Koronate Mikroembolisierung — Bedeutung bei akuten koronaren Syndromen und bei interventionellen Eingriffen

Abstract

The diagnosis coronary artery disease is classically based on patient's symptoms and morphology, as analyzed by angiography. The importance of risk factors for the development of coronary atherosclerosis and disturbance of coronary vasomotion is clearly established. However, microembolization of the coronary circulation has also to be taken into account. Microembolization may occur as a single or as multiple, repetitive events, and it may induce inflammatory responses. Spontaneous microembolization may occur, when the fibrous cap of an atheroma or fibroatheroma (Stary i.v. and Va) ruptures and the lipid pool with or without additional thrombus formation is washed out of the atheroma into the microcirculation. Such events with progressive thrombus formation are known as cyclic flow variations. Plaque rupture occurs more frequently than previously assumed, i.e. in 9% of patients without known heart disease suffering a traffic accident and in 22% of patients with hypertension and diabetes. Also, in patients dying from sudden death microembolization is frequently found. Patients with stable and unstable angina show not only signs of coronary plaque rupture and thrombus formation, but also microemboli and microinfarcts, the only difference between those with stable and unstable angina being the number of events. Appreciation of microembolization may help to better understand the pathogenesis of ischemic cardiomyopathy, diabetic cardiomyopathy and acute coronary syndromes, in particular in patients with normal coronary angiograms, but plaque rupture detected by intravascular ultrasound. Also, the benefit from glycoprotein IIb/IIIa receptor antagonist is better understood, when not only the prevention of thrombus formation in the epicardial atherosclerotic plaque, but also that of microemboli is taken into account. Microembolization also occurs during PTCA, inducing elevations of troponin T and I and elevations of the ST segment in the EKG. Elevated baseline coronary blood flow velocity, as a potential consequence of reactive hyperemia in myocardium surrounding areas of microembolization, is more frequent in patients with high frequency rotablation than in patients with stenting and in patients with PTCA. The hypothesis of iafrogenic microembolization during coronary interventions is now supported by the use of aspiration and filtration devices, where particles with a size of up to 700 microns have been retrieved. In the experiment, microembolization is characterized by perfusion-contraction mismatch, as the proportionate reduction of flow and function seen with an epicardial stenosis is lost and replaced by contractile dysfunction in the absence of reduced flow. The analysis of the coronary microcirculation, in addition to that of the morphology and function of epicardial coronary arteries, and in particular appreciation of the concept of microembolization will further improve the understanding of the pathophysiology and clinical symptoms of coronary artery disease.

Diagnostic accuracy of stress myocardial perfusion MRI and late gadolinium-enhanced MRI for detecting flow-limiting coronary artery disease: a multicenter study

“…Several studies have demonstrated that combining LGE MRI with stress-rest perfusion MRI can improve the sensitivity of MRI for obstructive CAD without deteriorating the specificity when only obvious myocardial infarction (i.e., LGE consistent with a coronary distribution) were considered [28,29]. However, correlating the presence of LGE with flow-limiting obstructive CAD can be inappropriate since microinfarcts may occur without coronary artery narrowing as a result of plaque rupture/ ulceration and subsequent washout of the lipid pool with or without additional thrombus formation into the microcirculation [30,31]. As a result, the scar can be atypical for myocardial infarction.…”

Establishment and Characterization of an Experimental Model of Coronary Thrombotic Microembolism in Rats

“…The ratio of NF/left ventricle area (NF/LV) from all examined slices were calculated and averaged. Even slices (2,4,6,8,10) were used for light and transmission electron microscopic analysis.…”

“…Atherosclerotic embolization in the microvasculature is associated with adverse prognosis. [1][2][3][4] Research results derived from suitable experimental models of coronary microembolism would help clinicians to understand the underlying pathological mechanisms and to develop effective therapies of coronary microembolism induced by atherosclerotic embolization in the microvasculature.5 Until now, plastic microspheres ranging from 20 to 900 m in diameter were injected into the coronary microcirculation to establish the coronary microembolism models in dog, swine and sheep.6 -11 Experimental models were also made by injecting adenosine-diphosphate or catecholamine to induce platelet aggregation in coronary microcirculation in pigs.12-13 However, injecting microspheres with unique sizing would only occlude respective vessels with comparable sizes, while thrombotic debris in patients might vary greatly in sizing and affect vessels with different diameters. Models using adenosine diphosphate or catecholamine could mimic the platelet aggregation process during coronary microthrombosis but could not reflect the influences of various embolism components of atherosclerotic plaques.…”

“…Atherosclerotic embolization in the microvasculature is associated with adverse prognosis. [1][2][3][4] Research results derived from suitable experimental models of coronary microembolism would help clinicians to understand the underlying pathological mechanisms and to develop effective therapies of coronary microembolism induced by atherosclerotic embolization in the microvasculature. 5 Until now, plastic microspheres ranging from 20 to 900 m in diameter were injected into the coronary microcirculation to establish the coronary microembolism models in dog, swine and sheep.…”

Embolic Protection With Filtering or Occlusion Balloons During Saphenous Vein Graft Stenting Retrieves Identical Volumes and Sizes of Particulate Debris

“…[1][2][3] Pharmacological approaches such as glycoprotein IIb/IIIa inhibition or direct stenting have not been shown to reduce complications resulting from distal embolization in SVG stenting. 4 -7 Distal protection devices 8 -17 have been developed, intended to trap plaque-derived emboli during interventions and prevent embolization into the distal vascular bed.…”