Abstract
Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated afterload. Considerable clinical and experimental animal studies have shown that abnormalities of endothelial function represent a hallmark of heart failure. However, the relationships between right coronary endothelial dysfunction and the development of heart failure remain to be fully established especially in the right heart. Synchrotron radiation (SR) microangiography has provided the temporal and spatial resolution required to visualize microvessels of various organs in vivo [1]. Therefore, in this study, we aimed to validate a new approach for the in vivo assessment of endothelial coronary function of the rat right heart using SR microangiography.
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Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated afterload. Considerable clinical and experimental animal studies have shown that abnormalities of endothelial function represent a hallmark of heart failure. However, the relationships between right coronary endothelial dysfunction and the development of heart failure remain to be fully established especially in the right heart. Synchrotron radiation (SR) microangiography has provided the temporal and spatial resolution required to visualize microvessels of various organs in vivo [1]. Therefore, in this study, we aimed to validate a new approach for the in vivo assessment of endothelial coronary function of the rat right heart using SR microangiography.
Imaging of the right coronary circulation was performed under pentobarbital anesthesia with monochromatic SR at 33.2Â keV for producing maximal absorption contrast of the iodine contrast agent in the vascular lumen (Fig. 25.1a). ImageJ (ver. 1.41, NIH, Bethesda, MD) was used to identify coronary vessels and determine their caliber. Vessels were labeled and classified according to branching orders from first-order main segment (Fig. 25.1b). The visible vessel internal diameter (ID) of each vessel was determined from a single field of view for all cine sequences. The ID of each vessel was averaged over at least ten consecutive frames [2].
The figure shows a typical imaging pattern of right coronary arteries from the aortic root to the third or fourth branching. It was possible to observe an arteriole with a diameter of about 50 μm (Fig. 25.1c). The ID of the first, second, and third branches were 312.7 ± 15.4, 159.3 ± 12.4, and 113.1 ± 7.5 μm, respectively (Fig. 25.1d). The present investigation demonstrates the ability to clearly visualize the right coronary circulation of the closed-chest anesthetized rat using SR microangiography. The use of SR microangiography provides a powerful tool for assessing coronary hemodynamics in unprecedented detail in PH models. Ultimately, future studies using SR microangiography will provide important new insights into the pathophysiology of right heart failure.
References
Shirai M, et al. Synchrotron radiation imaging for advancing our understanding of cardiovascular function. Circ Res. 2013;112:209–21.
Jenkins MJ, et al. Dynamic synchrotron imaging of diabetic rat coronary microcirculation in vivo. Arterioscler Thromb Vasc Biol. 2012;32:370–7.
Acknowledgments
Experiments were performed at the Japan Synchrotron Radiation Research Institute (SPrimg-8, BL28B2, Proposals 2014B1801 and 2015A1868). This work was supported by JSPS KAKENHI JP25860184 to T.I.
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Inagaki, T. et al. (2020). Impaired Right Coronary Vasodilator Function in Pulmonary Hypertensive Rats Assessed by In Vivo Synchrotron Microangiography. In: Nakanishi, T., Baldwin, H., Fineman, J., Yamagishi, H. (eds) Molecular Mechanism of Congenital Heart Disease and Pulmonary Hypertension. Springer, Singapore. https://doi.org/10.1007/978-981-15-1185-1_25
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DOI: https://doi.org/10.1007/978-981-15-1185-1_25
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