Cardiac arrhythmias (also called dysrhythmias) are abnormal heart beats or heart rhythms that originate from sites other than the usual site (in the sinus node). The term “palpitations” refers to the sensation felt by the affected person with a cardiac arrhythmia. Such individuals may feel that their heartbeat is irregular, stronger than usual or too fast or slow. A normal heart rate ranges between 50 to 100 beats per minute for most people. Cardiac arrhythmias can occur with a normal heart rate, or with heart rates that are too slow (below 50 beats per minute) or too fast (greater than 100 beats per minute). In addition to feeling palpitations, patients with arrhythmias may also experience other symptoms, such as dizziness, lethargy, breathlessness and sudden blackouts.
Arrhythmias may be caused by a variety of factors. These include:
Some patients with apparently “normal” hearts may also experience arrhythmias due to underlying electrical abnormalities in their hearts that cannot be detected with standard imaging tests. Patients with arrhythmias should therefore seek expert help from a cardiologist for accurate diagnosis and treatment.
An arrhythmia may be silent and not cause any symptoms. This is particularly true of atrial fibrillation (AF), which may be picked up by your doctor during a routine medical check up. When symptoms do occur, they may include:
This is a rapid heart rate, usually with a regular rhythm, that originates from above the ventricles. SVT begins and ends suddenly and can affect people of all ages, including children and older adults. It is not usually life-threatening, although the symptoms can be very unpleasant and occur unpredictably. Most SVT will recur and can be safely and very effectively treated with a procedure called catheter ablation. There are two main types of SVT:
AV nodal re-entrant tachycardia (AVNRT): This is due to more than one pathway through the AV node, which normally connects the atria and ventricles. This extra pathway allows a circuit to form within the AV node that can lead to very fast heart rates and symptoms of palpitations.
Accessory pathway tachycardias: These are due to an extra electrical pathway (accessory pathway) between the atria and ventricles that allows the electrical impulses to travel very quickly in a circuit around the heart, causing the heart to beat unusually fast. The accessory pathway is present from birth and may sometimes be seen on the normal resting ECG (in this case, the condition is termed Wolff-Parkinson-White syndrome or WPW).
These are abnormally slow heart rhythms that impair the ability of the heart to supply blood to the rest of the body leading to symptoms such as dizziness, lethargy, breathlessness and blackouts. These arrhythmias may be due to disease in the heart’s electrical conduction system at several points:
Sinus node dysfunction: due to an abnormal sinus node (the natural pacemaker of the heart). Significant sinus node dysfunction that causes symptoms is treated by insertion of a permanent pacemaker.
Heart block: Due to partial or complete block of electrical impulses travelling between the atria and ventricles. This may lead to the ventricular rate being too slow, despite the atrial rate being adequate. The heart may beat irregularly and too slowly. Some forms of heart block may require treatment with a permanent pacemaker.
The following tests may be required to diagnose an arrhythmia: