It is the season of the heart, which is the symbol of Valentine's Day and is the centre of our being, emotions and sensibilities. The heart gives us the capacity to 'feel' love, and to experience compassion, sentiments and affection.

As I reflect on a song (which we'll probably hear repeatedly on Valentine's Day), the 1971 Bee Gees' How Can You Mend A Broken Heart?, my pharmaceutical sentiments kick in and I write about treatments for a disturbance in the blood-pumping heart.

Our heart has its own natural pace-maker (nerve tissue) which produces electricity to coordinate the pumping action of its two sets of chambers. These electrical impulses cause the heart to beat with a regular rhythm. When there is an abnormal rate and/or rhythm of the heartbeat, an arrhythmia may be diagnosed. The heart rate is usually too high, too low or just irregular.

Reduced blood supply

Most arrhythmias are caused by heart disease, which reduces the blood supply to the heart and to the electrical system (pacemaker) which controls the heart rate. The following may also cause arrhythmias:

♥ heart-related birth defects

♥ an over-active thyroid gland

♥ caffeine

♥ potassium in excess

♥ drugs in tobacco.

Atrial fibrillation, a type of arrhythmia, if diagnosed early enough, is successfully treated with cardioversion, a technique in which a brief electric shock is applied to the heart.

In some types of arrhythmias such as complete heart block, damage to the heart's conductive tissue, blocks the pathways for impulses to travel to the lower chambers of the heart, and the heart rate becomes dangerously slow or the heart fails to beat. One option, in such cases, is to use surgery to fit a permanent artificial pacemaker.

If an arrhythmia is sudden and severe, it may be necessary for a doctor to immediately inject a drug in order to restore normal heart function.

When the heart's pumping action is seriously affected by arrhythmia to the extent where there is inefficient circulation of blood throughout the body, drugs are normally used. The different drugs for arrhythmias (anti-arrhythmic drugs) work in different ways to restore a regular heart rhythm.

Digoxin

Digoxin is a common anti-arrhythmic drug. Digoxin reduces the flow of electrical impulses in the heart, causing the heart to beat more slowly. Remember that when the heart beats too fast or if the heart muscle becomes damaged, the pumping action of the heart itself can become weak.

So digoxin, by slowing down the heart rate, also improves the force of the muscle contraction each time the heart receives the impulses.

The improvement is particularly helpful to persons who have had a heart attack, which harms heart muscles and causes the heart to lose power. The amount of digoxin needed to help most people may be close to the toxic dose, so monitoring the pulse for changes in the rate is usually necessary. The doctor should be informed about any symptoms which are experienced, for example, excessive tiredness, confusion or vomiting.

Beta Blockers

These anti-arrhythmics block the pacemaker's ability to send signals to the upper chambers of the heart, thereby preventing attacks of arrhythmia, or reducing the frequency and severity of the arrhythmia. Atenolol, propranolol and metoprolol are examples.

Calcium Channel Blockers

Calcium channel blockers, for example, verapamil, slow the passage of electrical signals through the heart muscle, easing the heart's workload. Other anti-arrhythmics such as disopyramide, procainamide and quinidine act in a similar fashion, and affect the response of the heart muscles to signals received.

Dahlia McDaniel is a pharmacist and final year doctoral candidate in public health at the University of London; email: yourhealth@gleanerjm.com.