冠状动脉微循环及微血管性心绞痛的研究进展

冠状动脉微循环在心肌的血供中起着重要作用。心肌声学造影是诊断微循环水平心肌灌注的新技术,可同时观察心脏的结构、心肌局部和整体功能以及心肌的各级血流灌注,有利于研究冠状动脉微循环的病理生理机制并可能检出早期微血管内皮功能不全。在正常健康人,肌源性血流依赖性微动脉扩张和微循环代谢产物导致的冠状动脉微循环收缩形成互相制约的平衡调节机制,保持正常血流灌注。在冠心病心肌缺血如劳力性心绞痛时由于心肌代谢增加氧耗增加导致心肌缺血时,微血管反而收缩加剧缺血。研究表明这类患者是由于小冠状动脉扩张储备减低或冠状动脉收缩而导致心肌缺血,冠状前小动脉是调节心肌血液灌注的主要功能部位。     

冠状动脉微循环障碍检测方法进展

冠状动脉再灌注后微循环障碍极大地影响着急性心肌梗死患者的预后。目前,临床上有多种检测微循环障碍的方法。心脏磁共振成像是非侵入性评估心肌微循环功能的金标准,但其在临床上的普及不及心肌声学造影。冠状动脉TIMI血流分级、校正TIMI计帧法(CTFC)、心肌灌注分级(TMPG)、心肌呈色分级(MBG)及TIMI心肌灌注帧数计算(TMPFC)能直接通过造影图像评估微循环功能。冠状动脉微循环阻力指数等技术方法利用特殊导丝对微循环功能进行检测。本文将对上述方法进行总结归纳,为临床工作者选择微循环障碍评估手段提供参考。     

冠状动脉微循环解剖、生理和病理学认识与展望

正心脏是维持生命的重要器官,其营养需要冠状动脉循环供应,因此冠状动脉循环在各个器官循环中占有重要地位。冠状动脉循环在解剖学、血流动力学、可调节机制方面与其他器官相比均存在很大的差异。冠状动脉微循环是心肌氧供的关键环节,冠状动脉微循环功能在冠状动脉循环血供中起主要作用。冠状动脉微循环解剖和生理学特点一、冠状动脉微循环解剖学特点冠状动脉系统是由3个功能不同的部分组成,     

冠状动脉微循环障碍对心肌纤维化的影响及研究现状

正冠状动脉微循环障碍是在多种致病因素的作用下,微循环固有的结构和(或)功能异常,损伤心肌灌注,进而引起缺血的临床综合征[1]。既往认为冠状动脉微循环障碍会导致患者出现无症状性心肌缺血,也可表现为心绞痛甚至心肌梗死,会增加不良心血管事件发生的风险,随着研究的深入,冠状动脉微循环障碍可能会造成心肌纤维化,甚至心力衰竭的发生。     

冠状动脉微循环功能障碍的研究进展

冠状动脉微循环对血流代谢性调节发挥重要作用,微血管通过收缩和舒张功能调节冠状动脉血流量,影响心肌灌注。心外膜冠状动脉功能正常的情况下,心绞痛的发作与冠状动脉微循环功能障碍密切相关,可见微血管在调节心肌血流灌注中起关键作用。     

替格瑞洛改善急性冠脉综合征患者冠脉微循环机制的研究进展

正冠状动脉(冠脉)微循环系统由微动脉、毛细血管和微静脉构成,是心肌组织细胞发生营养交换的场所,其结构、功能的正常是心脏完成其生理功能的保证。冠状动脉微循环障碍(CMD)是指冠状动脉微血管阻力异常,导致不能以心外膜冠脉病变解释的心肌灌注受损和/或心肌缺血。约10%的男性患者和25%的女性患者以急性冠脉综合征(ACS)入院,而"冠脉造影正常"[1],这颠覆了既往认为未发现心外膜冠脉狭窄就等同于不存在缺血的观点,考     

冠状动脉微循环功能障碍研究新进展

冠状动脉微循环通过收缩和舒张功能调节冠脉血流量,影响心肌灌注,对于冠心病和心肌病患者的预后有着深远影响。随着近期无创和有创技术的发展,药物治疗领域不断更新,对于冠状动脉微循环功能障碍的认识也不断深入。本文就冠脉微循环功能障碍的新进展做如下综述。     

心肌造影超声心动图评价冠状动脉微循环:现今与未来的临床应用

心肌造影超声心动图(MCE)是一项较新技术。血管内注射的微小气泡,如其直径小得足够通过冠状动脉微循环时,则如同红细胞流动,滞留在血管内空间,使心肌产生无回声区,根据心肌无回声区的存在与否及其范围来评价心脏冠状动脉微循环状况。     

心肌造影超声心动图评价冠状动脉微循环：现今与未来的…

心肌造影声心动图是一项较新技术。血管内注射的微小气泡，如其直径小得足够通过冠状动脉微循环时，则如同红细胞流动，滞留在血管内空间，使心肌产生无回声区，根据心肌无回声区的存在与否及其范围来评价心脏冠状动脉微循环状况。     

冠心病患者测定微循环阻力指数的临床意义

冠状动脉微循环在心肌灌注和心肌代谢中起着至关重要的作用。大量研究显示,冠状动脉微血管的功能异常是很多心脏疾病发生的重要病因,评估冠状动脉微循环的功能状态是评价很多心脏疾病,尤其是急性ST段抬高型心肌梗死预后的重要指标。微循环阻力指数(IMR)与实际微血管阻力(TMR)有很好的相关性。在稳定期冠心病患者和接受急诊经皮冠状动脉介入治疗术后的ST段抬高型心肌梗死患者中证实IMR与TMR也有很好的相关性。     

State of the blood platelet link of hemostasis and microcirculation in patients with ischemic heart disease during plasmapheresis treatment

The paper provides the results of studies into plasmapheresis-induced changes in the thrombocytic link of hemostasis and microcirculation in 40 patients with coronary heart disease (CHD). Repeated sessions of plasmapheresis (P) were found to produce an inhibitory effect on platelet aggregation and to improve microcirculation in CHD patients with signs of increased platelet functional activity. In CHD patients with low platelet functional activity, the first P session was demonstrated to cause an increase in platelet functional activity whereas the subsequent sessions inhibited platelet aggregation. No significant microcirculatory improvement was seen in this group of patients. Heparin and rheopolyglucin given to control patients exerted no substantial effect on the thrombocytic link of hemostasis and microcirculation.     

Positron emission tomography to assess the haemodynamics of the coronary circulation.

Positron emission tomography (PET) allows the non-invasive measurement of absolute myocardial blood flow (ml/min/g of myocardium) in man. This has made possible the measurement of myocardial blood flow and the coronary vasodilator reserve (an index of the ability of the coronary microcirculation to dilate) in healthy volunteers to establish the normal values and ranges of these parameters. This technique allows the assessment of the functional significance of epicardial coronary stenoses as well as the investigation of the function of the coronary microcirculation in patients with and without coronary artery disease.     

Coronary computed tomography angiography in patients with stable coronary artery disease

The treatment of coronary artery disease (CAD), which is defined by stable anatomical atherosclerotic and functional alterations of epicardial vessels or microcirculation, focuses on managing intermittent angina symptoms and preventing major adverse cardiovascular events with optimal medical therapy. When patients with known CAD present with angina and no acute coronary syndrome, they have historically been evaluated with a variety of noninvasive stress tests that utilize electrocardiography, radionuclide scintigraphy, echocardiography, or magnetic resonance imaging for determining the presence and extent of inducible myocardial ischemia. Patient event-free survival, however, is largely driven by the coronary atherosclerotic disease burden, which is not directly assessed by functional testing. Direct evaluation of coronary atherosclerotic disease by coronary computed tomography angiography (coronary CTA) has emerged as the first line noninvasive imaging modality as it improves diagnostic accuracy and positively influences clinical management. Compared to functional assessment of CAD, coronary CTA-guided management results in improved patient outcomes by facilitating prevention of myocardial infarction. Other strengths of coronary CTA include detailed atherosclerotic plaque characterization and the ability to assess functional significance of specific lesions, which may further improve risk assessment and prognosis and lead to more appropriate referrals for additional testing, such as invasive coronary angiography.     

The coronary circulation and blood flow in left ventricular hypertrophy

Two distinct types of left ventricular hypertrophy (LVH) have been described: the so called "physiologic" hypertrophy, which is normally found in professional athletes, and "pathologic" LVH which is found in patients with inherited heart muscle disease such as hypertrophic cardiomyopathy (HCM) or patients with cardiac and systemic diseases characterized by pressure or volume overload. Patients with pathologic LVH have often symptoms and signs suggestive of myocardial ischemia despite normal coronary angiograms. Under these circumstances ischemia is due to coronary microvascular dysfunction (CMD). The abnormalities of the coronary microcirculation may be unrelated to the degree of LVH and cause a reduction in maximum myocardial blood flow which, in the absence of epicardial stenoses, is suggestive of CMD. There is no technique that enables direct visualization of coronary microcirculation in vivo in humans. Therefore, its assessment relies on the measurement of parameters which reflect its functional status, such as myocardial blood flow and coronary flow reserve which is an integrated measure of flow through both the large epicardial coronary arteries and the microcirculation. In this review article we discuss the pathophysiological mechanisms responsible for CMD in patients with primary and secondary LVH and how the recognition of this phenomenon is providing new important information on patient stratification and prognosis. Finally, we discuss how assessment of CMD may be used as a valuable surrogate marker to test the efficacy of old and new drugs. This article is part of a Special Issue entitled "Coronary Blood Flow".     

Ventricular function following drug-induced regression of hypertensive left ventricular hypertrophy

Drug-induced regression of left ventricular hypertrophy (LVH) due to arterial hypertension is generally accompanied by improved cavity filling because of changes in the structural and functional determinants of diastolic efficiency. In hypertensive patients in whom regression of LVH is achieved, systolic function also improves in the long term, at least when the therapeutic drug used is an ACE inhibitor. That the return to pretreatment blood pressures which occurs upon sudden withdrawal of medication is not accompanied by similar deterioration of ventricular function suggests regression of histological remodeling (i.e., not only a reduction in myocyte and interstitial volume, but also the amelioration of endothelial dysfunction and structural alterations in coronary microcirculation).     

Endothelial Dysfunction and Coronary Vasoreactivity - A Review of the History,Physiology, Diagnostic Techniques,and Clinical Relevance

The fervency for advancement and evolution in percutaneous coronary intervention has revolutionised the treatment of coronary artery disease. Historically, the focus of the interventional cardiologist was directed at the restoration of luminal patency of the major epicardial coronary arteries, yet whilst this approach is evolving with much greater utilisation of physiological assessment, it often neglects consideration of the role of the coronary microcirculation, which has been shown to clearly influence prognosis. In this review, we explore the narrative of the coronary circulation as more than just a simple conduit for blood but an organ with functional significance. We review organisation and physiology of the coronary circulation, as well as the current methods and techniques used to examine it. We discuss the studies exploring coronary artery endothelial function, appreciating that coronary artery disease occurs on a spectrum of disorder and that percutaneous coronary intervention has a latent effect on the coronary circulation with long-term consequences. It is concluded that greater recognition of the coronary artery endothelium and mechanisms of the coronary circulation should further guide revascularisation strategies.     

Myocardial perfusion echocardiography and coronary microvascular dysfunction

Our understanding of coronary syndromes has evolved in the last two decades out of the obstructive atherosclerosis of epicardial coronary arteries paradigm to include anatomo-functional abnormalities of coronary microcirculation. No current diagnostic technique allows direct visualization of coronary microcirculation, but functional assessments of this circulation are possible. This represents a challenge in cardiology. Myocardial contrast echocardiography (MCE) was a breakthrough in echocardiography several years ago that claimed the capability to detect myocardial perfusion abnormalities and quantify coronary blood flow. Research demonstrated that the integration of quantitative MCE and fractional flow reserve improved the definition of ischemic burden and the relative contribution of collaterals in non-critical coronary stenosis. MCE identified no-reflow and low-flow within and around myocardial infarction, respectively, and predicted the potential functional recovery of stunned myocardium using appropriate interventions. MCE exhibited diagnostic performances that were comparable to positron emission tomography in microvascular reserve and microvascular dysfunction in angina patients. Overall, MCE improved echocardiographic evaluations of ischemic heart disease in daily clinical practice, but the approval of regulatory authorities is lacking.     

Aetiology of Diabetic Foot Ulceration: A Role for the Microcirculation?

Neuropathy, mechanical stress, and macrovascular disease are involved in the pathogenesis of diabetic foot ulceration. Implicit in the development of gangrene and ulceration is the recognition that these factors interact with the microcirculation, resulting in the failure of skin capillary flow to meet nutritive requirements. There is little evidence to associate structural microangiopathy with foot microcirculatory failure. Significant functional abnormalities of the microcirculation have been defined. In accord with the haemodynamic hypothesis early hyperaemia and capillary hypertension promote more sinister late functional abnormalities with increasing duration of diabetes. These late functional abnormalities include loss of autoregulation and reduced hyperaemic responses which interact with loss of neurogenic flow regulation, disturbed endothelial function, and abnormal rheology to produce the familiar clinical picture of the diabetic foot. Ischaemia secondary to multi-segment arterial disease induces additional abnormalities of microcirculatory function which are superimposed on the pre-existing diabetic microvascular structural and functional microangiopathy.     

Structural and functional abnormality of systemic microvessels in cardiac syndrome X

BACKGROUND AND AIM: Microvascular damage of coronary bed has been considered the main pathogenetic factor of cardiac syndrome X (chest pain, exercise-induced ischemic ST-segment changes and angiographically normal coronary arteries). Previous studies have demonstrated that vascular abnormalities are not confined to the heart, suggesting a peripheral vascular dysfunction. On the hypothesis of a generalized microvascular disturbance in cardiac syndrome X, we performed a morphologic and functional study of systemic microcirculation in patients with syndrome X compared to normal subjects. METHODS AND RESULTS: Microvessels were evaluated with intravital videocapillaroscopy (VCP) executed in peripheral and conjunctival observation sites which explore micro and paramicrocirculation; biohumoral study included markers of inflammation and of endothelial function, coagulative-fibrinolytic system and lipid metabolism. Videocapillaroscopy showed several morphologic changes (present in high percent of patients with syndrome X and not in controls) and significant quantitative alterations (capillary density, granular flow score, alterations of vessel profile, length of capillary loop branches and of arteriole/venule diameter) which indicated a severe alteration of whole vessel structure and an important rearrangement of microvascular disposition. In a similar way, the humoral study showed some significant changes of endothelial (vWF, ICAM-1, E-sel, PAI-1), inflammatory (C-reactive protein (CRP), fibrinogen) and metabolic factors (HDL-chol) which are commonly associated with inflammatory response. CONCLUSIONS: We conclude that patients with cardiac syndrome X exhibited some structural and functional alterations of systemic microvasculature; the pattern is similar to that detected in systemic inflammatory diseases and suggests a vascular lesion of inflammatory type. The same changes could be operating also in coronary microvessels of patients with syndrome X.     

Coronary microcirculation. Physiologic and pathologic aspects]

The coronary circulation has a protective regulation system which, in extreme haemodynamic conditions, compensates increased myocardial oxygen demand. The coronary reserve, based on this concept defines the capacity of the system to increase flow temporally, and, thereby, myocardial oxygen supply. The introduction of new methods of investigating the coronary microcirculation has enabled the study of this phenomenon in several cardiovascular pathologies. Two types of investigation are used currently for studying the coronary microcirculation: 1) invasive methods, especially the recently developed intracoronary Doppler and pressure guide, 2) non-invasive methods, and, in particular, contrast echocardiography, position emission tomography and magnetic nuclear resonance. These investigations allow measurement of the coronary reserve or the assessment of the myocardial consequences of abnormalities of the microcirculation. Some workers use these methods to investigate pathological coronary microcirculation in different cardiomyopathies, in the presence of different cardiovascular risk factors (hypertension, diabetes, smoking, hypercholesterolaemia) and after cardiac transplantation.