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J Nucl Med. 2008; 49 (Supplement 1):30P
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Cardiovascular: Basic Science

New Approaches Using SPECT, PET and Hybrid Imaging

Tissue heterogeneity and impaired sympathetic innervation in the viable borderzone of myocardial infarction: An integrated PET-CT analysis of markers of arrhythmogenic potential

Riikka Lautamäki1, Andrew Holz1, Tetsuo Sasano1, Daniel Holt1, John Hilton1, Jennifer Merrill1, Albert Lardo1, Robert Dannals1, M. Roselle Abraham1 and Frank Bengel1

1 Johns Hopkins U, Baltimore, Maryland

120

Objectives: Areas of tissue heterogeneity in the infarct borderzone(BZ) contribute to ventricular arrhythmia and can be identified by MR or CT as mild delayed contrast enhancement. Likewise,impaired innervation of viable myocardium also contributes to arrhythmia. Combination of PET-CT may improve assessment of arrhythmogenic risk.We performed an initial feasibility study in an infarct(MI) model prone to arrhythmia.

Methods: 7 pigs underwent PET-CT using 64-slice GE Discovery Rx VCT 4-6 weeks after experimental MI.PET imaging of perfusion and sympathetic innervation was conducted with 13N-ammonia and 11C-epinephrine.CT was performed for coronary angiography and 10min delayed enhancement. Polarmap analysis was conducted to measure PET MI sizes(threshold 60%) and CT enhancement. On delayed CT, MI was defined as density>3.5SD, and BZ as density 2.5-3.5SD from remote.

Results: During the study, 3 arrhythmic events were recorded.On CT, overall MI size was 31±8% and BZ was 9±3%.On PET, normally perfused areas with impaired innervation were identified in BZ, comprising 6±3% of LV.Extent of BZ with CT and innervation/perfusion mismatch did not correlate significantly(r=0.44). In CT BZ,there was a relative reduction of innervation compared to perfusion, while this was not the case in remote myocardium (p=0.009). Density in PET mismatch areas was 25% higher than in remote on delayed CT.

Conclusions: Tissue heterogeneity as well as impaired innervation of viable myocardium are observed in the BZ of MI, and show only partial agreement.These two arrhythmia markers are thus complementary rather than competitive and may be integrated in a single PET-CT session for improved characterization of the arrhythmogenic substrate.





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Right arrow Articles by Bengel, F.
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Right arrow Articles by Bengel, F.