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Biomedical subjects

R W Parkey

Publications and source records attributed to R W Parkey.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1980

A computer-based scintigraphic method for sizing acute inferior myocardial infarcts.

A modeling procedure, employing multiple 99mTc-PYP myocardial scintigrams, was applied to acute inferoposterior myocardial infarcts in 12 dogs. Four modeling schemes were developed, and the model volume predictions were correlated with morphometrically determined infarct masses. Correlation values ranged from r = 0.66 (p less than 0.02) to r = 0.80 (p less than 0.005), suggesting that the method may enable noninvasive quantitative sizing of acute inferoposterior myocardial infarcts.

Animals↗
PubMed1980

Modified technetium-99m heparin for the imaging of acute experimental myocardial infarcts.

We have reported previously that technetium-99m heparin (TcH) accumulates in, and allows scintigraphic identification of, damaged canine myocardium occurring with temporary occlusion and reperfusion of the left anterior descending (LAD) coronary artery. A recent modification consists of using heparin from sheep lung, with stannous phosphate as the reducing agent. In 12 dogs with permanent LAD occlusion, six were injected intravenously with TcH (3--6 mCi) at 24 hr after occlusion, and six at 48 hr. Each experimental animal demonstrated relatively high TcH uptake in the left-ventircular infarct region as compared with normal myocardium. The in vivo scintigrams in all animals with gross myocardial infarcts were positive. The results suggest that this modified TcH has value for identifying experimental myocardial infarcts and that the reduced bone uptake, compared with that occurring with Tc-99m phosphates, may be an advantage for scintigraphic infarct detection.

Animals↗
PubMed1979

ST isopotential precordial surface maps in patients with acute myocardial infarction.

ST amplitude distributions were studied in 41 patients with acute myocardial infarction by deriving isopotential maps from a 5 x 7 electrode precordial matrix. Independent data on infarct size and localization were obtained utilizing the technetium 99m stannous pyrophosphate scintigraphic method. The locus of maximal ST elevation was stable for at least two days in 86% of 27 patients with anterior infarction. A single maximum or maximum-minimum was found in 88% but 22% of the patients had multiple maxima and/or minima in at least two maps. Areas of significant ST elevation were often excluded from the precordial matrix. The site of maximal ST elevation correlated with scintigraphic infarct site but was displaced medially in lateral infarction. The relation between infarct size and sigmaST elevation was significant and curvilinear. sigmaST underestimated size in large anterior infarction. The correlation of the size and the number of sites with ST elevation greater than or equal to 1.5 mm was weak (r = 0.56). The degree of ST abnormality in 14 patients with inferior infarction decreased significantly during the initial 24 hours. The isopotential maps were similar to those obtained in anterior infarction but the polarity was reversed. The results provide limited support for the continued exploration of ST analysis as a clinical method but suggest that sizing methods should be based on total body surface mapping, taking into account the geometry and electrical properties of the torso.

Action Potentials↗
PubMed1979

Clinicopathologic findings in 52 patients studied by technetium-99m stannous pyrophosphate myocardial scintigraphy.

Scintigraphic, clinical and pathological findings were correlated in 52 patients studied by technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigraphy before death or surgical resection of myocardium. Fifty-nine clinical events were studied with scintigraphy in the 52 patients; 41 of the 59 were associated with one or more abnormal 99mTc-PYP studies and 18 with normal 99mTc-PYP scintigrams. Myocardial scintigrams were positive in 29 of 31 cases with clinicopathological evidence of a corresponding discrete, grossly obvious acute myocardial infarct, including 16 of 16 transmural myocardial infarcts and 13 of 15 subendocardial infarcts. In 16 of 18 cases, negative myocardial scintigrams correlated with the absence of acute myocardial infarction determined by clinicopathological evidence. In two cases small subendocardial infarcts (less than 3 g) were not detected by 99mTc-PYP myocardial scintigraphy. Of the 12 additional instances of positive 99mTc-PYP myocardial scintigrams, five were associated with clinical unstable angina pectoris and seven were in the category of persistently positive scintigrams, since the scans were obtained 2.5 months or longer after proven or suspected acute myocardial infarcts. In all 12 instances, the positive 99mTc-PYP scintigrams were associated with evidence of multifocal irreversible myocardial damage consisting of myocytolysis, coagulation necrosis and/or fibrosis, and the histological age of the lesions was compatible with acute injury corresponding to the time of scintigraphy. The findings indicate that a positive 99mTc-PYP myocardial scintigram is a sensitive indicator of significant myocardial injury which may occur as confluent coagulation necrosis corresponding to clinical acute myocardial infarction, or as multifocal coagulation necrosis or myocytolysis associated with unstable angina pectoris or recurrent ischemic heart disease, especially after previous infarctions.

Acute Disease↗
PubMed1979

Detection of myocardial infarct extension by CK-B radioimmunoassay.

Myocardial infarct extension after the acute event was defined as a second reise in the myocardial isoenzyme of serum creatine kinase (CK-B) after the initial return of CK-B to normal values. In 43 patients with acute myocardial infarcts, CK-B was measured by radioimmunoassay every 12 hours for 14 days. Nineteen patients had anterior transmural myocardial infarcts AMI, 14 had inferior transmural myocardial infarcts (IMI) and 10 had subendocardial myocardial infarcts (SEMI). Infarct extension as detectd by a second rise in serum CK-B occurred in six patients (32%) with AMI, two (14%) with IMI and two (20%) with SEMI; these differences are not statistically significant. Infarct extension for all patients combined was 23%. Four patients with AMI also had infarct extension as determined by recurrent chest pain. ECG alterations and other enzyme changes. In the other six, the infarct extension was undetected clinically. Four patients with AMI and infarct extension died within 3 weeks after hospitalization. We did not note any additional morbidity or mortality in patients with infarct extension who had IMI or SEMI. There was no significant difference in the frequency of previous myocardial infarction, history of hypertension, diabetes mellitus or smoking history in patients with and without infarct extension shown by serum CK-B isoenzyme elevations. The measurement of serum CK-B values with a quantitative and sensitive assay suggests that myocardial infarct extension occurs more commonly than clinically recognized, but the frequency of extension may be less than that reported in patients in whom precordial mapping and total serum CK values were measured to identify this phenomenon.

Adult↗