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Biomedical subjects

S E Lewis

Publications and source records attributed to S E Lewis.

At least 163 records · Page 9Linked to original sources
PubMed1981

The prognostic value of submaximal exercise testing with radionuclide ventriculography before hospital discharge in patients with recent myocardial infarction.

To test the hypothesis that patients at risk of future cardiac events can be identified by sub-maximal exercise testing with radionuclide ventriculography (RVG), 61 patients were studied a mean of 19 +/- 1.0 days (+/- SEM) after acute myocardial infarction (MI). RVGs were used to measure left ventricular ejection fraction (LVEF), wall motion score (WMS), end-diastolic volume (EDV) and end-systolic volume (ESV), and the ratio of systolic blood pressure to ESV (P/V index) at rest and during submaximal exercise. Frank lead ECGs were analyzed for ST-segment change and arrhythmias. These patients were followed for a mean of 9.6 months (60 for 6 months or more and one for 3 months) to determine the incidence of cardiac death, recurrent MI, unstable or medically refractory angina, persistent congestive heart failure (CHF) or limiting angina; these problems were considered to be important cardiac events. At the 6-month follow-up, 37 patients had important complications: four patients died, five had MI, seven had unstable or medically refractory angina, 11 had persistent CHF and 10 had severe limiting angina. The sensitivity and specificity of RVG in predicting the important postinfarct complications listed above were 95% and 96% for failure to increase LVEF by at least 5 units, 95% and 96% for an increase in ESV of more than 5%, 97% and 88% for failure of the P/V index to increase by more than 35%, and 81% and 88%, respectively, for a decrease in WMS. The sensitivity and specificity of the ECG in predicting important complications were 54% and 58%, respectively. The rest and submaximal exercise RVG variables, the ECG, a history of MI, the location of the infarction, Killip class III, age, sex, and maximal work load performed were analyzed statistically to determine the best predictors of prognosis. The change with exercise in LVEF, ESV and the P/V index were most significant variables in predicting prognosis during the 6-month follow-up period. When patients with subsequent cardiac events were separated into those with death, recurrent MI and unstable or medically refractory angina as major cardiac events, and patients with persistent CHF and limiting angina as less important ("minor") cardiac events, only the peak submaximal exercise LVEF and history of MI were significant in distinguishing these groups. In patients without important cardiac events during the 3- and 6-month follow-up, 70% and 88%, respectively, no abnormality in the responses of LVEF, ESV, or P/V index to submaximal exercise. These results suggest that submaximal exercise testing with RVG is a highly sensitive means of classifying patients at the time of hospital discharge after MI according to the likelihood of having cardiac events during the ensuing 6 months.

Adult↗
PubMed1981

Quantitation of experimental canine infarct size using multipinhole single-photon tomography.

A four-pinhole longitudinal tomographic system, with collimator and software, was developed for a standard-field portable scintillation camera. This system was used with technetium--99m pyrophosphate (Tc-PPi) to quantify the volume of infarcted myocardium in 27 dogs with experimental myocardial infarcts. These were induced by ligation of the left anterior descending (LAD) or the circumflex coronary artery. Tomographic estimations of scintigraphic infarct size agreed well with postmortem findings when the circumflex group (r = 0.87) and LAD group (r = 0.83) were considered separately, but the correlation fell when the groups were pooled (r = 0.73). Whereas multipinhole tomography extends Tc-PPi infarct sizing capability in animals to include posterior and subendocardial infarcts as well as anterior lesions, the tomographic sections contain enough blur artifacts to lower the sizing accuracy of the method. The main advantage of the technique may well be its ability to aid in detection and location of small myocardial infarcts.

Animals↗
PubMed1981

Quantitation of experimental canine infarct size with multipinhole and rotating-slanthole tomography.

Myocardial infarct size was estimated by three methods in a canine model, using Tc-99m pyrophosphate at 24 and 48 hr after coronary ligation. A gamma camera provided anterior, LAO, and lateral views, and was then fitted with multipinhole (MPH) and rotating-slanthole (RSH) collimators for tomographic studies, processed by computer to display frontal sections of the chest. Infarct weight was measured postmortem for comparison. All transmural infarcts were detected by all three imaging techniques. RSH tomography was superior to both MPH tomography and planar imaging for the detection of nontransmural infarction. Infarcts as small as 1.0 g were detected. Estimates of infarct volume measured from RSH slices showed an excellent correlation with infarct weight (r = 0.89) and were reproducible within acceptable limits. Estimates on infarct volume measured from MPH slices demonstrated a significantly poorer correlation with infarct weight (r = 0.48, p less than 0.01). Both tomographic techniques may improve infarct visualization by suppressing overlying activity and increasing contrast between infarct and background, but both produce significant blur artifacts that hamper their utilization by inexperienced observers.

Animals↗
PubMed1981

Osmotic blood-brain barrier disruption: pharmacodynamic studies in dogs and a clinical phase I trial in patients with malignant brain tumors.

Infusion of 25% mannitol in saline into the internal carotid artery of dogs disrupts the blood-brain barrier (BBB) in a controlled and reproducible manner (osmotic disruption), whereas mannitol infused through the common carotid artery produces variable disruption of the BBB. Compared to controls, infusion of methotrexate in dogs after osmotic disruption produced significantly higher drug levels in brain. We report very preliminary data on the effects of osmotic disruption with mannitol in five patients harboring malignant brain tumors.

Animals↗
PubMed1981

Simultaneous display of gated technetium-99m stannous pyrophosphate and gated blood-pool scintigrams.

We have developed a method by which any two sets of R-wave-synchronized radionuclide images may be registered, color-coded, and displayed in cinematic fashion so that the image sets are superimposed and shown simultaneously in contrasting colors. The technique has been applied to technetium-99m stannous pyrophosphate (Tc-99m PPi) and equilibrium blood-pool images. Gated Tc-99m PPi and gated blood-pool image sets (16 frames per cardiac cycle) were acquired in identical projections. Image sets were then registered, if necessary, and color-coded by a computer algorithm. Our initial experience suggests that this overlay technique may be of value to: (a) detect right ventricular infarction with greater precision; (b) provide a better estimate of anatomic location and circumferential extent of Tc-99m PPi myocardial uptake relative to the ventricular blood pool; and (c) distinguish between segmental contraction abnormalities caused by recent infarction (identified by abnormal Tc-99m PPi uptake) and segmental contraction abnormalities caused by ischemia or previous myocardial infarction.

Adult↗
PubMed1981

Effect of coronary blood flow and site of injection on Tc-99m PPi detection of early canine myocardial infarcts.

The effect of blood flow and site of injection on Tc-99m PPi uptake in acute myocardial infarction was studied in a group of 24 dogs. Temporary (3 hr) and permanent LAO occlusion models were used. Animals with the temporary occlusions showed scintigraphic visualization of the infarcts and reversal of the normal epito-endocardial Tc-99m PPi ratio in contrast to those with permanent coronary occlusions. The data demonstrate that early (within 3 hr) experimental canine myocardial infarcts can be detected with Tc-99m PPi if reflow to the area of infarction is provided. Delayed development of abnormal Tc-99m PPi scintigrams with acute infarction is related primarily to the initial lack of adequate blood flow to the damaged tissue, with subsequent development of adequate collateral flow allowing delivery and uptake of sufficient amount of the radiopharmaceutical for in vivo scintigraphic detection of the damaged area(s).

Animals↗
PubMed1980

Effect of selective coronary arteriography on left ventricular volumes and ejection fraction in man.

This study was performed to assess the influence of selective coronary arteriography on left ventricular volumes and ejection fraction in man. In 30 patients with assorted cardiac diseases, left ventricular end-diastolic and end-systolic volumes and ejection fraction were quantitated immediately before and after selective coronary arteriography. In 19 patients (Group A), contrast left ventriculography was performed immediately before and after selective coronary arteriography. In the remaining 11 patients (Group B), multigated equilibrium blood pool imaging was performed just before and after coronary arteriography. In both groups, mean systemic arterial pressure and heart rate did not change from just before the first to immediately before the second assessment of left ventricular volumes and ejection fraction, but left ventricular end-diastolic pressure increased. End-diastolic and end-systolic volume indexes, and ejection fraction did not change from just before to immediately after selective coronary arteriography. Therefore, selective coronary arteriography (1) consistently causes an increase in left ventricular end-diastolic pressure but (2) exerts no effect on left ventricular volumes and ejection fraction, even in patients with severely compromised left ventricular function.

Adult↗
PubMed1980

Nongeometric determination of left ventricular volumes from equilibrium blood pool scans.

This study assesses the utility of a scintigraphic, nongeometric technique for the determination of left ventricular volumes. Accordingly, gated blood pool scintigraphy and cineangiography were performed within a 24 hour period in 22 patients. Scintigraphic volume measurements were calculated from individual frames of a modified 35 degrees left anterior oblique projection using an algorithm designed to consider (1) the background-corrected left ventricular activity normalized for activity per milliliter of peripheral venous blood; (2) total study time; (3) number of frames acquired per cardiac cycle; and (4) percent of the cardiac cycle acquired. Angiographic volumes were calculated by the area-length method and the Kennedy regression equation. There was an excellent correlation between scintigraphic and angiographic methods for all volume measurements grouped together (r = 0.985, standard error of the estimate [SEE] = 14.6 ml) as well as for segregated end-diastolic volumes (r = 0.985, SEE = 16.2 ml) and end-systolic volumes (r = 0.988, SEE = 14.7 ml). Prospective testing of the independent ability of scintigraphy to estimate ventricular volumes was provided for by studying an additional 13 patients, and good agreement was found between scintigraphic and angiographic determinations of left ventricular end-systolic and end-diastolic volumes. Thus, radionuclide techniques, which are independent of geometric assumptions, may be utilized for the quantitation of left ventricular volumes.

Adult↗
PubMed1980

Cell surfaces and embryos: expression of the F9 teratocarcinoma antigen in T-region lethal, other lethal, and normal pre-implantation mouse embryos.

F9 teratocarcinoma antigen is expressed normally on embryos which are homozygous recessive for each of 4 mutations lethal in early development, including t12. Homozygosity for two post-implantation T-region developmental lethal genes, tw5 and T0r1, may alter F9 antigen expression but the results were not definitive. In addition, the time of appearance of the antigen may be affected by some of the genotypes.

Animals↗
PubMed1980

Radionuclide evaluation of cardiac trauma.

Radionuclides were first used in the evaluation of myocardial trauma as a noninvasive means to detect hemopericardium. At present an important use is in the diagnosis of myocardial contusion, which can be difficult to recognize clinically, and often has nonspecific EKG and enzyme alterations. Technetium-99m pyrophosphate scintigraphy has been shown to be of significant value in confirming this diagnosis. Myocardial scintigrams are helpful in determining the degree of damage produced by penetrating wounds of the heart and can also detect electrical injury to the heart from accidental shock or cardioversion. In addition, multiple gated blood pool scans can determine the hemodynamic significance of mycardial trauma and evaluate for late sequelae such as aneurysm formation.

Contusions↗
PubMed1980

Pathophysiologic considerations and clinicopathological correlates of technetium-99m stannous pyrophosphate myocardial scintigraphy.

99mTc-PYP myocardial scintigrams represent a means to detect and localize acute myocardial necrosis. These scintigrams are expected to be abnormal with acute myocardial infarcts of at least 3 grams in weight if serial imaging is utilized and proper attention to technique is provided. Any etiology of myocardial necrosis may produce abnormal 99mTc-PYP scintigrams if the damage is relatively localized and includes at least 3 grams of tissue. It is possible to accurately size acute anterior and anterolateral transmural myocardial infarcts using area or 2 dimensional measurements. Further development in imaging cameras and computer techniques allowing three dimensional reconstruction of myocardial infarcts with this and similar imaging techniques may allow relatively precise quantitation of other types of myocardial infarcts. The "doughnut" and "persistently abnormal" 99mTc-PYP scintigrams appear to have anatomic and prognostic significance at least in subsets of patients studied, but larger numbers of individuals need to be evaluated before final conclusions regarding their ultimate prognostic significance can be reached.

Animals↗
PubMed1980

Localization of anti-mitochondrial antibody in experimental canine myocardial infarcts.

Alterations in cell and subcellular membrane integrity occur during evolving ischemic myocardial injury. We tested the hypothesis that an antibody against human liver mitochondria [anti-mitochondrial antibody developing in a patient with primary biliary cirrhosis] could identify altered cell membrane integrity in experimental canine myocardial infarcts. The proximal left anterior descending coronary arteries of 12 dogs were ligated and 1 hr later 131I-labeled F(ab')2 fragments from either a control human IgG (6 dogs) or anti-mitochondrial IgG (6 dogs) were injected. The 131I-labeled F(ab')2 anti-mitochondrial fragments concentrated maximally in the central infarct subendocardium [infarct-to-normal ratio of 9.2 +/- 3.5 (mean +/- SD) vs. 4.6 +/- 3.3 for control F(ab')2 IgG, P < 0.05]. There was also 1 1/2- to 2-fold greater anti-mitochondrial antibody F(ab')2 accumulation in the central infarct epicardium and the peripheral infarct subendocardium and subepicardium. Thus, an anti-mitochondrial antibody obtained from a patient with primary biliary cirrhosis concentrates in irreversibly damaged myocardium after experimental canine myocardial infarction. Presumably this occurs because of altered cell membrane integrity, which allows exposure of mitochondria to the anti-mitochondrial antibody. The F(ab')2 fragments of anti-mitochondrial antibodies labeled with suitable radionuclides should allow noninvasive scintigraphic detection of experimental acute myocardial infarcts.

Animals↗
PubMed1980

Acute subendocardial myocardial infarction: its detection by Tc-99m stannous pyrophosphate myocardial scintigraphy.

Sixty-two patients hospitalized because of prolonged chest pain and initial electrocardiographic (ECG) changes of ST depression and T-wave inversion suggestive of acute subendocardial myocardial infarction were evaluated to determine the ability of Tc-99m-stannous pyrophosphate mycardial scintigraphy to detect the presence or absence of acute subendocardial myocardial necrosis. Three groups of patients were designated. Group A consisted of eight patients (13%) who developed reduction of R-waves of more than 25% or new Q-waves broader than 0.03 seconds; of these patients with acute transmural myocardial infarction, all had well-localized, abnormal scintigrams. Group B consisted of 30 patients with ECG changes and subsequent enzymatic documentation, including elevated serum creatine kinase-B levels as determined by radioimmunoassay, of the presence of acute subendocardial myocardial infarction. Of these, 27 had abnormal scintigrams, including 18 with well-localized patterns and nine with "poorly localized" patterns. Group C consisted of 24 patients (39%) with chest pain, but without enzymatic documentation of the presence of acute myocardial infarction (acute coronary insufficiency). Eight of these had abnormal scintigrams, including one with a well-localized pattern and seven with "poorly localized" patterns. In four of the latter, the scintigrams were "persistently positive" several weeks to months after a previous myocardial infarct. Serial myocardial imaging will be necessary to identify such patients.

Adult↗