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Impaired Right Coronary Vasodilator Function in Pulmonary Hypertensive Rats Assessed by In Vivo Synchrotron Microangiography

  • Tadakatsu Inagaki
  • Hirotsugu Tsuchimochi
  • James T. Pearson
  • Daryl O. Schwenke
  • Keiji Umetani
  • Mikiyasu Shirai
  • Yoshikazu NakaokaEmail author
Open Access
Conference paper
  • 601 Downloads

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.

Keywords

Coronary microangiography Synchrotron radiation Right heart failure Endothelial dysfunction 

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 33.2 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].
Fig. 25.1

SR microangiography for assessing vascular function in a rat. Schematic of SR microangiography for the rat right coronary artery using SPring-8 facilities (a). Typical SR angiogram image of the right coronary vasculature (b). Schematic of right coronary arteries in lateral view depicting the coronary branching nomenclature used in this study (c). Range of vessel size at each of the branching generations of right coronary circulation in the normal rat (d). Asterisks indicate ~50 μm vessels not included in (d)

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.

Notes

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.

References

  1. 1.
    Shirai M, et al. Synchrotron radiation imaging for advancing our understanding of cardiovascular function. Circ Res. 2013;112:209–21.CrossRefGoogle Scholar
  2. 2.
    Jenkins MJ, et al. Dynamic synchrotron imaging of diabetic rat coronary microcirculation in vivo. Arterioscler Thromb Vasc Biol. 2012;32:370–7.CrossRefGoogle Scholar

Copyright information

© The Author(s) 2020

Open Access This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

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Authors and Affiliations

  • Tadakatsu Inagaki
    • 1
  • Hirotsugu Tsuchimochi
    • 2
  • James T. Pearson
    • 2
  • Daryl O. Schwenke
    • 3
  • Keiji Umetani
    • 4
  • Mikiyasu Shirai
    • 5
  • Yoshikazu Nakaoka
    • 1
    Email author
  1. 1.Department of Vascular PhysiologyNational Cerebral and Cardiovascular CenterOsakaJapan
  2. 2.Department of Cardiac PhysiologyNational Cerebral and Cardiovascular CenterOsakaJapan
  3. 3.Department of PhysiologyUniversity of OtagoDunedinNew Zealand
  4. 4.Japan Synchrotron Radiation Research InstituteSayo-gunJapan
  5. 5.Department of Advanced Medical Research for Pulmonary HypertensionNational Cerebral and Cardiovascular CenterOsakaJapan

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