MAGNETIC RESONANCE IMAGING IN POSTERIOR CIRCULATION INFARCTION: IMPACT ON DIAGNOSIS AND MANAGEMENT

To compare the diagnostic yield of magnetic resonance imaging (MRI) with computed tomography (CT) in posterior circulation infarction, we used proton MRI with a 0.3 Tesla magnet and a 3rd generation CT scanner in 25 patients. Age-matched controls were compared in a blinded fashion. Seventeen patients (68%) showed relevant pathology on MRI not seen on CT, 11 with normal CT and six with more extensive lesions, chiefly in the brain stem. Evidence of abnormal vertebrobasilar blood flow was seen in 8/25 (32%) of patients, suggested by vascular high intensity signals on MRI. Two tissue and one flow abnormality were seen in the control group. MRI provides additional information concerning infarct site, extent and pathogenesis in posterior circulation infarction.     

Termination Of Sustained Tachycardia By External Noninvasive Pacing

Invasive cardiac pacing has proved useful in the induction and termination of reentrant sustained tachycardias. In one of our two cases, programmed ventricular extra-stimulation was used to induce sustained ventricular tachycardia from the endocardial surface of the right ventricle. Induced ventricular tachycardia was terminated by burst ventricular pacing with an external cardiac pacemaker. In our second patient, external pacing was effective at inducing and terminating sustained supraventricular tachycardia. These patients illustrate that the principles of terminating sustained reentrant tachycardia with invasive pacing may also apply to noninvasive external pacing. The usefulness of this approach in treating reentrant tachycardias needs further evaluation.