Search PubMed⌕ Search

Biomedical subjects

K P Lyons

Publications and source records attributed to K P Lyons.

At least 19 recordsLinked to original sources
PubMed1991

Malignant transformation of a Hürthle cell tumor: case report and survey of the literature.

Hürthle cell carcinoma is a relatively uncommon type of well-differentiated thyroid carcinoma. Its diagnosis has been controversial due to the difficulty in separating Hürthle cell adenoma from Hürthle cell carcinoma, thus the term Hürthle cell tumor is often used to describe both lesions. The present case of anaplastic giant-cell carcinoma in an 81-yr-old woman arose in a Hürthle cell tumor. This case illustrates the propensity of Hürthle cell tumor to undergo "malignant transformation" and argues for a more aggressive approach to such tumors.

Adenoma↗
PubMed1988

Factors affecting sensitivity and specificity of a diagnostic test: the exercise thallium scintigram.

Technical and methodological factors might affect the reported accuracies of diagnostic tests. To assess their influence on the accuracy of exercise thallium scintigraphy, the medical literature (1977 to 1986) was non-selectively searched and meta-analysis was applied to the 56 publications thus retrieved. These were analyzed for year of publication, sex and mean age of patients, percentage of patients with angina pectoris, percentage of patients with prior myocardial infarction, percentage of patients taking beta-blocking medications, and for angiographic referral (workup) bias, blinding of tests, and technical factors. The percentage of patients with myocardial infarction had the highest correlation with sensitivity (0.45, p = 0.0007). Only the inclusion of subjects with prior infarction and the percentage of men in the study group were independently and significantly (p less than 0.05) related to test sensitivity. Both the presence of workup bias and publication year adversely affected specificity (p less than 0.05). Of these two factors, publication year had the strongest association by stepwise linear regression. This analysis suggests that the reported sensitivity of thallium scintigraphy is higher and the specificity lower than that expected in clinical practice because of the presence of workup bias and the inappropriate inclusion of post-infarct patients.

Adult↗
PubMed1988

Ferrioxamine as a magnetic resonance contrast agent. Preclinical studies and phase I and II human clinical trials.

The preclinical and clinical trial experience with ferrioxamine (S-FDF; Salutar, Inc.) as a contrast agent for magnetic resonance imaging (MRI) is summarized. The results in 44 patients or subjects show that the drug is safe and well tolerated when given intravenously. In certain conditions, early results show that the use of this contrast agent provides more information than can be obtained with MRI alone.

Adult↗
PubMed1988

Methodologic problems in exercise testing research. Are we solving them?

To evaluate the comparative effects of methodologic factors on the reported accuracies of two standard exercise tests, 56 publications comparing the exercise thallium scintigram with the coronary angiogram were analyzed for conformation to five methodologic standards. Analyzed were adequate definition of study group, avoidance of a limited challenge group, avoidance of workup bias, and blinded analysis of the coronary angiogram and myocardial scintigram. Study group characteristics and technical factors were also reviewed. Better conformation with methodologic standards was found than has been reported previously for treadmill exercise testing. Furthermore, study group characteristics and technical factors were better predictors of sensitivity and specificity than were methodologic deficiencies. Only workup bias and test blinding were significantly associated with test accuracy. The percentage of patients with previous myocardial infarction had the highest correlation and was independently and directly related to sensitivity and inversely related to specificity.

Coronary Angiography↗
PubMed1988

Quantitation and fractionation of nutrient hepatic blood flow in normal persons, in persons with portal hypertensive cirrhosis, and after small-diameter portacaval H grafts.

Patients maintaining portal perfusion following small-diameter portacaval H grafts have better survival and lower portasystemic encephalopathy rates than those with reversed flow. To determine why this is so, we measured nutrient hepatic blood flow with the use of 99m-Tc-diisopropyl-IDA (DISIDA) clearance pharmacokinetics fractionated into its hepatic arterial and portal venous components. Patients with cirrhosis and portal hypertension had significantly lower nutrient hepatic blood flow than normal persons; this was due almost entirely to reduced portal flow. In patients with prograde portal flow after small-diameter H grafts nutrient hepatic blood flows were nominally reduced from levels seen in patients with portal hypertensive cirrhosis. Postoperative patients with reversed portal flow had significantly less nutrient hepatic blood than those with prograde flow. There was no evidence of significant hepatic arterial compensation for lost portal flow. Of four hemodynamic variables--portal flow direction, portal flow, arterial flow, and nutrient hepatic blood flow--only nutrient hepatic blood flow showed an independent correlation with clinical outcome. Portal perfusion is a critical factor in maintenance of adequate nutrient hepatic blood flow, primarily because hepatic arterial flow does not compensate chronically for lost portal perfusion.

Hemodynamics↗
PubMed1987

Regional myocardial perfusion of cardioplegic solutions.

We compared the regional myocardial perfusion of blood cardioplegic solution (BCP) and crystalloid cardioplegic solution (CCP) in 14 mongrel dogs. Cardiopulmonary bypass was established at 28 degrees C, and a hydraulic occluder was placed around the proximal left anterior descending (LAD) coronary artery. In group 1 (N = 7) collateral coronary arteries were ligated; in group 2 (N = 7) collateral coronary arteries were left in situ. After the aorta was clamped, BCP and CCP were alternately perfused at 200 ml/min. The occluder was inflated to produce moderate, severe, and critical LAD stenosis, and regional perfusion was measured by xenon-133 washout with the Silicon Avalanche Radiation Detector. BCP infusion produced a consistently higher aortic pressure, but CCP flow was better than BCP flow under all conditions, particularly without coronary collaterals (p less than .05). Regional myocardial perfusion of CCP is superior to BCP.

Animals↗
PubMed1987

Myocardial infarct imaging in patients with technetium-99m 2,3-dimercaptosuccinic acid. Superiority of technetium-99m pyrophosphate.

Technetium-99m 2,3-dimercaptosuccinic acid (Tc-99m DMSA) has been used successfully for imaging acute myocardial infarction in a canine model. The application in humans, however, has not been previously reported. In order to determine the feasibility of using this agent in clinical studies and to compare the agent to technetium-99m pyrophosphate (Tc-99m PPi), ten patients with proven myocardial infarction were studied. While imaging of transmural infarctions in humans was achieved using Tc-99m DMSA, scores for the Tc-99m DMSA images (1.8 +/- 0.96) were not as high as for Tc-99m PPi (2.5 +/- 0.45) (P less than 0.05). Discordance among four independent interpreters was greater for images obtained with Tc-99m DMSA. The superiority of Tc-99m PPi was evident whether images were obtained early (within 24 hours) or late (within five days). Although DMSA images were not obscured by rib uptake, they were less sensitive (63%) than Tc-99m PPi (97%). A potential advantage of Tc-99m DMSA in imaging acute myocardial infarction is that radiotracer concentration in the infarct occurs primarily in the early postinfarction period. The longer postinfarction that Tc-99m DMSA imaging was attempted, the lower the concentration of radiotracer. Thus, Tc-99m DMSA would not be expected to have the same persistence pattern as Tc-99m PPi into the remote postinfarction period. The persistent positivity of Tc-99m PPi has made it difficult to diagnose reinfarction.

Aged↗
PubMed1987

Metoclopramide-induced normalization of impaired gastric emptying in spinal cord injury.

In a partial, two-way crossover study of gastric emptying (GE) in spinal cord injury (SCI), fasted, healthy, unmedicated male volunteers were given a 99mTc-labeled liquid meal on two occasions. Metoclopramide (10 mg) was administered intravenously to each subject before the second evaluation of GE. We used single and multiexponential models with linear and nonlinear least-squares regression techniques to study the time-course of the disappearance of 99mTc from the stomach. The GE pattern in all subjects was most accurately characterized by nonlinear analysis (NONLIN) and consisted of two components, an initial adynamic phase and a phase of rapid emptying. The GE t1/2 of a liquid meal decreased from 106.6 +/- 58.3 min (mean +/- SD) in all SCI subjects (quadriplegic plus paraplegic) prior to treatment to 21.6 +/- 8.2 min after the intravenous administration of metoclopramide (p less than 0.006). Significant correlations between GE t1/2 and injury duration (yr) or level of spinal injury were observed. Impaired gastric emptying in SCI can be pharmacologically modified by metoclopramide to resemble a normal gastric emptying profile. Metoclopramide-altered gastric emptying in SCI may be expected to result in changes in the therapeutic efficacy of orally administered drugs when drug absorption is dependent on gastric motility or emptying efficiency.

Analysis of Variance↗
PubMed1986

A randomized controlled trial of intravenous streptokinase in evolving acute myocardial infarction.

To determine the efficacy of intravenous streptokinase in acute myocardial infarction, 52 patients were randomized to intravenous streptokinase or control groups. Time from onset of infarction to randomization was similar in the streptokinase group and control group, 4.9 +/- 2.1 hours vs 5.4 +/- 2.4 hours, respectively. The 28 streptokinase patients received an intravenous infusion of 700,000 units of streptokinase followed by full-dose anticoagulation. The 24 control patients received normal saline solution followed by full-dose anticoagulation. Of 28 streptokinase patients, 12 (43%) had noninvasive evidence of reperfusion by early peaking of serum creatine kinase (peak creatine kinase less than 16 hours after onset of infarction) vs 3 of 24 control patients (13%), p less than 0.02. Two streptokinase patients (7%) had reperfusion arrhythmias during streptokinase infusion. One streptokinase patient (4%) and two control patients (8%) died during hospitalization. At angiography (16 +/- 5 days after infarction) 22 of 26 streptokinase patients (85%) had a patent infarct-related coronary artery compared to 8 of 20 control patients (40%), p less than 0.01. Comparison of radionuclide left ventricular ejection fraction assessed acutely (28 +/- 10 hours after infarction) with left ventricular ejection fraction at hospital discharge (15 +/- 3 days after infarction) showed no significant improvement in either the streptokinase or control group, 0% and +1%, respectively. At follow-up 13 +/- 7 months after infarction, total mortality rate was similar in the streptokinase group and control group, 17.8% (5 of 28 streptokinase patients) and 20.8% (5 of 24 control patients), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Serial measurement of portal hemodynamics after partial portal decompression.

In a serial analysis of splanchnic hemodynamics, we compared partial with total portal decompression in 16 alcoholic cirrhotic patients who underwent portacaval shunts for variceal hemorrhage. Partial decompression was achieved with 8 or 10 mm polytetrafluorethylene portacaval H grafts and aggressive collateral ligation. Total decompression was achieved with larger diameter H grafts (12 or 14 mm). Early and follow-up (mean interval, 18 months) postoperative studies of portal hemodynamics included: direct measurement of shunt gradients, scintigraphic quantitation of portal and mesenteric flow distribution to the liver, and a portal and splenic collateral scoring system developed from standardized splenic venography. Partial portal decompression reduced portal pressure by 43% +/- 8% compared with 81% +/- 5% after total decompression (p less than 0.01). Scintigraphy demonstrated that partial decompression provided a greater fraction of portal flow to the liver than did total decompression (57% +/- 9% versus 2% +/- 1% intrahepatic radioactivity) and mesenteric flow distribution (14.5% +/- 5.4% versus 1.2% +/- 0.7%). Only one patient with partial decompression had a significant loss of portal perfusion during the interval studies. Significantly more residual collaterals were visualized in patients with partial decompression than in those with total decompression, and interval studies showed no significant changes from early studies. We conclude that partial decompression maintains higher portal pressures, more residual collaterals, and a greater fraction of portal and mesenteric flow to the liver than does total decompression. A modest but uniform reduction of portal pressure minimizes stimulus for new collateral formation and further shunting of portal flow.

Collateral Circulation↗
PubMed1979

Prognostic value of a persistently positive technetium-99m stannous pyrophosphate myocardial scintigram after myocardial infarction.

Technetium-99m stannous pyrophosphate myocardial scintigrams were obtained in 138 clinically stable patients 32.7 +/- 47.3 weeks (range 6 to 260) after acute myocardial infarction. Of the 138 patients, 74 (54 percent) had a persistently positive scintigram. Patients with such a scintigram were more likely to have severe angina pectoris, compensated congestive heart failure, anterior location of acute myocardial infarction, Q waves and S-T segment elevation in the electrocardiograms, cardiomegaly, left ventricular dyssynergy (dyskinesia or global dyssynergy), and an ejection fraction of less than 50 percent. During a follow-up period of 11.6 +/- 6.9 months after scintigraphy, 42 percent of the patients with a persistently positive scintigram had either a cardiac death, a nonfatal myocardial infarction, unstable angina pectoris or decompensated congestive heart failure compared with 13 percent of the patients with a negative scintigram (P less than 0.001). Of the 14 patients with cardiac death, 13 (93 percent) had a persistently positive scintigram. A persistently positive scintigram not only was the best single predictor of cardiac death and combined end points, but also added significantly to the predictive ability of the other clinical variables, including age, location of acute myocardial infarct, clinical status, electrocardiographic findings, and chest X-ray findings. It is concluded that technetium-99m stannous pyrophosphate myocardial scintigraphy has prognostic value in patients after acute myocardial infarction.

Adult↗
PubMed1979

Dental lesions causing abnormalities on skeletal scintigraphy.

The dental lesions of periodontitis, periodontal cysts, and tooth extraction were studied by Tc-99m phosphate scintigraphy of the jaws. Inflamed apical periodontal lesions caused a localized area of increased concentration of radiotracer regardless of the presence or absence of symptoms. Scintigrams may be positive up to eight months after dental extractions but tend to return to normal thereafter unless complications arise.

Diagnosis, Differential↗
PubMed1978

New technique for localization of therapeutic emboli using radionuclide labeling.

A sensitive method for localizing the resting place of catheter-injected therapeutic gelatin emboli is described. Surgical gelatin (Gelfoam) is labeled with 99mTc and each embolus observed on the persistence scope of a gamma camera after injection. This technique reduces the chance of obstructing blood vessels other than those intended. Two cases of embolization, one arterial and one venous, are illustrated.

Adult↗
PubMed1978

Correlations of Tc-99m pyrophosphate myocardial scintigraphy and the results of coronary-artery bypass surgery.

This study indicates that abnormal myocardial scintigrams with Tc-99m pyrophosphate tend to improve after coronary-artery bypass surgery, frequently changing from positive to normal. The significance of this change is uncertain. It does not correlate well with the clinical state but may simply reflect the natural course of myocardial scintigraphy in response to hospitalization, medical management, and presumably improved myocardial oxygenation. Postoperative myocardial scintigrams are useful in detecting perioperative infarction. ECG interpretation may be difficult in the immediate postoperative period and, in three cases, there were scintigraphic criteria of perioperative infarction without diagnostic changes on ECG. Patients with positive preoperative scintigrams, especially in association with Functional Class IV angina, are at increased risk during coronary-artery bypass surgery.

Coronary Artery Bypass↗
PubMed1978

Changing manifestations of brown tumors on bone scan in renal osteodystrophy.

In a patient with chronic renal failure and secondary hyperparathyroidism, brown tumors, visualized initially as photon-deficient areas on bone scintigraphy, reverted to areas of abnormally increased activity following parathyroidectomy. This dual appearance on bone scan paralleled the functional state of the parathyroid gland. The possible relationship of hyperhosphatemia to the increased bone-scan activity noted in the calvarium, mandible, and facial bones is discussed.

Adult↗
PubMed1977

Follow-up technetium-99m stannous pyrophosphate myocardial scintigrams after acute myocardial infarction.

Technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigrams were obtained in 68 patients during acute myocardial infarction (AMI) and at follow-up 15.9 +/- 8.8 weeks later. All patients with AMI had a positive scintigram (2+ or greater); only one of 46 control patients (2%) had a positive (2+) scintigram. At follow-up scintigraphy 6 to 37 weeks following AMI, 57% of patients had a persistently positive scintigram even though recurrent AMI was suspected in only one of these patients. Patients with persistently positive scintigrams tended to have more severe disease as evidenced by compensated congested heart failure (41%) persistent angina (77%), and ECG evidence of ventricular dyssynergy (51%), We conclude that 1) in patients with prior AMI, a 2+ abnormality on 99mTc-PYP scintigram may not represent new AMI; 2) a persistently positive 99mTc- PYP scintigram may have prognostic implications since it occurs predominantly in patients with severe symptomatic coronary disease.

Acute Disease↗