Correlation of myocardial p-(123)I-iodophenylpentadecanoic acid retention with (18)F-FDG accumulation during experimental low-flow ischemia.
Myocardial ischemia is associated with reduced free fatty acid (FFA) beta-oxidation and increased glucose utilization. This study evaluated the potential of dynamic SPECT imaging of a FFA analog, p-(123)I-iodophenylpentadecanoic acid (IPPA), for detection of ischemia and compares retention of IPPA with (18)F-FDG accumulation.


METHODS
In a canine model of regional low-flow ischemia (n = 9), serial IPPA SPECT images (2 min per image) were acquired over 52--90 min. In a subset of dogs (n = 6), (18)F-FDG was injected after completing SPECT imaging and allowed to accumulate for 40 min before killing the animals. Flow was assessed with radiolabeled microspheres. Myocardial metabolism was evaluated independently by selective coronary arterial and venous sampling.


RESULTS
Serial IPPA SPECT images showed an initial defect in the ischemic region (0.70% plus minus 0.03% ischemic-to-nonischemic ratio), which normalized within 48 min because of the slower IPPA clearance from the ischemic region (t(1/2) = 54.2 plus minus 3.3 min) relative to the nonischemic region (t(1/2) = 36.7 plus minus 5.6 min) (P < 0.05). Delayed myocardial IPPA and (18)F-FDG activities were correlated (r = 0.70; n = 576 segments), and both were maximally increased in segments with a moderate flow reduction (IPPA, 151% of nonischemic; (18)F-FDG, 450% of nonischemic; P < 0.05).


CONCLUSIONS
Serial SPECT imaging showed delayed myocardial clearance of IPPA in ischemic regions with moderate flow reduction, which lead to increased late myocardial retention of IPPA. Retention of IPPA correlated with (18)F-FDG accumulation, supporting the potential of IPPA as a noninvasive marker of ischemic myocardium.
Shi
Cindy Q
CQ
Experimental Nuclear Cardiology Laboratory, Division of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8017, USA.
Young
Lawrence H
LH
Daher
Edouard
E
DiBella
Edward V R
EV
Liu
Yi-Hwa
YH
Heller
Eliot N
EN
Zoghbi
Sami
S
Wackers
Frans J Th
FJ
Soufer
Robert
R
Sinusas
Albert J
AJ
D000818:Animals; D003326:Coronary Circulation; D004285:Dogs; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006321:Heart / Q000000981:diagnostic imaging*; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007462:Iodobenzenes / Q000493:pharmacokinetics; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C025391:omega-(4-iodophenyl)pentadecanoic acid