Aortic arch thrombus caused by nitrous oxide abuse.

Nitrous oxide is a recreational drug gaining in popularity for its deemed innocence. However, side effects have recently been reported. In this case, a patient suffered major aortic arch thrombus resulting in arterial occlusion of his arm and temporary cerebral infarction and later deep venous thrombosis and pulmonary embolism. No common causes for thrombus in this high-flow vessel were identified. The authors state that the patient's chronic nitrous oxide abuse might have led to this thrombus, although it has never been described previously. This hypothesis is supported with laboratory tests at several presentations.

Day-to-day test-retest variability of CBF, CMRO2, and OEF measurements using dynamic 15O PET studies.

PURPOSE: We assessed test-retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF) measurements derived from dynamic (15)O positron emission tomography (PET) scans. PROCEDURES: In seven healthy volunteers, complete test-retest (15)O PET studies were obtained; test-retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO(2) in arterial flow territories were calculated. RESULTS: Whole-brain test-retest coefficients of variation for CBF, CBV, CMRO(2), and OEF were 8.8%, 13.8%, 5.3%, and 9.3%, respectively. Test-retest variability of CBV left-to-right ratios was <7.4% across all territories. Corresponding values for CBF, CMRO(2), and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively. CONCLUSIONS: The test-retest variability of CMRO(2) measurements derived from dynamic (15)O PET scans is comparable to within-session test-retest variability derived from steady-state (15)O PET scans. Excellent regional test-retest variability was observed for CBF, CMRO(2), and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF.

Hemodynamic changes in ipsi- and contralateral cerebral arterial territories after carotid endarterectomy using positron emission tomography.

BACKGROUND: The purpose of this study was to characterize ipsi- and contralateral cerebral hemodynamics before and after CEA. METHODS: Cerebral blood flow, CBV, and MVTT were measured in 10 patients before and after CEA using PET. Absolute and relative values of these parameters were calculated bilaterally for the entire arterial territories and hemispheres. RESULTS: For all territories in both hemispheres, the mean absolute postoperative CBF was significantly increased compared with preoperative CBF (P < .05). Only in MCA was this increase higher in the ipsilateral than in the contralateral hemisphere (P = .02). Cerebral blood volume was unaffected, whereas MVTT decreased in ipsilateral MCA (P = .05). CONCLUSIONS: The present findings suggest that, on the first day after CEA, absolute CBF is increased in all arterial territories on both ipsi- and contralateral sides, but that there are only minor changes in the relative distribution, whereas the CBV was unaffected.

Evaluation of basis function and linear least squares methods for generating parametric blood flow images using 15O-water and Positron Emission Tomography.

PURPOSE: Parametric analysis of (15)O-water positron emission tomography (PET) studies allows determination of blood flow (BF), perfusable tissue fraction (PTF), and volume of distribution (V (d)) with high spatial resolution. In this paper the performance of basis function and linear least squares methods for generating parametric flow data were evaluated. PROCEDURES: Monte Carlo simulations were performed using typical perfusion values for brain, tumor, and heart. Clinical evaluation was performed using seven cerebral and 10 myocardial (15)O-water PET studies. Basis function (BFM), linear least squares (LLS), and generalized linear least squares (GLLS) methods were used to calculate BF, PTF, or V(d). RESULTS: Monte Carlo simulations and human studies showed that, for low BF values (<1 ml/min(-1)ml(-1), BF, PTF, and V(d) were calculated with accuracies better than 5% for all methods tested. For high BF (>2 ml/min(-1)ml(-1)), use of BFM provided more accurate V(d) compared with (G)LLS. CONCLUSIONS: In general, BFM provided the most accurate estimates of BF, PTF, and V(d).

Endovascular repair of a type B aortic dissection with transposition of a coexistent aberrant subclavian (lusorian) artery.

PURPOSE: To report the endovascular treatment of a relatively uncommon entity: an aortic type B dissection combined with an aberrant subclavian artery (SA). CASE REPORT: A 59-year-old patient was admitted with chest pain and interscapular back pain. A transesophageal ultrasound and magnetic resonance angiography revealed a type B aortic dissection originating at the level of an aberrant SA orifice. After failure of medical therapy, the dissection was treated by transluminal implantation of an Excluder stent-graft covering the entry site of the dissection at the aberrant SA orifice. Prior to the endovascular procedure, a transposition of the aberrant SA to the right carotid artery was performed through a supraclavicular approach. The patient remains asymptomatic at 19 months after the endovascular repair. CONCLUSIONS: Endovascular repair of a type B aortic dissection in the presence of a lusorian artery appears to be a feasible, safe, and less invasive alternative to conventional surgery. The need for concurrent transposition of the SA remains to be determined.