Mechanisms of myocardial infarction without obstructive coronary artery disease

Angiography in patients with myocardial infarction (MI) most commonly reveals one or more significantly narrowed coronary arteries, but a substantial minority of patients with spontaneous MI have no obstructive coronary artery disease (CAD) at angiography. This review summarizes evidence for the most commonly hypothesized mechanisms, including plaque disruption, plaque erosion, vasospasm, embolism, and spontaneous coronary dissection. In addition, tako-tsubo syndrome and myocarditis are discussed. The best treatment of MI without obstructive CAD is likely to differ substantially based on the underlying cause. Additional mechanistic research is needed to facilitate the design of research studies aimed at documenting the best treatments for these patients, numbering as many as 225,000 per year in the US.     

Myocardial infarction without obstructive coronary artery disease

The present report describes five cases of transmural myocardial infarction occurring in patients without occlusive coronary artery disease or other discernible abnormalities. It is apparent from these cases and others described in the literature that such patients may present with or without angina and, in some, the clinical course will be complicated by recurrent infarction and/or significant residual myocardial dysfunction. At present the exact incidence and natural history of this syndrome is unclear. Undoubtedly the increasing application of coronary arteriography will identify many more such patients. Delineation of the genesis and the full clinical spectrum of myocardial infarction without coronary artery disease warrants further investigative attention.     

Exercise-induced myocardial ischemia in patients with coronary artery ectasia without obstructive coronary artery disease

BACKGROUND: Aetiology, clinical significance and treatment options for coronary artery ectasia/aneurysm is not clear. OBJECTIVE: We sought to determine whether exercise can induce coronary ischemia in patients with coronary artery ectasia/aneurysm without significant coronary stenosis. METHODS: Coronary artery ectasia was defined as 1.5-2-fold, aneurysm as >2-fold luminal dilatation of the adjacent normal segment. The study patients could have irregularities with ectatic coronaries but they did not have stenotic lesions >50% with visual assessment of two blinded observers. Patients having coronary artery ectasia or aneurysm with prior myocardial infarction, dilated cardiomyopathy, valvular heart disease, bundle branch block, significant ST-T changes were excluded. The control group was formed from a well matched population of 32 patients with normal coronary arteries who have not performed a treadmill test before coronary angiography. The study group underwent a symptom limited treadmill test if they did not have one before coronary angiogram, all control patients underwent treadmill test. RESULTS: Thirty-three patients with coronary artery ectasia/aneurysm (ranging from one to three vessels) but without significant stenosis were derived from 4470 cardiac catheterization procedures between January 1998 and July 2000. In the study group, 17 of the patients had positive treadmill tests with respect to five patients in the control group (P = 0.004). In subgroup analysis, diffuse ectasia/aneurysm (involving 2-3 vessels) was found to be strongly related with ischemia (P = 0.005) with respect to local disease. CONCLUSION: Coronary artery ectasia/aneurysm may lead to exercise induced ischemia, especially in the diffuse form.     

Intracoronary ultrasound measurements in women with myocardial infarction without significant coronary lesions

METHODS: Morphologic characteristics of coronary arteries in eight women with myocardial infarction and angiographically normal or not significantly stenosed vessels were investigated with intracoronary ultrasound. The infarct-related vessel was assessed by three-dimensional volumetric analysis and compared with a control vessel from a noninfarcted area. RESULTS: Atherosclerosis was found in all infarct-related arteries. The plaques were predominantly soft, eccentric, poorly calcified, and with little lipid pools or none at all. Although the average area and thickness of plaques and cross-sectional narrowing of the infarct-related arteries were greater than those of control arteries, there were no pathognomonic characteristics of plaques in the infarct-related vessels. CONCLUSION: The possibility that atherosclerosis is the main etiologic factor for myocardial infarction can not be excluded even for women without an angiographically obvious coronary stenosis in the infarct-related vessels.     

血管内超声对冠状动脉弥漫性斑块的应用价值

目的:应用血管内超声(IVUS)对冠状动脉(冠脉)弥漫性斑块患者进行检查,比较IVUS与冠脉造影(CAG)对冠脉弥漫性斑块的诊断价值。方法:对经CAG发现冠脉弥漫性狭窄或可疑的39例患者(39支冠脉血管,其中左前降支16例,左回旋支12例,右冠脉11例)同时进行IVUS检查,对照这2种检查结果进行比较。结果:CAG显示的病变血管狭窄程度(面积狭窄率)及斑块累及长度明显低于IVUS所示的结果,而IVUS显示斑块累及范围明显大于CAG结果[(39.48±9.33)mm∶(30.26±8.57)mm],在弥漫性斑块累及冠脉的狭窄率上IVUS高于CAG[(67.2±8.1)%∶(60.3±7.3)%],二者差异具有统计学意义(P<0.05)。CAG无法显示冠脉内形态及斑块性状,而通过IVUS可以清晰显示斑块的形态与性状。结论:对于冠脉内弥漫性斑块,CAG低估了病变程度,IVUS可以直接看到冠脉的横截面,从而明确冠脉狭窄的性状和严重程度,相对于CAG来说,IVUS是评价弥漫性斑块的一种精确方式。     

Sex differences in morphology of coronary artery plaque assessed by intravascular ultrasound

BACKGROUND: Results of autopsy studies have suggested that there are sex differences in morphology of coronary-artery plaques, but these differences have yet to be adequately evaluated in vivo. DESIGN AND METHODS: We performed preintervention intravascular ultrasound (IVUS) measurements on coronary plaques in a consecutive series of 76 men and 30 women with unstable angina pectoris. Both the target lesion and an adjacent reference site were evaluated. Arterial, plaque, and luminal areas were measured by planimetry. Plaques were classified as either calcified or uncalcified, and relative density of plaque was quantitatively assessed by videodensitometry, using a linear gray scale normalized with respect to density of adventitia. RESULTS: Although women were older than men (mean age 55.0 +/- 10.9 versus 60.4 +/- 12.2 years, P = 0.02), their target lesions were less dense (74.6 +/- 23.4 versus 86.2 +/- 22.2% of adventitial density, P = 0.02) and less often found to be calcified (20.0 versus 38.2%, P = 0.05). Similarly, reference sites in female subjects were less dense (77.6 +/- 15.3 versus 97.1 +/- 19.4% of adventitial density, P = 0.01). There was no sex difference in the severity of coronary stenosis. CONCLUSIONS: Both qualitative and quantitative sex differences in in-vivo morphology of coronary plaques morphology were detected by IVUS measurement. Plaques in women appear less videodense and are less often calcified than are those in men. Future studies employing sequential IVUS examinations are needed in order to determine whether these morphologic differences relate to a delay in initiation of plaques, slower progression of plaques, or other sex-specific modulators of plaque composition.     

应用血管内超声评价心肌桥壁冠状动脉压缩比对其近段冠状动脉粥样斑块的影响

目的:应用血管内超声(IVUS)评价左前降支心肌桥及壁冠状动脉(冠脉)压缩与其近段冠脉粥样硬化程度的关系。方法:入选2015-01-2018-05入住我院心内科患者80例,所有患者冠脉造影证实无明显狭窄病变,而IVUS检查发现左前降支存在心肌桥。应用IVUS测量心肌桥位置、心肌桥长度、心肌桥厚度等解剖参数;IVUS测量壁冠脉压缩比以及心肌桥近端20mm内冠脉的最大斑块负荷(Max PB_prox)。单元线性回归分析壁冠脉压缩程度与心肌桥长度、厚度、位置的关系。根据Max PB_prox三等分点将患者分为A、B、C 3组,比较3组间的临床资料、IVUS测量值是否有统计学差异。结果:(1)测得所有患者心肌桥长度为(20.8±12.7)mm,心肌桥厚度为(0.71±0.49)mm,心肌桥位置为(37.4±11.3)mm,壁冠脉压缩比为(23.9±11.8)%,单元线性回归分析显示壁冠脉压缩程度与心肌桥长度(r=0.287,P=0.067)、心肌桥厚度(r=0.296,P=0.086)和心肌桥位置(r=0.301,P=0.073)均无显著相关性。(2)根据Max PB_prox三等分点分组后,Max PB_prox严重程度与壁冠脉压缩比呈正相关(P<0.05),而与心肌桥长度(P=0.450)、心肌桥厚度(P=0.126)及心肌桥位置(P=0.364)无关。结论:心肌桥近端冠脉粥样斑块负荷与壁冠脉压缩比呈正相关,而与心肌桥长度、厚度及位置无关,这有助于识别高危心肌桥病变患者。壁冠脉压缩程度与心肌桥长度、厚度及位置无显著相关。     

Characteristics of atherosclerotic plaque distribution in coronary artery bifurcations: an intravascular ultrasound analysis

OBJECTIVE: Vessel bifurcations are prone to atherosclerotic plaque accumulation. Using volumetric intravascular ultrasound analysis, we investigated atheroma distribution at human coronary bifurcations in vivo. METHODS: We analyzed plaque distribution in 49 left anterior descending coronary artery-diagonal and 20 left circumflex coronary artery-obtuse marginal bifurcations with <50% angiographic stenosis. Cross-sections were analyzed at 1 mm intervals in segments 5 mm proximal and distal from the bifurcation. Planimetry of the lumen and external elastic membrane (EEM) was performed and plaque thickness measured at four different points relative to the branch: 0 degrees, 90 degrees, 180 degrees and 270 degrees. EEM, lumen and plaque volume and percentage plaque burden (plaque volume/EEM volume) were calculated in the proximal and distal segments. The side-branch take-off angle was analyzed in the cross-sectional images. RESULTS: Volumetric analysis showed that EEM, lumen and plaque were larger (P<0.001) in proximal segments than distal segments, whereas percent plaque burden was similar in these segments. Plaque accumulated on the opposite wall to the flow divider. Plaque distribution tended to be more eccentric in distal segments (P=0.05) compared to proximal segments. In 26 of 69 lesions, an asymmetric side-branch take-off was found and was associated with asymmetric plaque distribution compared to those lesions that had a symmetric side-branch take-off (P<0.01). CONCLUSION: We found characteristic patterns of plaque distribution at coronary bifurcations. Proximal segments demonstrated larger plaque volume than distal segments, despite similar percentages of plaque burden. Plaque volume accumulated opposite to the flow divider, especially in distal segments. The side-branch take-off angle in the cross-sectional plane influenced the plaque distribution in bifurcation lesions.     

增龄性冠状动脉斑块钙化特征分析在男性冠心病防治中的应用价值

目的利用血管内超声(IUVS)评价增龄性冠状动脉钙化斑块的形态学特征并分析其在冠心病防治中的应用价值。方法选取行冠状动脉造影(CAG)及IVUS检查的青年组、中年组、老年组三组不同年龄段男性冠心病患者103例,在介入治疗前对钙化病变血管进行IVUS检查,获取血管外弹力膜面积、斑块狭窄面积、管腔钙化斑块狭窄率,测量病变钙化弧度、钙化长度比与钙化指数,并进行年龄因素相关分析。结果①随着年龄的增长,各组靶血管病变的血管外弹力膜面积和斑块面积均有逐步减少与升高的变化趋势,差异有统计学意义(P<0.05)。②钙化弧度、重度钙化率、钙化长度比随着年龄增长而呈现显著增加趋势,在老年组变化程度最明显(P<0.05)。③相关性分析发现钙化相关指标与增龄后的管腔斑块狭窄等指标有显著正相关(P<0.05)。结论随着年龄的增长,斑块钙化的程度逐渐加重,且呈现向心性演变趋势。在IVUS辅助下进行钙化特征相关指标的测定对指导男性冠心病患者复杂钙化病变的介入治疗有重要意义。     

Unique single coronary artery with acute myocardial infarction: observation of the culprit lesion by intravascular ultrasound and coronary angioscopy

We report an acute myocardial infarction in a patient with a single coronary artery. The right coronary artery arose from the middle portion in the left anterior descending artery through the transverse branch. This type of single coronary artery has not been previously reported. Moreover, this is the first report in which the culprit lesion in a patient with a single coronary artery was observed by intravascular ultrasound and coronary angioscopy. The patient underwent successful coronary stent deployment.