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The heart is a muscle about the size of your fist. It pumps blood around your body and beats approximately 70 times a minute. After the blood leaves the right side of the heart, it goes to your lungs where it picks up oxygen. The oxygen-rich blood returns to your heart and is then pumped to the body's organs through a network of arteries. The blood returns to your heart through veins before being pumped back to your lungs again.

This process is called circulation. The heart gets its own supply of blood from a network of blood vessels on the heart's surface called coronary arteries. Page last reviewed: 7 April Next review due: 7 April Symptoms of coronary heart disease CHD The main symptoms of CHD are: chest pain angina heart attacks heart failure You can also experience other symptoms, such as heart palpitations and unusual breathlessness. But not everyone has the same symptoms and some people may not have any before CHD is diagnosed.

Causes of coronary heart disease CHD Coronary heart disease is the term that describes what happens when your heart's blood supply is blocked or interrupted by a build-up of fatty substances in the coronary arteries. Over time, the walls of your arteries can become furred up with fatty deposits.

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Human data with year follow-up confirm that when such patients are deferred from PCI, the clinical event rate remains low, demonstrating a clear paradox between hyperaemic measurements of pressure and flow. Resting MVR reduces with increasing stenosis severity. Theoretically, microcirculatory angiogenesis and arteriogenesis could explain this.

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Our results indicate that this is not the case and instead we confirm observations from smaller studies, that hyperaemic MVR increases in critical stenoses. We presume this observed rise in hyperaemic MVR, can be attributed to the contribution of collateral circulation. Because collateral arteries connect with the receiving vessel distal to the position of the pressure—flow wire, flow supplied by the collateral arteries will not be detected, while collateral pressure is transmitted through the vessels and can be detected by the wire.

Microvascular resistance is calculated as the ratio of distal pressure elevated by collateral supply and flow, and the calculated MVR will falsely rise accordingly. In the intravenous subgroup, collateral supply may be diminished due to the coronary steal phenomenon during hyperaemia and thereby the MVR in these severe stenoses remains at normal values. However, this analysis has the limitation that coronary steal phenomenon might still apply in the intracoronary subgroup for the left coronary artery. Further work to assess the collateral flow or pressure during diastole is required to understand this in detail.

In this study, we provide flow velocity and resistance data from a wide spectrum of coronary stenoses and reference vessels. These data are valuable for accurate development and improvement of computer flow dynamics models. For current flow models, such as CT-FFR, data were derived from animals and small human studies without significant disease.

Secondly, the data presented here provide reference values stratified according to stenosis severity for the most commonly used physiological indices. Exploration of less commonly used physiological parameters such as the instantaneous hyperaemic diastolic velocity—pressure slope IHDVPS and zero-flow pressure ZFP may be of future interest to better indicate their clinical applicability. Furthermore, our findings demonstrate that the wave-free period consistently provides a higher flow velocity and a lower MVR than assessment over the whole cardiac cycle at rest.

To provide a definitive answer to which physiological index is preferable, randomized clinical outcome data are needed.

This large multicentre study of coronary pressure—velocity measurements shows that with progressive stenosis severity, TG rises, while resting coronary flow is maintained by compensatory reduction of MVR. This suggests that resting pressure indices can be used to detect the haemodynamic significance of coronary artery stenoses.

Our results confirm the applicability of the general principles of coronary physiology determined in animals to patients with atherosclerotic lesions. This study has a number of limitations. Volumetric flow was not assessed because of the limitations of accurate stenosis and vessel dimension calculation, as well as determining the mass of the subtended myocardium which can only be estimated from angiographic parameters. Since vessels taper, flow velocity will fall less than volumetric flow and without knowledge of subtended mass, flow velocity might be preferable to volumetric flow.

Wedge pressure was not routinely measured and therefore definitive assessment of the impact of collaterals on the results cannot be made. However, measurements were not made in vessels with visible collaterals. While reference vessels were free of angiographic disease, intravascular ultrasound studies demonstrated significant burden of atherosclerosis in apparently unobstructed coronary arteries.

It remains uncommon to routinely perform intravascular imaging in unobstructed vessels and therefore, together with the large number of unobstructed vessels, our findings should be applicable to patients undergoing coronary angiography. In the presence of microcirculatory dysfunction, FFR may underestimate true haemodynamic stenosis significance. However, both measures are easy to comprehend and familiar to clinicians providing a familiar conceptual framework to interpret the data.

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Finally, it must be borne in mind, however, that our results are inferred on group basis and heterogeneous factors such as microvascular dysfunction and diffuse epicardial disease could obscure these findings on a patient-specific level. When there are discrepancies between resting and hyperaemic factors, it remains unclear which parameters provide prognostic information. Randomized clinical outcome studies are currently being undertaken to assess the safety and performance of resting parameters to guide revascularization.

Supplementary material is available at European Heart Journal online. Conflict of interest: J. National Center for Biotechnology Information , U. Eur Heart J. Published online Nov Sukhjinder S.

Coronary Pressure

Nijjer , Guus A. Piek , Justin E. Davies , and Niels van Royen.

Author information Article notes Copyright and License information Disclaimer. Corresponding author. This article has been cited by other articles in PMC.

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Abstract Background Our understanding of human coronary physiological behaviour is derived from animal models. Methods and results Five hundred and sixty-seven simultaneous intracoronary pressure and flow velocity assessments from patients were analysed for coronary flow velocity, trans-stenotic pressure gradient TG , and microvascular resistance MVR. Conclusions With progressive stenosis severity, TG rises. Keywords: Autoregulation, Microvascular resistance, Physiological lesion assessment, Stenosis.

Introduction The physiological behaviour of human coronary stenoses has been inferred from animal experiments that studied changes of flow velocity and pressure in the presence of artificially created stenoses.

Coronary perfusion pressure

Coronary catheterization Coronary angiography and pressure—flow assessments of coronary stenoses were performed using conventional approaches. Stenosed and reference vessels Five hundred and sixty-seven coronary assessments were made. Stenosis stratification Both FFR and diameter stenosis assessed by quantitative angiography QCA were used to stratify stenosis severity. Calculation of hemodynamic parameters Flow velocity was assessed over four periods: first, flow velocity at rest over the entire cardiac cycle and secondly over the specific diastolic wave-free period during which iFR is calculated , which was detected using the ECG signals.

Open in a separate window. Results Patient and vessel characteristics Five hundred and sixty-seven coronary assessments were derived from patients age Whole cycle pressure—flow velocity relationships A given stenosis has a unique curvilinear relationship between the flow velocity and the TG across the stenosis. Diastolic pressure and flow velocity relationships Pressure—flow velocity relationships were calculated over the wave-free period specifically, both at rest and hyperaemia.

Discussion In this study, we describe the relationship between coronary flow velocity, TG, and MVR, estimated from measurements obtained over the whole cardiac cycle or selectively within the wave-free period, under resting and hyperaemic conditions. Auto-regulation ensures that resting blood flow remains stable Maintenance of resting coronary flow is regulated by endogenous adenosine release, changes in intrinsic myogenic tone, endothelial cell signalling and neurohumoral control, which combine to produce continuous auto-regulatory adaption of arteriolar vessel diameter. The use of resting parameters to assess stenoses The stability of resting flow velocity for the majority of stenoses means that resting flow alone cannot distinguish between stenosis severities.

Microvascular remodelling Resting MVR reduces with increasing stenosis severity.

Clinical implications In this study, we provide flow velocity and resistance data from a wide spectrum of coronary stenoses and reference vessels. Conclusion This large multicentre study of coronary pressure—velocity measurements shows that with progressive stenosis severity, TG rises, while resting coronary flow is maintained by compensatory reduction of MVR. Limitations This study has a number of limitations. Supplementary material Supplementary material is available at European Heart Journal online.

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References 1. Physiologic basis for assessing critical coronary stenosis: instantaneous flow response and regional distribution during coronary hyperemia as measures of coronary flow reserve. Am J Cardiol The hemodynamics of coronary arterial stenosis. Cardiovasc Clin Hemodynamic principles in the control of coronary blood flow.