The First Private Teaching Hospital in South Africa, Johannesburg

Heart Rhythm Awareness

By Dr Keir McCutcheon – Cardiologist at Wits Donald Gordon Medical Centre

Heart rhythm abnormalities

Heart rhythm abnormalities, or arrhythmias, are conditions commonly treated by cardiologists and electrophysiologists (cardiologists with special training in heart rhythm problems). They originate from aberrations in the electrical system of the heart and result in the heart rate becoming abnormally slow, fast and/or irregular. Although there are some hereditary conditions that result in arrhythmias early in life, most arrhythmias are seen in older patients. The most common arrhythmias include atrial fibrillation, heart blocks (with very slow heart rates), extra or ectopic beats and life-threatening tachy- (fast) arrhythmias. Patient with arrhythmias can be totally asymptomatic or present with a wide variety of symptoms including palpitations, breathing difficulty, and, of more concern, stroke and death. Sometimes patients will need to undergo long term monitoring (such as a 24-hour ECG or an implantable loop recorder) in order to make the diagnosis of an arrhythmia.

Atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia and is becoming progressively more prevalent with population aging. This arrhythmia causes an irregular heart rhythm and has two major consequences for the patient. Firstly, it predisposes the patient to thrombus (clot) formation in the left atrium of the heart with the risk of that thrombus dislodging from the heart and blocking any small artery in the circulatory tree. Of particular concern is the risk for stroke due to obstruction of blood flow to the brain. Therefore, most patients are treated with medication to ‘thin’ the blood to prevent thrombus formation and reduce the risk of stroke. These include warfarin and newer, more predictable, oral anti-coagulants. Secondly, this arrhythmia can result in a very fast heart rate, which can cause shortness of breath, palpitations, dizziness and fainting. There are a number of approaches to the treatment of this fast and irregular heart rhythm including medication, electrical cardioversion and, more recently, atrial fibrillation ablation therapy.

Heart blocks

Heart blocks occur when the electrical signal from the sinus node (where the electrical signal of the heart is generated) fails to reach the pumping ventricles of the heart. There are various types of heart block but some result in an extremely slow heart rate which, besides being potentially fatal, can cause patients to faint or be fatigued and out of breath. Fortunately these arrhythmias are relatively easily treated by implantation of a pacemaker, which is a common procedure performed by cardiologists. Pacemaker implantation usually involves a short admission to hospital and a small incision in the skin below either the left or right collar bone. A pacemaker generator is then implanted under the skin and connected to the heart by one, two or three wires. The device is able to sense electrical activity in the heart and activate the heart to contract at an appropriate rate, which reduces the risk of death and improves symptoms dramatically.

Life-threatening tachy-arrhythmias

Some patients are at increased risk of life-threatening tachy-arrhythmias or have sustained these arrhythmias in the past. In some of these patients an implantable defibrillator-cardioverter (ICD) is indicated and is implanted in a similar manner to pacemaker implantation.

Complicated heart arrhythmias

Complicated heart arrhythmias are usually referred to an electrophysiologist, who is able to determine the cause of the arrhythmia and the required treatment by inserting specialised catheters through a leg vein up to the heart, which enables electrical current readings and ablation of abnormal electrical activity. These are performed only in specialised units in the country.