Cardioembolic stroke: when a clot travels from the heart

In atrial fibrillation the upper chambers quiver rather than contracting, so blood can pool and clot, particularly in a small pouch called the left atrial appendage. When normal rhythm returns or fragments break off, a clot can be ejected into the circulation. Because the internal carotid and vertebral arteries carry a large share of the heart's output, the brain is a common landing site.

Other cardiac conditions produce emboli by different routes. After a large heart attack a clot may form on damaged heart muscle; in a weakened ventricle blood flows slowly; in valve disease, mechanical valves and endocarditis, clots or infected material can detach. A shunt such as a patent foramen ovale can let a clot from the veins pass to the arterial side, although it is mostly considered in younger patients without other explanation.

The NHS describes atrial fibrillation as an irregular heartbeat with a pulse that is not steady, which may cause palpitations, tiredness, breathlessness or no symptoms at all. Its risk factors include increasing age, obesity, smoking, high blood pressure, heart failure, diabetes, sleep apnoea and thyroid problems. Because it can come and go, it may be missed on a single ECG; after a stroke, longer heart monitoring is often arranged, sometimes with an implanted loop recorder.

Treatment of atrial fibrillation has two parts. Rate or rhythm control manages symptoms using medicines, cardioversion or catheter ablation. Anticoagulation reduces the risk of stroke and is decided largely by stroke risk scores, not by how the heart feels, so people with no symptoms may still need it.

Symptoms are those of any stroke, with FAST features of facial droop, arm weakness and speech difficulty, though embolic strokes often cause sudden severe deficits including loss of vision or language. A brain scan confirms the infarct, and additional investigations hunt for the source: an ECG, prolonged rhythm monitoring, an echocardiogram to assess heart size, valves and clot, and sometimes a transoesophageal echocardiogram or bubble study.

Imaging of the brain arteries is also done to exclude carotid disease and distinguish a cardiac source from other causes, because several mechanisms can coexist in older people.

• ECG at presentation and extended monitoring afterwards.

• Echocardiogram to look at the heart structure.

• Neck and brain artery imaging.

• Blood tests including glucose, cholesterol and clotting.

For atrial fibrillation, the NHS describes anticoagulants used to prevent clots, with beta blockers or other medicines for rate control and procedures such as cardioversion, ablation or pacemaker implantation. Timing of starting an anticoagulant after a stroke depends on the size of the infarct and the risk of bleeding, and is decided by the stroke team using imaging.

Blood pressure, cholesterol and diabetes still need treatment, because a heart source does not remove the risk from blocked arteries. Alcohol reduction, weight loss and treating sleep apnoea reduce atrial fibrillation burden. People with mechanical heart valves need warfarin specifically rather than newer anticoagulants.

Anticoagulants increase the chance of bleeding, so any head injury, black stools, vomiting blood or unusual bruising should be reported promptly. Carry an alert card, tell dentists and pharmacists, and do not start herbal or over-the-counter medicines without checking for interactions. Missing doses reduces protection, so use reminders or a dosette box if helpful.