Related Experiment Video
Updated: Aug 11, 2026
In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography
Published on: February 16, 2016
Regional myocardial perfusion and wall thickening during ischemia in conscious dogs
Abstract:
We examined in conscious dogs the effects of reductions in myocardial blood flow (MBF) in three different layers across the wall on regional myocardial contractile function in the ischemic zone, measured as systolic wall thickening (%WT). In 16 dogs, %WT was measured with sonomicrometry and MBF was determined with microspheres (10- to 12-microns diam) during coronary stenosis of the left circumflex coronary artery. The stenoses were categorized into six groups by the effect on %WT (each group representing progressive 20% decrements in %WT from control), and individual and pooled regression analyses were performed on data from six of the dogs having multiple data points to evaluate the shape (linear or curvilinear) of the relationships between MBF and changes in %WT. Transmural contractile function was highly sensitive to acute reductions in MBF, especially reductions in the subendocardium. The shape of the normalized subendocardial MBF-%WT relation was mildly curvilinear by regression analysis (quadratic equation, gamma = -0.75x2 + 2.15x -0.39, r2 = 0.92). Likewise, mean transmural and midmyocardial MBF correlated well and closely with changes in %WT. Subepicardial MBF, however, correlated poorly with changes in %WT, there being no change in subepicardial MBF until %WT had been reduced more than 50%.
Insights
Myocardial blood flow (MBF) reductions significantly impact heart muscle function, particularly in the subendocardium. Reduced blood flow, especially to the subendocardium, impairs systolic wall thickening more than to other layers.
Area of Science:
- Cardiovascular Physiology
- Myocardial Ischemia Research
Background:
- Regional myocardial contractile function is crucial for cardiac health.
- Understanding the relationship between myocardial blood flow (MBF) and function is vital for treating ischemic heart disease.
Purpose of the Study:
- To investigate the effects of reduced MBF in different myocardial layers on regional contractile function.
- To determine the relationship between MBF and systolic wall thickening (%WT) across the heart wall during ischemia.
Main Methods:
- Conscious dogs underwent coronary stenosis of the left circumflex artery.
- Myocardial blood flow (MBF) was measured using microspheres.
- Regional myocardial contractile function was assessed via sonomicrometry to measure systolic wall thickening (%WT).
Main Results:
- Transmural contractile function is highly sensitive to acute MBF reductions, with the subendocardium being most affected.
- A mildly curvilinear relationship was observed between normalized subendocardial MBF and %WT.
- Mean transmural and midmyocardial MBF correlated well with %WT, while subepicardial MBF showed poor correlation until %WT decreased by over 50%.
Conclusions:
- The subendocardium is the most vulnerable layer to reductions in MBF regarding contractile function.
- MBF reduction has a differential impact on myocardial layers, with implications for understanding and managing myocardial ischemia.
