Technetium-99m stannous pyrophosphate "hot spot" imaging to detect acute myocardial infarcts.
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Animals↗
Biomedical subjects
R W Parkey
Publications and source records attributed to R W Parkey.
Scintigraphic evaluation of left ventricular function.
Scintigraphic studies, performed with a scintillation camera and a small computer, can provide information concerning total and regional left ventricular function (Table 1). Of the two types of studies (first-pass and gated blood pool) the gated blood study is more appropriate for studies of regional function than is the first-pass method. Ejection fraction, an index of global ventricular function, is measureable from first-pass or gated blood pool studies. Gated blood pool studies allow visual assessment of net ventricular function as well as the local functional status of the myocardium. Multiple gated blood pool studies allow computation of ventricular volume curves, from which ejection fraction and ejection rate may be determined. There are several areas of application for these relatively inexpensive and virtually noninvasive studies. In patients with recent myocardial infarction, visual assessment of regional ventricular wall motion and quantitative measurement of ejection fraction provide additional prognostic information, especially when measured serially. In patients with coronary artery disease, the development of regional ventricular wall motion abnormalities may indicate local myocardial ischemia. Consequently, scintigraphic imaging may add significantly to the usefulness of exercise stress testing.
Heart Ventricles↗
Unstable angina pectoris: a randomized study of patients treated medically and surgically.
Fifty patients with the clinical syndrome of unstable angina pectoris were evaluated. Twenty-seven were randomized into medical or surgical treatment groups and subsequently followed up. The results of the study reveal that: (1) there is approximately a 16 percent incidence rate of significant left main coronary artery disease in patients with this entity at our institution; (2) 10 percent of patients do not have angiographically significant coronary artery disease; (3) pain relief is better in the surgically treated patients, but the 1 1/2 year survival rate is not significantly different between the groups; (4) 50 percent of the medically treated patients again had the syndrome of unstable angina pectoris in the initial few months of the follow-up period; (5) the operative and late postoperative mortality rate in patients presenting with unstable angina pectoris and left main coronary artery disease in this small group of patients was 43 percent; and (6) four of six patients with this syndrome whose condition was deemed inoperable and who were not randomized died within the subsequent few months.
Angina Pectoris↗
Submaximal exercise testing after acute myocardial infarction: myocardial scintigraphic and electrocardiographic observations.
The relation between global and regional left ventricular function and electrocardiographic signs of ischemia at rest and during submaximal supine exercise was studied in 27 patients 2 to 3 weeks after acute myocardial infarction. Dynamic myocardial scintigraphy was performed at rest and during submaximal exercise utilizing an in vivo method of labeling red blood cells with technetium-99m pertechnetate. Gated radionuclide blood pool scintigrams were obtained in a modified left anterior oblique, and in some patients also in the right anterior oblique projection, to measure left ventricular ejection fraction and segmental wall motion. Electrocardiographic monitoring of heart rate and rhythm was provided during the exercise. The submaximal exercise test was terminated when the patient's heart rate reached 125 beats/min or if angina, malignant ventricular ectopy or electrocardiographic evidence of myocardial ischemia developed before this rate was reached. The data demonstrate that patients with a recent anterior myocardial infarct, in contrast to patients with a recent inferior or nontransmural infarct, manifest a significant reduction in left ventricular ejection fraction with submaximal exercise. Of the eight patients with an anterior infarct, seven had segmental wall motion abnormalities at rest. Four of these eight manifested more severe abnormalities with submaximal exercise; three had abnormalities at rest that did not change with exercise. Four of the eight had a positive electrocardiographic response during exercise (two were taking digoxin). Of these four, only two had more marked wall motion abnormalities with effort. Of the 13 patients with an inferior infarct, 11 had apparently normal wall motion in the modified left anterior oblique projection at rest, including 2 who manifested segmental wall motion abnormalities with submaximal exercise; the 2 remaining patients had wall motion abnormalities at rest that, on exercise, became more marked in one and were unchanged in one. Four of the 13 had a positive electrocardiographic response with exercise (one was taking digoxin); only one of these had a detectably more severe wall motion abnormality with exercise. Of the six patients with a nontransmural infarct, four had no identifiable wall motion abnormalities at rest; in one of these, an abnormality developed with exercise. The remaining two patients had wall motion abnormalities at rest; in one, a positive electrocardiographic ischemic response developed with exercise. Patients with an anterior infarct appear to have a different functional ventricular response to submaximal exercise at the time of hospital discharge than patients with an inferior or nontransmural infarct. To identify ischemic responses with submaximal exercise in these patients one should ideally use both electrocardiographic monitoring and dynamic myocardial scintigraphy.
Adult↗
Thallium-201 myocardial perfusion studies in patients with the mitral valve prolapse syndrome.
To determine whether regional myocardial ischemia plays a role in patients with the mitral valve prolapse syndrome, we examined myocardial perfusion with exercise stress testing and thallium-201 myocardial scintigraphy. Twelve patients were studied, 11 women and one man aged 18 to 56 years, mean age 30 years. In all patients, mitral valve prolapse was documented by echocardiography or phonocardiography. Patients over 35 years of age underwent cardiac catheterization. Electrocardograms disclosed abnormalities during maximal exercise in eight of the 12 patients. In two patients, angina developed during exercise. Thallium-201 (201Tl) scintigrams were normal in the 11 patients with presumed or documented normal coronary arteries. One patient, in whom an apical defect was demonstrated on scintigraphy, had significant disease of the left main and left anterior descending coronary artery. Repeat testing after successful aortocoronary bypass grafting revealed improved exercise capacity and a normal 201Tl myocardial scintigram. The data indicate that patients with mitral valve prolapse alone do not have regional myocardial ischemia and that the presence of a defect on 201Tl myocardial scintigraphy following maximal stress testing would suggest the existence of concomitant coronary artery disease.
Adolescent↗
Radionuclide brain imaging--its role and relation to CT scanning.
Separate CNS disease entities are discussed with either the complementary or exclusive indications for radionuclide brain imaging and computerized cranial tomography. Either modality alone has a potential overall precision somewhat in excess of 90% in the localization of cerebral lesions with the effectiveness of each modality differing according to the histology and anatomic location of the lesion. Most investigators agree that the combined application of the two procedures is far superior to their separate use. Routine dynamic isotope studies are essential and in addition, new radiopharmaceuticals and technological advances may improve the radionuclide evaluation of CNS disease. Areas discussed include: primary and secondary CNS neoplasms; acute cerebrovascular accidents; arteriovenous malformations; traumatic cerebrovascular disease; hydrocephalus and dementia; and intracranial inflammatory processes.
Adult↗
Computed tomography for localization and sizing of experimental acute myocardial infarcts.
Computed tomography (CT) has been used to quantitate acute myocardial infarct size in isolated, arrested canine hearts. Acute myocardial infarcts were produced in 20 hearts by either left anterior descending (13 dogs) or circumflex coronary artery ligation (seven dogs). Each animal was given iodinated contrast media intravenously immediately before sacrifice 24--72 hours postinfarction. All infarcts greater than 1 g and one of three infarcts 0.5 g or less were detected by CT imaging. Infarct volume determined by CT correlated with gross infarct weight (r=0.83). CT imaging, however, consistently underestimated infarct volume; underestimation was largest in a group of patchy, predominantly subendocardial infarcts. As adequate equipment and techniques for in vivo studies are developed, CT imaging of the heart may become important in clinical evaluation of myocardial infarction.
Acute Disease↗
Fatty acid accumulation and abnormal lipid deposition in peripheral and border zones of experimental myocardial infarcts.
Twenty-eight dogs with acute anterior myocardial infarcts due to proximal occlusion of the left anterior descending coronary artery (LAD) were studied at various periods following the occlusion to determine: (a) the time course and location of abnormal lipid accumulation after infarction, (b) the degree of muscle-cell injury associated with increased lipid deposition, and (c) whether uptake of fatty acid from the circulating fat pool contributes to lipid accumulation in certain myocardial regions. The findings show that myocardial lipid accumulation begins as early as 6 hr after proximal LAD occulsion. The increased lipid deposition occurs as nonmembrane-bound lipid droplets in muscle cells with and without ultrastructural evidence of irreversible injury. Analysis of tissue uptake of intravenoulsy injected [14C] oleic acid conjugated with albumin revealed relatively selective concentration of label in the peripheral and border regions of the infarct, but occasionally even the central subendocardial portion of the infarct concentrated the fatty acid. Thin-layer chromotography showed that most of the label was associated with the triglyceride fraction when the radiolabeled fatty acid was injected 6 or 24 hr after LAD occlusion. These myocardial cellular and topographical alterations will have to be considered when labeled fatty acids are used for imaging acute myocardial infarcts and/or if attempts are made to identify myocardial fat-laden cells scintigraphically.
Animals↗
Technetium-labeled heparin: preliminary report of a new radiopharmaceutical with potential for imaging damaged coronary arteries and myocardium.
Heparin has been labeled with [99mTc] pertechnetate and its ability to image damaged coronary vessels and myocardium during and following myocardial ischemia has been studied in experimental animals. The data obtained indicate that Tc-99m heparin localizes in damaged myocardium and coronary vessels in canine models of temporary myocardial ischemia and reperfusion and in damaged myocardium during fixed coronary occlusion. Scintigraphic detection of damaged myocardium was possible in both models, but the highest levels of Tc-99m heparin in damaged myocardial tissue were found in those dogs with temporary coronary occlusion and reflow. The data suggest that Tc-99m heparin may be of value as a positive imaging agent when coronary arteries or myocardium are injured and either reperfusion is allowed and/or significant blood flow persists in the damaged area.
Animals↗
Is there a need for additional means of recognizing myocardial necrosis?
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Acute Disease↗
Intestinal duplication detected with technetium-99m sodium pertechnetate imaging of the abdomen.
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Child↗
Myocardial infarct imaging with technetium-99m phosphates.
Technetium-99m-phosphate imaging is particularly valuable in detecting (1) small transmural infarcts (3 g and larger in size); (2) new acute transmural infarcts in or near regions of old infarction; (3) acute subendocardial infarcts (larger than 3 g in size); (4) acute infarction in patients with left bundle branch block; and (5) perioperative myocardial infarction. Localization of inferior and posterior myocardial infarction is improved with imaging. Sizing of acute anterior and lateral infarcts has been accurately done in dogs and should prove helpful in patients. Extensive evaluation in both experimental animals and in patients has shown 99mTc-phosphate myocardial imaging to be a useful clinical tool, and it may be one of the most sensitive noninvasive ways presently available to identify acute myocardial necrosis. It is important to understand that 99mTc-phosphate imaging has a different pathophysiology basis from EKG's or serum enzymes. These tests do not compete but instead should complement one another.
Acute Disease↗
Sizing acute myocardial infarcts: present limitations and potential approaches.
It is now possible by scintigraphic imaging to identify the presence of acute transmural or nontransmural myocardial infarcts by noninvasive techniques and to localize acute transmural infarcts. Radionuclide blood-pool scintigraphy allows assessment of the impact of old and new myocardial damage on left ventricular function.
Heart↗
Infarct sizing with technetium-99m stannous pyrophosphate scintigraphy in dogs and man; relationship between scintigraphic and praecordial mapping estimates of infarct size in patients.
The present study was performed in order to evaluate the ability of technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigrams to size infarcts in experimental animals and man. In 10 dogs with proximal left anterior descending coronary artery occlusion and acute anterior myocardial infarcts, there was a significant correlation between scintigraphic infarct size and histological infarct weight (P less than 0.01). In 25 patients with acute anterior or anterolateral myocardial infarcts, there was a significant correlation between relatively large infarct size determined scintigraphically and the acute development of left ventricular failure. There was some overlap, however, in 99mTc-PYP scintigraphic infarct size between patients who did and did not develop left ventricular failure with infarction. Presumably this is explained by some patients having had earlier myocardial damage and thus developing left ventricular failure with relatively small new infarcts. There was also a statistically significant, but weak, correlation in patients between scintigraphic infarct size and precordial ST segment mapping including peak ST segment elevation (P less than 0.05) and the number of praecordial sites with ST segment elevation equal to or greater than 2 mm (P less than 0.01). The data suggest that 99mTc-PYP scintigrams and praecordial mapping measure some similar but some dissimilar aspects of infarct size in patients, and that 99mTc-PYP scintigraphy does size acute anterior and anterolateral infarcts in experimental animals and patients.
Animals↗
Computed tomography: in vitro evaluation of myocardial infarction.
An in vitro study of computed tomographic (CT) scanning of experimental myocardial infarction (MI) was performed by studying isolated canine hearts 18 to 48 yrs. post-infarction. CT scanning does not detect histologically present calcification in the area of an MI, but can be used to identify wall thickness changes in these areas. Decreased attenuation coefficients are found infarcted myocardium where thinning is present. The potential CT scanning to detect areas of MI is confirmed.
Animals↗
Positive 99mTc-stannous pyrophosphate myocardial image in a patient with carcinoma of the lung.
A "false-positive" 99mTc-stannous pyrophosphate (99mTc-PYP) myocardial image was seen in a patient with epidermoid carcinoma of the lung. The location of the increased activity corresponded to an area of direct invasion of the heart by carcinoma with associated multiple microscopic foci of myocardial necrosis. Metastatic carcinoma with myocardial necrosis should therefore be considered as a possible cause of a positive 99mTc-PYP myocardial image.
Aged↗
Clinicopathologic study of persistently positive technetium-99m stannous pyrophosphate myocardial scintigrams and myocytolytic degeneration after myocardial infarction.
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Acute Disease↗
Sites and mechanisms of localization of technetium-99m phosphorus radiopharmaceuticals in acute myocardial infarcts and other tissues.
This study was performed to elucidate the localization at the cellular level of technetium-99m phosphorus ((99m)Tc-P) radiopharmaceuticals in acute myocardial infarcts and the mechanisms responsible for (99m)Tc-P uptake in acute myocardial infarcts and other tissues. In 20 dogs with proximal left anterior descending coronary arterial ligation for 1-3 days, elevated calcium levels were measured at all sites of increased (99m)Tc-P uptake (acute myocardial infarcts, necrotic thoracotomy muscle, lactating breast, and normal bone); however, a consistent linear relationship between (99m)Tc-P and calcium levels was not observed. A strong correlation (r = 0.95 and 0.99, n = 2 dogs) was demonstrated between levels of (3)H-diphosphonate and (99m)Tc-P in infarcted myocardium. Autoradiographic studies with (3)H-diphosphonate revealed extensive labeling in the infarct periphery which contained necrotic muscle cells with features of severe calcium overloading, including widespread hypercontraction as well as more selective formation of mitochondrial calcific deposits. Autoradiography also demonstrated labeling of a small population of damaged border zone muscle cells which exhibited prominent accumulation of lipid droplets and focal, early mitochondrial calcification. Cell fractionation studies revealed major localization of both (99m)Tc-P and calcium in the soluble supernate and membrane-debris fractions of infarcted myocardium and less than 2% of total (99m)Tc-P and calcium in the mitochondrial fractions; however, electron microscopic examination showed that mitochondria with calcific deposits were not preserved in the mitochondrial fractions. In vitro studies evaluating the role of serum protein binding on tissue uptake of (99m)Tc-P agents demonstrated that, in spite of significant complexing with serum proteins, serum (99m)Tc-P activity retained the ability to adsorp to calcium hydroxyapatite and amorphous calcium phosphate. In vivo studies showed that concentration of human serum albumin (labeled with iodine-131) in infarcted myocardium reached a maximum of only 3.8 times normal after a circulation time of 96 h, whereas (99m)Tc-P uptake was at least 10 times normal after a circulation time as short as 1 h. It is concluded that: (a) (99m)Tc-P uptake in acutely infarcted myocardium, and possibly other types of soft tissue damage, is limited to necrotic and severely injured cells; (b) concentration of (99m)Tc-P results from selective adsorption of (99m)Tc-P with various forms of tissue calcium stores, including amorphous calcium phosphate, crystalline hydroxyapatite, and calcium complexed with myofibrils and other macromolecules, possibly supplemented by calcium-independent complexing with organic macromolecules; and (c) lack of a linear relationship between (99m)Tc-P and tissue calcium levels mainly results from local differences in composition and physicochemical properties of tissue calcium stores and from local variations in levels of blood flow for delivery of (99m)Tc-P agents.
Animals↗