Atrial Fibrillation

Apollo Doctors Talk

Atrial Fibrillation

Introduction – The Normal Heart Rhythm

The heart is an electro-mechanical pump. It has two upper chambers called atria and two lower chambers called ventricles. Perfectly timed contractions of upper chambers and lower chambers maintain efficient pumping action of the heart. This results in distribution of adequate blood to all parts of the body. The timing and sequence of heart contractions are controlled by the electrical system of the heart.

The electrical impulse begins in the Sinoatrial (SA node), located in the right atrium. It is called the pacemaker of the heart. The SA node increases the rate of impulses during exercise and decreases the rate of impulses during sleep.

Atrial Fibrilation

Normally, all muscle fibers of the atria get electrically activated in a sequence, and all fibers contract at a time to maintain forward flow of blood and emptying of the blood into the ventricle. When different muscle fibers contract or relax at different times due to abnormal electrical autonomic foci, effective forward flow of blood cannot be maintained.

Atrial fibrillation is the most common irregular heart rhythm. It starts in the atria. Instead of one impulse being generated by the SA node, many autonomous foci develop in different portions of the atria.This leads to mechanical dysynchronous contractions of individual muscle fibres of the atria.

The atria is seen to be only shivering and not effectively contracting as one unit leading to a chaotic rhythm

When the ventricles contract irregularly it leads to rapid and irregular heartbeat. The rate of impulses in the atria can range from 300 to 600 beats per minute, but all impulses are prevented from reaching the ventricle by a structure called AV node.

Types Of Atrial Fibrilation

There are two types of atrial fibrillation

Paroxysmal – intermittent (it comes and goes)

Continuous – persistent

Atrial fibrillation can be threatening. When there is no effective contraction of the atria, owing to stasis of blood, it ends in the formation of clots. They can travel to any place in the body like brain (leading to stroke), kidneys, intestines, etc; and cause damage to those structures. Atrial fibrillation is associated with an increased risk of stroke, heart failure and even death.

Causes

In most cases, atrial fibrillation is caused due to a preexisting heart condition.

Coronary artery disease
Hypertension (high blood pressure)
Chronic lung disease
Cardiomyopathy
Heart failure
Congenital heart disease
Heart valve disease
After heart surgery
Pulmonary Embolism
Thyroid disease
Pericarditis
Viral infection

However, in 10 – 15% of the cases, it occurs with no underlying heart disease. In such cases, it may be related to any of the following

Alcohol or excessive caffeine use
Stress
Specific drugs usage
Electrolyte or Metabolic Imbalances
Severe infections
Genetic factors
Age (particularly after 60)

Symptoms

Heart palpitations: Sudden pounding, fluttering or racing sensation in the chest
Lack of energy
Dizziness with or without fall in blood pressure
Chest discomfort: Pain, pressure or discomfort in the chest
Shortness of breath: Having difficulty breathing during normal activities and even at rest

Sometimes, it may also present with absolutely zero symptoms

Diagnosis

Electrocardiogram (ECG)

Holter monitor: It is a wearable ECG recorder and records the ECG for 24 to 48 hours. This is useful when the atrial fibrillation occurs intermittently.

Event Loop Recorders: These can record ECG for a longer period of time like 7 to 10 days. They alert the occurrence of abnormal beats and the information can be received by E-mail/SMS.

Management

Managing Atrial fibrillation consists of

Restoring normal heart rhythm (sinus rhythm)
Controlling the heart rate
Thinning of blood to prevent formation and migration of blood clots and reducing the risk of stroke

Lifestyle Changes

Stop Smoking
Moderate alcohol intake
Avoid use of caffeine or caffeinated products (tea, coffee, energy drinks, coca-cola)
Control blood pressure
Achieve desirable weight
Control blood sugar levels
Look out for sleep apnea