Distribution of coronary blood flow in the left ventricular wall of dogs evaluated by the uptake of Xe-133.
The distribution of coronary blood flow was estimated in anesthetized dogs by counting the activity in tissue blocks of the left ventricular free wall immediately after bolus injection of Xe-133 into the aortic root. No differences in the uptake of isotope were observed between the apex and the base of the heart; between areas supplied by the anterior descending and circumflex branches of the left coronary artery; or between the endo- and epicardial halves of the wall. In most experiments a bolus injection of the isotope into the left coronary artery was followed by a difference in activity between areas supplied by the left anterior descending and left circumflex branches. This indicated inadequate mixing of blood and isotope in the main stem of the artery. The uneven distribution did not result in differences between the epi- and endocardial activity concentrations. The results from one normal, anesthetized dog in which tissue activities were measured after constant rate infusion of Xe-133 into the left coronary artery for 8 min were in accordance with the general assumption of equal epi- and endocardial volumes of distribution (values of lambda).
Distribution of coronary blood flow in the left ventricular wall of dogs evaluated by the uptake of Xe-133. The distribution of coronary blood flow was estimated in anesthetized dogs by counting the activity in tissue blocks of the left ventricular free wall immediately after bolus injection of Xe-133 into the aortic root. No differences in the uptake of isotope were observed between the apex and the base of the heart; between areas supplied by the anterior descending and circumflex branches of the left coronary artery; or between the endo- and epicardial halves of the wall. In most experiments a bolus injection of the isotope into the left coronary artery was followed by a difference in activity between areas supplied by the left anterior descending and left circumflex branches. This indicated inadequate mixing of blood and isotope in the main stem of the artery. The uneven distribution did not result in differences between the epi- and endocardial activity concentrations. The results from one normal, anesthetized dog in which tissue activities were measured after constant rate infusion of Xe-133 into the left coronary artery for 8 min were in accordance with the general assumption of equal epi- and endocardial volumes of distribution (values of lambda).