Atrial fibrillation often goes unnoticed until a stroke reveals it
More than 33 million people worldwide have atrial fibrillation, the most common serious heart rhythm disorder. Many feel nothing at all. Some only learn they have it from a routine check-up, and for others the first sign is a stroke. With age it climbs from one person in a thousand to one in seven.
In atrial fibrillation the heart's two upper chambers beat fast and chaotically. It tends to start as brief episodes that grow longer until they become constant. When it does cause symptoms, people describe palpitations, breathlessness, light-headedness or fainting, because a disorganised rhythm pumps less blood. Over the long term it raises the risk of heart failure, dementia and stroke. On an electrocardiogram the telltale pattern is irregularly spaced heartbeats with no P waves.
The misfiring often starts in muscle bundles that reach from the left atrium into the pulmonary veins. That is why doctors can sometimes restore a normal rhythm by using a catheter to electrically isolate those veins, a procedure called ablation. As the condition becomes entrenched, the left atrium itself turns into an independent source of chaos. The first known report of an irregular pulse came from Jean-Baptiste de Sénac in 1749, and Thomas Lewis first recorded the rhythm on an ECG in 1909.
High blood pressure and valve disease are the most common risk factors that can be changed. Obesity, sleep apnoea, heavy drinking, smoking, diabetes and thyroid problems also contribute, as do stress hormones and possibly night shifts. Surprisingly, caffeine does not seem to be linked, while extreme endurance exercise such as marathon running brings a modest rise in older people. A parent or sibling with the condition lifts the risk by about 40 percent. Even so, roughly half of cases have none of the usual risk factors.
Treatment either slows the heart to a near-normal rate or tries to reset the rhythm with drugs or an electric shock. Most people with the condition face a higher chance of stroke, so those beyond low risk are usually offered blood thinners such as warfarin, which cut strokes but increase serious bleeding. Losing weight, exercising more and drinking less can lower both the risk and the burden.
Source: Atrial fibrillation
