Recent advances in atrial fibrillation and stroke

Abstract

it is necessary to identify the underlying cause of the event, so that the appropriate therapy can be identified to maximally reduce risk of recurrence. Antiplatelet agents are not anticoagulants; they reduce the risk of stroke from embolisation of platelet aggregates, sometimes called ‘white thrombus’ (Fig. 1) in the setting of fast flow along the arterial wall or heart valves, but to prevent thrombus in the setting of stasis (‘redthrombus’, afibrin polymer with entrapped red cells), it is necessary to use anticoagulants. With recent improvements in blood pressure control and lipid-lowering therapy, the proportion of lacunar strokes due to small vessel disease and strokes due to large artery disease has declined significantly in the past 10 years, and in consequence the proportion of cardioembolic strokes has risen; our group found 2 that between 2002 and 2012, cardioembolic stroke increased from 26 to 56% of ischaemic stroke, among patients attending an ambulatory Urgent TIA Clinic. It is thus increasingly important for physicians to have a high index of suspicion for cardioembolic stroke, and to investigate patients intensively if they have no other apparent cause of stroke (‘cryptogenic stroke’). In the diagnosis of cardioembolic stroke, there are two sides to the coin: (1) negative evidence: the absence of other causes of stroke such as hypertension, large artery disease, dissection, or vasculitis; and (2) positive evidence such as the presence of cortical infarctions and/or TIA in multiple vascular territories, cardiac abnormalities such cardiomyopathy, a prosthetic or stenosed valve, a right-to-left shunt, evidence of atrial fibrillation, or clinical clues to paradoxical embolism. The latter includes a previous history of deep vein thrombosis (DVT), pulmonary embolism, the presence of venous insufficiency or varicose veins, a history of prolonged sitting (such as a long flight or sitting at a computer for many hours), dyspnoea or a Valsalva manoeuvre at the onset of the stroke, a history of sleep apnoea, or waking up with stroke. 3 A special case is atrial fibrillation (AF). This condition is particularly important because it is associated with larger strokes that are more disabling, is increasing in frequency because of the ageing of the population, is frequently missed by routine Holter recordings, andthere is aseriousproblemof under-use of anticoagulants, 4 particularly in the elderly, who are disproportionately more likely to benefit from anticoagulants. 5