When the heart beats faster than normal, it is called tachycardia and when the heart beats too slowly, it is called bradycardia.
When the heart doesn't beat properly, it can't pump blood effectively. When the heart doesn't pump blood effectively, the lungs, brain and all other organs can't work properly and may shut down or be damaged.
The heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of the heart is normally controlled by a natural pacemaker (the sinus node) located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat.
From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles.
The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) — usually the only pathway for signals to travel from the atria to the ventricles.
The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.
In a healthy heart, this process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.
Causes of arrhythmia or abnormal heart rhythm
In case of arrhythmia or abnormal heart rhythm the electrical impulses comes from another part of the heart and not the natural pacemaker sinus node. Or the electrical impulses come from the sinus node, but go to the lower chambers of the heart by an unusual path.
Many factors can contribute to arrhythmia such as:
- A heart attack or scarring of heart tissue from a prior heart attack as well as blocked arteries (coronary artery disease)
- Changes to the structure of the heart for example; cardiomyopathy
- High blood pressure
- Overactive thyroid gland (hyperthyroidism)
- Underactive thyroid gland (hypothyroidism)
- Drinking too much alcohol or caffeine
- Drug abuse
- Sleep apnea
- Genetics factors
Types of arrhythmias or abnormal heart rhythm
Arrhythmias can be classified according to origin (atria or ventricles) or speed of heart rate such as:
Tachycardia - This refers to a fast heartbeat — a resting heart rate greater than 100 beats a minute.
Bradycardia - This refers to a slow heartbeat — a resting heart rate less than 60 beats a minute.
It is very important to note that not having tachycardia or bradycardia means that a person has heart disease. For example, during exercise it's normal to develop a fast heartbeat as the heart speeds up to provide body tissues with more oxygen-rich blood. During sleep or times of deep relaxation, it's not unusual for the heartbeat to be slower.
Symptoms of arrhythmia
- Arrhythmias may not cause any signs or symptoms. However, noticeable arrhythmia symptoms may include:
- A fluttering in the chest
- A racing heartbeat (tachycardia)
- A slow heartbeat (bradycardia)
- Chest pain
- Shortness of breath
- Lightheadedness or dizziness
- Fainting (syncope) or near fainting
- Tests for abnormal heart rhythms
- It depends on the symptoms but the routine recommendations are ECG, echocardiography or electrophysiological (EP) study to help diagnose an abnormal heart rhythm.
Treatment of arrhythmia depends on the type of abnormal heart rhythm, sometimes it only needs medication to stop, prevent or control arrhythmia. Alternatively are certain procedures such as cardioversion or catheter ablation, or surgery to insert an implantable cardioverter defibrillator (ICD) or pacemaker.
In my next story I will talk in detail about the types of arrhythmia.