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Biomedical subjects

H Etani

Publications and source records attributed to H Etani.

At least 37 records · Page 2Linked to original sources
PubMed1987

Effect of hypocapnia on cerebral oxygen metabolism and blood flow in ischemic cerebrovascular disorders.

Effects of hypocapnia on cerebral oxygen consumption (CMRO2) and blood flow (CBF) in cerebral ischemia were studied in 19 patients. The CMRO2 did not change significantly during hypocapnia within the whole group of patients, because 10 out of 19 cases showed a decrease (p less than 0.001) and other 9 showed an increase (p less than 0.01) of CMRO2 during hypocapnia. The first 10 showed higher resting CMRO2 (p less than 0.001) and arteriovenous differences of oxygen content (AVDO2; p less than 0.02) than the other 9. However, the resting CBF and CO2 reactivity to hypocapnia were not different between them, and clinical situations were also similar. A dissociation between flow and metabolism was suggested in the first 10 with rather preserved CMRO2, while reduced metabolic demands were suggested in the other 9. Different responses of CMRO2 to hypocapnia are expected in cerebral ischemia, i.e. in cases with rather preserved CMRO2 it decreases despite an AVDO2 increase, suggesting a capability of CMRO2 to respond to CBF reduction, while it increases in cases with more decreased CMRO2, as the AVDO2 increase exceeds the CBF reduction to maintain the decreased CMRO2 for a further CBF reduction. The vascular CO2 reactivity, therefore, might be maintained to be constant between these patients.

Adult↗
PubMed1987

Binding of 131I-labeled tissue-type plasminogen activator on de-endothelialized lesions in rabbits.

Tissue-type plasminogen activator (t-PA) which has a high affinity for fibrin in the clot, was labeled with 131I by the iodogen method, and its binding to de-endothelialized lesions in the rabbit was measured to assess the detectability of thrombi. The de-endothelialized lesion was induced in the abdominal aorta with a Fogarty 4F balloon catheter. Two hours after the de-endothelialization, 131I-labeled t-PA (125 +/- 46 microCi) was injected intravenously. The initial half-life of the agent in blood (n = 12) was 2.9 +/- 0.4 min. The degree of binding of 131I-labeled t-PA to the de-endothelialized lesion was evaluated at 15 min (n = 6) or at 30 min (n = 6) after injection of the agent. In spite of the retention of the biochemical properties of 131I-labeled t-PA and the presence of fibrin deposition at the de-endothelialized lesion, the binding of t-PA to the lesion was not sufficiently strong. Lesion-to-control ratios (cpm/g/cpm/g) were 1.65 +/- 0.40 (at 15 min) and 1.39 +/- 1.31 (at 30 min), and lesion-to-blood ratios were 1.39 +/- 0.32 (at 15 min) and 1.36 +/- 0.23 (at 30 min). These results suggest that radiolabeled t-PA may be inappropriate as a radiopharmaceutical for the scintigraphic detection of a pre-existing thrombotic lesion.

Animals↗
PubMed1986

Imaging platelet deposition on Dacron bifurcation grafts in man: quantification by a dual-tracer method using 111In-labeled platelets and 99mTc-labeled human serum albumin.

A dual tracer technique using 111In-labeled platelets and 99mTc-labeled human serum albumin was applied to evaluate the thrombogenicity of Dacron bifurcation arterial grafts. The level of platelet accumulation over the whole of the graft was estimated from the ratio of 111In-platelet radioactivity deposited on the vascular wall to these radioactivity circulating in the blood pool, i.e., the platelet-accumulation index (PAI). Furthermore, the PAI value was calculated for each pixel in digitized images and the PAI distribution image (PAI image) was reconstructed. Eighteen patients with DeBakey knitted Dacron bifurcation grafts and 11 normal volunteers were studied. Of the 18 patients, 11 had no graft occlusion (group I) and the remaining 7 (group II) had occlusion. The mean PAI value (+/- SD) over the whole of the graft in group I was 32.6% +/- 33.7% as compared to -8.8% +/- 4.5% in the control group (P less than 0.01). In group I, the PAI value over the entire graft decreased with the age of the graft (r = -0.763; P less than 0.01). In contrast, in group II, platelet accumulation did not diminish with time and persisted beyond the time of which platelet accumulation was no longer found in group I. Moreover, analysis of the PAI images revealed enhanced platelet accumulation on the proximal part of the graft to be more frequent in group II than in group I (6/7 vs 0/11; chi 2c = 10.55; P less than 0.005). The method used for platelet imaging in the present study may be useful in the study of platelet reactions on Dacron arterial prostheses.

Aged↗
PubMed1986

Echo-Doppler velocimeter in the diagnosis of hypertensive patients: the renal artery Doppler technique.

The renal blood flow velocity characteristics in 8 normal controls, 19 essential hypertensive patients and 8 hypertensive patients with renovascular disease were evaluated using echo-Doppler velocimetry. Two different approaches for ultrasonic detection of the renal artery, the translumbar and the transabdominal approach, were used. Renal Doppler sonograms were analyzed by measuring the acceleration index and the peak-systolic frequency/end-diastolic frequency (S/D) ratio. Renovascular patients who required surgery were examined before and after angioplasty. Doppler signals could be detected in all 35 subjects by using the translumbar approach. The acceleration index of the affected renal arteries significantly correlated to the percent stenosis of the renal artery determined by angiography. The acceleration index in the affected renal artery was improved by surgical treatment. The S/D ratio in essential hypertensives was significantly higher than that in the normal controls. There was a significant inverse correlation between the S/D ratio and creatinine clearance. Echo-Doppler velocimetry is considered to be useful in the diagnosis of renovascular disease and also in the evaluation of abnormalities of renal vascular resistance in hypertensive patients.

Adolescent↗
PubMed1986

Recurrent transient ischemic episodes after anticoagulation or bypass operation. Hemodynamic or embolic mechanism.

Three patients who suffered delayed transient ischemic episodes despite adequate anticoagulation or successful extracranial-intracranial (EC-IC) bypass anastomosis were studied. A hemodynamic mechanism was prominent in 1 patient with moderate orthostatic hypotension. After adequate anticoagulation he had further episodes of transient ischemia, which were finally controlled by an EC-IC bypass. Cerebral blood flow studies revealed flow changes with progression of the arterial lesion from stenosis to occlusion. The bypass was patent postoperatively, which suggested that the ischemia in this patient had been hemodynamic in origin. In the other patient the cerebral ischemic symptoms showed a remarkable improvement after the bypass operation. However, ischemia recurred after the operation until anticoagulants were started. Postoperative cerebral ischemia suggested microemboli, whereas preoperatively, it was presumably a hemodynamic phenomenon. In another patient where microembolism was more apparent, anticoagulation controlled the recurrent ischemia after a bypass operation. A hemodynamic as well as embolic mechanism needs to be considered in a cerebral ischemia which recurs after treatment.

Adult↗
PubMed1985

[Cerebral perfusion imaging with N-isopropyl-(123I) P-iodoamphetamine (123I-IMP): its planar imaging and semiquantitative analysis in cases with internal carotid occlusion].

Occlusion of internal carotid artery (ICA) is one of the most common cause of stroke, and the single common arterial lesion considered for extraintracranial bypass. The symptoms of ICA occlusion are not uniform; some shows transient ischemic attacks (TIAs), others completed stroke at the onset. So, measurement of cerebral blood flow might be needed to evaluate the prognosis, or to select surgical candidate in ICA occlusion. Several methods, such as Xe-133 intracarotid method, Xe-133 inhalation method etc, have been applied for the assessment of cerebral blood flow in cases with ICA occlusion. No previous report was found by the newly developed 123I-IMP in this connection. The purpose of the present study is first to demonstrate the feasibility of 123I-IMP planar brain scintigraphy and its semiquantitative analysis in 17 cases with ICA occlusion. After intravenous injection of 3 mCi of 123I-IMP, brain scintigrams were obtained from anterior, Towne, vertex, posterior, right lateral and left lateral views, and were recorded on magnetic tape and Poraloid films. Semiquantitative analysis was performed as a percent index of asymmetry (PIA) from the difference of each hemispheric count in the scintigrams by use of on-lined minicomputer system. Clinical manifestations of these 17 cases were, completed stroke in 10, TIAs in 4, and no neurological symptom in 3. 123I-IMP brain scintigrams demonstrated low flow lesion in 10 out of 10 completed stroke, in 2 out of 4 TIAs and normal perfusion in all cases with no neurological symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Improvement of cerebral blood flow and/or CO2 reactivity after superficial temporal artery-middle cerebral artery bypass in patients with transient ischemic attacks and watershed-zone infarctions.

The effect of extracranial-intracranial bypass anastomosis on cerebral blood flow and CO2 reactivity during hypocapnia was investigated in ten patients with transient ischemic attacks or watershed infarctions due to carotid occlusive diseases. Six patients had occlusion and four had stenosis (greater than 50%) of the internal carotid artery. Those with infarctions had increased cerebral blood flow and CO2 reactivity postoperatively, and improved clinically. Those with transient ischemic attacks due to stenosis (greater than 50%) of the internal carotid artery had increased CO2 reactivity postoperatively but constant normal regional blood flow. Cerebral blood flow improved in those with poorer flow, CO2 reactivity increased in those with better reactivity, and better CO2 reactivity preoperatively brought about a greater flow increase. The pre- and postoperative evaluation of cerebral blood flow and CO2 reactivity is believed to be useful in evaluating the effectiveness of bypass anastomosis. Preoperative evaluation might be informative in selecting candidates for bypass.

Aged↗
PubMed1984

Platelet accumulation in carotid atherosclerotic lesions: semiquantitative analysis with indium-111 platelets and technetium-99m human serum albumin.

To evaluate platelet accumulation in carotid atherosclerotic lesions semiquantitatively, a dual-tracer technique was applied, using In-111 platelets and Tc-99m human serum albumin. With this approach, we investigated the ratio of radioactivity in In-111 platelets deposited on the vascular wall to those circulating in the blood pool, platelet accumulation index ( PAI ). This study included 12 normal subjects and 25 patients with ischemic cerebrovascular disease (CVD). Angiographic abnormalities were observed at 34 of 50 carotid bifurcations in the CVD patients. The mean PAI value was significantly higher at the carotid bifurcations with angiographic abnormality than at the normal ones (p less than 0.001). Furthermore, elevations of mean PAI were prominent at the lesions with severe stenosis or ulceration. The degree of platelet accumulation was well demonstrated by this technique, which can also yield information on thrombogenicity and efficiency of antiplatelet therapy in carotid atherosclerotic disease.

Adult↗
PubMed1983

Bi-hemispheric CBF and its CO2 reactivity of TIAs and completed strokes in ICA occlusions.

Bi-hemispheric cerebral blood flow (CBF) measurements during rest and hyperventilation, with intra-arterial 133Xe injection method, were investigated in 19 cases, angiographically diagnosed as unilateral internal carotid artery (ICA) occlusion, including 8 cases with TIAs and 11 cases with completed strokes as the onset. Indices of cerebral vascular resistance and CO2 reactivity with decreasing arterial PCO2 were also investigated. A significant decrease (P less than 0.05) of hemispheric mean CBF was noted in the ischemic hemisphere, but normal flow values in the unaffected hemisphere and preserved CO2 responsiveness during hyperventilation were observed in both the affected and unaffected hemispheres in patients with TIAs. Moreover, a direct relationship between CBF and blood pressure, observed in 11 cases with completed strokes, was not recognized in 8 cases with TIAs. A degree of the abnormalities of the affected hemisphere in cerebral circulation was suggested to be somewhat different between TIAs and completed strokes in ICA occlusions, and bi-hemispheric CBF measurements would be an useful method for evaluating the various indices of the CBF in ICA occlusions.

Adult↗
PubMed1983

Cerebral blood flow and CO2 reactivity in transient ischemic attacks: comparison between TIAs due to the ICA occlusion and ICA mild stenosis.

Hemispheric mean cerebral blood flow (CBF), together with its CO2 reactivity in response to hyperventilation, was investigated in 18 patients with transient ischemic attacks (TIAs) by intraarterial 133Xe injection method in a subacute-chronic stage of the clinical course. In 8 patients, the lesion responsible for symptoms was regarded as unilateral internal carotid artery (ICA) occlusion, and in 10 patients, it was regarded as unilateral ICA mild stenosis (less than 50% stenosis in diameter). Resting flow values were significantly (P less than 0.05) decreased in the affected hemisphere of TIA due to the ICA occlusion as compared with the unaffected hemisphere of the same patient, regarded as the relative control. It was not decreased in the affected hemisphere of TIA due to the ICA mild stenosis as compared with the control. With respect to the responsiveness of CBF to changes in PaCO2, it was preserved in both TIAs, due to the ICA occlusion and ICA mild stenosis. Vasoparalysis was not observed in either types of TIAs in the subacute-chronic stage. However, in the relationship of blood pressure and CO2 reactivity, expressed as delta CBF(%)/delta PaCO2, pressure-dependent CO2 reactivity as a group was observed with significance (P less than 0.05) in 8 cases of TIA due to the ICA occlusion, while no such relationship was noted in 10 cases of TIA due to the ICA mild stenosis. Moreover, clinical features were different between TIAs due to the ICA occlusion and ICA mild stenosis, i.e., more typical, repeatable TIA (6.3 +/- 3.7 times) with shorter duration (less than 30 minutes) was observed in TIAs due to the ICA mild stenosis, while more prolonged, less repeatable TIA (2.4 +/- 1.4 times) was observed in TIAs due to fixed obstruction of the ICA. From these observations, two different possible mechanisms as to the pathogenesis of TIA might be expected, e.g., TIA of microembolic origin due to the ICA mild stenosis, and TIA of hemodynamic origin due to fixed obstruction of the ICA, for whom the bypass surgery might be beneficial, i.e., all TIAs are not based on the same mechanism.

Arterial Occlusive Diseases↗
PubMed1983

Demonstrating patency of STA-MCA anastomosis with Tc-99m albumin microspheres.

A patient with occlusion of the left internal carotid artery underwent an anastomosis between branches of the left superficial temporal and middle cerebral arteries (STA-MCA). A left carotid angiogram 9 days later showed extreme, tapered narrowing of the involved STA branch, with no filling of the MCA from the bypass. A year later, symptoms had improved slightly, and a minimally invasive study was made with Tc-99m human albumin microspheres. This showed patency of the bypass, with intracranial perfusion in the MCA field, findings later confirmed by a repeat left carotid angiogram. It appears that Tc-99m HAM scintigraphy will be useful in assessing the effectiveness of this and other bypass operations.

Cerebral Angiography↗
PubMed1982

Cerebral perfusion imaging with albumin microspheres tagged with Tc-99m and In-111 in cases with internal carotid occlusion.

Cerebral perfusion imaging with dual-tracer (Tc-99m and In-111) human albumin microspheres (HAM scintigraphy) was performed in 15 cases with unilateral occlusion of the internal carotid artery, for the diagnosis and evaluation of collateral circulation patterns. After injection of Tc-99m microspheres into one common carotid artery and In-111 HAMs into the other, two perfusion images, one for each carotid artery, were clearly differentiated by appropriate pulse-height discrimination. With this method, diagnosis of internal carotid artery occlusion was definitely made in eight patients, suspected in six, and missed in one. The collateral perfusion areas from the contralateral ICA and ipsilateral external carotid artery were well demonstrated by this method, and the scintigraphic results agreed well with the angiographic findings in all cases. Dual-tracer HAM scintigraphy is capable of adding information about collaterals at the capillary level to the anatomic information obtained by angiography.

Aged↗
PubMed1981

Internal carotid occlusion: assessment, by Tc-99m-tagged microspheres, of bypass from superficial temporal to middle cerebral artery.

The assessment of regional blood perfusion through the STA-MCA anastomosis was performed by the method of intracarotid injection of Tc-99m-labeled human albumin microspheres (HAM scintigraphy). This study included 11 anastomoses in 10 cases with occlusion of the internal carotid artery, who were treated by bypass surgery. The area of intracranial perfusion through the bypass was well defined in all cases by HAM scintigraphy. This method is excellent for imaging the regional blood perfusion through the anastomotic vessel, and the scintigraphic findings agree well with those of postoperative angiography. HAM scintigraphy will partially replace postoperative angiography because of its simplicity and low invasiveness.

Adult↗