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Biomedical subjects

J Krivokapich

Publications and source records attributed to J Krivokapich.

At least 19 recordsLinked to original sources
PubMed1992

Comparison of maximal myocardial blood flow during adenosine infusion with that of intravenous dipyridamole in normal men.

OBJECTIVE: This study compared quantitatively the efficacy of intravenous adenosine and dipyridamole for pharmacologic induction of myocardial hyperemia. BACKGROUND: Pharmacologic vasodilation is used increasingly for induction of myocardial hyperemia in conjunction with radionuclide imaging of myocardial blood flow. Although both intravenous dipyridamole and adenosine have been used, the magnitude of hyperemia induced by these agents and the hyperemia to baseline blood flow ratios have not been quantified and compared. METHODS: Twenty normal volunteers were studied with dynamic positron emission tomography (PET) and intravenous nitrogen-13 ammonia. Myocardial blood flow was quantified with a two-compartment tracer kinetic model. RESULTS: Myocardial blood flow at rest averaged 1.1 +/- 0.2 ml/min per g and increased significantly to 4.4 +/- 0.9 ml/min per g during adenosine and 4.3 +/- 1.3 ml/min per g after dipyridamole administration. Hyperemia to baseline flow ratios averaged 4.3 +/- 1.6 for adenosine and 4.0 +/- 1.3 for dipyridamole. The average flow ratios and the maximal flows achieved were similar for both agents, but there was considerable variation in the individual response to these agents, as indicated by the range of hyperemia to baseline flow ratios (from 2.0 to 8.4 for adenosine and from 1.5 to 5.8 for dipyridamole). In addition, the hyperemic responses to dipyridamole and to adenosine differed by greater than 1 ml/min per g in nine subjects. CONCLUSIONS: Despite these inter- and intraindividual differences, we conclude that both agents are equally effective in producing myocardial hyperemia.

Adenosine↗
PubMed1992

Quantitative assessment of prolonged metabolic abnormalities in reperfused canine myocardium.

BACKGROUND: Prolonged metabolic abnormalities have been demonstrated previously in postischemic myocardium, including relative increases in glucose uptake and abnormal fatty acid kinetics. However, quantitative metabolic information is limited, and the time course of changes in MVO2 in postischemic myocardium is unknown. To address these issues, chronically instrumented dogs were studied serially over 1 month after transient left anterior descending coronary artery (LAD) occlusion, using positron emission tomography. METHODS AND RESULTS: Dynamic imaging protocols were used in conjunction with tracer kinetic models to quantify blood flow and metabolic rates. Myocardial sectors were defined as normal, predominantly reversibly injured, and infarct-containing, based on occlusion blood flow images and postmortem histochemistry. Myocardial blood flow and metabolism were homogeneous at baseline. During LAD occlusion for 3 hours, myocardial blood flow in reversibly injured and infarct-containing sectors (determined with 13NH3) was decreased to 46% and 23%, respectively, of blood flow in normal tissue. MVO2, determined with [1-11C]acetate, was decreased less than myocardial blood flow, consistent with increased oxygen extraction in the ischemic tissue. After reperfusion, blood flow normalized rapidly in reversibly injured tissue but remained depressed in infarct-containing sectors. Regional myocardial function, assessed by two-dimensional echocardiography, was severely depressed during occlusion and did not improve significantly until 1 week after reperfusion. MVO2 remained depressed after reperfusion in both reversibly injured and infarct-containing sectors, did not improve from occlusion levels until 1 week after reperfusion, and remained significantly depressed 1 month after reperfusion even in reversibly injured sectors; [1-11C]palmitate kinetics were also abnormal in postischemic tissue. As reported previously, glucose metabolic rates were increased relative to baseline in normal but not in postischemic tissue 3 hours after reperfusion. Subsequently, glucose metabolism tended to be higher in postischemic relative to normal myocardium. CONCLUSIONS: The results demonstrate decreased oxidative metabolism in postischemic tissue, with concomitant abnormalities in palmitate kinetics and glucose metabolism. Oxidative metabolism and regional function demonstrated a parallel recovery with time.

Acetates↗
PubMed1991

Noninvasive detection of functionally significant coronary artery stenoses with exercise and positron emission tomography.

Positron emission tomography has been employed in vivo to assess flow using N-13 (nitrogen-13) ammonia and glucose metabolism, with the glucose analog F-18 (fluorine-18) fluorodeoxyglucose. Flow metabolism mismatches in which glucose metabolism is increased with respect to flow have been used to define ischemic, but viable myocardium. The feasibility of detecting exercise-induced ischemia using this technique was explored. Eleven normal volunteers and 16 patients who had undergone coronary arteriography were studied with N-13 ammonia at rest and with bicycle exercise, and with F-18 fluorodeoxyglucose in the postexercise period. Each image was divided into 16 sectors. Comparison of absolute net extractions of N-13 ammonia at rest and with exercise was not sensitive in detecting functionally significant coronary artery lesions. Myocardial uptakes of F-18 fluorodeoxyglucose and exercise N-13 ammonia were normalized to the sector with the highest N-13 ammonia uptake (corresponding to the highest flow rate). The differences and ratios of these normalized uptakes were successfully used to objectively define flow metabolism mismatches and to identify functionally significant coronary artery disease. Our data suggest that exercise flow and metabolic imaging are superior to rest and exercise flow imaging, particularly in patients with prior myocardial infarctions.

Ammonia↗
PubMed1991

Quantification of absolute myocardial perfusion at rest and during exercise with positron emission tomography after human cardiac transplantation.

The maximal exercise capacity of cardiac transplant recipients is reduced compared with that of normal subjects. To determine if this reduced exercise capacity is related to inadequate myocardial perfusion during exercise, myocardial perfusion was measured noninvasively with use of positron emission tomography and nitrogen (N)-13 ammonia. Twelve transplant recipients with no angiographic evidence of accelerated coronary atherosclerosis were studied. Serial N-13 ammonia imaging was performed at rest and during supine bicycle exercise. The results were compared with those from 10 normal volunteers with a low probability of having cardiac disease. A two-compartment kinetic model for estimating myocardial perfusion was applied to the data. Transplant recipients achieved a significant lower exercise work load than did the volunteers (42 +/- 16 vs. 128 +/- 22 W), but a higher venous lactate concentration (31.3 +/- 14.9 vs. 13.7 +/- 4.1 mg/100 ml). Despite the difference in exercise work load, there was no significant difference in the cardiac work achieved by transplant recipients and normal subjects as evidenced by similar rate-pressure products of 24,000 +/- 3,400 versus 21,300 +/- 2,800 betas/min per mm Hg, respectively. In addition, myocardial blood flow during exercise was not significantly different between the two groups (1.70 +/- 0.60 vs. 1.56 +/- 0.71 ml/min per g, respectively). This study demonstrates that the myocardial flow response to the physiologic stress of exercise is appropriate in transplant recipients and does not appear to explain the decreased exercise capacity in these patients.

Ammonia↗
PubMed1991

A quantitative index of regional blood flow in canine myocardium derived noninvasively with N-13 ammonia and dynamic positron emission tomography.

To derive a quantitative index of regional myocardial blood flow, the arterial input function of the flow tracer N-13 ammonia and the regional myocardial N-13 activity concentrations were noninvasively determined in 29 experiments in eight dogs. N-13 ammonia was administered intravenously and cross-sectional images were acquired dynamically using an ECAT III positron emission tomograph with an effective in-plane resolution of 13.46 mm full-width half-maximum. Time-activity curves were derived from the serial images by assigning regions of interest to the left ventricular myocardium and left ventricular blood pool. Tracer net extractions were estimated from the myocardial time-activity concentrations at various times after tracer injection and the integral of the arterial input function. Myocardial blood flow was altered by intravenous dipyridamole, morphine, propranolol and partial or complete occlusion of the left anterior descending coronary artery, and ranged from 9 to 860 ml/min per 100 g. Estimates of tracer net extractions were most accurate when determined from the myocardial N-13 activity concentrations at 60 s divided by the integral of the arterial input function to that time. These estimates correlated with regional myocardial blood flows determined independently by the microsphere technique by y = x (1 - 0.64(e-114/x); SEE = 22.9; r = 0.94). First pass extraction fractions of N-13 ammonia determined noninvasively with this approach declined with higher flows in a nonlinear fashion and were similar to those determined invasively by direct intracoronary N-13 ammonia injections. The findings indicate that an accurate index of regional myocardial blood flow can be obtained noninvasively by high temporal sampling of arterial and myocardial tracer activity concentrations with positron emission tomography. They also provide a basis for the in vivo application of tracer kinetic principles to derive quantitatively and noninvasively regional rates of functional processes in human myocardium.

Ammonia↗
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

Correlation of myocardial necrosis with kinetics of 111In-labeled myosin-specific antibody in isolated rabbit septum.

Radiolabeled monoclonal antibody fragments to myosin, specifically 111In-labeled antimyosin, have been shown to be effective for imaging areas of myocardial infarct. To determine if 111In-labeled antimyosin can be used to assess the extent of necrosis, we compared the tissue retention fraction of 111In-labeled antimyosin with the amount of creatine kinase (CK) released from the isolated, perfused, interventricular rabbit septum after an intervention to induce tissue necrosis. 111In-labeled antimyosin was injected and tissue radioactivity was monitored for a 60-min period under control conditions. Effluent samples were also collected during this period and assayed for CK content. After a period of Ca2+ depletion followed by Ca2+ repletion, 111In-labeled antimyosin was again injected, and washout and CK data were collected. Comparison of the changes in 111In-labeled antimyosin retention fraction from control to intervention with the corresponding increase in CK released during intervention resulted in a correlation coefficient of 0.83. To corroborate the findings of the Ca2+ depletion followed by repletion experiments, further experiments were conducted in which zero-flow ischemia followed by reperfusion was used as a means of introducing necrosis in the septum. The resulting correlation coefficient between CK release and 111In-labeled antimyosin retention fraction was 0.82. The results of these experiments indicate that 111In-labeled antimyosin can be used to quantitatively estimate the extent of necrosis in the rabbit septum, as determined by CK release, and endorse the potential use of tracer kinetics in humans for quantitation of myocardial necrosis in vivo.

Animals↗
PubMed1990

Noninvasive quantification of regional blood flow in the human heart using N-13 ammonia and dynamic positron emission tomographic imaging.

Evaluation of regional myocardial blood flow by conventional scintigraphic techniques is limited to the qualitative assessment of regional tracer distribution. Dynamic imaging with positron emission tomography allows the quantitative delineation of myocardial tracer kinetics and, hence, the measurement of physiologic processes such as myocardial blood flow. To test this hypothesis, positron emission tomographic imaging in combination with N-13 ammonia was performed at rest and after pharmacologically induced vasodilation in seven healthy volunteers. Myocardial and blood time-activity curves derived from regions of interest over the heart and ventricular chamber were fitted using a three compartment model for N-13 ammonia, yielding rate constants for tracer uptake and retention. Myocardial blood flow (K1) averaged 88 +/- 17 ml/min per 100 g at rest and increased to 417 +/- 112 ml/min per 100 g after dipyridamole infusion (0.56 mg/kg) and handgrip exercise. The coronary reserve averaged 4.8 +/- 1.3 and was not significantly different in the septal, anterior and lateral walls of the left ventricle. Blood flow values showed only a minor dependence on the correction for blood metabolites of N-13 ammonia. These data demonstrate that quantification of regional myocardial blood flow is feasible by dynamic positron emission tomographic imaging. The observed coronary flow reserve after dipyridamole is in close agreement with the results obtained by invasive techniques, indicating accurate flow estimates over a wide range. Thus, positron emission tomography may provide accurate and noninvasive definition of the functional significance of coronary artery disease and may allow the improved selection of patients for revascularization.

Adult↗
PubMed1990

Dynamic positron tomographic imaging with nitrogen-13 glutamate in patients with coronary artery disease: comparison with nitrogen-13 ammonia and fluorine-18 fluorodeoxyglucose imaging.

This study was designed to test the usefulness of nitrogen-13 (N-13) glutamate imaging with positron emission tomography in defining myocardial ischemia in humans. Seventeen patients who had undergone coronary arteriography were studied with N-13 glutamate at peak supine exercise using a bicycle ergometer, as well as with the flow tracer N-13 ammonia at peak exercise during a second similar exercise test. Six of the patients also underwent imaging with N-13 glutamate at rest before exercise testing; in the remaining 11 patients imaging with fluorine-18 (F-18) fluorodeoxyglucose was performed to assess glucose metabolism after the second exercise test. Seven patients had classic metabolism-flow mismatches consistent with ischemia (that is, decreased N-13 ammonia uptake in a region with relatively increased F-18 fluorodeoxyglucose uptake). There was no evidence of increased N-13 glutamate uptake in the ischemic mismatched regions in any of these patients. In all 17 patients, the uptake of N-13 glutamate during exercise paralleled the uptake of N-13 ammonia during exercise, suggesting that N-13 glutamate behaves as a flow tracer rather than as a metabolic marker of ischemia in humans.

Aged↗
PubMed1989

Regional myocardial blood flow and metabolism at rest in mildly symptomatic patients with hypertrophic cardiomyopathy.

Previous observations and clinical manifestations suggest the presence of ischemia in the disproportionately thickened septum of patients with hypertrophic cardiomyopathy. Metabolic consequences of ischemia can be demonstrated with positron emission tomography. Therefore, 10 patients with hypertrophic cardiomyopathy and an echocardiographic septum to posterior wall thickness ratio of 1.8 +/- 0.4 cm (range 1.3 to 2.5) were studied with the use of nitrogen (N)-13 ammonia, carbon (C)-11 palmitate and fluoro (F)-18 2-deoxyglucose as tracers of myocardial blood flow, fatty acid metabolism and exogenous glucose utilization. The results of positron emission tomography in 9 patients with hypertrophic cardiomyopathy were compared with those in 10 normal volunteers. In the hypertrophic cardiomyopathy group, observed myocardial activity of N-13 ammonia and C-11 palmitate in the septum was similar to that in the lateral wall. Septum to lateral wall tissue activity ratios averaged 1.04 +/- 0.15 for N-13 ammonia and 1.04 +/- 0.18 for C-11 palmitate, and were similar to those in the normal volunteers (0.98 +/- 0.07 and 0.98 +/- 0.03, respectively; p = NS). Myocardial clearance half-time and residual fraction of C-11 palmitate did not differ significantly between the septum and lateral wall. However, F-18 2-deoxyglucose uptake was significantly lower in the septum than in the lateral wall (15,768 +/- 4,314 versus 19,818 +/- 5,234 counts/pixel; p less than 0.003). The mean septum to lateral wall activity ratio of 0.83 +/- 0.21 was less than that observed in normal volunteers (0.92 +/- 0.07; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Rabbit myocardial 82Rb kinetics and a compartmental model for blood flow estimation.

Quantification of regional myocardial blood flow (MBF) with rubidium-82 (82Rb) and positron emission tomography (PET) requires the validation of a tracer kinetic model that adequately describes the kinetics of 82Rb in tissue. We performed 134 82Rb kinetic experiments in 24 isolated, arterially perfused rabbit interventricular septa at different flow rates (0.5-4.5 ml.min-1.g-1) and under the following conditions: varied concentrations of glucose (2.8-11 mM), insulin (0-5 mU/ml), and potassium (5-8 mM); varied pH (7.2-7.8); varied workload; and the addition of acetylstrophanthidin (1.0 microM). The measured 82Rb tissue time-activity curves consisted of two exponential components, with half times inversely related to MBF. The size of the slow component decreased as MBF increased (from 70% at 0.3 ml.min-1.g-1 to 30% at 2.0 ml. min-1.g-1). The kinetics were not strongly dependent on the conditions studied and were consistent with a compartmental model containing two communicating compartments. The volume of the fast exchangeable compartment and the transport rate constant from the fast to the slow compartment were found to be independent of MBF. Values of MBF were estimated with the compartmental model from 82Rb kinetics, and they correlated well with the directly measured MBF (r = 0.91; slope = 1.03).

Animals↗
PubMed1989

13N ammonia myocardial imaging at rest and with exercise in normal volunteers. Quantification of absolute myocardial perfusion with dynamic positron emission tomography.

Positron emission tomography (PET) was applied to the measurement of myocardial perfusion using the perfusion tracer 13N-labeled ammonia. 13N ammonia was delivered intravenously to 13 healthy volunteers both at rest and during supine bicycle exercise. Dynamic PET imaging was obtained in three cross-sectional planes for 10 minutes commencing with each injection. The left ventricle was divided into eight sectors, and a small region of interest was assigned to the left ventricular blood pool to obtain the arterial input function. The net extraction of 13N ammonia was obtained for each sector by dividing the tissue 13N concentration at 10 minutes by the integral of the input function from the time of injection to 10 minutes. With this approach for calculating net extractions, rest and exercise net extractions were not significantly different from each other. To obviate possible overestimation of the true 13N ammonia input function by contamination by 13N-labeled compounds other than 13N ammonia or by spillover from myocardium into blood pool, the net extractions were calculated using only the first 90 seconds of the blood and tissue time-activity curves. This approach for calculating net extractions yielded significant differences between rest and exercise, with an average ratio of exercise to rest of 1.38 +/- 0.34. Nonetheless, the increase was less than predicted from the average 2.7-2.8-fold increase in double product at peak exercise or the 1.7-fold increase in double product at 1 minute after exercise. However, when the first 90 seconds of dynamic data were fit with a two compartment tracer kinetic model, average perfusion rates of 0.75 +/- 0.43 ml/min/g at rest and 1.50 +/- 0.74 ml/min/g with exercise were obtained. This average increase in perfusion of 2.2-fold corresponded to similar average increases in double product. Thus, the noninvasive technique of PET imaging with 13N ammonia shows promise for future applications in determining absolute flows in patients with coronary artery disease.

Adult↗
PubMed1989

Simple noninvasive quantification method for measuring myocardial glucose utilization in humans employing positron emission tomography and fluorine-18 deoxyglucose.

To estimate regional myocardial glucose utilization (rMGU) with positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) in humans, we studied a method which simplifies the experimental procedure and is computationally efficient. This imaging approach uses a blood time-activity curve derived from a region of interest (ROI) drawn over dynamic PET images of the left ventricle (LV), and a Patlak graphic analysis. The spillover of radioactivity from the cardiac chambers to the myocardium is automatically removed by this analysis. Estimates of rMGU were obtained from FDG PET cardiac studies of six normal human subjects. Results from this study indicate that the FDG time-activity curve obtained from the LV ROI matched well with the arterial plasma curve. The rMGU obtained by Patlak graphic analysis was in good agreement with direct curve fitting results (r = 0.90). The average standard error of the estimate of the Patlak rMGU was low (3%). These results demonstrate the practical usefulness of a simplified method for the estimation of rMGU in humans by PET. This approach is noninvasive, computationally fast, and highly suited for developing parametric images of myocardial glucose utilization rate.

Adult↗
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↗
PubMed1988

Reassessment of echocardiographic criteria for diagnosis of mitral valve prolapse.

Commonly used echocardiographic criteria for mitral valve prolapse (MVP) include a sizable proportion of persons whose hearts are normal. Nevertheless, the echocardiogram is generally used as an independent standard for the diagnosis of MVP despite lack of consensus on the criteria to be used and the probability of interobserver variability. Conversely, there is a relatively uniform consensus that classic auscultatory signs establish the diagnosis of MVP beyond reasonable doubt. Accordingly, in 148 patients referred for evaluation of known or suspected MVP, the echocardiographic patterns that coincide with diagnostic auscultatory signs were studied prospectively to compare those patterns with criteria commonly used for the echocardiographic diagnosis of MVP and to determine interobserver variability in echocardiographic interpretation. Eighty patients (54%) had a classic mid- to late systolic click or an apical late systolic murmur, or both. Eleven patients (7%) had the apical holosystolic murmur of mitral regurgitation with no discernible clinical or echocardiographic cause other than the consideration of MVP. Doppler echocardiography was performed in 80 of the 148 patients. The degree of superior systolic bowing of each mitral leaflet and the location of leaflet coaptation relative to the presumed plane of the mitral anulus were graded on apical 4-chamber and parasternal long-axis views. The only patterns absolutely specific for auscultatory MVP were: severe bowing of the anterior or posterior leaflet; coaptation of leaflets on the left atrial side of the anular plane; moderate to severe Doppler mitral regurgitation accompanied by any degree of leaflet bowing; and mild Doppler mitral regurgitation accompanied by moderate bowing of a leaflet.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Comparison of two-dimensional and Doppler echocardiography and intracardiac hemodynamics for quantification of mitral stenosis.

Forty-three patients with mitral stenosis (MS) were studied to assess the relation of catheter-derived pressure gradient half-time (P 1/2), mitral valve areas (calculated by the Gorlin formula and 2-dimensional echocardiography [2-D echo]) to mitral valve areas derived from Doppler pressure half-time (T 1/2) in order to establish an accurate line-drawing method in nonlinear velocity tracings and to revalidate the use of the empiric constant of 220 ms as the T 1/2 that predicts a 1.0-cm2 mitral valve area. Mitral valve area could be quantified by 2-D echo in 39 of 43 patients and by Doppler in 31 of 34 patients, for a success rate of 91%. A reliable technique for measuring Doppler T 1/2 in nonlinear Doppler velocity tracings was a "mid-diastolic" line-drawing method, validated with the "anatomic" mitral valve area by 2-D echo (r = 0.89) and with the "hemodynamic" mitral valve area by the Gorlin formula (in pure MS without regurgitation) (r = 0.95). By both Doppler T 1/2 and hemodynamic P 1/2, the use of 220 ms to predict a mitral valve area of 1.0 cm2 was validated. Each T 1/2 and P 1/2 had an exponential inverse relation to the mitral valve area by the Gorlin formula in pure MS. Doppler and 2-D echocardiographic quantification of MS are complementary. Reliable measurement of T 1/2 in nonlinear velocity tracings is achieved by a mid-diastolic line-drawing method and use of the equation 220 ms/T 1/2 = mitral valve area accurately quantifies MS.

Adult↗
PubMed1987

Measurement of glucose and 2-deoxy-2-[18F]fluoro-D-glucose transport and phosphorylation rates in myocardium using dual-tracer kinetic experiments.

To examine the use of 2-deoxy-2-[18F]fluoro-D-glucose (2-FDG) as a glucose analog for measuring glucose utilization rate in myocardium, dual-tracer kinetic experiments with 2-FDG and 2-[3H]glucose were performed in the perfused, isolated rabbit interventricular septum to measure simultaneously the transport and phosphorylation rates of glucose and 2-FDG. Results of the present study indicated that, in the septum, the transport rate constants of 2-FDG and glucose were similar in magnitude, the phosphorylation rate constant for 2-FDG was about 60% of that of glucose, hypoxia caused an increase in phosphorylation rates of glucose and 2-FDG without affecting transport.

Animals↗