Assessment of coronary venous bypass graft function using krypton-81m

Area of Science:

• Cardiovascular Surgery
• Nuclear Cardiology
• Medical Imaging

Background:

• Intractable angina pectoris often necessitates coronary artery bypass graft (CABG) surgery.
• Assessing the functional patency and perfusion capacity of CABG is crucial for patient outcomes.
• Non-invasive methods for evaluating myocardial perfusion post-CABG are highly desirable.

Purpose of the Study:

• To evaluate the utility of krypton-81m (81mKr) scintigraphy for assessing myocardial perfusion supplied by coronary arterial bypass grafts.
• To measure myocardial blood flow rates in the distribution of individual grafts.
• To correlate perfusion patterns with patient history, particularly previous myocardial infarction.

Main Methods:

• Fifteen patients with intractable angina underwent CABG surgery.
• Postoperatively, 81mKr was continuously infused into each bypass graft.
• Regional myocardial perfusion was imaged using a gamma camera and multichannel analyzer.
• Myocardial flow rates were calculated based on the washout kinetics of 81mKr from the myocardium.

Main Results:

• High spatial resolution images of myocardial perfusion from individual grafts were obtained.
• Myocardial flow rates ranged from 0.5 to 2.0 ml/g per min in 13 patients without prior myocardial infarction.
• In two patients with prior anterior myocardial infarction, grafts to the left anterior descending artery showed poor perfusion to the anterior and apical ventricles.
• An experimental model confirmed 81mKr washout accurately measures myocardial flow per unit volume.

Conclusions:

• 81mKr scintigraphy provides a reliable method for evaluating myocardial perfusion from CABG grafts.
• The technique allows for quantitative assessment of graft flow and identification of perfusion deficits.
• This nuclear cardiology approach can aid in the assessment of CABG efficacy and patient management.