Effects of intracoronary dipyridamole infusion on regional myocardial blood flow and intrinsic thallium-201 washout in dogs with a critical coronary stenosis.
Intravenous dipyridamole (DP) infusion produces a significant endocardial-to-epicardial flow gradient distal to a critical coronary stenosis, resulting in diminished regional thallium-201 (Tl-201) uptake and washout. Intravenous DP can also produce a significant decrease in arterial blood pressure and therefore in coronary perfusion pressure. We determined to further clarify the mechanism of this transmural coronary "steal" employing intracoronary DP administration, thereby avoiding systemic hypotension. In five of eight dogs with a critical left anterior descending (LAD) stenosis, intracoronary DP caused no significant fall in systemic arterial pressure, a rise in epicardial flow from 1.15 +/- 0.2 to 1.75 +/- 0.2 ml/min/gm, and a slight fall in subendocardial flow from 1.15 +/- 0.2 to 1.03 +/- 0.5 ml/min/gm. Intracoronary DP caused no prolongation of the intrinsic Tl-201 washout rate. In three dogs that developed systemic hypotension after intracoronary DP, endocardial flow fell from 1.14 to 0.63 ml/min/gm, the epicardial/endocardial flow ratio fell to 0.35, and Tl-201 washout became more prolonged. Thus intracoronary DP in the setting of a critical LAD stenosis caused minimal endocardial-to-epicardial steal and had no effect on the intrinsic Tl-201 washout rate unless it was accompanied by a fall in systemic arterial pressure. The magnitude of the transmural steal was substantially less than reported in our previous experiments utilizing intravenous DP infusion. This study provides a further insight into the mechanism of DP-induced subendocardial ischemia and suggests that systemic hemodynamic alterations play an important role in the effects of the vasodilator on myocardial blood flow and Tl-201 kinetics.
Beller
G A
GA
Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Granato
J E
JE
Cannon
J M
JM
Belardinelli
L
L
Watson
D D
DD
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects*; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004176:Dipyridamole / Q000008:administration & dosage / Q000494:pharmacology*; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging*; D007261:Infusions, Intra-Arterial; D007262:Infusions, Intravenous; D011877:Radionuclide Imaging; D013794:Thallium Radioisotopes
D013794:Thallium Radioisotopes; D004176:Dipyridamole