Cardiac imaging and myocardial kinetics of technetium-tertiary butyl-isonitrile during dipyridamole-induced hyperemia.
To determine the myocardial kinetics of technetium-tertiary-butyl-isonitrile (Tc-TBI) during dipyridamole-induced hyperemia, the circumflex coronary arteries (LCX) of 15 dogs were partially occluded. Dipyridamole was then infused intravenously over 4 minutes, creating hyperemic flows in the anterior descending (LAD) coronary system. Tc-TBI was administered, then LAD and LCX regional myocardial Tc-TBI activities were continuously monitored with miniature detectors and gamma camera imaging over 3 hours. Microsphere-determined regional myocardial blood flows demonstrated an LCX/LAD flow ratio of 0.81 +/- 0.21 at rest and 0.45 +/- 0.24 (SD) during dipyridamole infusion. Three-hour fractional Tc-TBI clearance rates were minimal and were equal in the LAD (0.14 +/- 0.11) and LCX (0.13 +/- 0.12) zones (p = ns). Excellent gamma camera images, demonstrating the LCX defect, were obtained in all dogs. The correlation coefficient was 0.98 for regional myocardial blood flow vs initial Tc-TBI distribution.


CONCLUSIONS
(1) Dipyridamole vasodilation unmasked coronary stenoses despite no flow disparities at rest. (2) The initial distribution of Tc-TBI is proportional to regional myocardial blood flow. (3) There is minimal washout and no redistribution into the initial defect over time, and thus image quality is stable over time. (4) Tc-TBI myocardial kinetics may be applicable to closely related agents currently being developed.
Okada
R D
RD
Saint Francis Hospital Medical Research Institute, Cardiology of Tulsa, OK 74136.
Williams
S J
SJ
Glover
D K
DK
Dragatokis
D
D
D000818:Animals; D003326:Coronary Circulation; D003327:Coronary Disease / Q000000981:diagnostic imaging; D004176:Dipyridamole / Q000633:toxicity*; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging*; D006940:Hyperemia / Q000139:chemically induced* / Q000000981:diagnostic imaging; D008863:Microspheres; D009570:Nitriles; D009942:Organometallic Compounds; D015609:Organotechnetium Compounds; D011877:Radionuclide Imaging; D013667:Technetium
D009570:Nitriles; D009942:Organometallic Compounds; D015609:Organotechnetium Compounds; C043714:technetium Tc 99m hexakis(tert-butylisonitrile); D004176:Dipyridamole; D013667:Technetium