Ischaemic Strokes of Different Etiologies

Stroke due to cardio-embolism

Stroke due to cardio-embolic causes account for up to 25% of all ischaemic strokes. Emboli originating from the heart travel along the circulation supplying the brain and occlude one or more vessels resulting in a stroke. Common causes of emboli formation from the heart include 1) arrhythmias e.g. atrial fibrillation, 2) left ventricular aneurysms due to a prior history of myocardial infarction, 3) infective endocarditis or marantic endocarditis. Patients with deep venous thrombosis of the peripheral circulation and also an underlying patent foramen ovale may also be at increased risk of developing ischaemic stroke as the blood clot can travel to the systemic circulation via the shunt created by the patent foramen ovale.

The non-contrast CT shown here (Figure 1) is from a patient with an ischaemic stroke due to atrial fibrillation. As a result of the erratic contraction of the left atrium, a proportion of the blood within the atrium becomes static resulting in blood clot formation. These emboli can then travel down to the left ventricle and along the aorta to the cerebral and peripheral circulation resulting in ischaemic strokes as well as acute limb ischaemia. Often, the cardiac emboli can occlude multiple vessels of the cerebral vasculature and thus result in infarcts involving multiple territories. This is evident in this case as there are multiple areas of infarct noted – there are hypodensities involving both cerebellar hemispheres  (left side affected to a greater extent). Of note is that as a result of the cerebellar infarction, there is significant cytotoxic oedema and the 4th ventricle is obliterated . The patient should be monitored closely for any signs and symptoms of raised intracranial pressure and the Neurosurgical colleagues be consulted for surgical means to relieve intracranial pressure, as raised intracranial pressure could be life-threatening if not managed promptly.

Patients with ischaemic stroke due to atrial fibrillation should be managed with anticoagulation unless contra-indications are present. Nowadays, besides vitamin K antagonists (warfarin), novel oral anticoagulants (NOACs) are present (e.g. direct thrombin inhibitors and factor Xa inhibitors) which have the advantages of an reduced risk of intracerebral haemorrhage compared to warfarin. In addition, compared to warfarin, NOACs have reduced drug-drug and drug-diet interactions and also does not require regular monitoring of the International Normalised Ratio (INR).