Biomedical subjects

I Mena

Publications and source records attributed to I Mena.

At least 91 records · Page 5Linked to original sources

PubMed1986

Does positive hepatobiliary scan in cholecystitis stay positive, and for how long?

A prospective study of 11 patients who had undergone two sequential hepatobiliary scans prior to surgery demonstrated that initially positive scans could be due to acute cholecystitis, or chronic cholecystitis with exacerbation. A second hepatobiliary scan performed four to five days later differentiated acute from chronic cholecystitis. All five patients with surgery-proven acute cholecystitis remained hepatobiliary-positive, while patients with surgery-proven chronic cholecystitis reverted back to negative hepatobiliary scans if the second hepatobiliary scan was done properly.

Acute Disease↗

PubMed1986

Cardiac and vascular sequelae of sternal fractures.

A 5-year experience with 12 sternal fractures treated at the Los Angeles County Harbor/UCLA Medical Center is presented. Our data indicate that sternal fractures with roentgenographic mediastinal widening commonly have associated aortic injuries. There is an almost uniform depression of right ventricular or anterior left ventricular function associated with sternal fractures and these cardiac sequelae are documentable by first-pass biventricular radionuclide angiography including left ventricular segmental wall motion analysis. These data facilitate the management of patients with complex hemodynamic problems. In contrast, the incidence of displaced or unstable fractures is very low. Only one patient in this series had a depressed manubriosternal fracture, and no injury necessitated surgical stabilization. The outcome of isolated sternal fractures is benign, and they should be viewed as harbingers of the discovery of other injuries.

Accidents, Traffic↗

PubMed1986

99mTc-DTPA aerosol deposition and clearance in COPD, interstitial disease, and smokers.

The application of 99mTc-DTPA radioaerosols to a variety of clinical disorders is described. With the development of simple equipment that can deliver very small droplets, this approach has become increasingly popular for measurements of the distribution of ventilation in patients with obstructive lung disease and suspected pulmonary embolism. In addition, by determining the rate at which the radionuclide is cleared from the lung, information has been obtained concerning the permeability of the pulmonary epithelium to extracellular indicators. Accelerated clearance rates have been found in patients with a variety of chronic interstitial lung diseases indicating that epithelial permeability is increased. Accelerated clearance rates have also been found with acute inflammation of the lung such as the adult respiratory distress syndrome and pneumocystis pneumonia. Furthermore, rapidly reversible increases in 99mTc-DTPA clearance occur in smokers and may be related to the inflammatory changes that contribute to the development of emphysema.

Aerosols↗

PubMed1986

Relationship between 201Tl uptake and oxidative metabolism in cultured myocardial cells.

The uptake of thallium-201 (201Tl) by myocardial cells in cultures was assessed in the presence of 10(-3) M potassium cyanide (KCN), an inhibitor of mitochondrial respiration, and 10(-4) M dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. The cultures were incubated with 14C-glucose or 14C-octanoate, allowing the measurement of the oxidative metabolism and beta-oxidation from the production of 14CO2. The results demonstrated a moderate decrease in the ratio between the intra/extracellular concentration of 201Tl (Tl i/e) in the presence of KCN (28.9 +/- 8.1 versus 35.6 +/- 9.7 in the controls, n.s.) and no change with DNP (37.6 +/- 9.7). Glycolysis and fatty acid oxidation were lowered with KCN (-28 +/- 15 and -45 +/- 22% respectively, p less than 0.05 in both cases) and were non significantly increased with DNP (+37 +/- 23 and +10 +/- 52% respectively). These results show that 201Tl intracellular uptake is not related directly, but is not totally independent of glycolysis and fatty acid oxidation.

2,4-Dinitrophenol↗

PubMed1986

Use of factor analysis in the evaluation of left to right cardiac shunts.

We have compared two methods of data processing for the quantitation of left-to-right cardiac shunts using first-pass radionuclide angiography. These two methods are used for curve generation in the deconvolution analysis. The standard method involves manual definition of regions of interest. A newer method--factor analysis--provides automatic curve generation and is therefore more operator-independent. Both techniques yield curves of the venous input, lung, and background. The venous input curve is deconvolved by the lung curve, and the resultant unit impulse response is fitted by the gamma variate method to quantitate the left-to-right shunt fraction. Both techniques--factor analysis and regions of interest (ROIs)--separated the shunt patients (n = 16) from the control subjects (n = 20) with a p less than 0.001. There was less interobserver variability with the curves obtained by factor analysis than with those obtained by regions of interest. The coefficient of correlation of factor analysis results with oximetry, r, was 0.90. High sensitivity and specificity, each 94%, was achieved with curves generated by factor analysis. Time vs. activity curves generated by ROIs can achieve high sensitivity and low specificity, or vice versa, depending on the cutoff level defined for separation of the left-to-right shunt patients from the control group.

Adult↗

PubMed1986

Nuclear medicine: non-invasive evaluation of coronary artery disease.

Non-invasive evaluation of coronary artery disease is accomplished in Nuclear Medicine by resting and exercise right and left ventriculography and/or by myocardial perfusion studies performed also at rest and exercise by means of Thallium-201. The development of new radiopharmaceuticals such as ultra short-lived radionuclides and Technetium-99m labelled myocardial imaging agents allow simultaneous evaluation of both left ventricular function and left ventricular myocardial perfusion. Myocardial perfusion imaging is performed by means of planar imaging and recently by means of single photon emission tomography. The sensitivity and specificity of stress left ventriculography for uncomplicated coronary artery diseases are 85% and 95% respectively. For diagnosis of acute myocardial infarction with Thallium-201 in the first hours after onset of pain, the sensitivity is 99% and specificity is 80%. This diminishes after a 6 hour period to 90% and 80% respectively, while wall motion analysis stays with a sensitivity of 79% and 93%. The prognostic value of this determination is therefore a strong, cost-effective contributor to the non-invasive evaluation of coronary artery disease.

Cardiac Output↗

PubMed1985

Factor analysis in left ventricular first-pass radionuclide angiography: value of the ventricular factor to measure ejection fraction.

Factor analysis theoretically generates the time-activity curves of the various physiological compartments, or factors, which are superimposed in a dynamic series of scintigraphic frames. An image of the spatial distribution of each of these factors is also displayed. We tested the ability of one of these, the ventricular factor, to measure the left ventricular ejection fraction (LVEF) in first-pass radionuclide angiography (FPRA). Forty-nine patients divided into three groups were studied. In a group of 32 patients, factor analysis was compared to a conventional scintigraphic method and to contrast angiography. The coefficient of correlation was similar for both techniques (r = 0.83). To test reproducibility, another group of 10 patients received two successive injections of Au-195m, three minutes apart. The reproducibility of LVEF was r = 0.78 with factor analysis and r = 0.81 with the conventional method. In a third group of seven patients, three successive injections of Au-195m were performed in the right and in the left anterior oblique projections. The reproducibility of LVEF was r = 0.71 with factor analysis. However LVEF was significantly lower in LAO than in RAO, 50 +/- 11% vs 58 +/- 17% respectively. It is concluded that factor analysis does not offer a more reliable means of calculating LVEF than a conventional method.

Factor Analysis, Statistical↗

PubMed1985

Pulmonary imaging in pregnancy. Maternal risk and fetal dosimetry.

A Tc-99m macroaggregated albumin (MAA) perfusion lung scan and a Tc-99m DTPA aerosol ventilation scan were performed for suspicion of pulmonary embolism (PE) in a patient who was ten weeks pregnant. There was considerable reluctance on the part of the obstetricians to permit this study. Standard MIRD dose estimates to the fetus were performed, which showed a maximum fetal exposure of about 50 mrem. It was concluded that the risk to mother and fetus from undiagnosed and untreated PE is much greater than the negligible risk to the fetus from the radiation exposure; fear of fetal radiation damage should not be a deterrent to performing these scans.

Adult↗

PubMed1985

Small solute clearance from the lungs of patients with cardiogenic and noncardiogenic pulmonary edema.

The regional clearance of 99mTc-diethylenetriamine penta-acetate (99mTc-DTPA) from the lungs was measured in 14 patients with noncardiogenic pulmonary edema, six patients with acute pulmonary edema secondary to heart failure, and 29 normal subjects. The radionuclide was delivered in an aerosol which was inhaled for 120 seconds, and the subsequent decline of radioactivity from the lungs was monitored for seven minutes over each of six peripheral regions of interest with a computerized scintillation camera. The average 99mTc-DTPA clearance of these regions was accelerated above the 98 percent confidence limits in all but three of the patients with noncardiogenic edema. The mean clearance value in this group of patients was significantly greater than those in normal subjects or patients with cardiogenic pulmonary edema. Clearances returned toward normal in each of seven subjects who improved clinically. Only one of the patients with cardiogenic pulmonary edema had an elevated average clearance rate, and the mean clearance for this population was not statistically greater than normal. This procedure appears to detect increased epithelial permeability caused by lung injury and may help distinguish between cardiogenic and noncardiogenic pulmonary edema.

Adult↗

PubMed1985

Effects of grisorixin on the distribution of thallium-201 and on the oxidative metabolism in cultured myocardial cells.

Previous experiments in the dog and guinea-pig have shown that grisorixin, a monocarboxylic ionophore, can significantly increase the coronary blood flow and the myocardial uptake of 201Tl, as well as have a stimulant effect on the heart. In this study, cultures of myocardial cells were used in order to isolate the cells from the vascular and extracardiac influences so that any ionophorous effect on 201Tl could be evidenced. The effects of grisorixin on the oxidative metabolism were simultaneously studied. The technique described by Harary was used to prepare the cultures. The activity of the 14CCO2 produced by oxidation of [14C]glucose and [14C]octanoate added to the medium of culture and the intra/extracellular ratio of 201Tl concentrations (Tl i/e) were measured. In the controls (n = 8), the Tl i/e was 40 +/- 10 while it was 17 +/- 6 (p less than 0.05) in the cells that received 201Tl and grisorixin at the same time (n = 4), and 19 +/- 5 (p less than 0.05) in the flasks where 201Tl was injected after grisorixin (n = 7). A significant decrease of the [14C]octanoate oxidation was found in the flasks treated with grisorixin (n = 4, -50 +/- 16%, p less than 0.01) while the [14C]glucose oxidation was not significantly lowered (n = 3; -11 +/- 12%). The conclusion is that grisorixin decreases both the intracellular concentration of 201Tl and the fatty-acids oxidation in cultured myocardial cells. The beneficial effects previously observed in vivo were probably the consequence of the strong coronary dilatation and of an indirect stimulation.

Animals↗

PubMed1984

Combined contrast echocardiographic and radionuclide diagnosis of atrial septal defect: accuracy of the technique and analysis of erroneous diagnoses.

The utility of combined peripheral vein contrast 2-dimensional echocardiography (2-D echo) and radionuclide shunt detection was evaluated in 25 patients with suspected atrial septal defect (ASD) in whom the diagnosis was confirmed at cardiac catheterization: 14 patients had ASD and 11 had no intracardiac shunt. Contrast 2-D echo correctly diagnosed 13 of 14 patients with ASD, but there were 2 false-positive diagnoses in the 11 patients without ASD. Radionuclide shunt studies correctly identified all 14 patients with ASD, but yielded 5 false-positives results among the 11 without ASD. After altering the radionuclide processing technique, there were only 2 of 11 false-positive shunt studies, and the correlation of radionuclide shunt magnitude with cardiac catheterization improved (r = 0.49, p less than 0.025 to r = 0.75, p less than 0.001). Thus, the improved processing method improved both the qualitative and quantitative accuracy of radionuclide shunt detection. The combination of contrast 2-D echo and radionuclide shunt detection led to a proper diagnostic and therapeutic decision in 24 of 25 patients. Therefore, these combined modalities are clinically useful in the evaluation of patients with suspected ASD.

Adolescent↗

PubMed1984

Exercise subcostal two-dimensional echocardiography: a new method of segmental wall motion analysis.

This study determines the effectiveness of the subcostal view 2-dimensional (2-D) echocardiogram in providing images of left ventricular wall motion at rest and during symptom-limited upright bicycle exercise, and compares 2-D echocardiographic regional wall motion analysis with first-pass radionuclide angiography. Diagnostic-quality subcostal 2-D echocardiograms at rest were obtained in 95% of unselected persons studied (16 of 17 normal subjects and 23 of 24 patients who had had myocardial infarction [MI] ). All who had adequate studies at rest had diagnostic-quality maximal exercise studies. Segmental wall motion at rest and exercise determined by 2-D echocardiography correlated well with radionuclide angiography in both the normal and post-MI groups. The chi-squared values for the 3 segments analyzed were: anterior 52 (p less than 0.001), apical 56 (p less than 0.001) and inferior 37 (p less than 0.001). It is concluded that subcostal view 2-D echocardiography at rest and at the peak of symptom-limited upright bicycle exercise is a feasible and accurate noninvasive method for the analysis of segmental left ventricular function.

Adult↗

PubMed1984

Simultaneous maximal exercise radionuclide angiography and thallium stress perfusion imaging.

Gold-195m is a new ultra-short-lived radionuclide that can be used for cardiac studies. Accurate, reproducible ejection fraction and ventricular wall motion studies can be obtained from first-transit angiography using commercially available imaging and image-processing equipment. The short half-life of gold-195m (30.5 seconds) makes simultaneous dual isotope imaging possible and substantially reduces the radiation exposure from the isotope angiography. The feasibility and possible benefits of performing dual radionuclide studies were evaluated during a single exercise stress test in 24 subjects with known coronary artery disease (CAD) and in 20 normal volunteers. High-quality first-transit angiograms were obtained in all subjects. An 83% sensitivity and 95% specificity for detecting CAD with thallium-201 imaging was noted in this investigation, suggesting that its diagnostic accuracy was not altered by simultaneous dual isotone imaging. When segmental left ventricular (LV) wall motion was compared with thallium-201 perfusion imaging, divergent results were noted in 15 of 44 subjects. An analysis of the ejection fraction (EF) results at rest and stress provided additional information that could be useful in assessing the clinical significance of such differences in segmental wall motion and perfusion. Simultaneous dual isotope imaging appears to be appropriate for situations in which both LV perfusion and function require evaluation. The use of gold-195m allows such information to be obtained from a single exercise test and can thereby reduce the cost and time required for noninvasive evaluations of patients for CAD.

Adult↗

PubMed1984

Reproducibility and accuracy of left ventricular ejection fraction and wall motion determinations using gold-195m: a new ultrashort-lived radionuclide for cardiac studies.

Gold-195m has a halflife of 30.5 sec. Its ultrashort halflife and low radiation exposure (240 mrads to the kidney from a 20-mCi injection) make it an ideal agent for sequential first-transit studies of cardiac function. The reproducibility of ejection fraction and wall motion determinations were assessed from two gold-195m first-pass angiograms performed 3 min apart in 38 subjects. The accuracy of these evaluations was assessed by performing another first-transit study using technetium-99m. The correlation of the ejection fraction between the two gold-195m angiograms was 0.95 (standard error of the estimate (SEE) = 0.049) over an ejection fraction range of 20-78. The correlation of the ejection fraction using technetium-99m versus gold-195m was 0.95; SEE = 0.050. Only six minor discrepancies were noted when wall motion was evaluated in the gold-195m angiograms and compared with the technetium-99m study. We conclude that gold-195m can provide repeated, accurate, and reproducible ejection fraction and wall motion determinations with conventional imaging equipment at a substantially lower radiation exposure than with technetium-99m.

Angiography↗

PubMed1984

Left ventricular function at rest and during Raynaud's phenomenon in patients with scleroderma.

We evaluated left ventricular function in 10 scleroderma patients with signs and symptoms suggestive of congestive heart failure. M-mode and two-dimensional echocardiography demonstrated normal to increased systolic function in all patients. The presence of pulmonary venous congestion on the chest radiograph was not useful in assessing left ventricular systolic function. Five of nine patients with normal to increased left ventricular ejection fraction (LVEF) had increased cardiothoracic ratios and increased pulmonary vascular markings. Left ventricular hypertrophy was associated with a worse New York Heart Association functional class, more pulmonary vascular congestion, and greater left atrial size. In the presence of normal systolic function and ventricular hypertrophy, diminished left ventricular diastolic compliance may account for the cardiac dysfunction in these patients. Cold pressor testing induced peripheral Raynaud's phenomenon in nine of nine patients; however, no ST segment changes or chest pain was provoked. In seven of nine patients there was no abnormal fall in LVEF. The mechanism for the fall in ejection fraction seen in two patients may be related to an increase in afterload or myocardial ischemia secondary to coronary atherosclerosis. We found little to suggest that a myocardial Raynaud's phenomenon affects left ventricular perfusion or systolic function. Clinical signs and symptoms of congestive failure as well as chest radiographs are poor indicators of impaired systolic function in scleroderma patients. Based on these findings, it appears that evaluation of left ventricular systolic function should include echocardiographic or angiographic study before such patients are treated for heart failure with inotropic agents.

Adult↗

PubMed1984

Noninvasive measurement of the rest and exercise peak systolic pressure/end-systolic volume ratio: a sensitive two-dimensional echocardiographic indicator of left ventricular function.

Thirty-five patients with previous myocardial infarction and 25 normal subjects underwent subcostal view two-dimensional echocardiography at rest and at peak up-right bicycle exercise. The purpose was to assess changes in left ventricular volume with maximal upright bicycle exercise and to compare the utility of the peak systolic pressure/end-systolic volume index ratio and ejection fraction as indicators of left ventricular function. With exercise, normal subjects had a decrease in end-systolic volume index (22 +/- 8 to 11 +/- 3 ml/m2) (p less than 0.001); the normal ejection fraction (59 +/- 9 to 72 +/- 8%, p less than 0.001) and the pressure/volume ratio (6 +/- 3 to 18 +/- 6, p less than 0.001) increased. In patients with prior myocardial infarction there was no change in end-systolic volume index, ejection fraction or pressure/volume ratio with exercise. Although at peak exercise significant differences between normal subjects and patients with prior infarction were demonstrated in end-systolic volume index (p less than 0.001), ejection fraction (p less than 0.001) and pressure/volume ratio (p less than 0.001), the pressure/volume ratio provided sharper delineation between the two groups than did ejection fraction. The exponential relation of the pressure/volume ratio and ejection fraction at peak exercise demonstrates that the pressure/volume ratio is more sensitive as an indicator of normal or borderline left ventricular function and that ejection fraction is more sensitive in quantifying the degree of left ventricular dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1984

Traumatic myocardial dysfunction.

Traumatic myocardial dysfunction is a frequently unsuspected, undiagnosed contributor to deaths from trauma. Electrocardiography, serum enzymes, and radionuclide myocardial scans are insensitive indicators of cardiac injury following blunt chest trauma. First-pass biventricular radionuclide angiography can accurately determine right and left ventricular ejection fractions and assess left ventricular segmental wall motion. Since August, 1980, we have evaluated 74 consecutive patients with blunt chest and multisystem trauma. Electrocardiograms and measurements of the myocardial band isoenzyme of creatine kinase were obtained at admission and repeated at 24 hour intervals for 3 days. Radionuclide angiography was performed 24 to 48 hours after admission. The electrocardiogram was abnormal in 21 patients (28%), levels of creatine kinase isoenzyme were elevated in six, and radionuclide angiographic abnormalities were present in 55 patients (74%). Electrocardiographic abnormalities correlated anatomically with angiographic abnormalities in 16 patients (76%). On follow-up radionuclide angiography, abnormalities had disappeared in nine of 12 patients restudied at 3 weeks. This study documents that the electrocardiogram and creatine kinase isoenzyme elevations are static, insensitive indicators of traumatic myocardial dysfunction. Radionuclide angiography with studies of left ventricular segmental wall motion demonstrate that traumatic myocardial dysfunction, although sometimes transitory, is a dynamic phenomenon that is more common than previously suspected. First-pass radionuclide angiography and wall motion studies are practical and valuable adjuncts to the management of the injured patient.

Adult↗

PubMed1983

Myocardial dysfunction following blunt chest trauma.

We prospectively studied 35 patients with blunt chest trauma using ECG multi-gated and first-pass nuclear angiography. Radionuclide angiography (RNA) is a sensitive test of myocardial function demonstrating right and left ventricular ejection fractions. First-pass angiography, in addition, shows left ventricular segmental wall motion, a qualitative as well as anatomic indicator of left ventricular function. We saw RNA abnormalities in 26 patients (74.2%). Eight patients (22.8%) had ECG abnormalities, and these findings correlated with RNA, suggesting that this technique is a very sensitive indicator of myocardial dysfunction following trauma. These studies warrant further experimental and clinical evaluations to determine the cause, significance, and long-term prognosis of posttraumatic myocardial dysfunction.

Adult↗