Neurology and the heart

In the past, considerable attention focused on the extracranial vasculature as a source of embolism to the brain. With the advent of transoesophageal echocardiography, it has become apparent that the heart is a much more important cause of stroke than previously suspected. In young patients with cryptogenic stroke, cardiac structural abnormalities are probably the principal source of cerebral emboli.1 In these patients, there is often no atherosclerosis. On the other hand, even older patients with significant extracranial vascular disease may harbour a possible cardiac source of embolism. Thus between 15% and 35% of stroke patients with a significant (>60%) stenosis of the extracranial vasculature demonstrated by arteriography may also have a probable cardiac embolic source.2 3 Even lacunar infarcts (often thought to be secondary to disease of penetrating vessels in the brain as a result of hypertension) may be associated with potentially embolic cardiac pathology in 50% of cases.3 This review considers the currently debated cardiac issues faced by neurologists and cardiologists in the prophylaxis and management of stroke patients: anticoagulation for atrial fibrillation; incidence of cerebral haemorrhage and infarction, together with its prevention in infective endocarditis; and the cognitive and focal neurological consequences of cardiac surgery. In addition to the increasing importance of the heart as a possible source of cardiac embolism there is recent evidence implicating the brain in the production of cardiac structural abnormalities and in cardiac dysrhythmogenesis. These effects are most often encountered after subarachnoid haemorrhage, but recent experimental and clinical findings imply that they may well occur after ischaemic stroke. The mechanisms involved are discussed at the end of this chapter. ### ATRIAL FIBRILLATION Atrial fibrillation has the greatest documented potential of all cardiac arrhythmias to afford a milieu for cerebral embolisation. Chronic atrial fibrillation in the absence of rheumatic heart disease is associated with …