Electrophysiologic Changes and Ventricular Fibrillation in Acute Regional Ischemia in the Porcine Heart: The Concept of Wavelength

Early Electrophysiologic Changes in Acute Ischemia. Introduction: The purpose of this study was to match changes in conduction velocity, refractoriness, and wavelength during acute regional ischemia with initiation of ventricular fibrillation. Methods and Results: In 30 isolated, Langendorff-perfused pig hearts we measured refractory period duration and conduction velocity in ventricular myocardium during the first minutes of regional ischemia in an attempt to determine the minimal changes in these parameters related to the occurrence of ventricular fibrillation (VF). In addition, we wanted to evaluate whether wavelength, i.e., the product of conduction velocity and refractory period, was a useful parameter to predict the occurrence of arrhythmias, as has been shown to be the case for atrial arrhythmias.¹ The refractory period increased significantly after 1 minute of ischemia at basic cycle length and after one and two premature beats. Longitudinal and transverse conduction velocities varied with ischemic time. Compared to the preocclusion value, the longitudinal conduction velocity decreased significantly, but only after 2 minutes of ischemia and at basic cycle length. Wavelength was the least sensitive parameter for ischemia: neither in the longitudinal nor in the transverse direction did it change significantly even during 5 minutes of ischemia. VF was never induced by applying a single premature stimulus within the ischemic area. It occurred in 33% of the occlusions when three successive premature stimuli were delivered from within the ischemic zone, and in 100% when they were applied to the nonischemic myocardium. Whenever fibrillation was induced, it occurred within 3 minutes following coronary occlusions. Wavelength, neither before nor after coronary occlusion, could predict whether VF would occur. The only difference between hearts that fibrillated by stimulation of the ischemic myocardium and those that did not was that, in the first group, the refractory period at the site of stimulation prolonged significantly less than in the no-VF group. Since electrophysiologic changes within the ischemic zone are inhomogeneous,² an attempt was made to measure simultaneously at 52 sites the onset of inhomogeneity by determining the average interval between local depolarization during VF. This so-called VF interval is an index of local refractoriness.³ The coefficient of variation of the VF interval, taken as an index of spatial dispersion in refractoriness, increased significantly 1 minute after occlusion in the border zone and 2 minutes after occlusion in the central ischemic area. Conclusion: In conclusion, wavelength is not a useful parameter to predict the occurrence of VF in hearts with regional ischemia because of the inhomogeneity in refractoriness, which develops within 2 minutes of ischemia. VF occurs when hearts are stimulated from sites with relatively short refractory periods, either within or outside the ischemic zone. (J Cardiovasc Electrophysiol, Vol. 3, pp. 128–140, April 1992)     

Temazepam misuse in a group of injecting drug users

It is well recognized that many injecting drug users are poly-drug users. The intravenous use of Temazepam has become popular recently. In response to the ease of misuse, the pharmaceutical industry produced a formulation that would be as ‘resistant’ as possible to injecting. The preparation is a gel-fitted formulation, one proprietary name being Temazepam Gelthix. General Practitioners have been encouraged to prescribe gel-filled capsules to potential drug misusers in order to reduce the harm Temasepam can cause by its misuse. This study of 23 Temazepam injectors shows that the group still find the gel-filled preparation readily injectable. It appears to be more problematic in causing medical complications including superficial thrombophlebitis, abscesses and deep venous thrombosis. Temazepam misuse can cause drug users to become more chaotic. The study group recognize this and suggest there should be stricter control on the supply of Temasepam to drug dependents. General Practitioners, who are the main source of Temazepam prescribing, require additional training in prescribing to drug users.     

Effect of fluoride mouthrinsing on caries lesion development in shark enamel: an in situ caries model study

Abstract— Shark enamel consists of nearly pure fluorapatite and has been shown to demineralize in an in situ caries model. The present study was conducted to investigate whether additional fluoride supplementation in the form of mouthrinsing would inhibit lesion development in shark enamel. The study slabs of shark enamel were mounted in dental appliances. Six individuals wore the appliances while rinsing daily with a neutral 0.2% NaF solution for 4 wk. The specimens were analyzed by means of quantitative microradiography, and the data compared with a previous study using untreated shark enamel and the same participants. It was found that fluoride rinsing did not measurably inhibit enamel demineralization in 4 wk. Scanning electron microradiographs showed that calcium fluoride-like material was not formed on shark enamel after neutral fluoride treatment, supporting a previous study. The present study indicates, therefore, that formation of a calcium fluoride-like material on the enamel surface may be essential for the cariostatic effect of topical agents.     

Bilateral basal ganglia lesions in patients with end-stage diabetic nephropathy (Brief Communication)

Summary:   Acute movement disorder associated with reversible bilateral basal ganglia lesions is an increasingly recognized syndrome in patients with end-stage renal disease, especially in the setting of concurrent diabetes mellitus. We report an elderly man with end-stage diabetic nephropathy treated by daily automated peritoneal dialysis who developed subacute symptoms of gait disturbance, dysarthria, dysphagia and lethargy. Computed tomography and magnetic resonance imaging of the head revealed bilateral symmetrical basal ganglia lesions. Repeat imaging 3 weeks later showed that these lesions had regressed spontaneously. However, his neurological symptoms improved slowly. These findings were similar to 23 other cases in the literature. Review of these cases shows that clinical features were predominantly bradykinesia, gait disturbance and concurrent metabolic acidosis (observed in 90% of cases). The pathogenesis of this condition has not been clearly defined, but uraemia may be an aggravating factor in predisposed patients, particularly in the presence of diabetic microvascular disease. There is no specific treatment for this condition; supportive measures are the mainstay of management. In the majority of patients, neurological improvement lags behind regression of basal ganglia lesions seen with neuroimaging, and the long-term outcome is variable.     

HYDROPS FETALIS, HYDRAMNIOS AND HEPATIC VASCULAR MALFORMATION ASSOCIATED WITH CUTANEOUS HEMANGIOMA AND CHORIOANGIOMA

ABSTRACT. A premature baby presented with severe hydrops fetalis due to a multifocal angiomatous malformation of the liver. There were two other small vascular tumors: hemangioma of the skin and chorioangioma. Hydramnios and placental edema were also present. The association of severe hydrops fetalis and hydramnios with angiomatous malformation of the liver was not found in reviewing the literature.