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J Nucl Med. 2008; 49 (Supplement 1):31P
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Cardiovascular: Basic Science

New Approaches Using SPECT, PET and Hybrid Imaging

Multi-tracer PET characterization of impaired myocardial sympathetic innervation in viable infarct borderzone

Riikka Lautamäki1, Tetsuo Sasano1, Daniel Holt1, Jennifer Merrill1, John Hilton1, Stephan Nekolla1, Albert Lardo1, Robert Dannals1, M. Roselle Abraham1 and Frank Bengel1

1 Johns Hopkins U, Baltimore, Maryland

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Objectives: After myocardial infarction(MI),sympathetic nerve damage exceeds scar and promotes ventricular arrhythmia.We aimed to study the biology of neuronal damage using 3 tracers with different kinetic properties in a model of chronic MI.

Methods: A 2-day PET protocol was employed using GE Discovery Rx VCT in 7 pigs,4-6 weeks after reperfused MI.On day 1,perfusion was measured with N13-ammonia(NH3),followed by dynamic imaging with C11-epinephrine(EPI;vesicular storage with no significant washout in healthy subjects).On day 2,C11-hydroxyephedrine(HED;neuronal uptake with no significant washout)and C11-phenylephrine(PHEN;vesicular leakage with washout)were employed.Using polarmap analysis tracer retention and washout rates were compared globally and regionally in NH3-defined infarct(<60% uptake of maximum), borderzone(50-70%) and remote region(>70%).

Results: Pigs had LV dysfunction(EF 40.2±5.9%)and some had inducible VT. For all 3tracers,defect size exceeded perfusion defect(45±7%LV for EPI,43±7% for HED,48±5% for PHEN vs 39±8% for ammonia),and relative regional retention was below perfusion in borderzone,but not in infarct and remote areas. EPI showed global washout(1.2±0.3%/min),which was comparable to PHEN(1.1±0.3%/min),and absent with HED(-.6±.2%/min; p<.01).Regionally, EPI washout was 17/27% higher in the borderzone than in infarct/remote area.

Conclusions: In our model,neuronal damage in the infarct borderzone is mostly due to absolute denervation,as evidenced by reduced uptake of all 3 catecholaminergic tracers.Abnormally increased global and regional epinephrine washout suggests an additional component of impaired vesicular storage/increased catecholamine turnover which may represent reversible impairments and thus be a target of therapeutic intervention.





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