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Tune JD, Warne CM, Essajee SI, Tucker SM, Figueroa CA, Dick GM, Beard DA. Unraveling the Gordian knot of coronary pressure-flow autoregulation. J Mol Cell Cardiol 2024; 190:82-91. [PMID: 38608928 DOI: 10.1016/j.yjmcc.2024.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 03/27/2024] [Accepted: 04/09/2024] [Indexed: 04/14/2024]
Abstract
The coronary circulation has the inherent ability to maintain myocardial perfusion constant over a wide range of perfusion pressures. The phenomenon of pressure-flow autoregulation is crucial in response to flow-limiting atherosclerotic lesions which diminish coronary driving pressure and increase risk of myocardial ischemia and infarction. Despite well over half a century of devoted research, understanding of the mechanisms responsible for autoregulation remains one of the most fundamental and contested questions in the field today. The purpose of this review is to highlight current knowledge regarding the complex interrelationship between the pathways and mechanisms proposed to dictate the degree of coronary pressure-flow autoregulation. Our group recently likened the intertwined nature of the essential determinants of coronary flow control to the symbolically unsolvable "Gordian knot". To further efforts to unravel the autoregulatory "knot", we consider recent challenges to the local metabolic and myogenic hypotheses and the complicated dynamic structural and functional heterogeneity unique to the heart and coronary circulation. Additional consideration is given to interrogation of putative mediators, role of K+ and Ca2+ channels, and recent insights from computational modeling studies. Improved understanding of how specific vasoactive mediators, pathways, and underlying disease states influence coronary pressure-flow relations stands to significantly reduce morbidity and mortality for what remains the leading cause of death worldwide.
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Affiliation(s)
- Johnathan D Tune
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA.
| | - Cooper M Warne
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Salman I Essajee
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Selina M Tucker
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - C Alberto Figueroa
- Section of Vascular Surgery, Department of Surgery, University of Michigan, USA; Department of Biomedical Engineering, University of Michigan, USA
| | - Gregory M Dick
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, USA
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2
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Morse CJ, Boerman EM, McDonald MW, Padilla J, Olver TD. The role of nitric oxide in flow-induced and myogenic responses in 1A, 2A, and 3A branches of the porcine middle cerebral artery. J Appl Physiol (1985) 2022; 133:1228-1236. [PMID: 36227166 PMCID: PMC9715271 DOI: 10.1152/japplphysiol.00209.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 09/13/2022] [Accepted: 10/09/2022] [Indexed: 12/15/2022] Open
Abstract
Myogenic and flow-induced reactivity contribute to cerebral autoregulation, with potentially divergent roles for smaller versus larger arteries. The present study tested the hypotheses that compared with first-order (1A) branches of the middle cerebral artery, second- and third-order branches (2A and 3A, respectively) exhibit greater myogenic reactivity but reduced flow-induced constriction. Furthermore, nitric oxide synthase (NOS) inhibition may amplify myogenic reactivity and abolish instances of flow-induced dilation. Isolated porcine cerebral arteries mounted in a pressure myograph were exposed to incremental increases in intraluminal pressure (40-120 mmHg; n = 41) or flow (1-1,170 µL/min; n = 31). Intraluminal flows were adjusted to achieve 5, 10, 20, and 40 dyn/cm2 of wall shear stress at 60 mmHg. Myogenic tone was greater in 3A versus 1A arteries (P < 0.05). There was an inverse relationship between myogenic reactivity and passive arterial diameter (P < 0.01). NOS inhibition increased basal tone to a lesser extent in 3A versus 1A arteries (P < 0.01) but did not influence myogenic reactivity (P = 0.49). Increasing flow decreased luminal diameter (P ≤ 0.01), with increased vasoconstriction at 10-40 dyn/cm2 of shear stress (P < 0.01). However, relative responses were similar between 1A, 2A, and 3A arteries (P = 0.40) with and without NOS inhibition conditions (P ≥ 0.29). Whereas NOS inhibition increases basal myogenic tone, and myogenic reactivity was less in smaller versus larger arteries (range = ∼100-550 µM), neither NOS inhibition nor luminal diameter influences flow-induced constriction in porcine cerebral arteries.NEW & NOTEWORTHY This study demonstrated size-dependent heterogeneity in myogenic reactivity in porcine cerebral arteries. Smaller branches of the middle cerebral artery exhibited increased myogenic reactivity, but attenuated NOS-dependent increases in myogenic tone compared with larger branches. Flow-dependent regulation does not exhibit the same variation; diameter-independent flow-induced vasoconstrictions occur across all branch orders and are not affected by NOS inhibition. Conceptually, flow-induced vasoconstriction contributes to cerebral autoregulation, particularly in larger arteries with low myogenic tone.
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Affiliation(s)
- Cameron J Morse
- Department Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Erika M Boerman
- Department Medical Physiology and Pharmacology, University of Missouri, Columbia, Missouri
| | - Matthew W McDonald
- Department Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Jaume Padilla
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
- Department Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - T Dylan Olver
- Department Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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3
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Anbazhakan S, Rios Coronado PE, Sy-Quia ANL, Seow LW, Hands AM, Zhao M, Dong ML, Pfaller MR, Amir ZA, Raftrey BC, Cook CK, D’Amato G, Fan X, Williams IM, Jha SK, Bernstein D, Nieman K, Pașca AM, Marsden AL, Horse KR. Blood flow modeling reveals improved collateral artery performance during the regenerative period in mammalian hearts. NATURE CARDIOVASCULAR RESEARCH 2022; 1:775-790. [PMID: 37305211 PMCID: PMC10256232 DOI: 10.1038/s44161-022-00114-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 07/07/2022] [Indexed: 06/13/2023]
Abstract
Collateral arteries bridge opposing artery branches, forming a natural bypass that can deliver blood flow downstream of an occlusion. Inducing coronary collateral arteries could treat cardiac ischemia, but more knowledge on their developmental mechanisms and functional capabilities is required. Here we used whole-organ imaging and three-dimensional computational fluid dynamics modeling to define spatial architecture and predict blood flow through collaterals in neonate and adult mouse hearts. Neonate collaterals were more numerous, larger in diameter and more effective at restoring blood flow. Decreased blood flow restoration in adults arose because during postnatal growth coronary arteries expanded by adding branches rather than increasing diameters, altering pressure distributions. In humans, adult hearts with total coronary occlusions averaged 2 large collaterals, with predicted moderate function, while normal fetal hearts showed over 40 collaterals, likely too small to be functionally relevant. Thus, we quantify the functional impact of collateral arteries during heart regeneration and repair-a critical step toward realizing their therapeutic potential.
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Affiliation(s)
- Suhaas Anbazhakan
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- These authors contributed equally
| | - Pamela E. Rios Coronado
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- These authors contributed equally
| | | | - Lek Wei Seow
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Aubrey M. Hands
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Mingming Zhao
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Melody L. Dong
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Martin R. Pfaller
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305
| | - Zhainib A. Amir
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Brian C. Raftrey
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | | | - Gaetano D’Amato
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Xiaochen Fan
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Ian M. Williams
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Sawan K. Jha
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Daniel Bernstein
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Koen Nieman
- Departments of Cardiovascular Medicine and Radiology, School of Medicine, Stanford University, Stanford, CA, 94305, USA
| | - Anca M. Pașca
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305
| | - Alison L. Marsden
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Kristy Red Horse
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford, CA, 94305, USA
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4
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Saemann L, Großkopf A, Hoorn F, Veres G, Guo Y, Korkmaz-Icöz S, Karck M, Simm A, Wenzel F, Szabó G. Relationship of Laser-Doppler-Flow and coronary perfusion and a concise update on the importance of coronary microcirculation in donor heart machine perfusion. Clin Hemorheol Microcirc 2021; 79:121-128. [PMID: 34487033 DOI: 10.3233/ch-219116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Machine perfusion (MP) is a novel method for donor heart preservation. The coronary microvascular function is important for the transplantation outcome. However, current research on MP in heart transplantation focuses mainly on contractile function. OBJECTIVE We aim to present the application of Laser-Doppler-Flowmetry to investigate coronary microvascular function during MP. Furthermore, we will discuss the importance of microcirculation monitoring for perfusion-associated studies in HTx research. METHODS Porcine hearts were cardioplegically arrested and harvested (Control group, N = 4). In an ischemia group (N = 5), we induced global ischemia of the animal by the termination of mechanical ventilation before harvesting. All hearts were mounted on an MP system for blood perfusion. After 90 minutes, we evaluated the effect of coronary perfusion pressures from 20 to 100 mmHg while coronary laser-doppler-flow (LDF) was measured. RESULTS Ischemic hearts showed a significantly decreased relative LDF compared to control hearts (1.07±0.06 vs. 1.47±0.15; p = 0.034). In the control group, the coronary flow was significantly lower at 100 mmHg of perfusion pressure than in the ischemia group (895±66 ml vs. 1112±32 ml; p = 0.016). CONCLUSIONS Laser-Doppler-Flowmetry is able to reveal coronary microvascular dysfunction during machine perfusion of hearts and is therefore of substantial interest for perfusion-associated research in heart transplantation.
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Affiliation(s)
- Lars Saemann
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany.,Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Anne Großkopf
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany
| | - Fabio Hoorn
- Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany.,Faculty Medical and Life Sciences, Furtwangen University, Villingen-Schwenningen, Germany
| | - Gábor Veres
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany
| | - Yuxing Guo
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany
| | - Sevil Korkmaz-Icöz
- Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Matthias Karck
- Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Andreas Simm
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany
| | - Folker Wenzel
- Faculty Medical and Life Sciences, Furtwangen University, Villingen-Schwenningen, Germany
| | - Gábor Szabó
- Department of Cardiac Surgery, University Hospital Halle (Saale), Halle (Saale), Germany.,Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany
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Fan L, Namani R, Choy JS, Awakeem Y, Kassab GS, Lee LC. Role of coronary flow regulation and cardiac-coronary coupling in mechanical dyssynchrony associated with right ventricular pacing. Am J Physiol Heart Circ Physiol 2020; 320:H1037-H1054. [PMID: 33356963 DOI: 10.1152/ajpheart.00549.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanical dyssynchrony (MD) affects left ventricular (LV) mechanics and coronary perfusion. To understand the multifactorial effects of MD, we developed a computational model that bidirectionally couples the systemic circulation with the LV and coronary perfusion with flow regulation. In the model, coronary flow in the left anterior descending (LAD) and left circumflex (LCX) arteries affects the corresponding regional contractility based on a prescribed linear LV contractility-coronary flow relationship. The model is calibrated with experimental measurements of LV pressure and volume, as well as LAD and LCX flow rate waveforms acquired under regulated and fully dilated conditions from a swine under right atrial (RA) pacing. The calibrated model is applied to simulate MD. The model can simultaneously reproduce the reduction in mean LV pressure (39.3%), regulated flow (LAD: 7.9%; LCX: 1.9%), LAD passive flow (21.6%), and increase in LCX passive flow (15.9%). These changes are associated with right ventricular pacing compared with RA pacing measured in the same swine only when LV contractility is affected by flow alterations with a slope of 1.4 mmHg/mL2 in a contractility-flow relationship. In sensitivity analyses, the model predicts that coronary flow reserve (CFR) decreases and increases in the LAD and LCX with increasing delay in LV free wall contraction. These findings suggest that asynchronous activation associated with MD impacts 1) the loading conditions that further affect the coronary flow, which may explain some of the changes in CFR, and 2) the coronary flow that reduces global contractility, which contributes to the reduction in LV pressure.NEW & NOTEWORTHY A computational model that couples the systemic circulation of the left ventricular (LV) and coronary perfusion with flow regulation is developed to study the effects of mechanical dyssynchrony. The delayed contraction in the LV free wall with respect to the septum has a significant effect on LV function and coronary flow reserve.
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Affiliation(s)
- Lei Fan
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan
| | - Ravi Namani
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan
| | - Jenny S Choy
- California Medical Innovation Institute, San Diego, California
| | - Yousif Awakeem
- California Medical Innovation Institute, San Diego, California
| | | | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan
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Namani R, Lanir Y, Lee LC, Kassab GS. Overview of mathematical modeling of myocardial blood flow regulation. Am J Physiol Heart Circ Physiol 2020; 318:H966-H975. [PMID: 32142361 DOI: 10.1152/ajpheart.00563.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxygen consumption by the heart and its extraction from the coronary arterial blood are the highest among all organs. Any increase in oxygen demand due to a change in heart metabolic activity requires an increase in coronary blood flow. This functional requirement of adjustment of coronary blood flow is mediated by coronary flow regulation to meet the oxygen demand without any discomfort, even under strenuous exercise conditions. The goal of this article is to provide an overview of the theoretical and computational models of coronary flow regulation and to reveal insights into the functioning of a complex physiological system that affects the perfusion requirements of the myocardium. Models for three major control mechanisms of myogenic, flow, and metabolic control are presented. These explain how the flow regulation mechanisms operating over multiple spatial scales from the precapillaries to the large coronary arteries yield the myocardial perfusion characteristics of flow reserve, autoregulation, flow dispersion, and self-similarity. The review not only introduces concepts of coronary blood flow regulation but also presents state-of-the-art advances and their potential to impact the assessment of coronary microvascular dysfunction (CMD), cardiac-coronary coupling in metabolic diseases, and therapies for angina and heart failure. Experimentalists and modelers not trained in these models will have exposure through this review such that the nonintuitive and highly nonlinear behavior of coronary physiology can be understood from a different perspective. This survey highlights knowledge gaps, key challenges, future research directions, and novel paradigms in the modeling of coronary flow regulation.
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Affiliation(s)
- Ravi Namani
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan
| | - Yoram Lanir
- Faculty of Biomedical Engineering, Technion, Israel Institute of Technology, Haifa, Israel
| | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan
| | - Ghassan S Kassab
- The California Medical Innovations Institute Incorporated, San Diego, California
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7
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Li Q, Fung E. Multifaceted Functions of Epithelial Na + Channel in Modulating Blood Pressure. Hypertension 2019; 73:273-281. [PMID: 30580685 DOI: 10.1161/hypertensionaha.118.12330] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Qi Li
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
| | - Erik Fung
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Gerald Choa Cardiac Research Centre, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
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8
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Guensch DP, Fischer K, Jung C, Hurni S, Winkler BM, Jung B, Vogt AP, Eberle B. Relationship between myocardial oxygenation and blood pressure: Experimental validation using oxygenation-sensitive cardiovascular magnetic resonance. PLoS One 2019; 14:e0210098. [PMID: 30650118 PMCID: PMC6334913 DOI: 10.1371/journal.pone.0210098] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 12/16/2018] [Indexed: 12/14/2022] Open
Abstract
Background The relationship between mean arterial pressure (MAP) and coronary blood flow is well described. There is autoregulation within a MAP range of 60 to 140 mmHg providing near constant coronary blood flow. Outside these limits flow becomes pressure-dependent. So far, response of myocardial oxygenation to changes in pressure and flow has been more difficult to assess. While established techniques mostly require invasive approaches, Oxygenation-Sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a technique that can non-invasively assess changes in myocardial tissue oxygenation. The purpose of this study was to follow myocardial oxygenation over a wide range of blood pressure variation within and outside known coronary autoregulatory limits using OS-CMR, and to relate these data to coronary hemodynamics. Methods Ten anaesthetized swine (German Large White) underwent left-sided thoracotomy and attachment of a perivascular flow probe to the proximal left anterior descending (LAD) coronary artery for continuous measurement of blood flow (QLAD). Thereafter, animals were transferred into a 3T MRI scanner. Mean arterial pressure (MAP) was varied in 10–15 mmHg steps by administering alpha1-receptor agents phenylephrine or urapidil. For each MAP level, OS-CMR images as well as arterial and coronary sinus blood gas samples were obtained simultaneously during brief periods of apnea. Relative changes (Δ) of coronary sinus oxygen saturation (ScsO2), oxygen delivery (DO2) and demand (MVO2), extraction ratio (O2ER) and excess (Ω) from respective reference levels at a MAP of 70 mmHg were determined and were compared to %change in OS-signal intensity (OS-SI) in simultaneously acquired OS-CMR images. Results QLAD response indicated autoregulation between MAP levels of 52 mmHg (lower limit) and127 mmHg (upper limit). OS-CMR revealed a global myocardial oxygenation deficit occurring below the lower autoregulation limit, with the nadir of OS-SI at -9.0%. With MAP values surpassing 70 mmHg, relative OS-SI increased to a maximum of +10.6%. Consistent with this, ΔScsO2, ΔDO2, ΔMVO2, ΔO2ER and ΔΩ responses indicated increasing mismatch of oxygenation balance outside the autoregulated zone. Changes in global OS-CMR were significantly correlated with all of these parameters (p≤0.02) except with ΔMVO2. Conclusion OS-CMR offers a novel and non-invasive route to evaluate the effects of blood pressure variations, as well as of cardiovascular drugs and interventions, on global and regional myocardial oxygenation, as demonstrated in a porcine model. OS-CMR identified mismatch of O2 supply and demand below the lower limit of coronary autoregulation. Vasopressor induced acute hypertension did not compromise myocardial oxygenation in healthy hearts despite increased cardiac workload and O2 demand. The clinical usefulness of OS-CMR remains to be established.
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Affiliation(s)
- Dominik P. Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- * E-mail:
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- McGill University Health Centre, Montreal, QC, Canada
| | - Christof Jung
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Samuel Hurni
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernhard M. Winkler
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernd Jung
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Andreas P. Vogt
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Balthasar Eberle
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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9
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Kiel AM, Goodwill AG, Baker HE, Dick GM, Tune JD. Local metabolic hypothesis is not sufficient to explain coronary autoregulatory behavior. Basic Res Cardiol 2018; 113:33. [PMID: 30073416 DOI: 10.1007/s00395-018-0691-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 06/19/2018] [Accepted: 07/04/2018] [Indexed: 01/21/2023]
Abstract
The local metabolic hypothesis proposes that myocardial oxygen tension determines the degree of autoregulation by increasing the production of vasodilator metabolites as perfusion pressure is reduced. Thus, normal physiologic levels of coronary venous PO2, an index of myocardial oxygenation, are proposed to be required for effective autoregulation. The present study challenged this hypothesis through determination of coronary responses to changes in coronary perfusion pressure (CPP 140-40 mmHg) in open-chest swine in the absence (n = 7) and presence of euvolemic hemodilution (~ 50% reduction in hematocrit), with (n = 5) and without (n = 6) infusion of dobutamine to augment MVO2. Coronary venous PO2 decreased over similar ranges (~ 28-15 mmHg) as CPP was lowered from 140 to 40 mmHg in each of the groups. However, coronary venous PO2 was not associated with changes in coronary blood flow (r = - 0.11; P = 0.29) or autoregulatory gain (r = - 0.29; P = 0.12). Coronary zero-flow pressure (Pzf) was measured in 20 mmHg increments and determined to be directly related to vascular resistance (r = 0.71; P < 0.001). Further analysis demonstrated that changes in coronary blood flow remained minimal at Pzf > 20 mmHg, but progressively increased as Pzf decreased below this threshold value (r = 0.68; P < 0.001). Coronary Pzf was also positively correlated with autoregulatory gain (r = 0.43; P = 0.001). These findings support that coronary autoregulatory behavior is predominantly dependent on an adequate degree of underlying vasomotor tone, independent of normal myocardial oxygen tension.
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Affiliation(s)
- Alexander M Kiel
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA.,Weldon School of Biomedical Engineering, Purdue University, 206 S Martin Jischke Dr, West Lafayette, IN, 47907, USA
| | - Adam G Goodwill
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Hana E Baker
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Gregory M Dick
- California Medical Innovations Institute, 11107 Roselle Street, San Diego, CA, 92121, USA
| | - Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA.
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