Probing the Depth of the Myocardium: Vasculature, Transit Time, and Perfusion Within the Left Ventricular Wall
The branching architecture of arterial trees traversing the thickness of the left ventricular wall is studied to determine the way in which adequate blood supply is provided to myocardial tissue at different depths within the wall thickness from arterial trees originating at the epicardial surface. The study is based on micro-CT images of tissue biopsies, coupled with a dedicated vascular tree analysis program. The results show that this combination of methodologies allows a more detailed and much more accurate exploration of the vasculature within the sampled tissue than is possible by histological means. The spatial density of the smallest resolvable “end” arterioles is found to be higher in the sub-endocardial region than in the sub-epicardial region, with vascular branching architecture consistent with a fractal structure. The concept of “transit time” is introduced as an approximate measure of the time it takes bulk flow to reach different regions of the myocardium. Our data suggest that a transit time differential is a major contributor to the equalization of transmural perfusion gradient against unequal distribution of “end’ arteriolar density.
KeywordsMyocardial perfusion Vascular trees Microvasculature Terminal arterioles Transit time Fractals
This work was funded in part by National Institutes of Health grant, R021 HL-117359. Special thanks to Ms. J. L. Anderson and Mr. S. M. Jorgensen for their performance of the animal experiment and micro-CT scanning as well as Ms. D. C. Darling for assembling and formatting this manuscript.
Conflict of Interest
There are no conflict of interests with any one of the authors.
- 1.Ashikaga, H., B. A. Coppola, K. G. Yamazaki, J. Villarreal, J. H. Omens, and J. W. Covell. Changes in regional myocardial volume during cardiac cycle: implications for transmural blood flow and cardiac structure. Am. J. Physiol. Heart Circ. Physiol. 295:H610–H618, 2008.CrossRefPubMedPubMedCentralGoogle Scholar
- 9.Jorgensen, S. M., O. Demirkya, and E. L. Ritman. Three-Dimensional imaging of vasculature and parenchyma in intact rodent organs with X-ray micro-CT. Am. J. Physiol. Heart Circ. Physiol. 44:1033–1114, 1998.Google Scholar
- 13.Larghat, A., J. Biglands, N. Maredia, J. P. Greenwood, S. G. Ball, M. Jerosch-Herold, A. Radjenovic, and S. Plein. Endocardial and epicardial myocardial perfusion determined by semi-quantitative and quantitative myocardial perfusion magnetic resonance. Int. J. Cardiovasc. Imaging 28:1499–1511, 2012.CrossRefPubMedGoogle Scholar
- 19.Pullen, B. R., R. T. Ritchings, and I. Isherwood. Accuracy and meaning of computed tomography attenuation values. In: Technical Aspects of Computed Tomography, edited by T. H. Newton, and D. G. Potts. St. Louis: Mosby, 1981, pp. 3904–3917.Google Scholar
- 23.Van Horssen, P., J. P. P. M. van de Wijngaard, M. J. Brandt, I. E. Hoeffer, J. A. E. Spaan, and M. Siebes. Perfusion territories subtended by penetrating coronary arteries increase in size and decrease in number toward the subendocardium. Am. J. Physiol. Heart Circ. Physiol. 306:H496–H504, 2014.CrossRefPubMedGoogle Scholar