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Biomedical subjects

R C Brunken

Publications and source records attributed to R C Brunken.

At least 37 records · Page 2Linked to original sources
PubMed1992

Positron emission tomography detects metabolic viability in myocardium with persistent 24-hour single-photon emission computed tomography 201Tl defects.

BACKGROUND: Four-hour 201Tl redistribution images underestimate myocardial viability in patients with coronary artery disease (CAD). Because 4-hour defects often redistribute late, delayed imaging may enhance assessment of tissue viability. Myocardial metabolic activity was therefore assessed with positron emission tomography (PET) in 26 CAD patients with impaired ventricular function (ejection fraction, 32.1 +/- 13.9%) and 24-hour single-photon emission computed tomography (SPECT) 201Tl defects. METHODS AND RESULTS: On circumferential profile analysis, PET ischemia was defined by preserved glucose metabolism in hypoperfused myocardium, and PET infarction was defined by concordant reductions in perfusion and metabolism. On 19 stress-redistribution and seven rest-redistribution SPECT studies, four observers visually scored 201Tl activity in eight segments on a scale from 0 (normal) to 3 (complete defect). Using an improvement in visual score > or = 0.75 to define redistribution, there were 100 fixed, 17 partially reversible, and 12 completely reversible defects. PET identified tissue metabolic activity in 51 (51%) segments with fixed defects (21 PET ischemia, 30 PET normal) and nine (53%) segments with partially reversible defects (five PET ischemia, four PET normal). When grouped by 24-hour score, the proportion of fixed defects with metabolic activity varied from 84% (scores < or = 1.4) to 15% (scores > 2.6). For partially reversible defects, only 53% with scores < 2.0 and one of two with scores > or = 2.0 were considered metabolically viable on PET. Of 12 completely reversible defects, six (50%) were normal, five (42%) had PET ischemia, and one (8%) had PET infarction. The proportion of fixed defects with metabolic activity did not depend on whether a rest or stress study was performed or on the change in visual score used to define 201Tl redistribution (0.25, 0.50, 0.75, and 1.00). CONCLUSIONS: In CAD patients, PET identifies glucose metabolic activity in the majority of fixed 24-hour 201Tl defects. However, very severe (near-complete) 24-hour 201Tl defects are less likely to exhibit metabolic activity on PET imaging than are defects with less-pronounced reductions in segmental 201Tl activity.

Coronary Angiography↗
PubMed1992

Semiquantitative assessment of myocardial blood flow and viability using polar map displays of cardiac PET images.

Preserved glucose metabolism in ischemically injured, dysfunctional myocardial tissue as demonstrated on PET imaging predicts functional improvement after revascularization. To characterize more precisely the relationship between regional myocardial blood flow, viability and extent and severity of flow and metabolism abnormalities, we developed a PC-based semiquantitative analysis technique using 13N-ammonia and 18F-deoxyglucose polar map displays. A data base for mean values (m) and standard deviations (s.d.) for relative 13N activities reflecting regional myocardial blood flow, relative 18F activities normalized to normal flow regions reflecting regional glucose utilization and the difference of normalized 18F and 13N activities as an index of a flow-metabolism mismatch was established in 11 normals. Parametric polar maps were derived by comparing patient data to a normal range defined as greater than m - 2 s.d. for relative myocardial blood flow and less than m + 2 s.d. for both relative glucose utilization and the difference between normalized 18F and 13N activities. Semiquantitative indices of extent and severity of blood flow defects, of relative increases in glucose utilization and of flow-metabolism mismatch areas are generated for the entire myocardium and the three coronary territories. The approach promises to be clinically useful to confirm presence and absence of flow and metabolic abnormalities and to assess their extent as a potential predictor of functional outcome after therapy.

Adult↗
PubMed1991

Metabolic and functional recovery of ischemic human myocardium after coronary angioplasty.

Although revascularization of hypoperfused but metabolically active human myocardium improves segmental function, the temporal relations among restoration of blood flow, normalization of tissue metabolism and recovery of segmental function have not been determined. To examine the effects of coronary angioplasty on 13 asynergic vascular territories in 12 patients, positron emission tomography and two-dimensional echocardiography were performed before and within 72 h of revascularization. Ten patients underwent late echocardiography (67 +/- 19 days) and eight underwent a late positron emission tomographic study (68 +/- 19 days). The extent and severity of abnormalities of wall motion, perfusion and glucose metabolism were expressed as wall motion scores, perfusion defect scores and perfusion-metabolism mismatch scores. Angioplasty significantly increased mean stenosis cross-sectional area (from 0.95 +/- 0.9 to 2.7 +/- 1.4 mm2) and mean cross-sectional luminal diameter (from 0.9 +/- 0.6 to 1.9 +/- 0.5 mm) (both p less than 0.001). Perfusion defect scores in dependent vascular territories improved early after angioplasty (from 116 +/- 166 to 31 +/- 51, p less than 0.002) with no further improvement on the late follow-up study. The mean perfusion-metabolism mismatch score decreased from 159 +/- 175 to 65 +/- 117 early after angioplasty (p less than 0.01) and to 26 +/- 29 at late follow-up (p less than 0.001 vs. before angioplasty; p = NS vs. early after angioplasty). However, absolute rates of glucose utilization remained elevated early after revascularization, normalizing only at late follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1991

Differentiating cardiomyopathy of coronary artery disease from nonischemic dilated cardiomyopathy utilizing positron emission tomography.

To determine if imaging of blood flow (using N-13 ammonia) and glucose metabolism (using F-18 2-deoxyglucose) with positron emission tomography can distinguish cardiomyopathy of coronary artery disease from nonischemic dilated cardiomyopathy, 21 patients with severe left ventricular dysfunction who were evaluated for cardiac transplantation were studied. The origin of left ventricular dysfunction had been previously determined by coronary angiography to be ischemic (11 patients) or nonischemic (10 patients). Images were visually analyzed by three observers on a graded scale in seven left ventricular segments and revealed fewer defects in dilated cardiomyopathy compared with ischemic cardiomyopathy for N-13 ammonia (2.7 +/- 1.6 versus 5 +/- 0.6; p less than 0.03) and F-18 deoxyglucose (2.8 +/- 2.1 versus 4.6 +/- 1.1; p less than 0.03). An index incorporating extent and severity of defects revealed more homogeneity with fewer and less severe defects in subjects with nonischemic than in those with ischemic cardiomyopathy as assessed by imaging of flow (2.8 +/- 1.8 versus 9.2 +/- 3; p less than 0.001) and metabolism (3.8 +/- 3.3 versus 8.5 +/- 3.6; p less than 0.005). Diagnostic accuracy for distinguishing the two subgroups by visual image analysis was 85%. Using previously published circumferential count profile criteria, patients with dilated cardiomyopathy had fewer ischemic segments (0.4 +/- 0.8 versus 2.5 +/- 2 per patient; p less than 0.01) and infarcted segments (0.1 +/- 0.3 versus 2.4 +/- 1.4 per patient; p less than 0.001) than did patients with cardiomyopathy of coronary artery disease. The sensitivity for differentiating the two clinical subgroups using circumferential profile analysis was 100% and the specificity 80%. An index incorporating both number and severity of defects derived from circumferential profile analysis was significantly lower in subjects with dilated cardiomyopathy than in ischemic cardiomyopathy (0.3 +/- 0.8 versus 2.7 +/- 2.4; p less than 0.005). Thus, noninvasive positron emission tomographic imaging with N-13 ammonia and F-18 deoxyglucose is helpful in distinguishing patients with severe left ventricular dysfunction secondary to coronary artery disease from those with nonischemic cardiomyopathy, and a semiquantitative index such as circumferential profile analysis is superior to that of visual analysis alone.

Adult↗
PubMed1991

Noninvasive quantification of hepatic arterial blood flow with nitrogen-13-ammonia and dynamic positron emission tomography.

To determine if dynamic PET and 13N-ammonia can be utilized to quantitate regional hepatic arterial blood flow (rHABF) noninvasively, eight anesthetized dogs and eight human volunteers were examined with PET following intravenous bolus administration of 13N-ammonia. Hepatic time-activity curves and the arterial input function were derived from ROIs drawn over the right lateral superior segment of the liver and the left ventricle of the heart, respectively. rHABF was quantitated using a two-compartment model, with comparison with simultaneously acquired microsphere blood flow measurement (MS) in the canine studies. rHABF derived from canine dynamic PET with 13N-ammonia were linearly related to microsphere values (rHABF = 0.92 x MS + 0.04, r = 0.98), with a mean of 0.40 ml/min/g. The results in eight normal volunteers gave a rHABF value of 0.26 +/- 0.07 ml/min/g. Dynamic 13N-ammonia hepatic PET allows noninvasive quantification of rHABF.

Adult↗
PubMed1991

Ischemic cardiomyopathy. Criteria for coronary revascularization and cardiac transplantation.

Because of the shortage of donor hearts, 16 (33%) of 48 patients with ischemic cardiomyopathy died awaiting transplantation. Determining factors that predict effective coronary revascularization and identifying patients who may benefit from revascularization is crucial. From 1984 to 1990, 207 ischemic cardiomyopathy patients were evaluated for heart transplantation; 131 were accepted (83 transplanted), 54 were not accepted, and 22 were revascularized (19 underwent bypass graft surgery and three underwent percutaneous transluminal coronary angioplasty). Four bypass patients failed early (less than or equal to 30 days, three deaths and one urgent heart transplant) and two late deaths (greater than or equal to 1 year) occurred. Overall mortality was 27%. Three-year survival of revascularized and transplanted patients was 72 +/- 10% and 73 +/- 6%, respectively. Successfully revascularized patients had preoperative ejection fraction, left ventricular end-diastolic dimension, and New York Heart Association functional class of 26 +/- 9%, 68 +/- 3 mm, and 3.9 +/- 0.4, respectively, compared with 36 +/- 9% (p less than 0.05), 64 +/- 6 mm (p = NS), and 1.2 +/- 0.4 (p less than 0.05) after revascularization. Preoperative ejection fraction of patients failing revascularization was 15 +/- 4% (p = NS compared with successful revascularization), and left ventricular end-diastolic dimension was 81 +/- 4 mm (p less than 0.05). Preoperative positron emission tomography imaging myocardial blood flow and glucose metabolism was performed in 12 patients: 10 patients with scans predicting reversible ischemia were successfully revascularized, and two patients with negative scans had failed revascularization.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1991

Use of the metabolic tracer carbon-11-acetate for evaluation of regional myocardial perfusion.

The high first-pass myocardial extraction fraction of carbon-11-acetate suggests that its initial uptake depends on blood flow. Accordingly, regional uptake of 11C-acetate at 4 min was compared to regional perfusion determined with nitrogen-13-ammonia in 119 segments in 15 patients with stable coronary artery disease by two methods. A close correlation was observed between initial relative myocardial concentrations (segmental activity normalized to maximal activity) of both tracers (11C-acetate = 0.88; 13N-ammonia + 0.079; s.e.e. = 0.064, r = 0.94, p less than 0.001). Furthermore, segmental net extractions (E.F), as calculated from the input function and segmental activities, of the two tracers correlated closely by E.FC-11 = 0.55E.FN-13 + 0.080 (s.e.e. = 0.045, r = 0.87, p less than 0.001). These relationships indicate that initial regional myocardial uptake of 11C-acetate reflects perfusion and that 11C-acetate permits near simultaneous evaluation of regional oxidative metabolism and of regional myocardial perfusion.

Acetates↗
PubMed1991

Parametric images of myocardial metabolic rate of glucose generated from dynamic cardiac PET and 2-[18F]fluoro-2-deoxy-d-glucose studies.

We describe a method for generating parametric images of the myocardial metabolic rate of glucose (MMRGlc) with positron emission tomography (PET). The method employs serially acquired images of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake and a Patlak graphical analysis of the image data. The arterial input function is derived from images of the left ventricular blood pool calibrated with 18F-plasma measurements. The approach is computationally fast enough to be used in a clinical environment. The MMRGlc parametric images improve myocardial contrast relative to non-parametric images, especially in studies with poor myocardial uptake of FDG. In addition, MMRGlc parametric images consolidate the large amount of data in a dynamic PET study into a clinically usable image set.

Adult↗
PubMed1990

Afterload reduction with vasodilators and diuretics decreases mitral regurgitation during upright exercise in advanced heart failure.

In advanced heart failure, mitral regurgitation increases the burden of the failing ventricle and decreases effective stroke volume. Although tailored afterload reduction decreases mitral regurgitation at rest, it is not known if this benefit is maintained during upright exercise. Simultaneous radionuclide ventriculography and thermodilution stroke volumes were compared to measure the forward ejection fraction in 10 patients during upright bicycle exercise before and after therapy with vasodilators and diuretics tailored to decrease pulmonary capillary wedge pressure and systemic vascular resistance. Ventricular volumes, total ejection fraction and the forward ejection fraction did not change during exercise at baseline. At rest, tailored therapy decreased average pulmonary capillary wedge pressure from 36 to 19 mm Hg (p less than 0.01), systemic vascular resistance from 1,570 to 1,210 dynes.s.cm-5 (p less than 0.05), and left ventricular volume index from 251 to 177 ml/m2 (p less than 0.01), while increasing the forward ejection fraction from 0.53 to 0.85 (p less than 0.01) without change in total ejection fraction (0.18 from 0.17). During steady state exercise at low work load, tailored therapy decreased left ventricular volume index from 279 to 213 (p less than 0.05) and increased forward ejection fraction from 0.52 to 0.79 (p less than 0.01) without change in total ejection fraction (0.20 from 0.19). The total stroke volume during exercise was not increased after therapy; the increase in forward stroke volume after therapy appeared to result instead from the decrease in mitral regurgitant flow. The benefits of tailored afterload reduction are maintained throughout upright exercise.

Bumetanide↗
PubMed1990

Cardiac positron emission tomography: the foundations and clinical applications.

Cardiac PET studies may have a role in the early detection of coronary artery disease. The early prediction of the ultimate fate of reperfused myocardium with cardiac PET imaging remains elusive. At present the predominant clinical use of PET scans lies in the identification of ischemic but viable tissue. Cardiac PET imaging with a combination of perfusion and metabolic tracers can distinguish those patients with a history of previous infarctions and severe heart failure who will benefit from therapeutic revascularization. Conversely, the group that is not expected to improve will be spared needless and risky attempts at revascularization and will become candidates for cardiac transplantation at an earlier stage.

Coronary Disease↗
PubMed1989

PET detection of viable tissue in myocardial segments with persistent defects at T1-201 SPECT.

To assess myocardial glucose metabolism and perfusion in 142 myocardial segments with defects seen at thallium-201 single photon emission computed tomography (SPECT), 27 studies with positron emission tomography (PET) utilizing nitrogen-13 ammonia and fluorine-18 deoxyglucose were performed in 26 patients. Myocardial infarction was defined on the basis of concordant reductions in segmental perfusion and glucose utilization; myocardial ischemia, on the basis of preservation of glucose utilization (metabolic viability) in segments with hypoperfusion at rest. Of the 142 segments analyzed, 101 had fixed defects, 31 had partially reversible defects, and ten had completely reversible defects. Preserved glucose utilization was identified in 47 (46.5%) of the segments with fixed defects and 20 (64.5%) of the segments with partially reversible defects. Of the ten segments with completely reversible defects, five (50%) were normal, and five (50%) exhibited ischemia at PET. Visual improvement in a persistent thallium defect at delayed imaging was not associated with residual glucose metabolic activity. Thus, PET can be used to detect glucose metabolic activity in a significant proportion of myocardial segments with fixed or partially redistributing defects seen at thallium SPECT, which suggests that the extent of tissue viability in patients with ischemic heart disease is underestimated at thallium scintigraphy.

Aged↗
PubMed1989

Regional myocardial oxygen consumption determined noninvasively in humans with [1-11C]acetate and dynamic positron tomography.

Experimental studies of animals have previously demonstrated the validity of [1-11C]acetate as a tracer of oxidative metabolism for use with positron emission tomography. The present study was undertaken to define in normal human volunteers the relation between myocardial clearance kinetics of [1-11C]acetate, and the rate-pressure product as an index of myocardial oxygen consumption. Twenty-two studies were performed of 12 volunteers. The rate-pressure product was increased with continuous supine bicycle exercise in six studies. Of the 16 resting studies, seven were performed in the fasted state and nine following an oral glucose load, to define possible effects of substrate availability on the tracer-tissue kinetics. Myocardial tissue time-activity curves were biexponential. Clearance of activity was homogeneous throughout the myocardium. The rate constants k1, obtained from biexponential fitting, and kmono, obtained by monoexponential fitting of the initial linear portion of the time-activity curves, correlated well with the rate-pressure product. Although the correlation coefficient was higher for k1 than for kmono (0.95 vs. 0.91), analysis on a sectorial basis showed less regional variability in kmono. This suggests that kmono, which is more practical than k1 because it requires shorter acquisition times, may be more clinically and experimentally useful for detection of myocardial segments with abnormal oxygen consumption. Overall, changes in myocardial substrate supply were without significant effect on the relation between the rate constants (k1 and kmono) and the rate-pressure product, although a small decrease in kmono/rate-pressure product was observed following oral glucose by paired analysis in four subjects. It is concluded that [1-11C]acetate can be used for the noninvasive measurement of myocardial oxygen consumption in humans with positron emission tomography, and, thus, has clinical and experimental potential as a tool for the understanding and diagnosis of myocardial disease.

Acetates↗
PubMed1989

Positron emission tomography in clinical cardiology.

Positron emission tomography of the heart is a physiologic imaging technique that enables both qualitative and quantitative assessment of regional myocardial blood flow and substrate utilization. Exercise or dipyridamole perfusion imaging with PET is both sensitive and specific for detecting coronary disease and may prove clinically useful in assessing the physiologic significance of anatomically defined stenoses and for noninvasively following stenosis progression or regression. PET can be used to localize and quantitate the extent of antecedent myocardial infarction, and frequently identifies viable tissue when routinely utilized clinical tests indicate completed infarction. The tissue characterization afforded by metabolic imaging with PET in coronary heart disease allows non-invasive identification of viable but jeopardized tissue in a variety of clinical ischemic syndromes, thereby permitting the cardiologist to intervene in anticipation of myocardial salvage. As future developments in PET imaging occur, our understanding of the basic biochemical abnormalities characterizing myocardial ischemia will be utilized with increasing frequency to improve the clinical care provided to patients with coronary heart disease.

Cardiomyopathies↗
PubMed1988

Assessment of mitral flow velocity with exercise by an index of stress-induced left ventricular ischemia in coronary artery disease.

Exercise-induced myocardial ischemia results in both diastolic and systolic left ventricular (LV) dysfunction. To investigate the utility of Doppler assessment of LV diastolic function with exercise, 28 consecutive patients underwent digital stress echocardiography, including measurement of mitral flow velocity by pulsed-wave Doppler and simultaneous stress thallium imaging. The mean mitral flow velocity was measured as the integrated area under the LV diastolic inflow Doppler spectral display. The change in mean mitral flow velocity from baseline to immediate postexercise was compared among 3 patient groups: (1) patients with thallium redistribution or exercise-induced wall-motion abnormalities, or both, consistent with exercise-induced ischemia (n = 18), (2) patients with no evidence of stress-induced ischemia, with or without resting wall-motion abnormalities (n = 10), and (3) 10 control subjects of similar age with normal resting 12-lead electrocardiograms, normal resting and postexercise 2-dimensional echocardiograms and normal electrocardiographic treadmill stress testing. The percent increase in mean mitral flow velocity was 101% (+/- 59) for controls and 86% (+/- 53) for patients without stress-induced ischemia versus 33% (+/- 24) in patients with stress-induced ischemia (p less than 0.005). An increase in mean mitral flow velocity with exercise of greater than 50% correctly identified 9 of 10 nonischemic control patients. An increase in mean velocity of less than 50% predicted ischemia in 15 of 18 patients with evidence of stress-induced ischemia (p less than 0.005) Thus, Doppler assessment of LV diastolic function with exercise expressed as a change in the mean velocity of mitral flow is a useful indicator of stress-induced ischemia.

Blood Flow Velocity↗
PubMed1987

Effects of afterload reduction (diuretics and vasodilators) on left ventricular volume and mitral regurgitation in severe congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

The mechanism by which afterload reduction increases left ventricular stroke volume while decreasing left ventricular filling pressure has not previously been established. In 15 patients with severe congestive heart failure due to ischemic or idiopathic dilated cardiomyopathy, absolute ventricular volume, ejection fraction and total stroke volume from radionuclide ventriculography were compared with thermodilution stroke volume before and after intensive afterload reduction with vasodilators and diuretics titrated to hemodynamic goals. After 48 to 72 hours, pulmonary artery wedge pressure decreased from 32 +/- 8 to 16 +/- 4 mm Hg and systemic vascular resistance from 1,960 +/- 700 to 1,200 +/- 400 dynes s cm-5. End-diastolic volume decreased from 390 +/- 138 to 301 +/- 126 ml (p less than 0.01) and end-systolic volume from 316 +/- 127 to 241 +/- 111 (p less than 0.01). Ejection fraction did not change and total stroke volume decreased from 74 +/- 22 to 59 +/- 20 ml (p less than 0.01). Simultaneous forward stroke volume by thermodilution increased from 37 +/- 14 to 52 +/- 14 ml (p less than 0.01), and forward fraction increased from 0.55 +/- 0.40 to 0.96 +/- 0.42. Intensive reduction of ventricular filling pressure and systemic vascular resistance decreased total ventricular stroke volume by 20% but increased forward stroke volume by 40%. The major effect of intensive afterload reduction for severe congestive heart failure may be the reduction of ventricular volume and mitral regurgitation.

Blood Pressure↗
PubMed1987

Beneficial effect of residual anterograde flow on tissue viability as assessed by positron emission tomography in patients with myocardial infarction.

With the advent of therapeutic interventions to restore blood flow in patients with acute infarction, early identification of salvageable myocardium has gained clinical importance. It was the purpose of this study to define regional blood flow and glucose metabolism in patients with acute myocardial infarction as assessed by positron emission tomography (PET) and to correlate these findings with coronary anatomy. In 15 patients blood flow as determined by N-13 ammonia was reduced in 37 left ventricular segments. In 20 segments there was a similar decrease in FDG uptake, consistent with tissue necrosis. In contrast, 17 segments with reduced blood flow revealed maintained FDG uptake suggesting residual viability in the electrocardiographically defined 'infarct segment'. PET viability and necrosis was significantly associated with presence or absence of anterograde flow in the infarct artery. Evaluation of regional wall motion did not distinguish segments with PET criteria for viability from segments with necrosis. Thus, in patients without thrombolytic therapy during evolving myocardial infarction, spontaneous reperfusion appears to be beneficial for tissue survival. PET offers the unique possibility to assess tissue viability early after the ischaemic injury where evaluation of wall motion fails to identify salvageable myocardium.

Adult↗
PubMed1983

Immunologic abnormalities in botryomycosis. A case report with review of the literature.

Botryomycosis in an uncommon chronic bacterial infection that mimics fungal disease clinically and histologically. Microscopically the hallmark of the disease is the presence of fungus-like granules in which the causative organism is embedded. A patient with typical cutaneous botryomycosis is presented, along with the immunologic abnormalities discovered on laboratory examination. The botryomycosis literature is reviewed, with special emphasis on the immunologic status of the host. Additional studies of the causative organism and cell-mediated immunity in the host in future patients with botryomycosis may help to further elucidate the pathogenesis of this most interesting disease.

Escherichia coli Infections↗