Microembolic signals and risk of early recurrence in patients with stroke or transient ischemic attack.

BACKGROUND AND PURPOSE: Asymptomatic microembolic signals (MES) can be demonstrated in patients with cerebral ischemia using transcranial Doppler (TCD) ultrasonographic monitoring of the middle cerebral artery. However, the clinical relevance of MES remains uncertain. The purpose of this study was to estimate the independent contribution of microembolism to the risk of early ischemic recurrence (EIR) in patients with stroke or transient ischemic attack (TIA) of presumed arterial origin. METHODS: We studied the incidence of EIR in 73 consecutive patients with carotid stroke or TIA in whom TCD scanning of the symptomatic middle cerebral artery was performed within 7 days from the onset of symptoms. Patients with a potential cardiac source of embolism were excluded from the study. RESULTS: Eight patients had EIR during a mean+/-SD follow-up of 10+/-8 days. The incidence of EIR was 4.3 per 100 patient-days in patients with MES and only 0.5 per 100 patient-days in patients without MES. The presence of MES was a significant predictor of EIR after adjustment for the presence of carotid stenosis or aortic arch atheroma, antiplatelet therapy during follow-up, and other potential confounding variables (relative risk, 8.7; 95% confidence interval, 2 to 38.2; P=0.0015). CONCLUSIONS: Microembolism is a significant independent predictor of EIR in patients with stroke or TIA of presumed arterial origin.

Cardiovascular adaptation during simulated microgravity: lower body negative pressure to counter orthostatic hypotension.

The cardiovascular function is one of the main functions disturbed by microgravity. It is particularly affected by the astronaut's return to Earth, where one of the symptoms of the cardiovascular adaptation syndrome is orthostatic hypotension; the clinical consequence can be presyncopal state or a syncope. Lower body negative pressure (LBNP) is intended to stimulate the venous system of the lower limbs. Studies performed in the U.S. have shown that LBNP constitutes an efficient countermeasure, but this approach is impractical because 4 to 6 h/d of application are required. Five volunteers took part in two recent antiorthostatic bed rest experiments for 30 days. In the first experiment, three subjects were submitted to several sessions of LBNP per day and two others were controls; in the second, the LBNP group of the first experiment became control and vice versa. Two orthostatic investigations were performed: 5 d before bed rest; and at the end of the 30-d bed rest period. The results showed that: 1) when the subjects were controls, a high orthostatic hypotension post bed rest with three syncopes and one presyncopal state during the first minutes of the tilt test appeared; 2) when the subjects were submitted to LBNP sessions, no orthostatic hypotension was noted. These two experiments proved the beneficial effects of the LBNP as a countermeasure against orthostatic hypotension.