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Radionuclide assessment of stunned myocardium by alterations in perfusion, metabolism and function
T Nishimura1, T Uehara, H W Strauss
1Department of Radiology, National Cardiovascular Center, Japan.
Insights
Diagnosing stunned myocardium is now possible using radionuclide cardiac imaging. This method assesses changes in myocardial perfusion, metabolism, and function for accurate acute diagnosis.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- A definitive method for diagnosing stunned myocardium remains elusive.
- Stunned myocardium has been observed post-intracoronary thrombolysis, unstable angina, and coronary revascularization.
Purpose of the Study:
- To evaluate the utility of radionuclide cardiac imaging in diagnosing stunned myocardium.
- To assess perfusion, metabolism, and function alterations in stunned myocardium.
Main Methods:
- Gated blood pool scanning in patients post-intracoronary thrombolysis.
- Semiquantitative assessment of thallium perfusion and regional wall motion in acute myocardial ischemia.
- Thallium and 123I-beta-methyliodophenyl pentadecanoic acid (BMIPP) fatty acid imaging in a canine reperfusion model.
Main Results:
- Early reperfusion (Rp < 4h) showed significant improvement in myocardial function compared to later reperfusion.
- Well-perfused asynergy (dissociation between perfusion and wall motion) was identified in 5.8% of segments in unstable angina patients, indicative of stunned myocardium.
- Mismatching of thallium and BMIPP uptake in the reperfusion model suggested increased myocardial triglyceride content and viability.
Conclusions:
- Radionuclide cardiac imaging can accurately diagnose stunned myocardium acutely.
- Assessment of perfusion, metabolism, and function provides a comprehensive approach to diagnosing stunned myocardium.
Abstract:
A method for the diagnosis of stunned myocardium has not yet been established, although it has been retrospectively demonstrated in patients after intracoronary thrombolysis, unstable angina, and coronary revascularization. In this study, radionuclide cardiac imaging was carried out to evaluate the existence of stunned myocardium. 1) Gated blood pool scanning was performed in patients undergoing intracoronary thrombolysis both at the time of reperfusion (Rp) and 10 days later. In the Rp less than 4 h group, about half of the initially abnormal segments showed complete improvement on quantitative wall motion analysis, which was more than in the Rp greater than 4 h and control groups. 2) In patients with acute myocardial ischemia, the correlation between thallium perfusion and regional wall motion was assessed semiquantitatively. In unstable angina, 5.8% of the ventricular wall segments showed dissociation between perfusion and wall motion (well-perfused asynergy). These segments had abnormal wall motion although perfusion was maintained, and were thought to be areas of stunned myocardium. 3) Fourteen dogs were studied using thallium and 123I-beta-methyliodophenyl pentadecanoic acid (BMIPP) fatty acid imaging to evaluate the relationship of perfusion to metabolism. In the reperfusion model, mismatching of the pattern of thallium and BMIPP uptake was observed. Reperfused myocardium probably has an increased triglyceride content, which is related to the degree of myocardial viability. In conclusion, stunned myocardium may be correctly diagnosed acutely on the basis of alterations in its perfusion, metabolism, and function by using radionuclide cardiac imaging.