Direct measurement of left ventricular interstitial adenosine

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering

Background:

• Accurate measurement of endogenous adenosine in the left ventricular (LV) interstitial compartment is vital for understanding its role in regulating coronary blood flow.
• Existing methods are indirect and rely on significant assumptions, limiting their reliability.

Purpose of the Study:

• To introduce a novel technique for direct, rapid measurement of LV interstitial adenosine concentration.
• To overcome limitations of existing indirect methods.

Main Methods:

• Development and utilization of a LV epicardial diffusion well for direct adenosine measurement.
• Experiments involving intramyocardial injections of methylene blue dye and [8-14C]adenosine.
• Analysis of adenosine diffusion across the parietal pericardial membrane.

Main Results:

• Direct measurement of LV interstitial adenosine concentration (555 pmol/ml in resting dogs) within the vasoactive range.
• Demonstration that adenosine originates from transmural LV interstitium, transported via lymphatics.
• Quantification of adenosine diffusion characteristics across pericardial membranes.

Conclusions:

• The new epicardial diffusion well method provides direct and reliable LV interstitial adenosine measurements.
• The parietal pericardium significantly influences adenosine concentration measurements, with standard methods potentially underestimating levels by over 50%.
• Higher resting adenosine levels suggest a more significant role in basal coronary blood flow regulation than previously recognized.