The condition is picked up later in women compared to men, which results in poorer treatment outcome
Mr P entered my consultation room in a wheelchair with his family in tow. After a brief introduction, it became evident that he had suffered a stroke. It had left him weak on his right side and he spoke with difficulty. What was unusual in his case was that he was an active, healthy 46-year-old man before his stroke. The only risk factor had been atrial fibrillation (AF). Mr P had silent atrial fibrillation which was diagnosed only at the time of his stroke. AF is the most common abnormal heart rhythm. It affects 1 to 2 per cent of the population. The risk of developing AF is 1 in 1,000 in those younger than 55 and increases to 1 in 10 for those aged above 80. AF can be due to abnormal heart valves. Often, AF is associated with hypertension, ischaemic heart disease, heart failure, infection and raised thyroid hormones. In about 10 to 15 per cent of cases, no underlying heart disease can be found. AF occurs when many electrical impulses in the atria (upper chambers of the heart) fire rapidly at the same time, causing a chaotic rhythm, often described as a fast and irregular pulse. As these electrical impulses are fast and chaotic, the atria cannot contract or pump blood into the ventricles (lower chambers of the heart) effectively. Subsequently, blood flow within the atria slows down and may cause blood clots to form. If these blood clots break into pieces, they may travel to the brain and cause a stroke.
Patients with AF have a five-fold increase in the risk of stroke and AF is responsible for approximately 15 per cent of strokes. The stroke risk persists even in asymptomatic patients. Furthermore, AF-related strokes are more severe, cause greater disability and result in worse outcome for patients than strokes in people without AF. Anti-coagulant or anti-platelet medication, which thins the blood, reduces the risk of a stroke in patients with AF. Warfarin has been used extensively. However, usage of warfarin needs to be monitored through regular blood tests. Additionally, warfarin has significant drug-drug and drug-food interactions. There are new types of medication, such as dabigatran and rivaroxaban, which are suitable alternatives to warfarin. Catheter ablation may be an option for patients who cannot tolerate medication or when medication is not effective in maintaining a normal heart rhythm. It is a minimally-invasive procedure performed by an interventional electrophysiologist (a cardiologist who specialises in treating heart rhythm conditions).
In this procedure, catheters (soft flexible tubes) are inserted into blood vessels of the groin or neck and guided to the atria. As AF usually begins in pulmonary veins or at their attachment to the left atrium, catheter ablation aims to render these regions electrically silent. By doing so, abnormal electrical impulses that originate from these pulmonary veins cannot be transmitted to the atria. The results of catheter ablation have been promising. The procedure has been proven to be more effective than medication in maintaining normal rhythm in patients with AF. I recall Mr S, a 40-year-old man who had paroxysmal AF, that is, he suffered from AF periodically. On such days, he experienced palpitations, got tired easily and was not able to run more than 500m. But on normal days, he could do a 5km run easily. Despite being placed on medication to maintain a normal heart rhythm, he continued to experience symptoms on and off. Hence, he decided to undergo catheter ablation to cure his AF.
Some patients may require a device called a pacemaker to be implanted to regulate the heart rhythm. Madam G, a 76-year-old grandmother who had persistent AF for years without problems, was recently admitted to the hospital for recurrent fainting spells. The last episode was particularly bad as she sustained a cut on her forehead. Continuous electrocardiogram (ECG) monitoring – which records the electrical activity of the heart – revealed AF with a long, slow heart rate. In fact, Madam G’s heart stopped for six seconds. In addition to medication to reduce her stroke risk, she had a pacemaker implanted. Fortunately, not all patients with AF develop strokes like Mr P. Some patients experience palpitations and breathlessness and get tired easily with reduced stamina, like Mr S. Other patients live for years with AF without problems, like Madam G. All these patients are now doing well. Mr P is on warfarin to reduce his risk of another stroke. He is motivated to continue with physiotherapy and aims to be able to walk into my consultation room at the next visit. It has been two years since Mr S underwent catheter ablation and his heart rhythm has remained normal without medication. Madam G has become reliant on her pacemaker as it prevents her heart rate from slowing. With an ageing population in Singapore, we are likely to see more patients with AF. Do not neglect that runaway heart rhythm. Ignorance is not bliss.
Dr Ching Chi Keong is a senior consultant at the department of cardiology and director, electrophysiology and pacing at the National Heart Centre Singapore. He is also an adjunct assistant professor at the Duke-NUS Graduate Medical School Singapore and a clinical tutor with the Yong Loo Lin School of Medicine at the National University of Singapore.