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Biomedical subjects

R Nohara

Publications and source records attributed to R Nohara.

At least 127 records · Page 7Linked to original sources
PubMed1990

[Evaluation of complete left bundle branch block with normal coronary artery using positron emission CT (PET) and Tl-201 scintigraphy].

False-positive Tl-201 scintigraphy in patients with complete left bundle-branch block (CLBBB) and normal coronary artery had been reported by several authors. However the reason for this phenomenon remained to be clarified. We investigated 2 patients (case 1; a 65-year-old male, case 2; a 58-year-old male) with CLBBB using positron emission computed tomography (PET). Coronary angiography revealed normal coronary artery in both cases. In both cases, Tl-201 stress scintigraphy demonstrated definite perfusion defect at the anteroseptal region without redistribution, although PET study using F-18 fluorodeoxyglucose (18F-FDG) revealed defect at the septal wall. This indicates that perfusion defect detected by Tl-201 scintigraphy relates rather not to ischemic myocardium with a viable region, but to necrotic or fibrous tissue. Thus, PET is a useful tool in investigating viability of abnormal myocardium when other study has failed to do so. Our cases with CLBBB suggested that there was abnormal flow and metabolism at the anteroseptal region, possibly relating to the pathogenesis of CLBBB.

Aged↗
PubMed1989

Transmural gradients of coronary flow reserve with physiologically and morphometrically defined stenoses in dogs.

Coronary angiography permits identification of stenotic lesions but underestimates their severity and does not provide information regarding their physiologic significance. Evaluation of coronary flow reserve by means of selective coronary artery Doppler flow catheters or quantitative arteriography has been proposed to obtain this information. However, these techniques may not accurately reflect transmural gradients in flow. We evaluated the relationship between flow reserve defined with an epicardial Doppler flow probe and the transmural gradient of flow measured with radiolabeled microspheres in 21 dogs with graded stenoses and correlated results with coronary artery geometry measured morphometrically. Four groups of dogs were studied. In five control dogs without stenosis, reactive hyperemia after 20 seconds of complete coronary occlusion was 4.5 +/- 1.5 (mean +/- SD) times resting flow with an endocardial/epicardial flow ratio at peak flow of 1.0 +/- 0.2. When reactive hyperemia was blunted (without affecting resting flow) by 50% (n = 6), 75% (n = 5), or was abolished completely (n = 5) by coronary stenosis, the endocardial/epicardial flow ratio at peak flow was 1.0 +/- 0.3, 0.7 +/- 0.2, and 0.5 +/- 0.1, respectively. Cross-sectional area of the stenosed segment was reduced by 85.6 +/- 3.5%, 91.1 +/- 2.2%, and 92.8 +/- 4.3% in these groups, respectively. Thus in dogs with stenoses exceeding 86% of the cross-sectional area, endocardial flow reserve is compromised disproportionately compared with epicardial flow reserve, suggesting that clinical measurements of coronary flow reserve may underestimate the physiologic significance of coronary stenoses.

Animals↗
PubMed1989

Optimal criteria for rapid detection of myocardial reperfusion by creatine kinase MM isoforms in the presence of residual high grade coronary stenosis.

Analysis of isoforms of MM creatine kinase (CK) in plasma is being developed as a means for rapid detection of coronary recanalization in patients given thrombolytic agents. To determine whether flow-limiting residual stenosis typical of that seen in patients affects plasma isoform profiles, stenosis sufficient to preclude reactive hyperemia was induced in dogs before coronary occlusion, followed by recanalization in 2 h. Plasma activities of the MM CK isoform released from myocardium (MM3) and its two conversion products elaborated sequentially (MM2 and MM1) were assayed in serial samples with a rapid quantitative chromatofocusing procedure. Reperfusion in 10 dogs shortened the mean intervals (+/-SD) to the occurrence of peak MM3 activity (3.7 +/- 0.9 h), peak MM3 expressed as a percent of total CK activity (MM3%, 2.5 +/- 0.3 h) and the maximal ratio of MM3 to MM1 (2.7 +/- 0.3 h) compared with results in 10 control dogs without reperfusion. Nevertheless, the appearance of these peaks was delayed by 8% to 57% when residual stenosis was present. In contrast, the rate of increase of MM3% was delineated before the peak, was fivefold greater with recanalization (1.19 +/- 0.46 versus 0.26 +/- 0.11% min-1 in control dogs) and was not attenuated by residual stenosis. Thus, this criterion appears capable of delineating recanalization early after thrombolysis whether or not high grade residual stenosis is present.

Animals↗
PubMed1989

[Assessment of myocardial viability by quantitative analysis of stress Tl-SPECT--comparison with FDG-PET].

Stress Tl-201 tomography (SPECT) is widely used for evaluating myocardial viability. To assess its value, redistribution (RD) on SPECT was compared with metabolic imaging using FDG. Thirty patients with coronary artery disease underwent stress-3 hour Tl-201 SPECT and PET using N-13 ammonia and FDG. RD was classified into 4 grading, including complete RD (CR), incomplete RD (IR), persistent defect (PD) and additional minimal RD (MR) defined as no definite RD on visual analysis but faint RD with Bull's eye quantitative analysis (QNT). All but one segment with CR or IR were viable regions (normal or ischemic regions) by PET. Of 74 segments without RD on visual analysis, 31 segments (42%) had RD by QNT (MR). All of them were viable regions by PET. Thus, QNT identified 31 segments (63%) of the metabolically viable segments which the visual Tl-201 analysis did not show RD and classified as myocardial scar. However, even such QNT cannot detect ischemic myocardium in 18 segments (42%) containing metabolic activity on PET. These data indicate that QNT of RD on Tl-201 SPECT is considered as a valuable means for assessing myocardial ischemia.

Aged↗
PubMed1989

[Serial assessment of cardiac function during and after exercise by an ambulatory ventricular function monitor (VEST)].

Cardiac function was serially assessed during and after exercise by an ambulatory ventricular function monitor (VEST) in 31 patients who received coronary angiography. Based on the study of fluctuation during the baseline recording, greater than or equal to 6% change in ejection fraction (EF) was considered significant. The serial changes in EF during exercise was divided into 5 types, including continuous increase (type A), initial increase but return to the baseline (type B), no change (type C), initial increase but later decrease below the baseline (type D), and continuous decrease (type E). Among 8 normal subjects, their EF changes during exercise showed type A in 3, type B in 2, type C in 2, and type D in 1. Among 21 patients with coronary artery disease, the EF changes showed type A in 5, type B in 4, type C in 4, type D in 5 and type E in 3. Thus, there was a significant overlap in EF response between normal and coronary patients. However, every patient showing type A and B had single-vessel disease, and 63% of them had persistent thallium defect without redistribution. After the exercise, 29 patients showed rapid increase in EF. The time to the peak EF was significantly longer in coronary patients (1.88 +/- 1.24 min) than that in normal cases (0.88 +/- 0.55 min) (p less than 0.05) particularly in patients with multi-vessel disease (2.22 +/- 1.29 min). In addition, those showing type C, D or E tended to have a longer time to peak EF and more increase in EF after exercise than those showing type A or B. These data suggest that VEST is suitable for continuous measurement of cardiac function during and after exercise which provided valuable indices for assessment of severity of ischemia in coronary artery disease.

Adult↗
PubMed1988

F-18 deoxyglucose and stress N-13 ammonia positron emission tomography in anterior wall healed myocardial infarction.

To evaluate myocardial blood flow and glucose utilization, N-13 ammonia (NH3) and F-18 deoxyglucose positron emission tomography scanning was performed in 22 patients with previous anterior wall myocardial infarction, using a high-resolution, multi-slice, whole-body scanner. The N-13 ammonia study was performed at rest and after exercise. The F-18 deoxyglucose study was performed at rest after fasting greater than 5 hours. The N-13 ammonia study revealed a hypoperfused area in 19 of the 22 patients (86%), that corresponded to the infarcted regions as diagnosed by electrocardiography, coronary arteriography and left ventriculography (21 patients). The hypoperfused areas expanded after exercise in 16 of 22 patients (73%). F-18 deoxyglucose uptake was observed in these hypoperfused areas, especially in patients with hypokinetic wall motion on left ventriculography and in exercise-induced hypoperfused areas. However, positron emission tomography demonstrated diffuse uptake of F-18 deoxyglucose in 3 of 8 patients with dyskinetic wall motion. Thus, metabolically active myocardium in infarcted areas or periinfarct ischemia can be visualized with F-18 deoxyglucose and stress N-13 ammonia studies.

Adult↗
PubMed1988

Prompt detection of myocardial injury by assay of creatine kinase isoforms in initial plasma samples.

To determine the sensitivity and specificity of assays of isoforms of the MM isoenzyme of creatine kinase (CK) and MB-CK for the diagnosis or exclusion of acute myocardial infarction in plasma samples obtained at the time of presentation to the emergency room of patients with suspected myocardial infarction, 50 patients in whom the diagnosis was ultimately established and 31 in whom infarction was ultimately excluded were evaluated. Of the 50 patients in whom infarction was ultimately established, 47 had an increased ratio of the MM3 to the MM1 isoform or elevated MB-CK in the plasma sample initially available. The specificity of the approach was 77%, sensitivity 94%. The availability of rapid assays for MM-CK isoforms and for MB-CK should facilitate determination of the presence or absence of acute myocardial injury sufficiently promptly so that decisions regarding treatment can be made optimally.

Adult↗
PubMed1988

Compromise of beneficial effects of reperfusion on myocardium supplied by vessels with critical residual stenosis.

Coronary thrombolysis in patients frequently unmasks high grade residual stenosis. To determine whether beneficial effects of reperfusion are compromised by critical residual coronary stenosis, 14 dogs were instrumented with an external left anterior descending coronary artery balloon occluder, Doppler flow probe and adjustable screw clamp. In eight of the dogs, critical stenosis (abolition of reactive hyperemia after a 20 s occlusion; 95.7 +/- 1.0% cross-sectional area reduction) was induced before occlusion and maintained. In the control group (n = 6), no stenosis was induced. Each dog was subjected to 2 h of myocardial ischemia followed by balloon deflation and 24 h of reperfusion. Myocardial blood flow assessed with microspheres was similar during balloon inflation in both groups and indicative of profound ischemia. Transmural blood flow to the reperfused zone assessed 1 min after balloon deflation was significantly greater in control dogs without residual stenosis (383% of normal compared with 120% of normal in dogs with stenosis) (p less than 0.01). Compromise of transmural flow persisted in dogs with stenosis (85% compared with 121% of normal in control dogs after 1 h, p less than 0.05; and 49% compared with 68% after 24 h of reperfusion, p less than 0.05). Diminution of subendocardial blood flow after reperfusion was particularly marked. The extent of infarction was greater in the heart of dogs with residual stenosis. Thus, residual critical coronary stenosis compromises nutritional perfusion and salvage of reperfused myocardium after recanalization. These observations underscore the need for prompt identification of patients with high grade residual stenosis early after coronary thrombolysis and the potential value of angioplasty or coronary surgery in selected patients soon after initial recanalization.

Angioplasty, Balloon↗
PubMed1988

Quantitative analysis for isoforms of creatine kinase MM in plasma by chromatofocusing, with on-line monitoring of enzyme activity.

Changes in the proportions of individual isoforms of the MM isoenzyme of creatine kinase (CK; EC 2.7.3.2) in plasma promptly reflect both myocardial infarction and coronary recanalization. However, quantitative methods developed thus far are too slow or cumbersome for routine use in making clinical decisions. We report a convenient, quantitative chromatofocusing assay with on-line fluorometric detection of isoform activity in the column eluent that provides results within 40 min from the time of sample application. Sample eluted from a microbore chromatofocusing column (1.8-mL bed volume) is split between a reaction stream, into which CK reagents are added, and a reference stream. After incubation at 37 degrees C, NADPH formed by reaction of isoforms with CK reagent is detected at 340 nm. The system can detect activity of individual isoforms in plasma samples having total CK activity greater than or equal to 21 U/L (30 degrees C). Results correlated closely with those obtained by previously validated, but slow, chromatofocusing (r = 0.98, n = 30) and protein immunoblotting (r = 0.90, n = 20) procedures.

Animals↗
PubMed1987

Early estimation of acute myocardial infarct size soon after coronary reperfusion using emission computed tomography with technetium-99m pyrophosphate.

Early appearance of positive findings on a technetium-99m pyrophosphate scan has been shown to be associated with the presence of a reperfused acute myocardial infarction (AMI). Early technetium-99m pyrophosphate imaging was performed by emission computed tomography to evaluate reperfusion and to test the feasibility of estimating infarct size soon after coronary reperfusion based on acute positive tomographic findings. Twenty-seven patients with transmural AMI who were treated with intracoronary urokinase infusion followed by percutaneous transluminal coronary angioplasty underwent pyrophosphate imaging 8.7 +/- 2.1 hours after the onset of AMI. None of the 8 patients in whom reperfusion was unsuccessful had acute positive findings. Of 19 patients in whom reperfusion was successful, 17 had acute positive findings (p less than 0.001). In these 17, tomographic infarct volumes were determined from reconstructed transaxial images. The threshold for areas of increased pyrophosphate uptake within the infarct was set at 60% of peak activity by the computerized edge-detection algorithm. The total number of pixels in all transaxial sections showing increased tracer uptake were added and multiplied by a size factor and 1.05 g/cm3 muscle to determine infarct volume. The correlations of tomographic infarct volumes with peak serum creatine kinase (CK) levels (r = 0.82) and with cumulative release of CK-MB isoenzyme (r = 0.89) were good. Moreover, the time to positive imaging was significantly shorter than that to peak CK level (8.5 +/- 2.3 vs 10.4 +/- 2.2 hours, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Interventricular septal motion in acute myocardial infarction with proximal and distal left anterior descending coronary lesions.

To evaluate the ability of echocardiography to detect and localize lesions of the proximal and distal left anterior descending (LAD) coronary arteries, the systolic excursion of the left side of the septum and the ratio of septal to posterior wall excursion (IVS/PW) were measured in 26 patients with acute myocardial infarction (AMI) and nine normal control subjects. The patients with proximal LAD lesions had septal wall excursions of less than 3 mm, whereas in those with distal LAD lesions septal wall excursions were more than 3 mm. All patients with proximal LAD lesions showed an IVS/PW ratio of less than 0.4, but in those with distal LAD lesions the ratio was 0.4 or greater. We conclude that reduced or absent interventricular septal motion in anterior AMI suggests an LAD lesion, and a septal excursion of less than 3 mm suggests involvement of the proximal LAD artery, whereas septal excursion of 3 mm or more indicates involvement of the distal LAD artery.

Adult↗
PubMed1987

Detection of coronary artery disease with 13N-ammonia and high-resolution positron-emission computed tomography.

In order to evaluate the detectability of coronary artery disease (CAD) with positron-emission computed tomography (PET), we performed 13N-ammonia myocardial PET scanning at rest and with exercise loading in 20 normal subjects and 40 patients with CAD, by means of a high-resolution, multi-slice, whole-body PET scanner. Myocardial PET scanning was performed 3 minutes after injection of 13N-ammonia at rest and during exercise. The circumferential profile analysis of resting PET images revealed regional hypoperfusion in 96% of CAD patients with previous myocardial infarction and in 29% of those without infarction. Exercise PET studies showed high sensitivity (93%) in detecting CAD without myocardial infarction, whereas no abnormal hypoperfusion was detected in normal subjects. Segmental analysis of regional myocardial perfusion with exercise stress identified 67 of 75 stenosed vessels (89%). We conclude that 13N-ammonia myocardial PET with exercise loading provides high-quality tomographic images of regional myocardial perfusion and is a valuable technique for detecting CAD.

Adult↗
PubMed1987

[Evaluation of coronary reperfusion for acute myocardial infarction by emission CT using technetium-99m pyrophosphate].

Twelve patients with acute transmural myocardial infarction (AMI) were treated with percutaneous transluminal coronary angioplasty (PTCA) following intracoronary thrombolysis using urokinase, and underwent technetium-99m stannous pyrophosphate (Tc-99m-PPi) imaging 9.2 +/- 2.1 hours after the onset of chest pain. The imaging was performed with emission computed tomography (ECT). Compared to planar imaging, this allowed more accurate detection of small myocardial infarcts and accurate measurements of infarcts irrespective of their location was also made. Early Tc-99m-PPi images were obtained to test the hypothesis that an early, abnormal Tc-99m-PPi image suggest successful reperfusion. The results were presented for two groups of patients: three with unsuccessful reperfusion (Group A) and nine with successful reperfusion (Group B). Eight of the nine patients with successful reperfusion had positive acute Tc-99m-PPi images. On the contrary, all the three patients for whom reperfusion failed had negative acute Tc-99m-PPi images. We also examined the feasibility of estimating infarct size using positive Tc-99m-PPi images in patients with successful reperfusion during the early phase of AMI. The Tc-99m-PPi uptake score (Tc-US) was used to measure infarct size in this study. Areas of increased Tc-99m-PPi uptake within myocardial infarcts were threshold at 60% of the peak activity. The Tc-US of each patient was obtained to sum the scores of all myocardial segments using a scoring system with a maximum score of 108. Using this method, Tc-US ranged from 2 to 39. The correlation of Tc-US with the peak serum creatine kinase level was significant (r = 0.91).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[Exercise 13NH3-positron emission computed tomography (PET) versus exercise single photon emission computed tomography (SPECT)].

The value of exercise positron emission computed tomography (PET) was determined by comparing it with exercise T1-201 single photon emission computed tomography (SPECT) using graded ergometer exercise in 10 anginal patients with left anterior descending coronary (LAD) involvement (stenosis greater than or equal to 75%) with or without other coronary stenosis. The distribution of N-13 ammonia or T1-201 was determined and expressed as percent count ot the highest count on the circumferential profile curve (CPC) in the transaxial image. Two standard deviations below the mean counts of six normal hearts for PET and ten for SPECT were considered as the lower limit of normal, and these were determined separately during exercise and at rest. The ischemic areas per total myocardial areas (%C), the accuracy in diagnosing coronary involvement and the identification of coronary branch involvement were determined by CPC analysis in three corresponding slices. Regional analyses revealed that accuracy in diagnosing proximal left anterior descending artery (LAD) involvement was higher with PET (9/10) than with SPECT (7/10), but the difference was not statistically significant. The accuracy in diagnosing right coronary or circumflex artery stenosis was 9/10 with PET and 8/10 with SPECT (NS); the %C was significantly higher with PET than with SPECT during exercise (PET: mean +/- SD = 56 +/- 21%, SPECT: 35 +/- 21%, p less than .01) in spite of smaller double products (x10(3] (PET: 18.9 +/- 4.7, SPECT: 23.5 +/- 5.7, p less than .02). Thus, exercise PET was more reliable in evaluating regional ischemia and in semiquantifying the ischemic area in the myocardium.

Ammonia↗
PubMed1987

[Colored spatial mapping electrocardiography for detecting myocardial infarction].

Colored spatial mapping electrocardiography (ECG) was developed for practical use from Frank lead vectorcardiography using a microcomputer system (CERX-CQ3001). Compared to body surface electrocardiography this new device facilitated easy recording and analysis for display on eight-colored spatial mapping electrocardiography at points equivalent to those on a terrestrial globe at intervals of 20 degrees longitude and 10 degrees latitude. In this study, the extent and direction of the Q waves were easily recognized with the aid of a colored display and mapping electrocardiography. To quantitatively evaluate infarct size, the total Q wave area (sigma Aq) was calculated from the mapping electrocardiograms of 12 patients with anteroseptal myocardial infarction, and compared with thallium defect scores obtained by single photon emission CT (SPECT) and the left ventricular ejection fraction (EF). Defect scores were calculated using short-axis images. Sigma Aq was correlated with defect scores and EF (r = 0.83, 0.45, respectively). This new type of colored spatial mapping electrocardiography proved useful for detecting myocardial infarction and for evaluating infarct size.

Color↗