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Wongchadakul P, Datta AK, Rattanadecho P. Tissue poromechanical deformation effects on steam pop likelihood in 3-D radiofrequency cardiac ablation. J Biol Eng 2023; 17:52. [PMID: 37550706 PMCID: PMC10408080 DOI: 10.1186/s13036-023-00365-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 07/05/2023] [Indexed: 08/09/2023] Open
Abstract
Radiofrequency Cardiac Ablation (RFCA) is a common procedure that heats cardiac tissue to destroy abnormal signal pathways to eliminate arrhythmias. The complex multiphysics phenomena during this procedure need to be better understood to improve both procedure and device design. A deformable poromechanical model of cardiac tissue was developed that coupled joule heating from the electrode, heat transfer, and blood flow from normal perfusion and thermally driven natural convection, which mimics the real tissue structure more closely and provides more realistic results compared to previous models. The expansion of tissue from temperature rise reduces blood velocity, leading to increased tissue temperature, thus affecting steam pop occurrence. Detailed temperature velocity, and thermal expansion of the tissue provided a comprehensive picture of the process. Poromechanical expansion of the tissue from temperature rise reduces blood velocity, increasing tissue temperature. Tissue properties influence temperatures, with lower porosity increasing the temperatures slightly, due to lower velocities. Deeper electrode insertion raises temperature due to increased current flow. The results demonstrate that a 5% increase in porosity leads to a considerable 10% increase in maximum tissue temperature. These insights should greatly help in avoiding undesirable heating effects that can lead to steam pop and in designing improved electrodes.
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Affiliation(s)
| | - Ashim K Datta
- Department of Biological & Environmental Engineering, Cornell University, Ithaca, NY, USA.
| | - Phadungsak Rattanadecho
- Center of Excellence in Electromagnetic Energy Utilization in Engineering (C.E.E.E.), Department of Mechanical Engineering, Faculty of Engineering, Thammasat University, Pathumthani, Thailand
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Stegehuis VE, Wijntjens GW, Murai T, Piek JJ, van de Hoef TP. Assessing the Haemodynamic Impact of Coronary Artery Stenoses: Intracoronary Flow Versus Pressure Measurements. Eur Cardiol 2018; 13:46-53. [PMID: 30310471 DOI: 10.15420/ecr.2018:7:2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Fractional flow reserve (FFR)-guided percutaneous coronary intervention results in better long-term clinical outcomes compared with coronary angiography alone in intermediate stenoses in stable coronary artery disease (CAD). Coronary physiology measurements have emerged for clinical decision making in interventional cardiology, but the focus lies mainly on epicardial vessels rather than the impact of these stenoses on the myocardial microcirculation. The latter can be quantified by measuring the coronary flow reserve (CFR), a combined pressure and flow index with a strong ability to predict clinical outcomes in CAD. However, combined pressure-flow measurements show 30-40 % discordance despite similar diagnostic accuracy between FFR and CFR, which is explained by the effect of microvascular resistance on both indices. Both epicardial and microcirculatory involvement has been acknowledged in ischaemic heart disease, but clinical implementation remains difficult as it requires individual proficiency. The recent introduced pressure-only index instantaneous wave-free ratio, a resting adenosine-free stenosis assessment, led to a revival of interest in coronary physiology measurements. This review focuses on elaborating the coronary physiological parameters and potential of combined pressure-flow measurements in daily clinical practice.
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Affiliation(s)
- Valérie E Stegehuis
- AMC Heart Center, Academic Medical Center, University of Amsterdam Amsterdam, the Netherlands
| | - Gilbert Wm Wijntjens
- AMC Heart Center, Academic Medical Center, University of Amsterdam Amsterdam, the Netherlands
| | - Tadashi Murai
- AMC Heart Center, Academic Medical Center, University of Amsterdam Amsterdam, the Netherlands
| | - Jan J Piek
- AMC Heart Center, Academic Medical Center, University of Amsterdam Amsterdam, the Netherlands
| | - Tim P van de Hoef
- AMC Heart Center, Academic Medical Center, University of Amsterdam Amsterdam, the Netherlands
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Murai T, Kanaji Y, Yonetsu T, Lee T, Matsuda J, Usui E, Araki M, Niida T, Isobe M, Kakuta T. Preprocedural fractional flow reserve and microvascular resistance predict increased hyperaemic coronary flow after elective percutaneous coronary intervention. Catheter Cardiovasc Interv 2016; 89:233-242. [DOI: 10.1002/ccd.26596] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/30/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Tadashi Murai
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Yoshihisa Kanaji
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Taishi Yonetsu
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Tetsumin Lee
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Junji Matsuda
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Eisuke Usui
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Makoto Araki
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Takayuki Niida
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
| | - Mitsuaki Isobe
- Department of Cardiovascular Medicine; Tokyo Medical and Dental University; Tokyo Japan
| | - Tsunekazu Kakuta
- Cardiovascular Medicine; Tsuchiura Kyodo General Hospital; Tsuchiura Ibaraki Japan
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van de Hoef TP, Meuwissen M, Piek JJ. Fractional flow reserve-guided percutaneous coronary intervention: where to after FAME 2? Vasc Health Risk Manag 2015; 11:613-22. [PMID: 26673639 PMCID: PMC4676623 DOI: 10.2147/vhrm.s68328] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Fractional flow reserve (FFR) is a well-validated clinical coronary physiological parameter derived from the measurement of coronary pressures and has drastically changed revascularization decision-making in clinical practice. Nonetheless, it is important to realize that FFR is a coronary pressure-derived estimate of coronary blood flow impairment. It is thereby not the same as direct measures of coronary flow impairment that determine the occurrence of signs and symptoms of myocardial ischemia. This consideration is important, since the FAME 2 study documented a limited discriminatory power of FFR to identify stenoses that require revascularization to prevent adverse events. The physiological difference between FFR and direct measures of coronary flow impairment may well explain the findings in FAME 2. This review aims to address the physiological background of FFR, its ambiguities, and its consequences for the application of FFR in clinical practice, as well as to reinterpret the diagnostic and prognostic characteristics of FFR in the light of the recent FAME 2 trial outcomes.
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Affiliation(s)
- Tim P van de Hoef
- AMC Heartcentre, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | | | - Jan J Piek
- AMC Heartcentre, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
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5
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Nolte F, van de Hoef TP, Meuwissen M, Voskuil M, Chamuleau SAJ, Henriques JPS, Verberne HJ, van Eck-Smit BLF, Koch KT, de Winter RJ, Spaan JAE, Tijssen JGP, Siebes M, Piek JJ. Increased hyperaemic coronary microvascular resistance adds to the presence of myocardial ischaemia. EUROINTERVENTION 2014; 9:1423-31. [PMID: 24755383 DOI: 10.4244/eijv9i12a240] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
AIMS It has been argued that hyperaemic microvascular resistance (HMR), defined as the ratio of mean distal coronary pressure to flow velocity, is overestimated in the presence of a coronary stenosis compared to actual microvascular resistance (MR), due to neglecting collateral flow. We aimed to test the hypothesis that HMR allows accurate identification of microvascular functional abnormalities by evaluating the association between high or low HMR and the presence of myocardial ischaemia on non-invasive stress testing. METHODS AND RESULTS Myocardial perfusion scintigraphy was performed in 228 patients, with 299 lesions to identify reversible myocardial ischaemia. Intracoronary distal pressure and flow velocity were assessed during adenosine-induced hyperaemia (20-40 µg, intracoronary) to determine hyperaemic stenosis resistance (HSR) and HMR. HMR >1.9 mmHg/cm/s was defined as high. The diagnostic odds ratio (OR) for myocardial ischaemia for lesions associated with high compared to low HMR was 2.6 (95% confidence interval [CI]: 1.5-4.4; p<0.001) overall, 3.3 (95% CI: 1.2-9.0; p=0.02) for lesions with HSR >0.8 mmHg/cm/s, and 1.3 (95% CI: 0.6-2.9; p=0.52) for lesions with HSR ≤0.8 mmHg/cm/s. CONCLUSIONS The increased risk of myocardial ischaemia in the presence of high HMR, uncorrected for collateral flow, demonstrates that HMR is reflective of an increase in actual MR, identifying pertinent pathophysiological alterations in the microvasculature.
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Affiliation(s)
- Froukje Nolte
- Department of Biomedical Engineering and Physics, University of Amsterdam, Amsterdam, The Netherlands
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van de Hoef TP, Nolte F, EchavarrÍa-Pinto M, van Lavieren MA, Damman P, Chamuleau SAJ, Voskuil M, Verberne HJ, Henriques JPS, van Eck-Smit BLF, Koch KT, de Winter RJ, Spaan JAE, Siebes M, Tijssen JGP, Meuwissen M, Piek JJ. Impact of hyperaemic microvascular resistance on fractional flow reserve measurements in patients with stable coronary artery disease: insights from combined stenosis and microvascular resistance assessment. Heart 2014; 100:951-9. [PMID: 24727867 DOI: 10.1136/heartjnl-2013-305124] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Fractional flow reserve (FFR) aims to identify the extent of epicardial disease, but may be obscured by involvement of the coronary microvasculature. We documented the impact of hyperaemic stenosis resistance (HSR) and hyperaemic microvascular resistance (HMR) on FFR, and its relationship with myocardial ischaemia in patients with stable coronary artery disease. METHODS AND RESULTS We evaluated 255 coronary arteries with stenoses of intermediate severity by means of intracoronary pressure and flow measurements to determine FFR, HSR and HMR. Myocardial perfusion scintigraphy (MPS) was performed to identify inducible myocardial ischaemia. In 178 patients, HMR was additionally determined in a reference coronary artery. Target vessel HMR was stratified according to reference vessel HMR tertiles. The diagnostic OR for inducible ischaemia on MPS of a positive compared with a negative FFR was significantly higher only in the presence of a high HMR (at the 0.75 and 0.80 FFR cut-off). Among stenoses with a positive FFR, the prevalence of ischaemia was significantly higher when HMR was high despite equivalent FFR across the HMR groups. This was paralleled by a concomitant significant increase in HSR with increasing HMR across groups. The relation between FFR and HSR (r(2)=0.54, p<0.001) was modulated by the magnitude of HMR, and improved substantially after adjustment for HMR (adjusted-r(2)=0.73, p<0.001), where, for epicardial disease of equivalent severity, FFR increased with increasing HMR. CONCLUSIONS Identification of epicardial disease severity by FFR is partly obscured by the microvascular resistance, which illustrates the necessity of combined pressure and flow measurements in daily practice.
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Affiliation(s)
- Tim P van de Hoef
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands Department of Biomedical Engineering and Physics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands Hospital Clínico San Carlos and Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain
| | - Froukje Nolte
- Department of Biomedical Engineering and Physics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Mauro EchavarrÍa-Pinto
- Hospital Clínico San Carlos and Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain
| | - Martijn A van Lavieren
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Peter Damman
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Michiel Voskuil
- Department of Cardiology, University Medical Centre, Utrecht, The Netherlands
| | - Hein J Verberne
- Department of Nuclear Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - José P S Henriques
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Berthe L F van Eck-Smit
- Department of Nuclear Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Karel T Koch
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Robbert J de Winter
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Jos A E Spaan
- Department of Biomedical Engineering and Physics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Maria Siebes
- Department of Biomedical Engineering and Physics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan G P Tijssen
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Jan J Piek
- AMC Heartcentre, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
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van de Hoef TP, Meuwissen M, Escaned J, Davies JE, Siebes M, Spaan JAE, Piek JJ. Fractional flow reserve as a surrogate for inducible myocardial ischaemia. Nat Rev Cardiol 2013; 10:439-52. [DOI: 10.1038/nrcardio.2013.86] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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8
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Remmelink M, Sjauw KD, Henriques JPS, de Winter RJ, Koch KT, van der Schaaf RJ, Vis MM, Tijssen JGP, Piek JJ, Baan J. Effects of left ventricular unloading by Impella recover LP2.5 on coronary hemodynamics. Catheter Cardiovasc Interv 2007; 70:532-7. [PMID: 17896398 DOI: 10.1002/ccd.21160] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVES We studied the effects of LV unloading by the Impella on coronary hemodynamics by simultaneously measuring intracoronary pressure and flow and the derived parameters fractional flow reserve (FFR), coronary flow velocity reserve (CFVR), and coronary microvascular resistance (MR). BACKGROUND Patients with compromised left ventricular (LV) function undergoing high-risk percutaneous coronary intervention (PCI) may benefit from LV unloading. Limited information is available on the effects of LV unloading on coronary hemodynamics. METHODS Eleven patients (mean LV ejection fraction of 35 +/- 11%) underwent PCI during LV support by the LV unloading device (Impella Recover LP2.5). Intracoronary measurements were performed in a nonstenotic coronary artery after the PCI, before and after adenosine-induced hyperemia at four different support levels (0-2.5 L/min). RESULTS Aortic and coronary pressure increased with increasing support levels, whereas FFR remained unchanged. Baseline flow velocity remained unchanged, while hyperemic flow velocity and CFVR increased significantly with increasing support levels (61 +/- 24 to 72 +/- 27 cm/sec, P = 0.001 and 1.88 +/- 0.52 to 2.34 +/- 0.63, P < 0.001 respectively). The difference between baseline MR and hyperemic MR significantly increased with increasing support levels (1.28 +/- 1.32 to 1.89 +/- 1.43 mm Hg cm(-1) sec, P = 0.005). CONCLUSIONS Unloading of the LV by the Impella increased aortic and intracoronary pressure, hyperemic flow velocity and CFVR, and decreased MR. The Impella-induced increase in coronary flow, probably results from both an increased perfusion pressure and a decreased LV volume-related intramyocardial resistance.
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Affiliation(s)
- Maurice Remmelink
- Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Westerhof N, Boer C, Lamberts RR, Sipkema P. Cross-Talk Between Cardiac Muscle and Coronary Vasculature. Physiol Rev 2006; 86:1263-308. [PMID: 17015490 DOI: 10.1152/physrev.00029.2005] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cardiac muscle and the coronary vasculature are in close proximity to each other, and a two-way interaction, called cross-talk, exists. Here we focus on the mechanical aspects of cross-talk including the role of the extracellular matrix. Cardiac muscle affects the coronary vasculature. In diastole, the effect of the cardiac muscle on the coronary vasculature depends on the (changes in) muscle length but appears to be small. In systole, coronary artery inflow is impeded, or even reversed, and venous outflow is augmented. These systolic effects are explained by two mechanisms. The waterfall model and the intramyocardial pump model are based on an intramyocardial pressure, assumed to be proportional to ventricular pressure. They explain the global effects of contraction on coronary flow and the effects of contraction in the layers of the heart wall. The varying elastance model, the muscle shortening and thickening model, and the vascular deformation model are based on direct contact between muscles and vessels. They predict global effects as well as differences on flow in layers and flow heterogeneity due to contraction. The relative contributions of these two mechanisms depend on the wall layer (epi- or endocardial) and type of contraction (isovolumic or shortening). Intramyocardial pressure results from (local) muscle contraction and to what extent the interstitial cavity contracts isovolumically. This explains why small arterioles and venules do not collapse in systole. Coronary vasculature affects the cardiac muscle. In diastole, at physiological ventricular volumes, an increase in coronary perfusion pressure increases ventricular stiffness, but the effect is small. In systole, there are two mechanisms by which coronary perfusion affects cardiac contractility. Increased perfusion pressure increases microvascular volume, thereby opening stretch-activated ion channels, resulting in an increased intracellular Ca2+transient, which is followed by an increase in Ca2+sensitivity and higher muscle contractility (Gregg effect). Thickening of the shortening cardiac muscle takes place at the expense of the vascular volume, which causes build-up of intracellular pressure. The intracellular pressure counteracts the tension generated by the contractile apparatus, leading to lower net force. Therefore, cardiac muscle contraction is augmented when vascular emptying is facilitated. During autoregulation, the microvasculature is protected against volume changes, and the Gregg effect is negligible. However, the effect is present in the right ventricle, as well as in pathological conditions with ineffective autoregulation. The beneficial effect of vascular emptying may be reduced in the presence of a stenosis. Thus cardiac contraction affects vascular diameters thereby reducing coronary inflow and enhancing venous outflow. Emptying of the vasculature, however, enhances muscle contraction. The extracellular matrix exerts its effect mainly on cardiac properties rather than on the cross-talk between cardiac muscle and coronary circulation.
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Affiliation(s)
- Nico Westerhof
- Laboratory of Physiology and Department of Anesthesiology, Institute for Cardiovascular Research Vrije Universiteit, VU University Medical Center, Amsterdam, The Netherlands
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Versluis JP, Heslinga JW, Sipkema P, Westerhof N. Microvascular pressure measurement reveals a coronary vascular waterfall in arterioles larger than 110 microm. Am J Physiol Heart Circ Physiol 2001; 281:H1913-8. [PMID: 11668051 DOI: 10.1152/ajpheart.2001.281.5.h1913] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pressure-flow relationships at the entrance of the coronary circulation in the diastolic myocardium exhibit a zero-flow pressure intercept (P(int)). We tested whether this intercept is the same throughout the vascular bed. Microvascular pressure-flow relationships were therefore measured in vessels of various sizes of the maximally dilated vasculature of perfused unstimulated papillary muscle using the servo-null technique. From these relationships, P(int) were calculated with nonlinear regression. The P(int) at the level of the septal artery (diameter, 150-250 microm) was 23.2 +/- 4.4 cmH2O (n = 12). In arterioles with a diameter range between 24 and 110 microm, P(int) was 1.7 +/- 0.5 cmH2O (n = 6, P < 0.01), significantly lower than in the septal artery but significantly higher than zero, and not dependent on vessel size. In venules with the same diameters, P(int) was 1.1 +/- 1.1 cmH2O (n = 4), which was not different from zero. We conclude that, in the dilated vascular bed of the papillary muscle, two vascular waterfalls are found. The first waterfall is located in arterioles between 150 and 110 microm. The second waterfall is probably located in the small postcapillary venules.
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Affiliation(s)
- J P Versluis
- Laboratory for Physiology, Institute for Cardiovascular Research, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands.
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Abstract
Coronary microvessels play a pivotal role in determining the supply of oxygen and nutrients to the myocardium by regulating the coronary flow conductance and substance transport. Direct approaches analyzing the coronary microvessels have provided a large body of knowledge concerning the physiological and pharmacological characteristics of the coronary circulation, as has the rapid accumulation of biochemical findings about the substances that mediate vascular functions. Myogenic and flow-induced intrinsic vascular controls that determine basal tone have been observed in coronary microvessels in vitro. Coronary microvascular responses during metabolic stimulation, autoregulation, and reactive hyperemia have been analyzed in vivo, and are known to be largely mediated by metabolic factors, although the involvement of other factors should also be taken into account. The importance of ATP-sensitive K(+) channels in the metabolic control has been increasingly recognized. Furthermore, many neurohumoral mediators significantly affect coronary microvascular control in endothelium-dependent and -independent manners. The striking size-dependent heterogeneity of microvascular responses to all of these intrinsic, metabolic, and neurohumoral factors is orchestrated for optimal perfusion of the myocardium by synergistic and competitive interactions. The regulation of coronary microvascular permeability is another important factor for the nutrient supply and for edema formation. Analyses of collateral microvessels and subendocardial microvessels are important for understanding the pathophysiology of ischemic hearts and hypertrophied hearts. Studies of the microvascular responses to drugs and of the impairment of coronary microvessels in diseased conditions provide useful information for treating microvascular dysfunctions. In this article, the endogenous regulatory system and pharmacological responses of the coronary circulation are reviewed from the microvascular point of view.
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Affiliation(s)
- T Komaru
- Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, 980-8574, Sendai, Japan.
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Spaan JA, Cornelissen AJ, Chan C, Dankelman J, Yin FC. Dynamics of flow, resistance, and intramural vascular volume in canine coronary circulation. Am J Physiol Heart Circ Physiol 2000; 278:H383-403. [PMID: 10666068 DOI: 10.1152/ajpheart.2000.278.2.h383] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Varying coronary volume will vary vascular resistance and thereby have an effect on coronary hemodynamics. Six ventricular septa were isolated from anesthetized dogs, dispersed in a biaxial stretch apparatus at diastolic stress, and perfused artificially with an oxygenated perfluorochemical emulsion at maximal vasodilation. Flow and thickness were measured continuously by an electromagnetic flow probe and sonomicrometer. Pressure was varied sinusoidally around 30, 50, and 70 mmHg with an amplitude of 7.5 mmHg; frequencies ranged between 0.015 and 7 Hz. Bode plots of admittance (flow/pressure) and capacitance (scaled thickness/pressure) were constructed. A two-compartment model was used in which the resistances vary with volume. Realistic values of microvascular compliance ( approximately 0.3 ml x mmHg(-1) x 100 g(-1)) were found. Values 10 times higher were then found when resistances were forced to be constant. We concluded that volume dependence of resistances have to be taken into account when dynamic or static pressure-flow relations are studied and conceal the effect of a large intramyocardial compliance on arterial hemodynamics.
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Affiliation(s)
- J A Spaan
- Department of Medical Physics, Cardiovascular Research Institute Amsterdam, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands.
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Hiramatsu O, Goto M, Yada T, Kimura A, Chiba Y, Tachibana H, Ogasawara Y, Tsujioka K, Kajiya F. In vivo observations of the intramural arterioles and venules in beating canine hearts. J Physiol 1998; 509 ( Pt 2):619-28. [PMID: 9575309 PMCID: PMC2230961 DOI: 10.1111/j.1469-7793.1998.619bn.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
1. To evaluate the effects of cardiac contraction on intramyocardial (midwall) microvessels, we measured the phasic diameter change of left ventricular intramural arterioles and venules using a novel needle-probe videomicroscope with a CCD camera and compared it with the diameter change in subepicardial and subendocardial vessels. 2. The phasic diameter of the intramural arterioles decreased from 130 +/- 79 ìm in end-diastole to 118 +/- 72 micron (mean +/- S.D.) in end-systole by cardiac contraction (10 +/- 6 %, P < 0.001, n = 21). 3. The phasic diameter in the intramural venules was almost unchanged from end-diastole to end-systole (85 +/- 44 vs. 86 +/- 42 micron, respectively, 2 +/- 6 %, n. s., n = 14). 4. Compared with intramural vessels, the diameters of subendocardial arterioles and venules decreased by a similar extent (arterioles: 10 +/- 8 %, P < 0. 001; venules: 12 +/- 10 %, P < 0.001) from end-diastole to end-systole, respectively, whereas the diameter of the subepicardial arterioles changed little during the cardiac cycle, and subepicardial venule diameter increased by 9 +/- 8 % (P < 0.01) from end-diastole to end-systole. These findings are consistent with our previous report. 5. We suggest that the almost uniform distribution of the cardiac contractility effect and arteriolar transmural pressure between the subendocardium and the midmyocardium, which together constitute the systolic vascular compressive force, accounts for the similarity in the arteriolar diameter changes in both myocardial layers. The smaller intravascular pressure drop from deep to superficial myocardium relative to the larger intramyocardial pressure drop explains the difference in the phasic venular diameter changes across the myocardium.
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Affiliation(s)
- O Hiramatsu
- Department of Medical Engineering and Systems Cardiology, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan.
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Affiliation(s)
- J A Spaan
- Department of Medical Physics, University of Amsterdam, The Netherlands
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