Linear relationship between the distribution of thallium-201 and blood flow in ischemic and nonischemic myocardium during exercise.

Abstract

SUMMARY The purpose of this study was to compare the myocardial distribution of thallium-201 and regional myocardial blood flow during ischemia and the physiologic stress of exercise. Studies were carried out in six dogs with chronically implanted catheters in the atrium and aorta and a snare on the circumflex coronary artery distal to the first marginal branch. Regional myocardial blood flow was measured during quiet, resting conditions using 7-10 , of radioisotope-labeled microspheres. Each dog was then exercised on a treadmill at speeds of 5-9 mph at a 50 incline. After 1 minute of exercise the circumflex coronary artery was occluded and thallium-201 and a second label of microspheres were injected. Exercise was continued for 5 minutes. The dogs were then sacrificed and the left ventricle was sectioned into approximately 80 1-2-g samples to compare thallium-201 activity and regional myocardial blood flow.The maximum increase in blood flow ranged from 3.3-7.2 times resting control values. Each dog had myocardial samples in which blood flow was markedly reduced, to less than 0.10 ml/min/g. In each dog there was a close linear relationship between thallium-201 distribution and direct measurements of regional myocardial blood flow. Linear regression analyses demonstrated a correlation coefficient of 0.98 or greater in each dog. These data indicate that during the physiologic stress of exercise, the myocardial distribution of thallium activity is linearly related to regional myocardial blood flow in both the ischemic and nonischemic regions.

Exercise thallium-201 scintigraphy in dogs: effects of long-term coronary occlusion and collateral development on early and late scintigraphic images.

“…[31][32][33] In particular this has been clearly demonstrated in an exercising canine preparation similar to the one used in this study.3' Our previous work has extended these conclusions to scintigraphic measurements of myocardial thallium activity.27 Therefore, increasing LCf/LAD (ischemic/normal) myocardial scintigraphic 201T1 ratios correlate with increasing tissue perfusion of the once ischemic myocardium. At 6 weeks, when scintigraphic defects were nearly absent, myocardial blood flow to muscle in the distribution of the occluded vessel was practically normal even during the stress of exercise.…”

Relation between Coronary Blood Flow and Left Ventricular Mass in Hypertension. Noninvasive Quantification of Coronary Blood Flow by Thallium-201 Myocardial Scintigraphy.

“…In fact, Ishii et al (17) and Owada et al (18) have already evaluated myocardial blood flow by thallium-201 myocardial scintigraphy. In addition, experiments in dogs have confirmed a close linear relationship between the distribution of thallium-201 in myocardium and direct measurements of regional myocardial blood flow (19).…”

“…As compared with these two tracers, the percentage of the total dose of thallium-201 concentrated in the myocardium is about 2-fold higher (27), and the hepatic and gastric uptake of thallium-201 is far less than that of either K-42 or Rb-86 (27). Thus, thallium-201 can be used to measure regional blood flow, especially CBF (19,28). CBF estimated noninvasively was compared with that determined by the Doppler guide wire method (26).…”

Incremental Prognostic Value of Rest-Redistribution 201 Tl Single-Photon Emission Computed Tomography

“…The initial myocardial uptake of 201 Tl is proportional to the coronary blood flow 11 and depends on intact cell membrane function for active transport against an electrochemical gradient. 12 After the injection of 201 Tl at rest, initial perfusion defects may disappear over time through the process of redistribution.…”