumstances.

2. Atrial Fibrillation

Atrial fibrillation is a kind of cardiac arrhythmia that happens to be one of the most common sustained forms of cardiac arrhythmia and it is significant due to the fact that it can cause stroke and other complications. In atrial fibrillation, the atria does not contract normally rather they quiver randomly and this causes an irregular heart beat.

There are some patients who suffer from the following symptoms:

  • Palpitations
  • Breathlessness
  • Tiredness
  • Dizziness
  • Exercise intolerance

On the other hand, there are some patients who do not show any symptoms at all and atrial fibrillation is diagnosed accidentally through ECG or a monitor.

3. Atrial Flutter

This resembles atrial fibrillation, but is somewhat different. It is usually associated with a large electric circuit, which is most commonly seen in the right upper chamber, or the right atrium. It looks similar to atrial fibrillation, except for the fact that the rhythm may be very regular and may lead to very fast heartbeats. As in the case of atrial fibrillation, the stroke risk is higher in these patients, and thus they may have to be on anticoagulation.

4. Premature Beats

Quite a few people have occasionally skipped beats, which are actually extra beats of the heart. They are generally premature contractions of either the atria or the ventricle. The former is called premature atrial contractions, while the latter one is known as premature ventricular beats. This feeling may sometimes be very dramatic.

When the heart has extra beats, there is usually a flip-flop feeling in the chest. They become more pronounced due to caffeine, alcohol, stress, fatigue, and sometimes medications. In the case of premature ventricular contractions, and in case their burden is really high, the patient needs a full assessment, as the burden of PVCs may sometimes weaken the heart muscle.

5. Ventricular Tachycardia

Ventricular tachycardia is the most dangerous of all arrhythmias, and it happens in the ventricles. Patients with previous heart attacks, cardiomyopathy, or other heart structural disease may get it.

It causes palpitations, dizziness, or even fainting; sustained ventricular tachycardia becomes dangerous as it may turn into ventricular fibrillation, when the whole heart quivers and the cardiac output does not occur anymore leading to cardiac arrest.

Thus, those patients with severe instances of ventricular arrhythmias need to have an implantable cardioverter-defibrillator (ICD) according to their heart condition.

6. Bradycardia

Slow heart rate is not always abnormal. May have a resting heart rate less than 60 beats per minute because of good cardiovascular condition. The problem comes when the heart rate is slow to give enough blood flow. Fatigue, dizziness, fainting, or lack of tolerance for exercise are the symptoms.

What Makes Atrial Fibrillation Significant?

One of the critical aspects of atrial fibrillation includes the potential for blood to become stagnant in the atria, specifically in the left atrial appendage, which is a small pouch projecting from the left atrium.

As a consequence of stagnant flow of blood, the formation of a thrombus becomes a possibility. If the thrombus detaches itself, it can travel in the bloodstream to the brain and result in a stroke.

This is why patients suffering from atrial fibrillation might have to take anticoagulant medications.

Anticoagulation is done by the treating physician after calculating the stroke risk of a patient as well as the bleeding risk of a patient using validated risk assessment scales.

The patient should be examined to find out whether he or she has a heart block of any kind, and if such a case is diagnosed, then a pacemaker will be required.

In case of any arrhythmia, one does not have to be panicked, but also cannot ignore the problem.

First, an ECG test should be taken. Based on how often the symptoms appear, either Holter monitoring or event monitoring may be suggested by the doctor. An echocardiography may also be considered for us to determine the presence of any heart disease.

If the rhythm itself is not seen, then it would be hard to diagnose the problems, since each of the mentioned arrhythmias has its own treatment.

(By Dr Ajit Menon, Director of the Department of Cardiology, Sir H. N. Reliance Foundation Hospital)

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