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R Nohara

Publications and source records attributed to R Nohara.

At least 73 records · Page 4Linked to original sources
PubMed1996

Metabolism and kinetics of iodine-123-BMIPP in canine myocardium.

UNLABELLED: The kinetics and metabolic fate of 123I-15-(p-iodophenyl)-3-(R,S)- methylpentadecanoic acid (BMIPP) in canine myocardium were studied in an open-chest dog model. METHODS: After left anterior descending artery injection of BMIPP, blood samples were collected from the corresponding great coronary vein (V) and femoral artery (A). On the basis of the A-V radioactivity difference as well as the HPLC elution profile at various time points, myocardial extraction, retention and metabolism of BMIPP were evaluated. RESULTS: BMIPP was instantly extracted from the plasma into the myocardium (74% of the injected dose) and was then retained (65.3%). Washout of the retained radioactivity was low (8.7%) and most of the washout was as alpha- and beta-oxidation metabolites (2.3 + 2.9 + 1.4%), with little loss of BMIPP itself (2.1 %). CONCLUSION: BMIPP is suitable for static SPECT imaging of the myocardium, and its slow washout appears to be due to metabolism through alpha- and beta-oxidation.

Animals↗
PubMed1996

Assessment of fatty acid uptake in ischemic heart disease without myocardial infarction.

UNLABELLED: To assess the clinical value of 123I fatty acid analog, 123I-beta-methyl iodophenyl pentadecanoic acid (BMIPP) was imaged at rest in coronary patients without prior myocardial infarction. The BMIPP findings were compared with various clinical parameters. METHODS: Thirty-one patients with ischemic heart disease (19 with unstable angina, 12 with stable angina), without myocardial infarction underwent BMIPP SPECT at rest, coronary arteriography, rest/stress thallium SPECT and left ventriculography exams. RESULTS: Regional decrease of BMIPP was seen in 63% of the myocardial areas at risk, whereas regional perfusion decrease at rest was observed only in 35% (p < 0.01). The BMIPP decrease was more often seen in the unstable group (79%) than stable group (38%) (p < 0.01). Stress-induced ischemia was seen in 77% of segments with decreased BMIPP uptake in unstable group and in 57% in the stable group. Frequency and severity of BMIPP abnormality increased with the severity of stress-induced ischemia (p < 0.005) and the severity of coronary artery stenosis (p < 0.005). In addition, regional BMIPP abnormality was related to severity of wall motion abnormalities (p < 0.005). While 67% of segments with a wall motion abnormality showed BMIPP decrease, 36% with normal wall motion also showed BMIPP decrease (p < 0.01). CONCLUSION: Abnormal fatty acid metabolism was often observed at rest in patients with ischemic heart disease without history of myocardial infarction, and the abnormalities were related to severe myocardial ischemia and regional wall motion abnormalities.

Aged↗
PubMed1995

Effects of nisoldipine in silent myocardial ischemia after healing of acute myocardial infarction.

Silent myocardial ischemia occurring after acute myocardial infarction is classified as Cohn type II and has a frequency of 20-30% in all patients with acute myocardial infarction. Follow-up data of patients with either silent or anginal ischemia show a poor prognosis. Thus, all ischemic episodes occurring after myocardial infarction should be treated aggressively. Many multicenter studies have evaluated whether drug treatment can improve prognosis or protect from a nonfatal second attack. Calcium antagonists, especially those that increase heart rate, have not been considered as drugs of choice for this purpose, despite the many beneficial effects shown on myocardial tissue in experimental studies. In the study reported here, the effect of nisoldipine on postinfarction silent myocardial ischemia was evaluated by ambulatory left ventricular function monitoring. Ten patients were selected for study who showed silent myocardial ischemia after their first acute infarction. Blood pressure fell significantly (p < 0.05) after 4 weeks of treatment with nisoldipine (5-10 mg/day), but heart rate showed no change at rest. Exercise time improved (p < 0.05), with increased peak double products. During exercise, there was no significant change in end-diastolic volume but there was a marked improvement in end-systolic volume, and at the submaximal point the ejection fraction was significantly (p < 0.05) increased. Ejection fraction at rest also improved. The deterioration in ejection fraction due to dipyridamole was ameliorated by nisoldipine. Ejection fraction and blood pressure improved during the calculation test, and work performance also improved.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Prediction of reversible ischemia after revascularization. Perfusion and metabolic studies with positron emission tomography.

BACKGROUND: Accurate noninvasive determination of myocardial viability is of paramount importance for the clinical identification of patients who will benefit most from revascularization. The preserved metabolic activity in the myocardium, as studied with positron emission tomography (PET), has been considered a gold standard for this purpose. However, recent reports show that moderate hypoperfusion or stress-induced ischemia may represent reversible ischemia. The present study was undertaken to compare the value of perfusion and metabolic studies with PET for predicting improvement in wall motion after revascularization. METHODS AND RESULTS: Of 61 patients who had regional asynergy and underwent PET before revascularization, 43 patients who had successful revascularization were included in the study. Each patient underwent rest-stress 13N-ammonia perfusion scans and 18F-fluorodeoxyglucose (FDG) scan at rest while in a fasting state. Reversible ischemia was considered to be present when the resting perfusion was > or = 50% of the peak value, stress-induced hypoperfusion was present, or an increase in FDG uptake was observed. Of 130 asynergy segments, 51 segments had improved wall motion after revascularization. The positive and negative predictive values for improvement in asynergy were 48% and 87% by the rest perfusion study, 63% (P = .05 versus the rest value) and 87% by the rest-stress perfusion study, and 76% (P < .01 versus the rest value) and 92% by the FDG study. CONCLUSIONS: FDG PET provided the best predictive value for improvement in wall motion after revascularization. On the other hand, 13N-ammonia PET is useful for predicting nonreversible myocardial scarring when it shows severe hypoperfusion at rest or hypoperfusion without stress-induced ischemia.

Adult↗
PubMed1995

Assessment of coronary vasodilator reserve by N-13 ammonia PET using the microsphere method and Patlak plot analysis.

UNLABELLED: Noninvasive quantification of regional myocardial blood flow (MBF) has been successfully achieved with N-13 ammonia. The microsphere method as a simple method for quantifying regional myocardial blood flow was reevaluated in comparison with Patlak graphical analysis. In addition coronary vasodilator reserve (CVR) was estimated by both methods. METHODS: Dynamic N-13 ammonia PET studies were performed in 10 healthy volunteers and 10 patients with coronary artery disease at baseline and after dipyridamole infusion (0.56 mg/kg). MBF was estimated by the microsphere method at various times and by Patlak graphical analysis. In order to reduce the noise level in the microsphere method, MBF estimates were also performed after data in 10-40 seconds were averaged. RESULTS: In the studies on normal subjects MBF (ml/min/g) determined by the microsphere method significantly differs from time to time. However, MBF determined by the modified microsphere method [with average (Extraction fraction) x MBF values obtained between 100 and 120 sec] linearly correlated well with MBF by Patlak graphical analysis (r = 0.97, slope = 0.98, intercept = 0.20). In the studies on patients with coronary artery disease a good agreement of the MBF estimates was also observed (r = 0.97, slope = 0.98, intercept = 0.22). In the studies on the normal subjects and patients with coronary artery disease, CVR obtained by the modified microsphere method after correcting the overestimated MBF values also correlated well with that by Patlak graphical analysis (r = 0.90, slope = 1.14, intercept = -0.15, and r = 0.92, slope = 0.82, intercept = 0.25, respectively). CONCLUSION: The modified microsphere method is a very simple and reliable approach for quantifying MBF with N-13 ammonia PET which is comparable to Patlak graphical analysis. It also makes possible CVR assessment as accurate as Patlak graphical analysis.

Adult↗
PubMed1995

Improvement of myocardial ischemic dysfunction with dichloroacetic acid: experimental study by repeated ischemia in dogs.

We investigated metabolic factors related to the recovery of myocardial function during ischemia and after reperfusion using dichloroacetic acid (DCA) in canine models with repeated 10-min regional ischemia and reperfusion. Administration of 100 mg/kg DCA, which activates pyruvate dehydrogenase, improved regional wall motion significantly as compared with the nontreated controls (p < 0.05). The mechanism was studied by determining changes in myocardial levels of pH, glucose, lactate, and nonesterified fatty acids (NEFA). Glucose extraction was increased significantly during ischemia and reperfusion by the pretreatment of DCA (p < 0.01). the calculated contribution of glucose to myocardial oxidative metabolism during ischemia and reperfusion was greater than that of NEFA and lactate in case of DCA treatment. The uptake of [99mTc]pyrophosphate (PYP), which reflects myocardial injury, was also significantly suppressed by DCA (p < 0.01). pH was not affected by an infusion of DCA. These findings suggest that the activation of glucose metabolism by DCA, which is impaired and reduced during ischemia and reperfusion, may be responsible for the improved myocardial function after reperfusion.

Animals↗
PubMed1995

Decreased uptake of iodinated branched fatty acid analog indicates metabolic alterations in ischemic myocardium.

UNLABELLED: We previously reported that uptake of 123I-labeled 15-iodophenyl 3-methyl pentadecanoic acid (BMIPP) was lower than that of thallium in ischemic myocardium. Such discordant findings between BMIPP and thallium were compared with those of PET using 18F-deoxyglucose (FDG) and 11C-acetate to assess metabolic alterations in such segment. METHODS: Sixteen patients with coronary artery disease underwent both BMIPP SPECT and PET. Relative FDG uptake (% FDG uptake) and the clearance rate constant (% Kmono) of 11C-acetate from the myocardium were calculated as markers of glucose and oxidative metabolism, respectively. RESULTS: Relative FDG uptake of the myocardial segments with reduced BMIPP uptake and normal thallium uptake (discordant segments) was similar (85.3 +/- 10.3) to that of the normal segments (86.5 +/- 11.7) but higher than that of segments with reduced uptake of both BMIPP and thallium (67.5 +/- 19.9). Similarly, the discordant segments showed a higher % Kmono value (77.8 +/- 13.1 versus 70.0 +/- 19.1) and FDG-to-perfusion ratio (1.15 +/- 0.08 versus 1.01 +/- 0.22) than in the concordantly reduced segments. CONCLUSION: BMIPP uptake appears to provide metabolic information independent of thallium uptake. Combined imaging of BMIPP and thallium may potentially identify ischemic but viable myocardium.

Acetates↗
PubMed1995

[Myocardial uptake ratio of iodine-123 labeled beta-methyl iodophenylpentadecanoic acid (123I-BMIPP) in relation to the concentration of the substrates of energy].

Iodine-123 beta-methyl iodophenylpentadecanoic acid (BMIPP) has been used for evaluating myocardial fatty acid metabolism in vivo. The whole body BMIPP imaging was acquired in 26 patients (11 with HCM, 11 with CAD and 4 with DCM) to calculate % uptake in the myocardium and to correlate its uptake with biochemical data, including blood sugar (BS), nonesterified fatty acid (NEFA) and insulin in the blood. BMIPP was administered at rest with overnight fasting state, and the anterior and posterior whole body imaging was performed one hour later. The background corrected whole myocardial counts were calculated to obtain %BMIPP uptake. In addition, the heart to mediastinum count ratio (H/M ratio) was calculated from the mean counts in the heart and the upper mediastinum in the anterior view. The %BMIPP uptake was 3.70 +/- 1.22% and H/M ratio was 2.30 +/- 0.23. The patients with DCM showed higher %BMIPP uptake values (DCM = 5.58 +/- 0.67% vs. CAD = 3.09 +/- 0.97% and HCM = 3.63 +/- 0.86%, both p < 0.01), but similar values of H/M ratio with other patients (DCM = 2.43 +/- 0.20, CAD = 2.22 +/- 0.25 and HCM = 2.32 +/- 0.20). Although the biochemical data varied at the time of the tracer administration, they were not significantly correlated with the %BMIPP uptake or H/M ratio. However, there was a significant correlation between %BMIPP uptake and H/M ratio with the correlation coefficient of 0.80 (p < 0.001). We conclude that the myocardial uptake of BMIPP is not influenced by the plasma substrate level under the fasting state.

Blood Glucose↗
PubMed1995

[Quantitative analysis of myocardial tracer distribution in patients with ischemic heart disease: comparison of 201T1 and 123I-15-(p-iodophenyl)-3-methylpentadecanoic acid (BMIPP)].

Quantitative assessment of myocardial tracer uptake in stress-delayed thallium and resting BMIPP imagings were performed in 24 patients with coronary artery disease. Each distribution was displayed on the bull's eye polar map and % uptake of each distribution was calculated as a mean value in 9 myocardial segments on the polar map. Redistribution index (% delayed uptake minus % stress uptake on thallium images) and discordance index (% delayed thallium uptake minus % BMIPP uptake) were also calculated. Each parameter was compared to the visual uptake score and wall motion score on contract left ventriculography. Excellent correlations were obtained between % uptake and the uptake score in each tracer. The % thallium and BMIPP uptake also correlated with regional wall motion score. Furthermore, a significant correlation was observed between redistribution and discordance indexes in the mildly hypoperfused segments. These data indicate that the quantitative analysis of thallium and BMIPP distributions seems to be valuable to understand relationship between perfusion and regional wall motion. The discordant BMIPP uptake may represent asynergic but viable segments. However, several important factors, such as attenuation factor should be also taken into consideration for such quantitative analysis.

Aged↗
PubMed1995

Modification of the circadian variation of symptom onset of acute myocardial infarction in diabetes mellitus.

BACKGROUND: The effects of diabetes mellitus and its treatment on the circadian variation of symptom onset in acute myocardial infarction were examined. METHODS: We obtained the time of symptom onset in 336 patients who had suffered acute myocardial infarction. RESULTS: As in earlier studies, the peak of symptom onset occurred in the late morning, between 6:01 a.m. and 12:00 noon. Although a similar circadian variation was observed in non-diabetic patients, the late-morning peak was less prominent in diabetic patients. In diabetic patients receiving treatment, however, the circadian pattern was well preserved, whereas in untreated diabetic patients there were no peaks in the distribution of symptom onset of acute myocardial infarction. CONCLUSION: These findings suggest that autonomic disturbances in diabetes mellitus may blunt the late-morning peak in the frequency of onset of acute myocardial infarction.

Aged↗
PubMed1994

Glucose metabolism in relation to perfusion in patients with ischaemic heart disease.

In order to correlate myocardial perfusion and residual metabolism in patients with coronary artery disease, the regional metabolic rate of glucose (rMRGlu) was compared with regional perfusion under glucose loading state (GL) and fasting state (FA). Fluorine-18 deoxyglucose dynamic scan was obtained in ten patients after oral GL and in 16 patients under FA. rMRGlu in seven segments was calculated using Patlak graphic analysis for comparison with normalized percent uptake of nitrogen-13 ammonia at rest in each segment. When perfusion was less than 45%, no segment showed an increase in rMRGlu (> or = 0.3 mumol/min/g) under either FA (0/6 segments) or GL (0/8 segments), indicating a certain threshold of perfusion for maintenance of glucose metabolism. When perfusion exceeded 45%, rMRGlu was higher in GL (0.37 +/- 0.18 mumol/min/g) than FA (0.15 +/- 0.12 mumol/min/g, P < 0.001) but there was very wide scatter of rMRGlu values under both states. Thus, both myocardium with preserved and myocardium with reduced glucose metabolism may exist when the perfusion exceeds 45%. In conclusion, a minimum threshold of perfusion for the maintenance of glucose metabolism may exist under both FA and GL. Below the threshold, irreversible damage may occur in the myocardium. Above the threshold, quantitative analysis of glucose metabolism should play an important role in differentiating reversibly injured myocardium from necrotic myocardium.

Ammonia↗
PubMed1994

Combined study with I-123 fatty acid and thallium-201 to assess ischemic myocardium: comparison with thallium redistribution and glucose metabolism.

To assess the clinical value of combined SPECT imaging with I-123-15-(p-iodophenyl)-3-methyl pentadecanoic acid (BMIPP) and thallium-201 (Tl), the findings were compared with those obtained in a stress Tl study and positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG) in 22 patients with myocardial infarction. In 20 patients who underwent a stress Tl study, among 75 hypoperfused segments, 27 segments exhibited less BMIPP uptake than Tl (discordant segments), and the remaining 48 segments showed a similar decrease in BMIPP uptake (concordant segments). Twenty-two of 27 discordant segments (81%) exhibited redistribution on stress Tl study. On the other hand, only one of the 48 concordant segments had redistribution (p < 0.001). In 10 patients who underwent a FDG PET study, among 33 hypoperfused segments, seven segments were discordant segments, and the remaining 25 segments were concordant segments. Seven of the eight discordant segments (88%) demonstrated an increase in FDG uptake. In contrast, only five of 25 concordant segments (20%) showed increase in FDG uptake (p < 0.01). Thus, the segments showing discordant BMIPP uptake are considered to be ischemic but viable myocardium. We conclude that combined imaging with BMIPP and Tl is a useful mean for evaluating tissue viability in patients with coronary artery disease, but it may underestimate the extent of tissue viability, compared with FDG PET imaging.

Adult↗
PubMed1994

Detection of exercise-induced silent ischemia and the sequence of ischemic events in coronary artery disease by radionuclide ambulatory ventricular function monitoring.

Twenty-seven patients with stable coronary artery disease were continuously monitored with an ambulatory radionuclide ventricular function monitor (VEST) during exercise to determine the prevalence of silent ischemia and the temporal sequence of events during ischemic episodes. Exercise-induced ejection fraction abnormality was considered a < 6% increase in the control value lasting for more than 60 sec. Patients performed exercise for 424 +/- 111 sec during VEST recording. Seventeen exercise-induced ejection fraction abnormalities were observed in 17 patients, of which eight (47%) were silent electrocardiographically and 12 (71%) were silent symptomatically. In all of the patients, exercise-induced ischemia occurred in a temporal sequence of ejection fraction abnormalities, ST depressions and then symptoms. In nine patients with ejection fraction and ST abnormalities, ejection fraction abnormalities occurred earlier (199 +/- 87 sec) than ST depressions (321 +/- 117 sec; p < 0.01). In five patients with symptoms (399 +/- 151 sec), the sequence was ejection fraction abnormalities (205 +/- 64 sec; P < 0.05) followed by ST depressions (266 +/- 101 sec; P < 0.05) and symptoms (399 +/- 151 sec; P < 0.01). After termination of exercise, ejection fraction (49 +/- 12 sec) recovered sooner than symptoms (102 +/- 27 sec; p < 0.01) or ST abnormalities (191 +/- 96 sec; p < 0.01). Thus, hemodynamic monitoring by VEST may be helpful in detecting ischemic episodes in coronary artery disease which remain electrocardiographically or symptomatically silent. Furthermore, exercise-stress induces a cascade of temporal changes in ischemic events which may be helpful in understanding the pathophysiology of ischemia.

Aged↗
PubMed1994

Clinical and angiographic determinants of ventricular remodeling after acute myocardial infarction.

BACKGROUND: Ventricular remodeling after acute myocardial infarction is a precursor of the development of overt heart failure and is an important indicator of mortality. However, clinical and angiographic determinants of ventricular remodeling have not been fully elucidated. The purpose of the present study was to evaluate the effects of long-standing preinfarction angina and the late reperfusion of the infarct-related coronary artery on ventricular remodeling and function. METHODS: Coronary angiography and left ventricular cineangiography were performed 35 +/- 16 days after the onset of acute myocardial infarction in 80 patients with a relatively recent anterior Q-wave myocardial infarction who had received conventional therapy. RESULTS: In patients with preinfarction angina that occurred more than 1 week before the onset of myocardial infarction, the left ventricular size and ejection fraction were better preserved than in those without preinfarction angina. On the other hand, the late reperfusion of the infarct-related coronary artery did not affect ventricular remodeling. CONCLUSION: Our results indicate that the presence of residual flow to the infarct area through the collateral circulation, presumably developed by repetitive ischemic stimuli, appears to be a crucial determinant of subsequent left ventricular size and function in patients with acute myocardial infarction who have had conventional therapy.

Adult↗
PubMed1994

[Noninvasive and simple method for the estimation of myocardial metabolic rate of glucose by PET and 18F-FDG].

To estimate regional myocardial metabolic rate of glucose (rMRGlu) with positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG), non invasive simple method has been investigated using dynamic PET imaging in 14 patients with ischemic heart disease. This imaging approach uses a blood time-activity curve (TAC) derived from a region of interest (ROI) drawn over dynamic PET images of the left ventricle (LV), left atrium (LA) and aorta. Patlak graphic analysis was used to estimate k1k3/(k2+k3) from serial plasma and myocardial radioactivities. FDG counts ratio between whole blood and plasma was relatively constant (0.91 +/- 0.02) both throughout the time and among different patients. Although TACs derived from dynamic PET images gradually increased at later phase due to spill over from the myocardium into the cavity, there were good agreements between the estimated K complex values obtained from arterial blood sampling and dynamic PET imaging (LV r = 0.95, LA r = 0.96, aorta r = 0.98). These results demonstrate the practical usefulness of a simplified and noninvasive method for the estimation of rMRGlu in humans by PET.

Aged↗