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Biomedical subjects

W Ashburn

Publications and source records attributed to W Ashburn.

51 records · Page 3Linked to original sources
PubMed1977

Usefulness of preoperative and postoperative Tc-99m (Sn)-pyrophosphate scans in patients with ischemic and valvular heart disease.

To assess the usefulness of myocardial imaging with technetium-99m-stannous pyrophosphate for detecting acute myocardial necrosis in patients undergoind cardiac surgery, 66 such patients were stldied. Tc-99m (Sn)-pyrophosphate scans were obtained in all patients 3 to 6 days postoperatively and in 45 preoperatively. Electrocardiograms and serum samples for measuring myocardial isoenzyme of creatine kinase (MB CK) levels were obtained before and serially after cardiac surgery. Seven of the 46 patients undergoing myocardial revascularization had a definite new myocardial infarction as indicated by electrocardiogram and MB CK isoenzyme concentrations, and postoperative pyrophosphate scans were abnormal in all but one. In addition, six of the eight patients with possible myocardial infarction (elevated MB CK levels and persistent ST-T wave depressions) had an abnormal scan postoperatively. Seven of the 20 patients undergoing aortic or mitral valve replacement, or both, had a possible postoperative myocardial infarction by electrocardiogram and MB CK criteria and the myocardial scan was positive in two. All the patients with a normal electrocardiogram and normal MB CK levels had a normal pyrophosphate scan. Preoperative scans were obtained in 22 patients wit; valvular heart disease and were positive in two with a heavy calcified mitral valve on fluoroscopy and in one with a calcified aortic valve. After valve replacement, the pyrophosphate scan became normal in two patients and remained abnormal in the third patient with electrocardiograms and MB CK levels suggesting acute myocardial infarction. We conclude that the Tc-99m (Sn)-pyrophosphate scan is useful for analyzing the occurrence of acute myocardial infarction in patients undergoing cardiac surgery and that, in conjunction with the electrocardiogram, it permits confirmation or exclusion of that diagnosis. Furthermore, false positive pyrophosphate scans may occur in patients with heavy valve calcifications.

Adult↗
PubMed1977

99mtechnetium penicillamine: a renal cortical scanning agent.

99mTechnetium penicillamine, a renal cortical imaging agent, can be used to provide a rapid, safe and non-invasive assessment of renal morphology and the renal vascular supply. Since this agent is not excreted significantly during the imaging procedure cortical scans of high quality can be obtained without image deterioration owing to a superimposed collecting system. These scans, which are clearly superior in anatomical detail to earlier scans using 131I hippuran, can be obtained along with the 131I hippuran renogram when the patient comes to the nuclear medicine department. Herein we demonstrate the anatomical detail it is now possible to achieve by presenting the cortical renal scans and accompanying radiograms from 5 patients with different renal pathology.

Adenocarcinoma↗
PubMed1977

Detection of perioperative myocardial damage after coronary artery bypass graft surgery.

In order to evaluate methods for detecting peri-operative myocardial damage we studied 41 patients before and serially following coronary artery bypass graft surgery utilizing the 12-lead ECG, serum MB-CPK measurements, and 99mTc pyrophosphate myocardial scans. Six of the 41 patients (15%) developed persistent new Q waves after surgery. Six other patients demonstrated ischemic ST-T wave changes that persisted for 48 hours or more. Mean total MB-CPK released was highest for the group with new Q waves [1598+/-545 (SE) I.U./L-hr] as compared to the group with ischemic ST-T wave changes 708+/-65 I.U./L-hr) or the group with no ECG changes (262+/-47 I.U./L-hr). Ten patients (24%) has positive postoperative pyrophosphate scans consistent with myocardial infarction. The three techniques were compared in these 41 patients utilizing 465 I.U./L.-hr as the upper limit of normal MB-CPK released after uncomplicated coronary bypass surgery (no ECG changes, negative scan). Five patients with ischemic ECG changes had a positive scan and high MB-CPK; six patients with no ECG changes had high MB-CPK but a negative scan; and one patient with high MB-CPK and new Q wave had a negative scan. We conclude 1) new Q waves on ECG underestimate the incidence of myocardial damage after coronary artery surgery; 2) MB-CPK alone overestimates the incidence of infarction; and 3) a combination of the three techniques is the best means for detecting myocardial damage after coronary artery bypass graft surgery.

Adult↗
PubMed1975

Left ventricular performance assessed by radionuclide angiocardiography and echocardiography in patients with previous myocardial infarction.

In 61 patients (77 studies) who had a transmural myocardial infarction, we compared the left ventricular ejection fraction by echocardiography with the ejection fraction determined by a computerized radioisotope technique that makes no assumptions regarding left ventricular geometry. In 31 studies of 26 patients with normal left ventricular wall motion by videotracking and normal left heart size, ejection fraction averaged 0.57 +/- 0.09 (SD) by ultrasound and 0.62 +/- 0.10 by the isotope method. Measurements of ejection fraction by both techniques correlated well (r = 0.86) and there was complete separation between patients with normal and reduced ejection fraction. In 46 studies of 35 patients in whom left ventricular wall motion abnormalities were recorded by videotracking, ejection fraction by the isotope method averaged 0.46 +/- 0.08, while average echo ejection fraction was 0.62 +/- 0.12. The correlation between the ultrasound and isotope methods in these 46 studies was poor (r = 0.33) and in 28 studies measurement of the ejection fraction by the two techniques was discordant. In 26 of the 27 studies where there was a reduced ejection fraction by the isotope method and a normal ejection fraction by echo, the dyssynergy involved the anterolateral left ventricular wall. These data indicate that echocardiographic measurements frequently overestimate left ventricular performance in patients with previous myocardial infarction associated with anterolateral wall motion disorders.

Acute Disease↗
PubMedDate not supplied

Detection, quantitation and contrast enhancement of myocardial infarction utilizing computerized axial tomography: comparison with histochemical staining and 99mTc-pyrophosphate imaging.

The potential role of the CAT scan in detecting and quantitating acute myocardial infarctions was assessed in the excised hearts of 25 dogs with 48-hour-old myocardial infarctions. The CAT scan detected the infarct in every instance and distinguished subendocardial from transmural infarctions. While the CAT scan slightly underestimated the volume of infarcted tissue, this volume had a close linear relationship to the true volume determined by histochemical staining. On the other hand, the 99mTc-pyrophosphate scintiscans grossly overestimated the volume of infarcted tissue. Intravenous administration of contrast material prior to sacrifice produced contrast enhancement either of the rim or diffusely throughout the infarct. Thus CAT should have an important role not only in detecting but also in estimating the volume of acute myocardial infarctions.

Animals↗
PubMedDate not supplied

A modeling analysis of rest-stress and stress-rest injection sequences in performing thallium-201 myocardial perfusion scintigraphy.

A new thallium-201 stress testing protocol is proposed in which rest images are obtained prior to stress images. The advantages of the new protocol are that it saves time and requires no special diet or activity restriction between imaging sets. A potential problem from reversing the standard imaging sequence is decreased sensitivity to stress perfusion defects owing to background counts from the rest image. Using a cardiac phantom, 74 sets of stress and rest images were simulated under the new protocol and the standard stress-redistribution-reinjection protocol. Seven observers were asked to classify the images as normal or abnormal and to distinguish ischemic from fixed defects. Differences in observer performances between the two protocols were compared. With the new protocol, observers had sensitivities of 75%-90% and specificities of 100% in identifying a perfusion defect on the stress study. Accuracy was improved if the image counts from the rest study contributed less than 40% of the final counts of the stress study. Detection of ischemic and fixed defects was as good as or better than with standard protocols. Based on the phantom model, rest followed immediately by stress imaging sequence is an advantageous alternative for thallium-201 stress testing. Clinical trials are necessary to further evaluate this new protocol.

Coronary Disease↗