Asynchronous transmural perfusion during coronary reactive hyperaemia.

Area of Science:

• Cardiovascular Physiology
• Myocardial Perfusion Dynamics

Background:

• Understanding myocardial blood flow (MBF) distribution is crucial for assessing cardiac health.
• Reactive hyperemia, a key indicator of coronary vasodilation, is influenced by flow dynamics.

Purpose of the Study:

• To investigate the dynamic transmural distribution of myocardial blood flow during reactive hyperemia.
• To analyze the endocardial to epicardial (endo/epi) flow ratios post-coronary artery occlusion.

Main Methods:

• Studied 36 anesthetized dogs with open chests.
• Measured myocardial blood flow using radioactive microspheres (9-10 micrometers).
• Induced reactive hyperemia via 90-second left anterior descending coronary artery occlusion.

Main Results:

• Observed asynchronous reactive hyperemic responses across the left ventricle free wall.
• Subepicardial flow predominated initially, shifting to subendocardial flow during recovery.
• Mean endo/epi ratios masked transmural asynchrony, with early ratios <1 and late ratios >1.

Conclusions:

• Regional asynchrony in peak reactive hyperemic flow causes the prolonged plateau in coronary artery measurements.
• Transmural flow asynchrony may lead to underestimation of ischemic vasodilator capacity.