Author + information
- Received May 23, 1983
- Revision received September 26, 1983
- Accepted September 30, 1983
- Published online March 1, 1984.
- Robert D. Okada, MD, FACCa and
- Gerald M. Pohost, MD, FACC
- ↵aAddress for reprints: Robert D. Okada, MD, Cardiac Unit, Massachusetts General Hospital, Boston, Massachusetts 02114.
To determine the effect of reduced coronary blood flow on myocardial thallium-201 clearance over a range of flows, miniature radiation detectors were inserted into the left ventricular apex and positioned against the anterior and posterior endocardial walls in 21 dogs. Thallium was administered intravenously and myocardial tracer activity was monitored continuously for 1 hour in both walls. A balloon occluder was then partially inflated around the left anterior descending coronary artery in 19 dogs, producing a range of anterior wall blood flow reductions as assessed by the microsphere technique. Thallium activity was monitored continuously for 3 hours in both walls. Two dogs served as control animals and had no coronary artery occlusion at 1 hour. At the end of the 4 hour experiment, the dogs were sacrificed and the hearts counted in a well counter.
The 19 dogs with coronary artery stenosis were divided into three groups (mild, moderate and severe flow reduction groups) on the basis of their poststenosis anterior/posterior wall regional myocardial blood flow ratios. The two control dogs had similar thallium clearances in the anterior and posterior left ventricular walls during the 3 hour period, as assessed by the radiation detectors, and by a final anterior/posterior wall thallium ratio near unity. All three groups of dogs with coronary stenosis had comparable fractional thallium clearances from the anterior and posterior walls before and after the balloon occluder inflation. The final anterior/posterior left ventricular wall thallium ratios were not significantly different than unity for all three groups of dogs.
In conclusion, after intravenous thallium administration, subsequent reductions in coronary artery blood flow do not alter the myocardial thallium clearance rate. When these data are applied to clinical exercise thallium imaging, they suggest that myocardial ischemia after the initial postexercise imaging probably will not affect the delayed images or the rate of thallium clearance as assessed by new quantitative computer programs.
- Received May 23, 1983.
- Revision received September 26, 1983.
- Accepted September 30, 1983.
- American College of Cardiology Foundation