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Title: Radionuclide methods for evaluating the results of thrombolytic therapy

Abstract

In summary, a variety of nuclear techniques may be used to investigate the effects of thrombolytic therapy and myocardial reperfusion. Assessments of global and regional ventricular function, myocardial perfusion, and metabolic integrity are available and appear to add substantially to conventional assessment. Timing of studies appears to be critical. Complementary data can be obtained in both the acute and convalescent phase of myocardial infarction. 49 references.

Authors:
;
Publication Date:
Research Org.:
Yale Univ. School of Medicine, New Haven, CT
OSTI Identifier:
6371716
Resource Type:
Journal Article
Resource Relation:
Journal Name: Circulation; (United States); Journal Volume: 76
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; FIBRINOLYTIC AGENTS; EVALUATION; HEART; DYNAMIC FUNCTION STUDIES; MYOCARDIAL INFARCTION; DIAGNOSIS; MEASURING METHODS; NUCLEAR MEDICINE; ORGANOMETALLIC COMPOUNDS; PYROPHOSPHATES; TECHNETIUM ISOTOPES; THALLIUM ISOTOPES; BODY; CARDIOVASCULAR DISEASES; CARDIOVASCULAR SYSTEM; DISEASES; DRUGS; HEMATOLOGIC AGENTS; ISOTOPES; MEDICINE; ORGANIC COMPOUNDS; ORGANS; OXYGEN COMPOUNDS; PHOSPHORUS COMPOUNDS 550601* -- Medicine-- Unsealed Radionuclides in Diagnostics

Citation Formats

Zaret, B.L., and Wackers, F.J. Radionuclide methods for evaluating the results of thrombolytic therapy. United States: N. p., 1987. Web.
Zaret, B.L., & Wackers, F.J. Radionuclide methods for evaluating the results of thrombolytic therapy. United States.
Zaret, B.L., and Wackers, F.J. 1987. "Radionuclide methods for evaluating the results of thrombolytic therapy". United States. doi:.
@article{osti_6371716,
title = {Radionuclide methods for evaluating the results of thrombolytic therapy},
author = {Zaret, B.L. and Wackers, F.J.},
abstractNote = {In summary, a variety of nuclear techniques may be used to investigate the effects of thrombolytic therapy and myocardial reperfusion. Assessments of global and regional ventricular function, myocardial perfusion, and metabolic integrity are available and appear to add substantially to conventional assessment. Timing of studies appears to be critical. Complementary data can be obtained in both the acute and convalescent phase of myocardial infarction. 49 references.},
doi = {},
journal = {Circulation; (United States)},
number = ,
volume = 76,
place = {United States},
year = 1987,
month = 8
}
  • Myocardial thallium-201 scintigraphy is being increasingly employed as a method for assessing the efficacy of coronary reperfusion in acute myocardial infarction. New thallium uptake after intracoronary tracer administration after successful recanalization indicates that nutrient blood flow has been successfully restored. One may also presume that some myocardial salvage occurred if thallium administered in this manner is transported intracellularly by myocytes with intact sarcolemmal membranes. However, if one injects thallium by way of the intracoronary route immediately after reperfusion, the initial uptake of thallium in reperfused myocardium may predominantly represent hyperemic flow and regional thallium counts measured may not be proportionalmore » to the mass of viable myocytes. When thallium is injected intravenously during the occlusion phase the degree of redistribution after thrombolysis is proportional to the degree of flow restoration and myocardial viability. When thallium is injected for the first time intravenously immediately after reperfusion, an overestimation of myocardial salvage may occur because of excess thallium uptake in the infarct zone consequent to significant hyperemia. Another approach to myocardial thallium scintigraphy in patients undergoing thrombolytic therapy is to administer two separate intravenous injections before and 24 hours or later after treatment. Finally, patients with acute myocardial infarction who receive intravenous thrombolytic therapy are candidates for predischarge exercise thallium-201 scintigraphy for risk stratification and detection of residual ischemia.« less
  • Thallium-201 imaging has been utilized to estimate myocardial salvage after thrombolytic therapy for acute myocardial infarction. However, results from recent animal studies have suggested that as a result of reactive hyperemia and delayed necrosis, thallium-201 imaging may overestimate myocardial salvage. To determine whether early overestimation of salvage occurs in humans, intracoronary thallium-201 scans 1 hour after thrombolytic therapy were compared with intravenous thallium-201 scans obtained approximately 10 and 100 days after myocardial infarction in 29 patients. In 10 patients with angiographic evidence of coronary reperfusion, immediate improvement in thallium defects and no interim clinical events, there was no change inmore » imaging in the follow-up studies. Of nine patients with coronary reperfusion but no initial improvement of perfusion defects, none showed worsening of defects in the follow-up images. Six of these patients demonstrated subsequent improvement at either 10 or 100 days after infarction. Seven of 10 patients with neither early evidence of reperfusion nor improvement in perfusion defects had improvement of infarct-related perfusion defects, and none showed worsening. In conclusion, serial scanning at 10 and 100 days after infarction in patients with no subsequent clinical events showed no worsening of the perfusion image compared with images obtained in acute studies. Therefore, there is no evidence that thallium-201 imaging performed early in patients with acute myocardial infarction overestimates improvement.« less
  • To investigate prospectively the occurrence and significance of postinfarction transient left ventricular dysfunction, 33 ambulatory patients who underwent thrombolytic therapy after myocardial infarction were monitored continuously for 187 +/- 56 min during normal activity with a radionuclide left ventricular function detector at the time of hospital discharge. Twelve patients demonstrated 19 episodes of transient left ventricular dysfunction (greater than 0.05 decrease in ejection fraction, lasting greater than or equal to 1 min), with no change in heart rate. Only two episodes in one patient were associated with chest pain and electrocardiographic changes. The baseline ejection fraction was 0.52 +/- 0.12more » in patients with transient left ventricular dysfunction and 0.51 +/- 0.13 in patients without dysfunction (p = NS). At follow-up study (19.2 +/- 5.4 months), cardiac events (unstable angina, myocardial infarction or death) occurred in 8 of 12 patients with but in only 3 of 21 patients without transient left ventricular dysfunction (p less than 0.01). During submaximal supine bicycle exercise, only two patients demonstrated a decrease in ejection fraction greater than or equal to 0.05 at peak exercise; neither had a subsequent cardiac event. These data suggest that transient episodes of silent left ventricular dysfunction at hospital discharge in patients treated with thrombolysis after myocardial infarction are common and associated with a poor outcome. Continuous left ventricular function monitoring during normal activity may provide prognostic information not available from submaximal exercise test results.« less
  • Fourteen patients with transmural acute myocardial infarction (AMI) were treated with intravenous streptokinase a mean of 4 +/- 1 hours after chest pain and underwent technetium-99m stannous pyrophosphate (Tc-99m-PPi) imaging 7 +/- 2 hours after the onset of chest pain. The early Tc-99m-PPi images were obtained to test the hypothesis that an early, strongly abnormal Tc-99m-PPi image suggests reperfusion. Eleven of 14 patients had early peaking (within 16 hours) serum creatine kinase isoenzyme levels (CK-B) at a mean of 11 +/- 3 hours. Ten of 14 patients had 3+ or 4+ acute Tc-99m-PPi images. Eight of 11 patients had patentmore » infarct-related vessels at cardiac catheterization 15 days after AMI. One patient who had both an early positive Tc-99m-PPi image and CK-B peak level had an occluded infarct-related artery at catheterization. Acute left ventricular (LV) ejection fraction (EF) by radionuclide ventriculography was compared with LVEF on day 15, and improved from 0.37 +/- 0.13 to 0.50 +/- 0.16 (p = 0.004) in the 10 patients with strongly positive acute Tc-99m-PPi images. LVEF also improved from 0.37 +/- 0.12 to 0.49 +/- 0.15 (p = 0.003) in the 11 patients with early peaking serum CK-B values. Three patients without evidence of reperfusion failed to improve the LVEF from the initial value to the one obtained at hospital discharge. Six control patients had acute Tc-99m-PPi images 10 +/- 2 hours after chest pain; none had strongly positive acute Tc-99m-PPi images, and the mean time to peak CK-B was 19 +/- 5 hours.(ABSTRACT TRUNCATED AT 250 WORDS)« less
  • Whereas coronary arteriography demonstrates success of reflow or recanalization after intracoronary thrombolysis, myocardial perfusion imaging with thallium-201 (/sup 201/Tl) permits assessment of viability of reperfused myocytes. The initial distribution of /sup 201/Tl in the myocardium immediately after intravenous injection is the result of both blood flow delivery of the radionuclide to the heart and the extraction fraction for /sup 201/Tl. If /sup 201/Tl is administered during a period of coronary occlusion, a scintigraphic defect will be observed in the territory of the occluded vessel. If, subsequently, blood flow is restored, as with reperfusion, and cellular kinetics transport of /sup 201/Tlmore » returns to normal, myocardial regions initially deprived of /sup 201/Tl will demonstrate delayed redistribution and the defect will tend to normalize within several hours. In a sustained coronary occlusion, the defect will persist after /sup 201/Tl injection. Specific imaging protocols that have been or can be used to assess thrombolytic therapy are reviewed. If intracoronary streptokinase infusion is associated with a substantial enhancement of perfusion and preservation of cellular integrity in the ischemic zone, delayed /sup 201/Tl images obtained several hours after intravenous injection of the radionuclide will demonstrate significantly more /sup 201/Tl activity than the images before reflow. Direct intracoronary injections of /sup 201/Tl down the infarct vessel have also been used to evaluate the benefit of thrombolytic therapy by the demonstration of increased /sup 201/Tl uptake after reperfusion in the ischemic zone. Finally, computer methods for subtracting serial images obtained after two separate intravenous /sup 201/Tl injections administered before and after streptokinase infusion might be used to derive a ''functional image'' of the ischemic region that would quantitatively be proportional to the amount of myocardial salvage achieved.« less