Many vascular diseases affect both the heart and the brain. Cardiac diseases often lead to lesions and dysfunction within the brain, and central nervous system (CNS) diseases can influence the heart and its function
BRAIN AND CEREBROVASCULAR COMPLICATIONS OF HEART DISEASE
Stroke is a common and devastating disease, the fifth leading cause of death and the leading cause of disability in the United States. On average, one American dies from a stroke every 4 minutes. Cardiogenic stroke can occur when (1) the heart pumps unwanted material into the circulation that reaches the brain (embolism), (2) pump function fails and the brain is hypoperfused, or (3) drugs given to treat cardiac disease have adverse neurologic effects.
Direct Cardiogenic Brain Embolism
Cardiogenic cerebral embolism is responsible for approximately 20% of ischemic strokes.1,2,3,4,5 Because many patients have coexisting cardiac and extracranial vascular disease,5 criteria for the diagnosis of cardiac embolism remain controversial even today. As more advanced diagnostic techniques have been developed, more causative cardiac abnormalities (and their association with stroke) have been recognized. Cardiac sources of brain emboli can be divided into several groups6:
Cardiac wall and chamber abnormalities
Aortic arch disease
Some cardiac sources have much higher rates of initial and recurrent embolism. The more common sources will be reviewed. The Stroke Data Bank7 in 1992 divided potential sources of brain embolism into strong sources (prosthetic valves, atrial fibrillation [AF], endocarditis, sick sinus syndrome, ventricular aneurysm, akinetic segments, mural thrombi, cardiomyopathy, and diffuse ventricular hypokinesia) and weak sources (myocardial infarct > 6 months old, aortic and mitral stenosis and regurgitation, congestive failure, mitral valve prolapse, mitral annulus calcification, and hypokinetic ventricular segments). Patients who have these weak sources are now often lumped within a category called cryptogenic stroke or cryptogenic embolism. The sources then deemed weak were frequent findings in patients who did not have brain embolism. Research is now directed into defining the frequency of these sources and identifying ways to determine in which patients they are the embolic source and in whom they are incidental findings. The risk of embolism varies within individual cardiac abnormalities depending on many factors. For example, in patients with AF, associated heart disease, patient age, duration, chronic versus intermittent fibrillation, and atrial size all influence embolic risk. The presence of a potential cardiac source of embolism does not mean that a stroke was caused by an embolus from the heart. Coexistent occlusive cerebrovascular disease is common. In the Lausanne Stroke Registry, among patients with potential cardiac embolic sources, 11% of patients had severe cervicocranial vascular occlusive disease (> 75% stenosis) and 40% had mild-to-moderate stenosis proximal to brain infarcts.5