Spectral analysis was used to examine 257 carotid arteries in 227 patients who had undergone carotid endarterectomy at 1, 3, 6, and 12 months after surgery and annually thereafter. Routine intraoperative completion angiography ensured that the operations were technically satisfactory. Postoperative restenoses were identified in 38 patients (15%). In 23 arteries (9%), the restenosis exceeded a 50% diameter reduction while in 15 arteries (6%) the stenosis was less than 50% of the diameter. Restenosis developed in 24/96 women (25%) and 14/161 men (9%). Twenty-nine (70%) stenotic lesions occurred within 12 months. In three patients early lesions regressed. Reoperation with patch angio-plasty was required in six patients. When the 219 carotid arteries that remained widely patent were compared to the 38 that restenosed , no differences were noted for age, diabetes mellitus, hypertension, smoking, or degree of preoperative stenosis. Early stenotic lesions appear to be due to myointimal hyperplasia, which is probably platelet mediated. The predominant female sex distribution may be explained by differences in platelet responsiveness in men and women.
Acute mountain sickness (AMS) is a prevalent illness seen in humans exposed to high altitudes. An increase in cerebral blood flow as a result of cerebrovasodilatation is felt by many to be responsible for its occurrence. Using the recently developed transcranial Doppler (TCD), it has become possible to detect and quantify flow velocity in the large cerebral vessels. By this method, intracranial arterial blood flow velocities and vasodilatation were measured at high altitude and correlated with clinical symptoms. Mean middle cerebral artery velocity (MCA-V) showed a significant increase from 55 +/- 7 cm/s at sea level to 71 +/- 13 cm/s at 13,500 feet. The pulsatility index (PI) and vasomotor reactivity (VMR) both decreased (.71 +/- .11 at sea level to .53 +/- .12 at 13,500 and 45 +/- 17% sea level to 23 +/- 15% at 8,000 feet, respectively). These preliminary studies indicated that TCD technique is a viable tool for measurement of cerebral blood flow velocities and cerebral arterial vasodilatation at altitude.
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