title: External detection and visualization of myocardial ischemia with 11C-substrates in vitro and in vivo.
abstract: To characterize externally detectable changes in myocardial metabolism of free fatty acids (FFA) and glucose associated with ischemia, isovolumically beating rabbit hearts were perfused under conditions of selected flows with cyclotron-produced, short-lived (t1/2 - 20.4 minutes), 11C-labeled isotopes of glucose and FFA. Tension-time index decreased 83% and lactate production increased from 0.5 +/- 1.9 (SE) to 5.3 +/- 2.1 mumol/min per g of dry weight reflecting myocardial ischemia after flow was reduced from 20 to 5 ml/min. After 30 minutes of low flow the myocardial accumulation of 11C-octanoate, expressed as the extraction fraction, declined from 56 +/- 15% to 30 +/- 3%, reflecting metabolic suppression of FFA extraction during low flow. Effects attributable exclusively to prolonged residence time were excluded. Similar results were obtained with 11C-palmitate. The myocardial avidity for 11C-palmitate was demonstrable by rectilinear whole body scanning in dogs given 5 mCi of the agent intravenously. Diminished 11C-palmitate uptake in zones of myocardium rendered ischemic for 20 minutes prior to reflow in intact dogs was delineated by electrocardiographically gated positron-emission transaxial computer reconstruction tomography. Thus, diminished 11C-FFA extraction, externally detectable, accompanies decreased perfusion in isolated perfused hearts, and decreased 11C-FFA uptake reflecting myocardial ischemia in vivo can be evaluated noninvasively by positron-emission transaxial tomography.
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D002210:Caprylates / Q000378:metabolism; D002250:Carbon Radioisotopes; D003327:Coronary Disease / Q000175:diagnosis* / Q000378:metabolism; D003936:Diagnosis, Computer-Assisted; D004285:Dogs; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010169:Palmitic Acids / Q000378:metabolism; D011817:Rabbits; D011877:Radionuclide Imaging / Q000379:methods*; D014054:Tomography / Q000379:methods*
chemical_list: D000418:Albumins; D002210:Caprylates; D002250:Carbon Radioisotopes; D005230:Fatty Acids, Nonesterified; D007773:Lactates; D010169:Palmitic Acids; D005947:Glucose