应用冠脉血流显像技术检测猪心外膜和心肌内冠脉血流特征的实验研究

目的：应用冠脉血流显像技术检测猪的冠脉血流，初步探讨心外膜和心肌内冠脉的时相性灌注特点及其在冠脉扩张状态下的变化。方法：5条实验小型猪，在麻醉状态下应用超声冠脉血流显像技术探测不同节段心外膜冠脉和左室心肌内的冠脉血流信号，记录其血流频谱曲线。观察心外膜及心肌内冠脉的时相灌注特点，测定冠脉血流速度，计算右冠脉和前降支的舒张期／收缩期峰值血流速度比值。观察静脉推注潘生丁（0．56mg/kg）后前降支和心肌内冠脉血流信号及其频谱曲线特点的变化。结果：所有动物均可检测较清晰的心外膜和心肌内冠脉血流信号；心外膜冠脉为全心动周期前向灌注，右 冠脉的收缩期血流速度明显高于前降支；心肌内冠脉的时相灌注特点为收缩期出现低速的逆向血流；静 注潘生丁使心外膜与心肌内冠脉的血流均明显增强，但灌注模式未变。结论：彩色多普勒冠脉血流显像技术为研究冠脉血流的时相性灌注特点提供了很好的无创性检测手段。     

CT Quantification of Epicardial Fat: Implications for Cardiovascular Risk Assessment

Epicardial fat, a local visceral fat depot around the heart, surrounds the coronary arteries for most of their course and may contribute to the development of coronary atherosclerosis through local production of inflammatory cytokines. Several studies which measured epicardial fat volume noninvasively from CT have shown a relationship of increased epicardial fat volume with coronary artery disease, the presence and progression of coronary plaque, major adverse cardiovascular events, myocardial ischemia, and atrial fibrillation. Noninvasive quantitative measurement of epicardial fat volume from CT is feasible, and may play a clinical role in cardiovascular risk assessment. The scientific evidence, to date, warrants larger studies with longer follow-up to further investigate the role of epicardial fat as an imaging marker with prognostic importance.     

Noninvasive test of nitrate-induced coronary vasomotion by 1.5-T whole-heart 3D magnetic resonance angiography using a T2-prepared SSFP sequence

This study was aimed to investigate the use of 1.5-T whole-heart 3D coronary MRA employing a T2-prepared SSFP sequence for assessing epicardial coronary artery vasodilation following exogenous nitrates. Navigator-gated whole-heart 3D coronary MRA was performed before and after sublingual nitroglycerin (NTG) in 22 volunteers and a T2-prepared SSFP sequence was used for imaging of coronary arteries without MR contrast agent. Coronary cross-sectional area was measured on pre- and post-NTG images of equivalent coronary segments in the major coronary arteries and whole-heart coronary vasodilation was analyzed quantitatively. Measurements were obtained by two independent investigators. Coronary vasodilation could be observed directly on multiplanar reformatted and three-dimensional volume-rendered MR images. On quantitative analysis, NTG administration results in the whole-heart coronary vasodilation by an average of 37.3?±?12.7%. There was moderate yet significant correlation between the NTG-induced vasodilation and age (r?=?-0.52, P?=?0.02). The mean absolute cross-sectional area of the coronary arteries was significantly higher after sublingual NTG in all the major coronary arteries. The coronary area measurements had an interobserver variability of 8?±?3% and an intraoberver variability of 4?±?2%. Non-contrast-enhanced 1.5-T SSFP whole-heart coronary MRA can noninvasively measure endothelium-independent coronary vasodilation over the entire heart with high feasibility and is a promising noninvasive method to explore whole-heart coronary smooth muscle cell function following exogenous nitrates in clinical practice.     

Three-dimensional visualization of coronary arteries in excised hearts.

OBJECTIVE: We sought to image coronary arteries in excised hearts. METHODS: Twelve excised pigs' hearts were imaged in a water bath. The aortic valve was closed surgically. A contrast agent (Echovist) was injected into the aortic root and selectively into single coronary arteries. Three-dimensional (3D) imaging was performed with TomTec Echoscan equipment. Mechanical rotations were performed at 1 degrees intervals. The hearts were visualized by InVivo software. Selective coloring of coronary arteries in 3D data sets was obtained by using color superpositioning, which differentiates information before and after injection of contrast. Distance measurements were performed in conventional 3D echocardiograms of coronary arteries and color-superimposed echocardiograms and compared with those from angiograms and casts. RESULTS: After a learning curve, during which optimal conditions for the visualization of coronary arteries were determined, a quick display of all major parts of the coronary tree was obtained. Distance measurements (n >400) revealed that fundamental contrast echocardiography overestimated angiography by 25% +/- 5% and casts by 28% +/- 6%. However, distances in color-superimposed echocardiograms (flow mode 4) were not significantly different from those obtained from angiograms and casts. In harmonic contrast echocardiograms, color super-positioning gave smaller distances compared with those from fundamental contrast echocardiograms, though they were still significantly larger than the reference diameters. CONCLUSIONS: The 3D imaging of epicardial coronary arteries under ideal conditions in a water bath seems feasible and provides insight into coronary visualization with the use of ultrasonography.     

Beta adrenoceptor subtype in isolated human, monkey and dog epicardial coronary arteries

Isolated human, Japanese monkey and dog epicardial coronary arteries and dog renal and mesenteric arteries treated with phentolamine responded to isoproterenol with a concentration-related relaxation. The KB values of metoprolol, a beta-1 antagonist, in the coronary arteries from different mammals did not differ, but were appreciably smaller than those in the dog renal and mesenteric arteries. Treatment with butoxamine, a beta-2 antagonist, inhibited the relaxation of dog mesenteric arteries to a greater extent than that of monkey and dog coronary arteries. Terbutaline, a beta-2 agonist, produced a greater relaxation in monkey mesenteric and dog renal and mesenteric arteries than in human, monkey and dog coronary arteries. Norepinephrine relaxed the monkey and dog coronary arteries dose-dependently via mainly beta-1 adrenoceptors, but elicited a contraction or a minute relaxation in dog mesenteric arteries even when treated with high concentrations of phentolamine. Contractile responses to electrical stimulation of adrenergic nerves in monkey coronary arteries were potentiated by treatment with metoprolol and propranolol, whereas the contractions in dog mesenteric arteries were unaffected. It is concluded that the amine-induced relaxation of human and monkey epicardial coronary arteries is mediated mainly by beta-1 adrenoceptor subtype, as is the response of dog coronary arteries. Involvement of beta-1 subtype in coronary artery relaxations would be a mechanism underlying potentiation by beta antagonists of the contraction caused by norepinephrine released from adrenergic nerves in primates.     

应用心腔内超声探查冠状动脉血流的实验研究

目的探讨相控阵心腔内超声显示冠脉血流的可行性。方法14只犬经股静脉置入心腔内超声导管,探查冠脉起始段、心外膜及心肌内冠状动脉（冠脉）血流频谱。结果分别有14、10、14、6只犬获得左主干、左前降支、左回旋支、右冠起始段血流频谱。5只犬中分别有3只、3只获得心外膜、心肌内血流频谱。结论相控阵心腔内超声可用于冠脉血流的检测。     

Acute pancreatitis mimicking myocardial infarction: evaluation with myocardial contrast echocardiography.

Acute pancreatitis has frequently been reported to be associated with transient electrocardiography changes mimicking myocardial infarction despite normal epicardial coronary arteries. Although these reports generally have not included simultaneous assessment of myocardial function, 1 previous report has documented suggestive electrocardiography changes associated with a transient regional wall-motion abnormality but normal epicardial coronary arteries. Although the origin of these findings is poorly understood, suggested mechanisms have included electrolyte abnormalities, a vagally mediated reflex, coronary vasospasm, and myonecrosis as a result of the release of pancreatic proteolytic enzymes. We report a case of acute pancreatitis with electrocardiography changes and a regional wall-motion abnormality despite normal epicardial coronary arteries. Myocardial contrast echocardiography performed in this patient to evaluate the coronary microcirculation allows further insight into the mechanism of these findings.     

Potassium channel openers dilate large epicardial coronary arteries in conscious dogs by an indirect, endothelium-dependent mechanism.

Cromakalim and pinacidil, two potassium channel openers, dilate both large and small coronary arteries in conscious dogs. Because flow-mediated dilation of large arteries is endothelium-dependent, the consequences of in vivo endothelium removal (balloon denudation) on the response of large epicardial coronary arteries to cromakalim (10 micrograms/kg) and pinacidil (30 micrograms/kg) were investigated in six dogs chronically instrumented for the measurement of arterial pressure, left circumflex coronary artery diameter and coronary blood flow. Endothelium removal abolished the dilation of large coronary arteries induced by acetylcholine (endothelium-dependent dilation) and reactive hyperemia (flow-mediated dilation), but only slightly reduced (-18%) that induced by nitroglycerin. Before endothelium removal, both cromakalim and pinacidil induced a significant decrease in coronary resistance (-71 +/- 2 and -63 +/- 2%, respectively) and a significant increase in coronary diameter (8.5 +/- 1.3 and 6.7 +/- 0.9%). After endothelium removal, the decreases in coronary resistance were unaffected, but the increases in coronary diameter were reduced by 93 and 98% as compared to predenudation responses with cromakalim and pinacidil, respectively (both P < .01). In contrast, in vitro studies performed in isolated large epicardial coronary arteries obtained from five additional dogs showed that cromakalim evoked relaxations that were not affected by prior in vivo endothelium removal. Thus, despite the presence of potassium channels in isolated denuded large coronary arteries, our data demonstrate that cromakalim- and pinacidil-induced dilation of large arteries in vivo is an indirect, flow-mediated effect which is entirely endothelium-dependent.     

Effects of inhibition of nitric oxide formation on basal vasomotion and endothelium-dependent responses of the coronary arteries in awake dogs.

The role of nitric oxide in basal vasomotor tone and stimulated endothelium-dependent dilations in the coronary arteries in chronically instrumented awake dogs was studied by examining the consequences of inhibiting endogenous nitric oxide formation with the specific inhibitor of nitric oxide formation, NG-monomethyl-L-arginine (L-NMMA). In four awake dogs, coronary dimension crystals were chronically implanted on the circumflex artery for the measurement of epicardial coronary diameter, and Doppler flow probes were implanted for quantitation of phasic coronary blood flow (vasomotion of distal regulatory resistance vessels). Basal epicardial coronary diameter, acetylcholine-stimulated endothelium-dependent dilation, and flow-induced endothelium-dependent dilation of the epicardial arteries and phasic blood flow were recorded before, and after 5, 15, 50, and 120 mg/kg of L-NMMA. L-NMMA induced a dose-related increase in basal epicardial coronary vasomotor tone. There was an accompanying increase in aortic pressure and a decrease in heart rate. At doses greater than or equal to 50 mg/kg, rest phasic coronary blood flow was also decreased. Left ventricular end-diastolic pressure and contractility were not significantly changed. In contrast, the flow-induced or acetylcholine-stimulated endothelium-dependent responses were attenuated only after infusion of the highest does of L-NMMA (120 mg/kg). The changes in the basal vasomotor tone and acetylcholine-stimulated endothelium-dependent responses returned towards the control states in the presence of L-arginine (660 mg/kg). These data support the view that nitric oxide plays a significant role in modulating basal vasomotion and endothelial-dependent dilation stimulated by acetylcholine or increase in blood flow in epicardial coronary arteries and also influence the regulation of coronary blood flow during physiologic conditions.     

3D全心冠状动脉MRI技术

近十年来,三维冠状动脉成像技术的图像信躁比和空间分辨率明显提高,为冠状动脉的无创检查提供了一种安全可靠的手段.西门子公司在1.5和3.0 T系统上都提供了靶容积与全心扫描的冠状动脉成像序列,作者主要针对全心冠状动脉成像的技术进行介绍.     

Cardiac CT and Stent Imaging: Update 2014

Percutaneous coronary intervention with stent implantation is a common technique for coronary revascularization. Despite the widespread use of drug-eluting stents in-stent restenosis (ISR) is still a major issue. Multidetector row computed tomography angiography of the coronary arteries is a well-established, noninvasive tool for the assessment of the coronary arteries. Stent imaging, however, is a challenging task with relevant rates of nondiagnostic scans due to motion and beam-hardening artifacts. Nevertheless, recent scanners provide excellent results for the exclusion of ISR with a negative predictive value of about 97 %. Further indications for CT imaging of coronary stents include the detection and visualization of stent-related complications such as stent fracture. During the last couple of years there have been some major advances in CT imaging of coronary stents relating to hardware and imaging protocols. This review describes recent advances in CT imaging of coronary stents and summarizes current results     

Anatomical and functional evaluation of myocardial bridging on the left anterior descending artery by cardiovascular magnetic resonance imaging.

A myocardial muscle bridge spans a segment of a major epicardial coronary artery that is located in the myocardium. This anatomic configuration can be responsible for angina pectoris, arrhythmias or even death. The current reference standard for diagnosis is conventional x-ray coronary angiography showing systolic compression of an epicardial vessel and the typical angiographic "milking effect." We report the case of a patient with myocardial bridging on the left anterior descending artery, in whom a combination of noninvasive high resolution display of the coronary artery lumen, visualization of the myocardium and functional assessment of blood flow during dobutamine stimulation by cardiovascular magnetic resonance imaging was performed.     

A Nonfluoroscopic Technique for Coronary Arteries Three‐Dimensional Mapping during Epicardial Ventricular Tachycardia Ablation

When performing epicardial ablation of ventricular tachycardia (VT), caution must be taken not to damage the coronary arteries. We report a case in which a new, nonfluoroscopic technique for incorporating an accurate, real‐time reconstruction of the main coronary vessels into a three‐dimensional electroanatomic map was used for epicardial VT ablation.     

Chronic Coronary Syndromes in Women: Challenges in Diagnosis and Management

Sex matters in science. This particularly applies to ischemic heart disease, which displays key differences in pathophysiology, presentation, and effectiveness in diagnostic strategies and management between women and men. However, underrepresentation of women in randomized trials has led to an evidence gap in clinical practice. Nevertheless, it has become clear that women present with a higher burden of symptoms and comorbidities, experience worse outcomes, but are less likely to have flow-limiting stenosis in epicardial coronary arteries than men. A major contributor to this paradox is coronary microvascular disease, a heterogeneous disorder with multifactorial etiology that predominantly affects women. There is a significant interplay between coronary microvascular disease, obstructive coronary artery disease, and the cardiovascular risk associated with it, with impaired vasomotor function often preceding the development of advanced atheroma. This novel concept has recently been referred to as chronic coronary syndromes, which better meets the female phenotype of ischemic heart disease, questioning current management recommendations that still largely apply to flow-limiting stenoses in epicardial coronary arteries typically found in men. The goal of this review is to highlight the most recent scientific advances in understanding chronic coronary syndromes in women. It provides practical advice with focus on challenges in diagnosis and management, and discusses perspectives towards the implementation of sex-specific, safer, and more effective therapeutic strategies.     

Endothelium-mediated coronary blood flow modulation in humans. Effects of age, atherosclerosis, hypercholesterolemia, and hypertension.

The effects of age, atherosclerosis, hypertension, and hypercholesterolemia on vascular function of the coronary circulation were studied by subselective intracoronary infusions of acetylcholine, which releases endothelium-derived relaxing factor, and papaverine, which directly relaxes vascular smooth muscle, in normal patients (n = 18; no risk factors for coronary artery disease), in patients with evidence of early atherosclerosis but normal cholesterol levels and normal blood pressure (n = 12), in patients with hypertension without left ventricular hypertrophy (n = 12), and in patients with hypercholesterolemia (n = 20). Papaverine-induced maximal increases in coronary blood flow were significantly greater in normals, but no differences were noted between the groups of patients with early atherosclerosis, with hypertension, and with hypercholesterolemia. The capacity of the coronary system to increase blood flow in response to acetylcholine was similar in normal and normocholesterolemic patients with epicardial atherosclerosis and/or hypertension but was significantly impaired in patients with hypercholesterolemia, irrespective of evidence of epicardial atherosclerotic lesions. Age (r = -0.62, P < 0.0001) and total serum cholesterol levels (r = -0.70; P < 0.0001) were the only significant independent predictors of a blunted coronary blood flow response to acetylcholine. Thus, hypercholesterolemia and advanced age selectively impair endothelium-mediated relaxation of the coronary microvasculature in response to acetylcholine, whereas endothelial dysfunction is restricted to epicardial arteries in age-matched normocholesterolemic patients with evidence of coronary atherosclerosis and/or hypertension.     

Difference in site and time course of coronary dilating effects of trapidil, nitroglycerin and dipyridamole in anesthetized dogs

Effects of trapidil, a non-nitrate type coronary vasodilator, nitroglycerin and dipyridamole on epicardial coronary diameter and total coronary resistance were studied in anesthetized open-chest dogs. The epicardial coronary diameter of the left circumflex coronary artery was measured by sonomicrometry and total coronary resistance was calculated by aortic pressure and coronary blood flow. Intravenous administration of Trapidil, as well as nitroglycerin, produced transient decreases in total coronary resistance followed by sustained dilation of the large coronary artery. Dipyridamole increased coronary blood flow by 2.7-fold, whereas diameter of the large coronary artery decreased along with the reduction of aortic pressure. The first peak of the biphasic increases in coronary blood flow and subsequent dilation of the large coronary artery appeared after an i.v. bolus administration of trapidil or nitroglycerin and remained even after beta adrenergic blockade. Intracoronary administration of either drug produced monophasic increases in coronary blood flow along with subsequent dilation of the large coronary artery. Thus, trapidil, like nitroglycerin, directly dilates the large and small coronary arteries.     

Stress perfusion magnetic resonance imaging of the heart

Extensive research has documented that rapid imaging during the first pass of a magnetic resonance imaging (MRI) contrast agent provides good sensitivity to detect myocardial blood flow deficits caused by coronary disease, cardiomyopathies, or microvascular dysfunction in patients without obstructive lesions in the coronary arteries. The autoregulatory mechanisms of the coronary circulation serve the purpose of maintaining sufficient blood flow at baseline in the presence of flow-obstructing coronary lesions. Stress testing is most commonly used in this setting to determine the hemodynamic effect of coronary lesions in the epicardial arteries when the small-vessel resistance has been minimized by vasodilation. The protocols for perfusion MRI combined with vasodilation have been successfully tested in large patient studies. Besides the absence of any ionizing radiation, MRI offers the advantages of relatively high spatial resolution to detect perfusion defects limited to the inner layer of the heart muscle. Furthermore, MRI can be used for noninvasive quantitative measurements of myocardial blood flow that compare well with invasive measurements with labeled microspheres. Additional useful markers, such as the dynamic distribution volume, the delay in the arrival of the contrast agent in a myocardial region relative to the enhancement in the arterial input, and the capillary permeability-surface area product, may, in the future, further enhance the capabilities to characterize with MRI coronary atherosclerosis, coronary vascular dysfunction, and adaptive mechanisms in the coronary circulation, such as arteriogenesis, that reduce ischemia.     

What have we learned about coronary artery disease from high-frequency epicardial echocardiography?

We have used a high frequency epicardial echocardiographic technique to visualize and measure coronary artery lumens and walls in patients undergoing cardiac surgery. A 12 MHz probe (Surgiscan, Biosound Corp.) is sterilized and placed on the exposed epicardial coronary arteries. Transverse cross-sectional views are obtained from the arteries on the anterior surface of the heart: the right coronary artery to the cardiac margin and the left anterior descending coronary artery to the cardiac apex. Numerous echocardiographic-angiographic-pathological correlations have been obtained from this work. We have validated the echocardiographic lumen and wall measurements by comparing the echo measurements to histological material from pressure-distended coronary arterial segments (from animals and fresh human autopsy specimens). We have shown by comparison with angiography that coronary arteries which appear normal or only minimally diseased by angiograms are often diffusely and severely atherosclerotic. We have also evaluated the shape of atherosclerotic lesions and demonstrated a wide range of lumen shapes (oval, circular, complex) and location within the residual coronary lumen (eccentric vs. concentric). Highly eccentric lesions are characterized by relative preservation of portions of the arterial wall, and this may preserve vasoreactivity of the atherosclerotic vessel. We have also demonstrated remodeling of atherosclerotic lesions: enlargement of the total arterial area (wall plus lumen) as a compensatory mechanism to preserve the arterial lumen in the face of encroaching atherosclerosis. High frequency epicardial echocardiography offers an accurate, real-time, in-vivo method for the anatomic and functional evaluation of coronary atherosclerosis. This dynamic, in-vivo technique supports and extends information previously obtainable only from pathologic studies. It contributes to our understanding of the pathologic anatomy of coronary artery disease.     

An intramural left ventricular fistula caused by left ventriculography

Congenital coronary sinus(CS)fistula is a rare form of cardiac abnormality.The fistula forms an abnormal communication between the cardiac chambers and the coronary arteries.The most common form of fistula arises from the right coronary arteries while the left ventricular and CS fistula is rare.Coronary slow-flow phenomenon(CSFP)is defined as a delayed opacification of distal vessels without any epicardial disease.[1]     

心外膜超声在非体外循环冠状动脉旁路移植术中对吻合口的评价

目的探讨心外膜超声技术在非体外循环冠状动脉旁路移植术中对吻合口的评价及临床意义.方法应用GE公司的新型心外膜超声探头对32例非体外循环左乳内动脉左前降支动脉旁路移植术中吻合口进行检测.应用二维超声显像法(2D)和彩色多普勒显像法(CDFI)获得吻合口的二维声像图并显示血流通畅情况,同时测量吻合口的相关径线.结果所有病例均获得质量好的吻合口2D声像图, CDFI显示吻合口均通畅.2D结合CDFI对吻合口的评价结果与术中瞬时测血流量技术(TTFM)的结果相一致,与术后立即进行的造影结果对比,符合率为100%.结论应用新型探头的心外膜超声技术对左乳内动脉左前降支动脉旁路移植术中吻合口的评价具有重要的临床意义.