Clinical findings and hemodynamic changes associated with severe occlusive carotid artery disease

OBJECTIVE: The purpose of the study was to evaluate the ophthalmologic findings and to analyze the retrobulbar hemodynamics of patients with severe (greater than 70% stenosis) occlusive carotid artery disease (OCAD) by means of color Doppler imaging (CDI). DESIGN: A case-controlled study. PARTICIPANTS: Fifty-six consecutive patients with severe OCAD and an age- and sex-matched control group consisting of 56 healthy patients without OCAD were studied. INTERVENTION: All 112 patients underwent a complete ophthalmologic examination. Color Doppler imaging of both orbits was performed by one masked investigator. MAIN OUTCOME MEASURES: Peak systolic velocity, end diastolic velocity, and the resistive index of the ophthalmic, central retinal, and temporal short posterior ciliary arteries were measured. The authors compared the hemodynamic parameters measured in patients with severe OCAD with those obtained in the control group. The hemodynamic parameters of patients with asymmetric OCAD (stenosis > 70% in one internal carotid artery and stenosis < 50% in the contralateral artery) were also compared. In an attempt to determine risk factors associated with the ocular ischemic syndrome (OIS), the authors compared patients with severe OCAD and OIS with patients with severe OCAD without OIS. RESULTS: Peak systolic and end diastolic velocities in the ophthalmic, central retinal, and temporal short posterior ciliary arteries were significantly lower in patients with severe OCAD (P < 0.01). The mean resistive indices in the central retinal and temporal short posterior ciliary arteries were higher in the group with severe OCAD (P < 0.01). Similar results were obtained in the analysis of 25 patients with asymmetric carotid stenosis. Younger age (P = 0.012), severe bilateral OCAD (P = 0.01), high-grade carotid stenosis (P = 0.013), and reversed ophthalmic artery flow (P = 0.038) were significant risk factors for OIS. CONCLUSIONS: Patients with severe OCAD show hemodynamic changes that suggest reduced retrobulbar blood flow. Patients with severe bilateral OCAD, high-grade carotid stenosis, and reversed ophthalmic artery flow may have a greater risk of developing OIS.     

A dehydroalanyl residue can capture the 5''-deoxyadenosyl radical generated from S-adenosylmethionine by pyruvate formate-lyase-activating enzyme

OBJECTIVE: To analyze the effects of carotid endarterectomy on the retrobulbar circulation of patients with severe occlusive carotid artery disease (OCAD) by means of color Doppler imaging (CDI). DESIGN: Prospective. PARTICIPANTS: A total of 17 consecutive patients with severe OCAD and neurologic symptoms (with a history of transitory ischemic attack or cerebral vascular accident) participated. INTERVENTION: All 17 patients underwent carotid endarterectomy. The CDI of both orbits was performed by one masked investigator before surgery and at 1 week and 1 month after surgery. MAIN OUTCOME MEASURES: Peak systolic velocity, end diastolic velocity, and resistive index of the ophthalmic, central retinal, and temporal short posterior ciliary arteries were measured. The authors compared the hemodynamic parameters at all intervals. RESULTS: Peak systolic and end diastolic velocities in the ophthalmic, central retinal, and temporal short posterior ciliary arteries increased significantly 1 week and 1 month after carotid endarterectomy (P < 0.05). After surgery, the resistive indices in the central retinal and temporal short posterior ciliary arteries decreased significantly at both intervals (P < 0.05). The six patients who had reversed ophthalmic artery flow before surgery showed forward ophthalmic artery flow after carotid endarterectomy. The contralateral orbits showed no significant hemodynamic change after endarterectomy (P < 0.05). CONCLUSIONS: Hemodynamic changes in patients with severe OCAD undergoing carotid endarterectomy suggest improvement in the ipsilateral retrobulbar blood flow.     

Acute renal failure complicating nonfulminant hepatitis A

PURPOSE: To compare the orbital blood flow velocities of patients with long-standing ocular hypertension and patients with primary open-angle glaucoma. METHODS: Twenty patients with ocular hypertension were recruited from our clinic and underwent color Doppler imaging evaluation of their retrobulbar vessels. The blood flow velocities and resistance index of their central retinal artery, temporal short posterior ciliary artery, and ophthalmic artery were compared with those of 20 glaucoma patients individually matched for age and level of the highest untreated intraocular pressure ever recorded. RESULTS: Glaucoma patients had significantly lower peak systolic velocity and end-diastolic velocity than did patients with ocular hypertension in their central retinal artery (p < 0.001). No significant difference between the groups was observed in the other vessels studied. CONCLUSIONS: Glaucoma patients had lower blood flow velocity in the central retinal artery compared with that of ocular hypertension patients of similar age and level of untreated intraocular pressure. This might be important in the development of glaucomatous damage in those patients.     

The hemodynamic characteristics of the central retinal artery and ophthalmic artery in atherosclerotic lesions of the carotid arteries based on the data from ultrasonic study methods

Central retinal artery and orbital artery were examined by ultrasonograph in 348 patients with atherosclerosis of the carotid arteries. Doppler shift of frequency spectrum was detected in the central retinal artery, which is typical of the ischemic syndrome of the eye. Its characteristics include decreased diastolic component of velocity and increased resistance index. The possibility of using duplex scanning with color Doppler flow mapping for assessing the treatment efficacy is demonstrated. A direct relationship between the degree of stenosis in the internal carotid artery and blood flow in the orbital artery is revealed. The detected changes do not notably affect the Doppler spectrum characteristics in the central retinal artery.     

Cerebral microembolism in patients with retinal ischemia

BACKGROUND AND PURPOSE: We investigated the frequency of cerebral microembolism detected by transcranial Doppler ultrasonography in patients with clinical evidence of retinal ischemia, including transient monocular blindness, central and branch retinal artery infarction, and ischemic oculopathy, and assessed its correlation with carotid artery stenosis. METHODS: Records of 331 consecutive patients examined during a 47-month period at the Neurovascular Laboratory were reviewed. Of the original 453 intracranial arteries, 186 middle cerebral arteries (MCAs) satisfied qualifying criteria that excluded patients with cardiac embolic sources. Forty-five MCAs ipsilateral to the symptomatic eye constituted the study group. The control group consisted of 141 asymptomatic MCAs. Microembolus detection studies were performed on transcranial Doppler instruments equipped with special software, and the degree of carotid artery stenosis was measured by cerebral or MR angiography or by color duplex studies. RESULTS: Microembolism was detected in 40.0% of study MCAs and 9.2% of controls (P < 0.001). In the study group, microembolic signals were detected in 61.9% of MCAs tested within a week of symptom onset and 20.8% of those tested afterward (P < 0.001). Severe (> or = 70%) carotid stenosis or occlusion was more frequent in the study group (P < 0.001). Microembolic signals were detected in 25.3% and 11.2%, respectively, of MCAs distal to carotid arteries with 70% to 100% and 0% to 69% stenosis (P = 0.013). CONCLUSIONS: In patients without cardiac embolic sources, cerebral microembolism is frequently present on the side of retinal ischemia, particularly during the week after onset of symptoms. It is often associated with severe stenosis or occlusion of the ipsilateral carotid artery.     

Reproducibility of color Doppler imaging in orbital vessels

The purpose of this study was to evaluate the short-term reproducibility, the long-term reproducibility, and the reproducibility of the measurements made between two different examiners of blood-flow velocity in extraocular vessels using color Doppler imaging (CDI). In a group of 10 healthy volunteers, measurements of the peak-systolic velocity (PSV), end-diastolic velocity (EDV), and resistivity index (RI) in the ophthalmic artery and the central retinal artery as well as one lateral and one medial short posterior ciliary artery were performed. The best intraindividual reproducibility, expressed as the relative error, was found for the PSV and RI measured in the ophthalmic artery (OA; PSV 5.9%, RI 3.1%) and the central retinal artery (CRA; PSV 7.7%, RI 4.7%). The PSV and RI determined in the posterior ciliary arteries were less reproducible but as much so as the EDV measured in the OA (11.8%) and CRA (19.9%). No systematic trend could be found between the first and second measurements. However, the long-term fluctuation was considerable high. Measurements of PSVs showed good concurrence between the two observers in all four vessels measured. The EDVs and RIs differed statistically significantly between the two observers. This difference was most pronounced in the posterior ciliary arteries.     

Noninavasive angiography for the diagnosis of carotid artery disease using Doppler ultrasound (carotid artery Doppler)

To detect stenosis in the carotid artery with a bidirectional continuous-wave Doppler ultrasound device, the following noninvasive procedure, applied on 800 patients and compared with 249 angiograms of 186 patients, has proved to be about 90% reliable. Measurements of flow signals were taken over the terminal branches of the ophthalmic artery (supratrochlear and supraorbital arteries) and averaged. Compression of superficial temporal and facial arteries revealed flow direction and common carotid artery compression revealed the supplying blood vessel and the effectiveness of the circle of Willis. Measurements over the common carotid arteries were used to evaluate peripheral resistance. A set of eight criteria was used; the diagnostic value of each criterion was calculated by comparing 138 pathological Doppler findings in 123 patients with the angiograms. If reverse flow direction in supratrochlear or supraorbital artery was used alone, only 43% correct diagnoses would have resulted. A more severe stenosis is not necessarily correlated with a more weighted criterion; a subset of criteria is less efficient than the combination of all criteria. Application during 32 extracranial endarterectomies on 28 patients informed the surgeon immediately about the hemodynamic effect of the surgical intervention. Rethrombosis was diagnosed in two patients by postoperative Doppler examination.     

Blood-flow velocities in the extraocular vessels in normal volunteers

PURPOSE: To determine normal values of blood-flow velocities in extraocular vessels. METHODS: In one eye each in 189 healthy adult volunteers, blood-flow velocities in the ophthalmic artery (OA), central retinal artery (CRA), central retinal vein (CRV), short lateral posterior ciliary artery (LPCA), and short medial posterior ciliary artery (MPCA) were measured by color Doppler imaging. In the arteries, peak systolic velocity (PSV), end diastolic velocity (EDV), and resistivity index (RI) were calculated. In the CRV, maximal and minimal blood-flow velocities were measured. Influence of age, gender, blood pressure, and heart rate on blood-flow velocities and the resistivity index were analyzed. RESULTS: Mean outcomes +/- S.D. cm/sec were as follows: in the OA, PSV was 39.2 +/- 5.3, EDV was 9.1 +/- 2.5, and RI was 0.77 +/- 0.05. In the CRA, PSV was 11.0 +/- 1.8, EDV was 3.3 +/- 0.9, and RI was 0.71 +/- 0.05. In the short LPCA, PSV was 11.2 +/- 1.7, EDV was 3.7 +/- 1.0, and RI was 0.68 +/- 0.06. In the short MPCA, PSV was 11.2 +/- 11.7, EDV was 3.6 +/- 0.9, and RI was 0.68 +/- 0.05. In the CRV, mean maximal velocity was 4.5 +/- 0.9, and mean minimal velocity was 3.3 +/- 0.7. Age, gender, systolic blood pressure, diastolic blood pressure, and heart rate had no consistent statistically significant influence on the measured and calculated variables. CONCLUSION: Normal values for blood-flow velocities in the extraocular vessels serve as a basis in deciding whether a measured value of a patient is normal or abnormal.     

Color Doppler ultrasonography in retinitis pigmentosa. Preliminary study

PURPOSE: Retinitis pigmentosa is a bilateral retinal degeneration. The primary disorder is still debated. METHODS: We performed a prospective investigation of the ocular circulation directly by color Doppler imaging (CDI). A total of 28 eyes of 14 patients (8 men and 6 women, affected with retinitis pigmentosa) were recruited for this study. For each case were evaluated protosystolic velocity and the resistive index of the ophthalmic artery, central retinal artery, posterior ciliary arteries and choroid. These values, furthermore, have been compared with a control group. RESULTS: The results of the CDI in the group of RP and in the CG were: in the OA: PSV 31.177 +/- 5.119 cm/sec vs 36.700 +/- 3.152 cm/sec (p < 0.007); RI 0.713 +/- 0.058 vs 0.717 +/- 0.019 (p < 0.0839); in the CRA PSV 7.075 +/- 1.611 cm/sec vs 12.710 +/- 2.795 cm/sec (p < 0.001); RI 0.560 +/- 0.062 vs 0.550 +/- 0.051 (p < 0.234); in the PCA: PSV 8.569 +/- 3.408 cm/sec vs 14.100 +/- 2.571 cm/sec (p < 0.001) with RI 0.634 +/- 0.090 vs 0.681 +/- 0.045 (p < 0.145). In the CHO: PSV 12.312 +/- 2.327 cm/sec vs 16.170 +/- 1.846 cm/sec (p < 0.001) with RI 0.581 +/- 0.072 vs 0.638 +/- 0.050 (p < 0.065). CONCLUSION: Our results suggest that in the affected eyes there is a statistically significant reduction in blood flow in ophthalmic and ciliary arteries. These data offer new views on the retinitis cause of pigmentosa and possible therapeutics to be studied.     

Comparison of magnetic resonance volume flow rates, angiography, and carotid Dopplers. Preliminary results

BACKGROUND AND PURPOSE: We compared the results of conventional angiography, carotid Doppler, and magnetic resonance angiography volume flow rates to determine the clinical utility of volume flow rate assessment of blood flow to the anterior circulation in patients with carotid occlusive disease. METHODS: From 11 symptomatic patients, a total of 22 extracranial carotid arteries were studied with all three techniques. The studies were independently read, and regression analysis was used to compare the measurements. RESULTS: Carotid Doppler measurements of the distal extracranial carotid arteries were proportional to the inverse of the extracranial carotid volume flow rate (r = .53, R2 = 29%, P < .01), volume flow rates were proportional to the inverse of measured percent stenosis on angiography (r = .84, R2 = 71%, P < .01), and Dopplers were proportional to angiography (r = .94, R2 = 90%, P < .01). Symptomatic Doppler systolic velocity was significantly higher (P < .002), symptomatic measured stenosis was significantly higher (P < .002), and symptomatic volume flow rate was significantly lower (P < .01) than their respective asymptomatic-side values. These preliminary observations, however, may well change once a large data set, especially one in which more patients with high-grade carotid stenosis are included, is studied. CONCLUSIONS: Assessment of carotid volume flow rates by magnetic resonance angiography quantifies flow reduction secondary to atherosclerotic occlusive disease. The easily obtained flow data add both documentation of arterial flow characteristics related to internal carotid stenosis and information regarding the adequacy of collateral pathways.     

Glucocorticoids inhibit the induction of nitric oxide synthase II by down-regulating cytokine-induced activity of transcription factor nuclear factor-kappa B

PURPOSE: This study was designed to assess the correlation between flow velocity, the resistive index and visual field defects in patients with chronic open angle glaucoma in comparison with a nonglaucomatous control population. METHODS: Color Doppler imaging was used to study flow velocity in the central retinal artery and short posterior ciliary arteries of 76 patients with chronic open angle glaucoma and 28 normal subjects. Velocity and resistive index were correlated with visual field abnormalities. RESULTS: The chronic open angle glaucoma patients showed a statistically significant lowering of the end diastolic velocity and a raised resistive index in all vessels studied. The end diastolic velocity of the central retinal arteries of glaucoma patients were significantly correlated with the Mean Deviation of the visual field (right eye, p = 0.0041; left eye, p = 0.0167). The glaucoma patients showed a statistically significant lowering of the end diastolic velocity and a raised resistive index in all vessels supplying those parts of the optic disc that corresponded to visual hemifield defects. CONCLUSION: Open angle glaucoma is associated with changes in central retinal and ciliary artery flow velocity and resistive index which suggest a compromised circulation in this region.     

Effect of coat on rate of temperature increase in muscle during ultrasound treatment of dogs

BACKGROUND AND PURPOSE: The vasomotor response can be tested by means of transcranial Doppler sonography. If a constant vessel diameter is assumed, the flow velocity changes will reflect blood flow volume changes. This hypothesis is difficult to verify. Simultaneous assessment of intracranial flow velocity and extracranial flow volume changes may solve this problem. METHODS: We tested vasomotor response in 32 volunteers (age, 42+/-18 years) with 5% CO2. Acetazolamide (1 g) was tested in 15 volunteers (age, 28+/-8 years). To evaluate drug-dependent flow changes in the external carotid artery territory, acetazolamide was administered in 7 patients with unilateral occlusion of the internal carotid artery without evidence of collateralization through the ophthalmic artery (age, 67+/-12 years). Simultaneous recording included measurements of flow volume in the common carotid arteries (M-mode color duplex system) and flow velocity in the middle cerebral arteries. RESULTS: With CO2 and acetazolamide, intracranial flow velocity increased by 31% and 39%, respectively, with a simultaneous increase of common carotid artery flow volume of 47% and 50%, respectively. No change in extracranial flow volume was observed in patients with an occluded internal carotid artery. CONCLUSIONS: These data show not only the expected increase of flow velocity in the middle cerebral artery but also suggest an increase in cross-sectional vessel diameter of 6% and 4% with CO2 and acetazolamide, respectively. It remains unresolved whether this observation is due to a direct effect of the drug on the vessel walls or is simply pressure dependent.     

Noninvasive angiography for the diagnosis of vertebral artery disease using Doppler ultrasound (vertebral artery Doppler)

A transoral noninvasive procedure in the oropharynx using local anesthesia was applied to detect flow in the vertebral arteries with a bidirectional continuous-wave Doppler ultrasound system. Common carotid artery compression was used to identify the vertebral artery. Flow direction, amplitude of flow signals, diastolic flow, and reaction of flow on common carotid artery compression served as diagnostic parameters. The procedure was applied in 90 patients of whom 42 underwent angiography. The method has proved to be 82% accurate. It was most reliable in the diagnosis of occlusion or aplasia, subclavian steal and normalcy, and was less reliable in the detection of stenosis or hypoplasia of a vertebral artery. Eleven patients with subclavin steal, five patients with a missing vertebral artery three patients with hypoplasia or stenosis, and 15 patients with normal angiorgraphical findings were correctly diagnosed by Doppler; normal Doppler findings were present in three patients with a mission or stenosed vertebral artery. Those patients (five) with Doppler indications of subclavian steal (one patient), missing vertebral artery (two patients), or stenosis (two patients) had normal angiograms. Application of the Doppler procedure, after 11 subclavin endarterectomies, informed the surgeon immediately about the hemodynamic effect of surgical intervention. Rethrombosis was diagnosed in two patients by postoperative Doppler examination.     

Asymptomatic occlusive lesions of carotid and intracranial arteries in Japanese patients with ischemic heart disease: evaluation by brain magnetic resonance angiography

BACKGROUND AND PURPOSE: The purpose of this study was to elucidate the prevalence and degree of asymptomatic occlusive lesions in the carotid and intracranial arteries in Japanese patients with ischemic heart disease (IHD). METHODS: We performed carotid and intracranial MR angiography (MRA) on 67 patients (49 men, 18 women; age range, 40 to 78 years; mean age, 60.1 years) who had received selective coronary angiography for the clinical diagnosis of IHD. On the basis of these images, degree of stenosis in the regions of the bilateral carotid artery bifurcation and five regions of the intracranial arteries, ie, bilateral intracranial portions of the internal carotid arteries and the middle cerebral arteries and the basilar artery were estimated. RESULTS: Stenosis of more than 25% narrowing of the diameter of the target arteries was found in 15 patients (22.4%) in the extracranial carotid arteries and in 11 patients (16.4%) in the intracranial arteries. Most of the stenotic lesions were mild. The incidence of extracranial carotid stenosis and the severity of coronary atherosclerosis showed a significant correlation. The mean age of the patients with intracranial arterial lesions was statistically higher than those without intracranial lesions. CONCLUSIONS: Our data suggest that asymptomatic occlusive lesions in the carotid and intracranial arteries are fairly common in Japanese patients with IHD, although the degree of stenosis is relatively mild. Coexistence of carotid atherosclerosis should be suspected in IHD patients with severe coronary atherosclerosis, and the possibility of atherosclerosis in the intracranial arteries should be considered in aged IHD patients.     

Impaired clearance of emboli (washout) is an important link between hypoperfusion, embolism, and ischemic stroke

OBJECTIVE: To explore the relationship between hypoperfusion, embolism, and brain infarction. DESIGN: We studied 4 situations in which brain infarction is related to hypoperfusion: extracranial and intracranial occlusive vascular disease, reduced functional vascular reserve in patients with carotid artery occlusive disease, reduced collateral blood flow in patients given thrombolytic treatment, and cardiac surgery. We reviewed results of emboli monitoring using transcranial Doppler ultrasonography. RESULTS: Hypoperfusion is strongly linked to brain ischemia and infarction. The evidence includes close correlation of (1) the severity of arterial stenosis with brain infarction; (2) impaired functional blood flow reserve in patients with carotid artery disease and subsequent brain infarction; (3) reduced collateral blood flow with poor prognosis after thrombolysis; and (4) stroke-related neurologic deficits after cardiac surgery to hypoperfusion during surgery. Microembolization is common in patients with severe symptomatic carotid artery stenosis and during and after cardiac surgery. CONCLUSIONS: Hypoperfusion and embolism often coexist and their pathophysiological features are interactive. Arterial lumenal narrowing and endothelial abnormalities stimulate clot formation and subsequent embolization. Reduced perfusion limits the ability of the bloodstream to clear or wash out emboli and microemboli and reduces available blood flow to regions rendered ischemic by emboli that block supply arteries. The brain border zones are a favored destination for microemboli that are not cleared. We posit that impaired washout is an important but neglected concept that intertwines hypoperfusion, embolization, and brain infarction.     

The agreement between colour Doppler systems in measuring internal carotid artery peak systolic velocities

The study was undertaken to determine if the internal carotid artery peak systolic velocities (ICA PSVs) measured by two colour Doppler imaging systems (Acuson 128 and Siemens Quantum) agree sufficiently for the two systems to be interchangeable in evaluating carotid artery disease. One operator obtained blinded measurements of ICA PSV in 63 prospective nonrandomized patients at risk of stroke. The operator examined 20 patients in the first cohort to assess the intraobserver variation, and 43 patients in the second cohort to assess the limits of agreement between the systems. In vitro comparisons of the systems were also undertaken, using both string and flow phantoms. Excluding one outlier, the intraobserver reproducibility coefficient for both machines was 0.48 m s-1. The limits of agreement (within which 95% of differences lie) between systems were -0.47 to 0.45 m s-1. This reduced to -0.39 to 0.33 m s-1 when the one outlier was excluded. This is within the intraobserver reproducibility range. In vitro data show little intersystem variation with phantom velocity. Intratransducer differences increase when the Doppler angle is increased using the string phantom; maximum differences: Acuson 0.30 m s-1 (42%) and Siemens 0.32 m s-1 (32%). These are within the in vivo reproducibility range. Intratransducer difference decreases when the Doppler angle is increased using the flow phantom, maximum differences: Acuson 0.05 m s-1 and Siemens 0.07 m s-1. The results show the systems agree sufficiently to be interchangeable in evaluating carotid artery disease; however, errors in maximum PSVs, caused by operator or system variation, may lead to errors in percent stenosis grading of the carotid arteries.     

Correlation of cine MR velocity measurements in the internal carotid artery with collateral flow in the circle of Willis: preliminary study

The velocity-phase relationship intrinsic to phase-contrast magnetic resonance (MR) angiography permits the quantitative and qualitative assessment of blood flow. The ability to measure velocity and vessel cross-sectional area allows noninvasive assessment of volume flow rate (VFR) in the internal carotid artery (ICA). Phase-contrast techniques also demonstrate flow direction. Using two-dimensional cine phase-contrast angiography, the authors evaluated VFR in the ICA and collateral flow about the circle of Willis in 15 patients with ischemic neurologic symptoms. The VFR in each carotid artery was correlated with the degree of stenosis and presence or absence of abnormal circle of Willis collateral flow. There was a correlation between a decrease in VFR and abnormal circle of Willis collateral flow. In addition, a correlation between severe stenosis and a decrease in VFR was found. In patients with ischemic neurologic symptoms without severe stenosis (< 70% diameter stenosis), no decrease in VFR was seen. It is hoped that flow quantification and directional flow imaging with phase-contrast angiography will help further characterize carotid artery occlusive disease by enabling assessment of VFR changes associated with ischemic neurologic symptoms. This study also supports the hypothesis that two mechanisms--hemodynamic and embolic--play a role in ischemic neurologic symptoms.     

Oxygen delivery and consumption in critically ill pregnant patients: association with ophthalmic artery diastolic velocity

OBJECTIVES: We aimed to investigate the relation between orbital vessel flow velocity and oxygen delivery, oxygen consumption, cardiac index, and systemic vascular resistance index in critically ill pregnant patients. STUDY DESIGN: Eighteen pregnant or early postpartum patients requiring invasive monitoring were prospectively studied with Doppler ultrasonography. The blood flow velocity and resistance index from the central retinal and ophthalmic arteries were plotted against the oxygen delivery index, oxygen consumption index, cardiac index, and systemic vascular resistance index. Linear and polynomial regression analysis and receiver-operator characteristic curves were used to examine the data. RESULTS: The ophthalmic artery resistance index correlated with oxygen consumption, oxygen delivery index, and cardiac index. Only the cardiac index was independently related to the the ophthalmic artery resistance index. The ophthalmic artery diastolic velocity correlated with oxygen consumption index, oxygen delivery index, and cardiac index. The ophthalmic artery diastolic velocity correlated independently with mixed venous oxygen content and arteriovenous oxygen content difference. The central retinal artery Doppler index did not correlate with any of the invasively measured parameters. An ophthalmic artery diastolic velocity of > 7.12 cm/sec identified 75% of patients with an oxygen consumption index of < 140 ml/min per square meter and 91% of patients with an oxygen delivery index of < 600 ml/min per square meter. CONCLUSIONS: These data suggest that the ophthalmic artery flow velocity is correlated with systemic oxygen delivery and consumption. This relationship may have potential research applications in the noninvasive assessment of oxygen delivery index and oxygen consumption index in critically ill pregnant patients.     

Does a visible retinal embolus increase the likelihood of hemodynamically significant carotid artery stenosis in patients with acute retinal arterial occlusion?

OBJECTIVE: To determine the value of visible retinal emboli as a diagnostic "test" for the detection of hemodynamically significant carotid artery stenosis in the setting of acute retinal artery occlusion. METHODS: A cross-sectional diagnostic accuracy study was performed in a tertiary North American center, with the results of the dichotomous diagnostic test (the presence or absence of visible retinal emboli) being placed against the dichotomous outcome of the presence or absence of hemodynamically significant carotid artery stenosis (defined as > or = 60%, or < 60%, carotid artery stenosis on either side). RESULTS: Forty-eight (18.7%) of our 256 patients had hemodynamically significant carotid artery stenosis. The sensitivity and specificity of retinal emboli for the detection of hemodynamically significant carotid artery stenosis were 39% and 68%, respectively. The presence of a visible retinal embolus generated a likelihood ratio of 1.24 (95% confidence interval, 0.84-1.86). This value corresponds to a patient with a pretest probability of 50% having a posttest probability of 55.3%. The absence of a visible retinal embolus generated a likelihood ratio of 0.88 (95% confidence interval, 0.68-1.15). CONCLUSIONS: The presence of a visible retinal embolus is a poor diagnostic test for the detection of hemodynamically significant carotid artery stenosis in the setting of acute retinal artery occlusion. Accordingly, the presence of an embolus should not influence the decision to perform carotid Doppler ultrasonography in patients with acute retinal arterial occlusion.     

Contrast-enhanced transcranial color-coded duplex sonography in ischemic cerebrovascular disease

BACKGROUND AND PURPOSE: Echo contrast agents have been shown to provide conclusive examinations in most patients with insufficient ultrasound penetration through the temporal bone. We investigated the diagnostic value of contrast-enhanced (CE) transcranial color-coded duplex sonography (TCCD) in patients with ischemic cerebrovascular disease and insufficient temporal windows and evaluated TCCD criteria that predict whether CE-TCCD studies may become conclusive. METHODS: Thirty-three patients presenting with ischemic strokes (n = 21) and transient ischemic attacks (n = 12) were investigated. Extracranial color duplex imaging showed normal findings in 24 patients, eight > or = 70% stenoses and one occlusion of the carotid arteries in 8 patients, and severe occlusive disease of both vertebral arteries in 1 patient. Seven carotid stenoses and vertebral artery obstructions were confirmed by angiography. The galactose/palmitic acid-based echo contrast agent was injected intravenously as bolus of 200, 300, or 400 mg/mL in a dosage of 10, 5, and 5 mL, respectively. RESULTS: Thirty-two of the 33 patients were completely examined because 1 patient who felt pain at the injection site declined further investigations. Twenty-one (66%) of 32 CE studies were conclusive and showed cross-flow through three anterior and two posterior communicating arteries, but no stenoses and occlusions. Precontrast identification of any cerebral artery provided an overall accuracy of 97% in predicting a conclusive CE investigation. Precontrast TCCD identified no arterial Doppler signals in patients with inconclusive CE studies. CONCLUSIONS: CE-TCCD provided conclusive examinations in two thirds of patients with ischemic cerebrovascular disease and ultrasound-refractory temporal windows. Precontrast detection of any cerebral artery reliably predicted a conclusive CE investigation.