Electrocardiographic manifestations of CNS events.

Certain intracranial events produce electrocardiographic abnormalities, most often involving the T wave with diffuse, deep inversions. The amplitude of the T wave inversion is impressive, approaching 15 mm in some cases. Morphologically, the T wave is asymmetric with a characteristic outward bulge in the ascending portion. In the setting of a CNS event, relatively minor degrees of ST segment elevation are also seen in leads with obviously abnormal T waves; the ST segment elevation frequently is less noticeable than the T wave changes and is usually less than 3 mm. The T wave inversions with associated ST segment elevation are most pronounced in the mid-precordial and lateral precordial leads; such findings are also noted to a less extent in the limb leads. Other electrocardiographic features associated with acute CNS injury include prominent U waves of either polarity and QT interval prolongation, often exceeding 60% of its normal value, as well as malignant forms of bradycardia and tachycardia.