Neurothanatology--clinical significance of cerebrally induced cardiac changes.

That cardiac changes occur following cerebral lesions is substantiated by over 40 years of clinical-and experimental research. The initial observation was prompted by a victim of subarachnoid haemorrhage (SAH) who developed new elect-rocardiogram (ECG) changes suggestive of acute myocardial infarction.' Various reports followed .2-4 Burch found similar ECG changes in victims of SAH, intracerebral haemorrhage and ischaemic stroke in the first systematic study of neurogenic cardiac effects.5 Principally, cardiac repolarization changes were noted. None of these early reports addressed the possible contribution of concomitant ischaemic heart disease. As autopsy evidence accrued, it became clear that neurogenic ECG changes occurred even in patients with normal coronary arteries.3'6-8 Moreover, in the majority of cases where coronary atheroma was present, there was no evidence of acute cardiac ischaemic change. However, several hours are required for the development of observable pathology following myocardial infarction. Similarly, intracoronary thrombus may fragment prior to death.9 In patients who die rapidly therefore, such changes may not appear, although this does not explain the occurrence of ECG changes in those with no atheroma. Goldstein7 lessened the effects of concomitant heart disease by comparing ictal ECGs with those obtained some 4 months prior to acute stroke. New ECG changes were identified in 74% of victims of strokes of all types, compared with 14% of the matched control population. ECG repolarization abnormalities generally are more frequent following subarachnoid or in-tracerebral haemorrhage (66%) than after ischaemic stroke.4'5'7 l0 The commonest alterations are: QT prolongation (32%), U wave alterations (13%), ST changes (21%), T wave inversion (15%).7 The similarity of such ECG changes to those of hypokalaemia suggests this as the basis of the phenomenon." No association has been found, however, between electrocardiographic changes and plasma potassium levels after SAH.L2-14 Conversely , a correlation was demonstrated between total exchangeable body potassium after SAH, and ECG changes.5 These measurements were made at least one week after the event, the majority of values being only in the low-normal range. Thus, the significance of this study is questionable. Repolarization changes indicate a propensity to arrhythmogenesis. The observed incidence of cardiac arrhythmias of all types is 98% after SAH, 71% after intracerebral haemorrhage and 39% after ischaemic stroke.7'6.'7 As yet, there is no definite clinical evidence identifying electrocardiographic effects with a specific neurological site. ECG changes are more frequent after hemispheric than brainstem infarc-tion,18'9 and a weak association exists with haematomas of the left frontal lobe.'7 Consideration …