Immediate and late outcomes of stenting for severe extracranial internal carotid artery stenosis in octogenarian patients.

Background: Multiple studies suggest that internal carotid artery stenting can be performed safely in octogenarians with low periprocedural complication rates. However, great concern still exists as to whether these patients will gain long-term benefits from this procedure given their advanced age and uncertain life expectancy. We decided to conduct a retrospective study to determine short-and long-term clinical outcomes and to analyze survival duration in this population. Methods and Results: Sixty-nine consecutive elderly patients with either symptomatic or asymptomatic stenosis ≥70% underwent 86 procedures. Immediate and late outcomes, as well as survival data, were analyzed retrospectively. Mean age was 83.1 ± 2.7 years. Mean survival was 49.3 ± 10.1 months. A complete neurological assessment was obtained at 1 and 2 years in 100% of patients, at 3 years in 90.7% of patients and at 5 years in 84.8% of patients. Two major and one minor ischemic strokes occurred during the periprocedural period. No death, myocardial infarction or intracranial hemorrhage was recorded. The mean follow-up period was 55.4 ± 24.6 months. Four patients experienced a minimum of 1 year of follow-up, and the longest is 8 years. Among the patients with the longest follow-up time, 6 had ischemic strokes, of which 2 were fatal. In total, 17 deaths occurred. Four patients experienced dementia without stroke. Survival at 3 and 5 years was estimated to be 90% and 73%, respectively. Conclusion: This study demonstrated that stenting in octogenarians was safe and effective during the periprocedural period. Long-term follow-up showed a low rate of fatal and nonfatal stroke, and patients survived long enough to benefit from the procedure. However, it was associated with a relatively high rate of long-term event. Though carotid artery stenting is a minimally invasive procedure, it should still be performed with great caution and only in carefully selected patients. The present study suggested that in this age population, carotid artery stenting might be considered as a revascularization option.

Stroke-prone renovascular hypertensive rat as an animal model for stroke studies: from artery to brain.

High blood pressure is a main risk factor for both initial and recurrent stroke. Compared to the post stroke situation in normotension, the brain lesion is larger in hypertension, and the treatments may not be as effective. Thus, the results from healthy individuals may not be directly applied to the hypertensive. In fact, the high prevalence of hypertension in stroke patients and its devastating effect urge the necessity to integrate arterial hypertension in the study of stroke in order to better mimic the clinical situations. The first step to do so is to have an appropriate hypertensive animal model for stroke studies. Stroke-prone renovascular hypertensive rat (RHRSP) introduced in 1998, is an animal model with acquired hypertension independent of genetic deficiency. The blood pressure begins to increase during the first week after constriction of bilateral renal arteries, and becomes sustained since around the 3rd month. Because the morphological and physiological changes of cerebral arteries are similar to those in hypertensive patients, the rats represent a higher than 60% incidence of spontaneous stroke. The animal model has several advantages: one hundred percent development of hypertension without gene modification, high similarity to human hypertension in cerebrovascular pathology and physiology, and easy establishment with low cost. Thus, the model has been extensively used in the investigation of ischemic stroke, and has been shown as a reliable animal model. This paper reviewed the features of RHRSP and its applications in the treatment and prevention of stroke, as well as the investigations of secondary lesions postischemic stroke.

Acid stability of carbon paste enzyme electrodes.

This note reports on the unusual protection of several enzymes against harsh pH conditions provided by carbon paste electrodes. Both glucose oxidase and polyphenol oxidase carbon paste amperometric biosensors display a remarkable resistance to acid deactivation compared to conventional biosensors prepared by electropolymeric entrapment of enzymes. For example, the carbon paste enzyme electrodes fully retain their activity upon stressing in strongly acidic conditions (pH approximately 2.0-2.5) for prolonged periods, where conventional (polymer-based) biosensors rapidly lose most of their response. Such unusual acid stability of carbon paste enzyme electrodes is attributed to the "pH memory" of enzymes in the hydrophobic paste environment, to the barrier to hydronium ions provided by the pasting liquid and to decreased conformational mobility.

Lactate biosensors for continuous monitoring.

Blood lactate concentration is a highly sensitive measure of tissue oxygen deprivation from ischemia, trauma, and hemorrhage, which can produce life-threatening shock. Significantly, blood lactate is the most reliable end point indicator of resuscitation and predictor of survivability. The need for continuous measurement of blood lactate, and the slowness of discrete conventional photometric assays, is leading to the development of monitoring systems based on electrochemical lactate biosensors. Research and development of both in vivo and ex vivo biosensor systems is ongoing. Ex vivo biosensors are used with implanted microdialysis or ultrafiltration probes. Lactate from the blood diffuses into the dialysate/filtrate is transported outside of the body for measurement. The external biosensors are protected from fouling or contamination from unwanted blood constituents, but at the cost of an inherent delay in response despite system miniaturization. In vivo biosensors provide a direct measurement of blood lactate concentration, providing rapid response to changes in lactate levels. In vivo sensors are placed in the skin or implanted subcutaneously. Response to changes in lactate concentration is rapid, but biocompatibility requirements are more stringent than for ex vivo sensors. As is the case with all microdialysis systems, some in vivo biosensors must be implanted into the body using an insertion needle or surgical means, limiting their use. However, small, inexpensive, disposable in vivo sensors are also being developed which can emplaced and removed by the user.

Oxygen-independent poly(dimethylsiloxane)-based carbon-paste glucose biosensors.

Several silicone oils have been assessed and compared as an internal source of oxygen in connection to their use as binders for carbon-paste glucose biosensors. All four poly(dimethylsiloxane) (PDMS) oils tested a dramatic increase in the oxygen capacity of carbon-paste enzyme electrodes to allow convenient biosensing under severe oxygen-deficit conditions. The resulting oxygen independence is better than that exerted by perfluorocarbon binders or that displayed by mediator-based bioelectrodes. The resistance to oxygen effects is indicated from the identical response (observed in the presence and absence of oxygen) up to 2 x 10(-2) M glucose and the slight (12%) sensitivity loss at 4 x 10(-2) M. The influence of the viscosity of the PDMS binder upon the internal oxygen supply is examined. The PDMS carbon-paste enzyme electrode displays a stable glucose response over prolonged (15 h) operation in an oxygen-free solution. On-line continuous testing indicates favorable dynamic properties with no carry-over effects over the physiological and pathophysiological range (3-12 mM glucose).