Listen to the beat and get down on it!

The dancers among us will find it natural to just wave and swerve to the rhythm of the music but if you are  anything like me, a guy with two left feet, you would quiver, shiver and move completely out of synch, and end up tripping on the floor! It is not a pretty sight.

"What on earth is he talking about this time?," some might ask. It is about the heart, of course. The heart beats around 100,000 times a day in a very regular and coordinated manner. It 'dances' to a certain beat. But, when the heart rhythm goes out of whack and does not follow a regular rhythm, it can spell trouble.

Following up on last week’s discussion on palpitation and cardiac arrhythmia (abnormal heart rhythm), a normal heart beat always starts from an electrical impulse from the sino-atrial node (SA  node) in the right atrium which then spreads to the AV node and later to the ventricles. Every atrial contraction is then followed by a ventricular contraction in a regular rate of 60 beats per minute. This is called sinus rhythm.

There exists a condition where the electrical impulse no longer starts from the SA node but instead from anywhere in the atria and the nearby pulmonary veins.

The signals do not travel normally, and they may spread throughout the atria in a rapid, disorganised manner causing the atria to quiver or fibrillate.

The abnormal electrical signals then flow to the ventricles in a very disorganised way. The resultant ventricular  contraction is irregular. Like my dancing, the heart beats completely out of rhythm and this abnormal phenomenon is called atrial fibrillation.

A trial Fibrillation Atrial fibrillation (AF) is the most common  cardiac arrhythmia and the incidence increases with age. About eight per cent of those above 80 years of age have AF.

In the non-elderly, AF occurs especially in those with underlying heart disease which include hypertension, coronary heart disease, heart failure, heart valve disease, myocarditis, pericarditis and sick sinus syndrome.

It can also occur in non-heart related conditions such as lung diseases, hyperthyroidism, alcohol excess and medications that stimulate the heart.

Most of those with AF do not have any symptoms, especially if they have had it for a long time. However, some may experience palpitations, dizziness and lethargy. In severe cases where the ventricular or heart rate is fast, there may be breathlessness or even chest pains.

In AF, the heart can go up in an uncontrollable way. It may even go up to 200 beats a minute. When this happens, there isn't enough time for the ventricles to be filled up with blood before they contract.

This will result in the pooling of blood in the atria and the subsequent back pressure to the lungs causing pulmonary oedema (water in the lungs).

The pooling of blood in the atria can also form clots which can dislodge from the heart and block a small vessel.

This is called thromboembolism and if this happens in the brain, it will lead to a stroke.

The diagnosis of AF is based on a simple electrocardiogram (ECG). If AF is not persistent and occurs  intermittently, then a 24-ECG recording called Holter monitor which is a small portable ECG machine that records all your heart beats in 24 or 48 hours, is ordered.

To find out the causes of AF, blood investigation is done to look for electrolyte abnormalities and elevated thyroid hormone levels. Echocardiogram and chest X-ray are done to exclude structural heart abnormalities and lung diseases respec-tively as possible causes of AF.

The treatment objectives are two-fold:
To correct the heart rhythm or if unsuccessful, to at least control the heart rate and to prevent thromboembolism.

Various drugs are used to convert AF back into normal sinus rhythm such as amiodarone and propafenone but they usually work if the onset of AF is recent.

Once AF is permanent and drugs have failed, a synchronised DC cardioversion may be done. It involves delivering an electrical shock or two to the heart through paddles or patches on your chest to restore normal rhythm which may still fail and if clinically indicated to correct the rhythm, a procedure called radiofrequency ablation can be done. It involves passing small catheters through the groin and directing radiofrequency energy to the heart area that trigger the abnormal electrical activity.

In many cases, AF remains despite various attempts to convert it back to sinus rhythm. The aim then is to control the heart rate to between 60 to 100 beats a minute to avoid complications. Betablocking drugs, calcium channel blockers and digoxin are used as well.

The risk of thromboembolism increases with age. Without blood-thinning treatment, stroke occurs in about 1.3 per cent of people with AF aged 50 to 59 every year and increases to 5 per cent per year for those who are older than 80 years of age.

So, it doesn’t matter if you cannot dance. What really matters is your heart dances to the correct rhythm.

If you have any queries or comments, please write to me at haizal@tropicanamedicalcentre.com. See you next
Wednesday.

Dr Haizal Haron Kamar
Consultant Cardiologist
Tropicana Medical Centre

Why do I get palpitation after meals?

Dear Dr Haizal

I READ your article Can you feel your heart beating? Recently, I have been having palpitations after my meals. I thought it was because I eat too much so I reduced my intake but the effects are the same. Even eating one slice of bread causes this palpitation. Each time the palpitation starts, I start to cough. But it only lasts for few minutes. Is this something I should be concerned about?

Christine

Dear Christine

When you eat, there is an increase in blood flow to your stomach and digestive system. The heart will have to work a bit harder to pump blood to support this extra requirement. Usually, this normal physiological response will go unnoticed but occasionally, it may manifest as palpitation.

Your experience of palpitation after eating, therefore, could be the result of an over-exaggeration of an otherwise normal process. However, it could also be because of an irregular eating habit  affecting the carbohydrate and glucose metabolism. Eating after prolonged hunger causes the blood
glucose to rise rapidly which, in turn, stimulates high levels of insulin. This may cause your heart rate to go up. The excessive insulin produced leads to the lowering of blood glucose which then triggers the release of sympathetic hormones like adrenaline that further increases the heart rate.

Palpitations after eating can also be due to underlying gastro-esophageal reflux disease. It is the spillover of acid into the oesophagus usually after a heavy meal or in certain positions like lying flat or stooping forward and manifests as chest discomfort. The vagus nerve regulates both swallowing and heart rhythm as well as transmits sensory information regarding the oesophagus to the brain.

Stimulation of the vagal nerve fibres may alter the neural tone that controls heart rhythm and cause palpitation.

The vagus nerve also stimulates the pharynx, larynx and bronchi — precisely the organs involved in the cough reflex.

When the vagus nerve stimulates the heart inappropriately and causes palpitation, it can also stimulate the cough reflex. To overcome the problem, avoid large meals and prolonged hunger and
reduce intake of sugar, drinks with high caffeine content and alcohol.

If the palpitation persists despite taking these measures, please consult your doctor.