Coronary microvascular dysfunction in primary cardiomyopathies
Coronary microvascular dysfunction in primary cardiomyopathies
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DOI：
10.1136/heartjnl-2013-304291
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发表时间：
2014-05-15
期刊：
影响因子：
5.7
通讯作者：
Camici, P. G.
中科院分区：
文献类型：
--
作者：
Spoladore, R.;Fisicaro, A.;Camici, P. G.
心肌缺血通常是由心外膜冠状动脉异常引起的。然而，在过去的30年里，一些研究表明，冠状动脉微循环异常也可能导致或促成几种情况下的心肌缺血。在一些没有任何明显心脏或全身疾病的心绞痛发作患者中，冠状动脉微血管功能障碍（CMD）被认为是症状的唯一原因。w1心肌血流（MBF）异常以及由此引起的与CMD相关的心肌改变可能与心外膜冠状动脉限流狭窄引起的心肌改变有很大不同。在后一种情况下，MBF的损伤通常是区域性的，分布在狭窄动脉所覆盖的区域内，导致可检测到的节段性收缩功能损伤。相反，CMD的异常不一定涉及冠状动脉主干所属的区域，但可能弥漫性影响整个左心室或呈散在性分布。1 w1 CMD可能由多种病理机制维持，包括结构、功能和血管外改变，这些机制可以以不同的方式促进疾病的发生。根据其发生的临床环境，CMD可分为四种类型：(1)在无冠心病和心肌疾病的情况下发生功能障碍；(2)无冠心病但有心肌疾病时发生的功能障碍；(3)伴有CAD的功能障碍；(4)医源性功能障碍。1心肌疾病时的CMD在大多数情况下是通过冠状动脉壁内不良重构维持的，可以通过有创或无创冠状动脉血流储备（CFR）评估来识别。cfr——冠状动脉血管近最大舒张期MBF与基底MBF的比值，是衡量大心外膜冠状动脉和微循环流量的综合指标，已被提出作为评价冠状动脉循环功能的间接参数。CFR异常可能是由于心外膜冠状动脉狭窄，或者在没有血管造影证实的动脉粥样硬化疾病的情况下，可能反映冠状动脉微循环功能障碍。最近有研究表明，在评估冠状动脉微循环时，最大MBF（即，在冠状动脉血管扩张接近最大时测量的MBF，例如，静脉注射腺苷后）可能优于CFR。这可以用以下事实来解释：CFR是一个比率（即最大MBF/基线MBF），影响分子或分母的因素都可能影响其计算。因此，低CFR并不一定反映最大流量的减少，但它可能是由于面对正常的充血流量时静息流量异常升高引起的。w3CMD存在于原发性和继发性心肌病中，具有重要的预后意义。心肌病是一类重要的异质性疾病，其分类非常复杂；事实上，多年来，已经提出了各种系统的分类。美国心脏协会最后一次专家共识小组提出的定义是：“与机械和/或电功能障碍相关的一组异质性心肌疾病，通常（但并非总是）表现出不适当的心室肥大或扩张，并由多种原因引起，通常是遗传的……
Myocardial ischaemia is usually caused by abnormalities of the epicardial coronary arteries. In the past 30 years, however, several studies have shown that abnormalities in the coronary microcirculation may also cause or contribute to myocardial ischaemia in several conditions. In a number of patients who present with anginal attacks in the absence of any apparent cardiac or systemic disease, coronary microvascular dysfunction (CMD) has been suggested to be the unique cause of symptoms. w1 Myocardial blood flow (MBF) abnormalities and the consequent myocardial alterations related to CMD may differ substantially from those caused by flow limiting stenoses in epicardial coronary arteries. In the latter case, the impairment of MBF is generally regional and distributed within the territories subtended by the stenosed artery, resulting in detectable segmental impairment of contractile function. In contrast, in the case of CMD, the abnormality may not necessarily involve the territory subtended by a major coronary branch, but it may affect the whole left ventricle diffusely or be distributed in a scattered manner. 1 w1 CMD may be sustained by several pathogenetic mechanisms including structural, functional, and extravascular alterations that can contribute to the condition in different ways. On the basis of the clinical settings in which it occurs, CMD can be classified into four types:(1) dysfunction occurring in the absence of coronary artery disease (CAD) and myocardial diseases;(2) dysfunction occurring in the absence of CAD, but in the presence of myocardial diseases;(3) dysfunction occurring concomitantly with CAD;(4) iatrogenic dysfunction. 1 CMD in the presence of myocardial diseases is sustained in most instances by adverse remodelling of intramural coronary arterioles, and can be identified by invasive or non-invasive assessment of coronary flow reserve (CFR). CFR—the ratio of MBF during near maximal coronary vasodilatation to basal MBF—is an integrated measure of flow through both the large epicardial coronary arteries and the microcirculation, and has been proposed as an indirect parameter to evaluate the function of the coronary circulation. An abnormal CFR can be due to narrowing of the epicardial coronary arteries or, in the absence of angiographically demonstrable atherosclerotic disease, may reflect dysfunction of the coronary microcirculation. 1 w2 More recently it has been suggested that maximum MBF (ie, MBF measured during near maximal coronary vasodilatation, eg, following intravenous adenosine) might be superior to CFR for the assessment of the coronary microcirculation. This could be explained by the fact that CFR is a ratio (ie, maximum MBF/baseline MBF) and factors that influence either the numerator or the denominator may affect its calculation. Therefore, a low CFR does not necessarily reflect a reduction of maximum flow, but it can be caused by an abnormally elevated resting flow in the face of a normal hyperaemic flow. w3CMD is found both in primary and secondary cardiomyopathies with very important prognostic implications. Cardiomyopathies are an important and heterogeneous group of diseases whose classification has proved to be exceedingly complex; indeed, through the years, various systematic classifications have been presented. The definition proposed by the last expert consensus panel of the American Heart Association is:“a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic …