A protected ectopic focus created in tissue excised from one heart was allowed to interact with the activity of the intact heart of another animal. The protected focus consisted of a Purkinje fiber in which a narrow central zone was rendered inexcitable. The model permitted us to study parasystole, modulated parasystole, reentry, and tachycardia in the same preparation. At moderate levels of electrotonic influence across the region of block, frequency scans revealed wide zones of pacemaker entrainment. The incidence and pattern of premature ventricular contractions generated were always a sensitive function of heart rate. Parasystolic patterns could be converted to apparent reentrant patterns by simple alteration of the atrial driving rate or the level of block. Suppression of pacemaker automaticity converted a modulated parasystole model to one of pure reentry. Reciprocation of the impulse across the inexcitable tissue segment generated a ventricular tachycardia that could be initiated and terminated by a single properly timed event. Our observations suggest that ectopic activity that behaves like parasystole and activity characteristic of what is commonly diagnosed as reentry, including tachycardia and idioventricular rhythms, may be a manifestation of a common mechanism whose arrhythmic expression differs as a continuous function of heart rate, level of block, or level of automaticity. Circulation 68, No. 5, 1101No. 5, -1115No. 5, , 1983 IN PREVIOUS communications from this laboratory we have used preparations of isolated Purkinje fibers and mathematical models to describe the electrotonic interactions between cardiac tissues across an area of impaired conductivity, and we have drawn conclusions that have some relevance to the behavior of parasystolic and reentrant idioventricular activity in the clinical situation. 14 The preparations we have studied have been useful in that certain patterns of parasystolic and extrasystolic activity observed in human electrocardiograms (ECGs) appear to fit the rules derived from them. Although the in vitro preparations developed have been useful in characterizing these mechanisms of arrhythmogenesis, they are less than ideal for

SummaryBackground: In hypertrophic cardiomyopathy (HCM), interstitial myocardial fibrosis is an important histological modification that has been associated with sudden death and evolution toward myocardial dilation.

This case report describes neurotoxicity in an older patient on cefepime 2 g twice a day. The 81-year-old male patient developed non-convulsive status epilepticus during cefepime treatment with 1 g twice a day. There was recovery 30 days after discontinuation of cefepime.

Paciente de 83 anos, feminina, com acidente vascular cerebral isquêmico por obstrução da artéria cerebral média direita. Realizada trombólise intra-arterial após cinco horas de evolução com controle da hipotensão usando noradrenalina obtendo sucesso na evolução e acompanhamento. Um aumento da morbidade e mortalidade em pacientes com hipotensão tem sido relatado. O controle da hipotensão arterial em pacientes com AVC é uma das medidas importantes na fase aguda da doença para uma boa evolução.