Biomedical subjects

R W Parkey

Publications and source records attributed to R W Parkey.

At least 145 records · Page 8Linked to original sources

PubMed1975

Acute subendocardial myocardial infarction in patients. Its detection by Technetium 99-m stannous pyrophosphate myocardial scintigrams.

Eighty-eight patients admitted to a coronary care unit with chest pain of varying etiology but without ECG evidence of an acute transmural myocardial infarction had myocardial scintigrams using technetium-99m stannour pyrophosphate (99m-Tc-PYP). Seventeen of these patients had ECG and enzymatic evidence suggestive of acute subendocardial myocardial infarction. In each of these the scintigrams were postivie demonstrating increased 99m-Tc-PYP uptake either in a faintly but diffusely positive pattern or in a well-localized strongly positive one. The remaining 71 patients did not evolve ECG or enzymatic evidence of acute myocardial infarction. In each of these patients the myocardial scintigram was negative. Thus 99m-Tc-PYP myocardial scintigrams are capable of identifying the presence of acute subendocardial myocardial infarction in patients. The absolute frequency with shich subendocardial myocardial infarction can be recognized utilizing this technique will have to be established in a larger number of patients in the future.

Acute Disease↗

PubMed1975

Technetium stannous pyrophosphate myocardial scintigrams in patients with chest pain of varying etiology.

Technetium-99m stannous pyrophosphate was utilized for myocardial imaging in 202 patients admitted to the hospital with chest pain of uncertain etiology. One hundred and one patients had clinical and evolved electrocardiographic and enzymatic evidence of acute myocardial infarction. Ninety-six of these 101 patients had increased myocardial uptake of the technetium stannous pyrophosphate and positive myocardial scintigrams; there was nearly precise correlation between the ECG and myocardial imaging localization of the area of infarction for acute transmural myocardial infarctions. In the five patients with negative myocardial images the scintigrams were obtained after seven or more days had elapsed following the myocardial infarction. In the remaining 101 patients no clinical, ECG, or enzymatic evidence of infarction developed; 92 of these patients had negative myocardial scintigrams. Seven of the remaining nine patients were admitted with "unstable angina pectoris", and despite the absence of diagnostic ECG and enzyme evolution each of these patients had faintly and diffusely positive myocardial scintigrams. The remaining two patients had positive myocardial scintigrams but no definite ECG or enzymatic evidence of acute myocardial infarction. Thus the technetium pyrophosphate imaging technique appears safe, inexpensive and to correlate well with ECG and enzyme identification of the presence of infarction and with ECG localization of myocardial infarction. In addition the positive myocardial scintigrams in some patients with "unstable angina" suggest that there may be limited myocardial necrosis that is ordinarily undetected by ECG and enzymes in these patients. The incidence of false positive and false negative scintigrams appears to be small.

Angina Pectoris↗

PubMed1975

Morphologic correlates of technetium-99m stannous pyrophosphate imaging of acute myocardial infarcts in dogs.

To obtain insight into the mechanism(s) responsible for the direct visualization of acute myocardial infarcts by myocardial scintigraphy with technetium-99m stannous pyrophosphate (99mTc-PYP), scintigraphic and morphologic studies were performed in 22 dogs subjected to occlusion of the proximal left anterior descending coronary artery (LAD). Grossly visible myocardial infarcts occurred in ten of 11 dogs with LAD occlusion for one day, five with LAD occlusion for two days, two with LAD occlusion for seven days and two with LAD occlusion for 13 days. Rare, microscopic foci of necrosis were observed in one dog with LAD occlusion for one day, and no lesions were present in two dogs subjected to temporary LAD occlusion for eight minutes and reflow for 24 hours. In the latter three dogs, 99mTc-PYP myocardial scintigrams were negative. In the 19 dogs with gross infarcts, 99mTc-PYP myocardial scintigrams were strongly positive at one and two days after LAD occlusion, much less positive at seven days and faintly positive at 13 days after occlusion. Positive myocardial scintigrams in most showed "doughnut" patterns, with marked peripheral concentration of radioactivity around central zones of much lower activity. On histologic examination, the one and two-day-old infarcts exhibited subendocardially located central zones and surrounding peripheral zones, both of which showed distinctive histopathological and histochemical features, including the selective occurrence in the peripheral zones of calcified muscle cells with ultrastructurally demonstrable apatite-like crystals in mitochondria. Selective occurrence of high tissue levels of 99mTc-PYP radioactivity also was demonstrated in the peripheral zones of four infarcts. Hearts with older infarcts (seven and 13 days) showed progressive replacement of necrotic myocardium by granulation tissue and progressive reduction in calcium deposits in the areas of damage. The data obtained in this study establish a temporal and topographical relationship between calcium accumulation in acute myocardial infarcts and 99mTc-PYP uptake responsible for scintigraphic detection of the lesions with this radionuclide in dogs subjected to proximal LAD occlusion.

Acute Disease↗

PubMed1975

Measurement of myocardial blood flow.

This paper represents a review of the recent literature on techniques to measure myocardial blood flow in man. A short discussion on flow meters in followed by a more detailed discussion of the radionuclide techniques used to measure myocardial blood flow. The radionuclide techniques are discussed in two groups: (1) qualitative measurement of blood flow using static images; and (2) quantitative measurements of blood flow using diffusible substances that actively enter the cell, radioactive labeled particles, and radioactive diffusible gases.

Absorptiometry, Photon↗

PubMed1975

Distributions of several agents useful in imaging myocardial infarcts.

Myocardial cell death due to infarction is accompanied by an influx of calcium ion. The calcium ion seems to localize in crystalline structures that form within mitochondria and resemble hydroxyapatite. Based on this phenomenon 99mTc-stannous pyrophosphate has been successfully used to image myocardial infarcts within 24 hr of infarction and 1 hr following tracer administration both in dogs and patient volunteers. In this report, canine distribution studies of 99m-Tc-pyrophosphate are compared with similar studies with 99mTc-stannous polyphosphate, 99mTc-stannous 1, hydroxy-ethylidene-1, 1-disodium phosphonate diphosphonate), and 18F as sodium fluoride. Pyrophosphate polyphosphate, and diphosphonate are each potentially useful in myocardial infarct imaging but bone uptake of 18F occurs sufficiently early to prevent the use of this radionuclide in infarct scintigraphy.

Animals↗

PubMed1974