As we grow older our heart and vessels undergo age related changes. Understanding these changes and the factors that predispose to these factors can lead to a healthy heart even as we advance to our golden years.
Have you ever had sudden onset of fast heart beat, sudden unexplained episodes of dizzy spells or transient shortness of breath, and when you check your pulse, you noticed that the heart rhythm is irregular? You may be having transient episodes of an abnormal heart rhythm called atrial fibrillation, which occurs with increasing frequency with age, affecting about one in 10 above the age of 65 years.
Atrial fibrillation is not just the usual abnormal heart rhythm but a serious problem with potentially dire circumstances. In atrial fibrillation, the left and right upper heart chambers (atria) are beating at the rate of about 400 per minute in an extremely irregular manner which means that the atria are “quivering” and are unable to pump blood into the lower heart chambers effectively.
Hence, when blood flows into the left atrium from the lungs, the blood flow is slowed down significantly. If the patient’s blood is “thick”, the slow flow can predispose to the formation of a blood clot in the left atrium.
If this clot dislodges from the left atrium, passes into the lower chamber and travels via the arteries to the brain, it can result in a major stroke. Atrial fibrillation is one of the most common cause of stroke in the elderly. In atrial fibrillation, the walls of the left upper heart chamber (atrium) and the lung veins bringing blood from the lungs into the left atrium undergo changes which result in instability of the electrical system of the heart.
This electrical instability results in atrial fibrillation originating from the left atrium or the lung veins. Depending on how frequent the electrical impulses from the atrium can pass through the heart’s electrical system into the lower chambers (ventricles), the heart rate can vary from heartbeat to heartbeat. For example, if about 1 in 4 beats are transmitted from the upper to the lower chambers, then the heart rate is 100 per minute.
Factors increasing stroke risk
If you have atrial fibrillation, recognise the risk factors for atrial fibrillation to prevent progression and reduce stroke risk. If you have atrial fibrillation but do not have any of the following risk factors: of female sex, aged 65 years or above, with high blood pressure, diabetes mellitus, heart failure, heart attack, narrowing of leg arteries or previous stroke, the annual risk of stroke without any blood thinning medication can be up to 3.2%.
If you have 3 of the risk factors, the annual stroke risk increases to 5.9% and for those with 6 risk factors, the annual stroke risk increases to 18.2%. The current advice is that if you have atrial fibrillation and have 2 risk factors or more, you should take blood thinning medications that can reduce the risk of blood clot formation in the heart. For those with zero or one risk factor, the need for blood thinning medication should be determined on a case-to-case basis.
Once you have been diagnosed to have atrial fibrillation, control of risk factors can reduce the frequency of atrial fibrillation and slow its progression. Among the risk factors, high blood pressure is the most common cause.
Valve disease and abnormal left ventricle function predisposing to atrial fibrillation are mostly due to heart muscle damage following blockage of a heart artery or a heart attack. Hence, if heart artery blockage can be detected early, heart attacks, valve damage and impairment of the function of the left ventricle can potentially be prevented.
Maintaining a normal heart rhythm
Once atrial fibrillation occurs, while risk factor control may reduce frequency, most often the patient will require medication or an invasive procedure called radiofrequency ablation to keep the rhythm normal.
In radiofrequency ablation, cardiologists insert special catheters into the left atrium via the leg vein and use the tip of these catheters to “burn” a ring shaped boundary around the entry of the lung veins into the left atrium to prevent the abnormal focus of electrical activity from spreading abnormal electrical impulses to the rest of the left atrium and the heart; essentially, it means isolating the focus of abnormal electrical activity from the rest of the heart.
Despite successful radiofrequency ablation treatment of atrial fibrillation, further stress on the heart can cause relapse of the condition. Identifying reversible factors and managing them may result in beneficial changes to the structural and electrical substrate of the left atrium. One common condition is obstructive sleep apnoea.
If you snore, open your mouth while sleeping and feel tired despite having adequate hours of sleep, it is likely that you have obstructive sleep apnoea which is a condition where your upper airway is obstructed during sleep resulting in decreased blood oxygen level during sleep.
Studies have shown that obstructive sleep apnoea is associated with increased stress of the left atrium resulting in 25% greater risk of recurrent atrial fibrillation after radiofrequency ablation treatment. However, if obstructive sleep apnoea is treated to ensure adequate oxygen during sleep, there is significant improvement in atrial fibrillation-free survival following ablation comparable to individuals without obstructive sleep apnoea.
For those with untreated obstructive sleep apnoea who undergo radiofrequency ablation, the success rate is comparable to those on medication alone, which means that most patients will suffer a relapse of atrial fibrillation. Obesity causes similar stress of the heart as obstructive sleep apnoea and in addition the fat surrounding the heart chambers can also exert stress on the heart.
Animal experiments in sheep have shown that significant weight gain has been associated with inflammation, scarring of the left atrium and damage to the atrial electrical system. When weight loss was induced in the sheep, favourable changes occurred in the heart.
While physical activity has been observed in many studies to be associated with decreased likelihood of atrial fibrillation, strenuous endurance exercise in those engaged in competitive sports such as marathon runners, cyclists, and cross-country skiers has been associated with an increased risk of atrial fibrillation.
Atrial fibrillation in the young
While atrial fibrillation predominantly affects elderly people, it can also affect younger people, especially those with excessive thyroid hormones (thyrotoxicosis) or those who had valve surgery. A close relative of mine in his fifties developed a massive stroke when he reached home and was rushed to the hospital. He had not known that he had thyrotoxicosis, a condition where his thyroid gland was overactive and produced excessive amounts of thyroid hormone.
This condition resulted in atrial fibrillation which then caused a clot to be formed in the left atrium and this clot travelled to his right main brain artery resulting in paralysis of his left side and a semi-comatose state. An X-ray computerised tomography scan of the head confirmed the presence of a huge clot in the brain. He was commenced on infusion of drugs to breakdown the clot in the brain artery.
Fortunately for him, the timely intervention within a 3 hour time frame resulted a full recovery from his life threatening condition.
Key points to remember
If you have palpitations, an irregular heart rhythm, and are 65 years old or older, look out for atrial fibrillation. For the young with thyrotoxicosis, be on the guard for occurrence of atrial fibrillation. Once atrial fibrillation has been diagnosed, see your physician to assess your stroke.
If you have a high risk of stroke, you should be commenced on blood thinning medication to prevent clot formation in the heart. For those with thyrotoxicosis, the atrial fibrillation is usually transient and resolves when the thyroid condition is controlled.
For most other conditions causing atrial fibrillation, patients will usually require long term medication or undergo radiofrequency ablation. Controlling blood pressure, and checking for heart artery blockage will reduce the likelihood of the transient atrial fibrillation developing into permanent atrial fibrillation.
If the atrial fibrillation has been treated with radiofrequency ablation, obstructive sleep apnoea treatment and weight reduction with moderate physical exercise can potentially reduce the likelihood of atrial fibrillation relapse.
If a stroke occurs, get to a hospital quickly, have a CT scan of the brain done to confirm the diagnosis and commence infusion of clot dissolving medication once the diagnosis is confirmed, and all these measures must be completed within 3 hours to get a good outcome.
Early recognition and management of atrial fibrillation is key to avoiding serious complications.