Published Online
on May 15, 2009

A more recent version of this article appeared on July 1, 2009

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Original Article

Integration of Infarct Size, Tissue Perfusion and Metabolism by Hybrid Cardiac PET–CT–Evaluation in a Porcine Model of Myocardial Infarction

Riikka Lautamäki¹; Karl H. Schuleri¹; Tetsuo Sasano¹; Mehrbod S. Javadi¹; Amr Youssef¹; Jennifer Merrill¹; Stephan G. Nekolla²; M. Roselle Abraham¹; Albert C. Lardo¹ and Frank M. Bengel^1,3

¹ Johns Hopkins Medical Institutions, Baltimore, MD;
² Universität München, München, Germany

³ E-mail: fbengel1{at}jhmi.edu

Background—Hybrid PET–CT allows for combination of PET perfusion/metabolism imaging with infarct detection by CT delayed contrast enhancement. We employed this technique to obtain bio-morphologic insights into the interrelation between tissue damage, inflammation and microvascular obstruction early after myocardial infarction.

Methods and Results—A porcine model of LAD occlusion/reperfusion was studied. 7 animals underwent PET–CT within 3 days of infarction, and a control group of 3 animals was scanned at >4 weeks. Perfusion and glucose uptake were assessed by [¹³N]-ammonia/ [¹⁸F]-deoxyglucose, and 64–slice CT delayed contrast enhancement was measured. In the acute infarct model, CT revealed a no-reflow phenomenon suggesting microvascular obstruction in 80% of all infarct segments. PET showed increased FDG uptake in 68% of the CT–defined infarct segments. Ex vivo staining and histology showed active inflammation in the acute infarct area as an explanation for increased glucose uptake. In chronic infarction, CT showed no microvascular obstruction and agreed well with matched perfusion/metabolism defects on PET.

Conclusions—Perfusion/metabolism PET and delayed enhancement CT can be combined within a single hybrid PET–CT session. Increased regional FDG uptake in the acute infarct area is frequently observed. In contrast to the chronic infarct setting, this indicates tissue inflammation which is commonly associated with microvascular obstruction as identified by no reflow on CT. The consequences of these pathophysiologic findings for subsequent ventricular remodeling should be explored in further studies.

Key Words: myocardial infarction • CT • PET • hybrid imaging