Prognostic Significance of Microvascular Obstruction by Magnetic Resonance Imaging in Patients With Acute Myocardial Infarction

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

The extent of microvascular obstruction during acute coronary occlusion may determine the eventual magnitude of myocardial damage and thus, patient prognosis after infarction. By contrast-enhanced MRI, regions of profound microvascular obstruction at the infarct core are hypoenhanced and correspond to greater myocardial damage acutely. We investigated whether profound microvascular obstruction after infarction predicts 2-year cardiovascular morbidity and mortality. Forty-four patients underwent MRI 10 +/- 6 days after infarction. Microvascular obstruction was defined as hypoenhancement seen 1 to 2 minutes after contrast injection. Infarct size was assessed as percent left ventricular mass hyperenhanced 5 to 10 minutes after contrast. Patients were followed clinically for 16 +/- 5 months. Seventeen patients returned 6 months after infarction for repeat MRI. Patients with microvascular obstruction (n = 11) had more cardiovascular events than those without (45% versus 9%; P=.016). In fact, microvascular status predicted occurrence of cardiovascular complications (chi2 = 6.46, P<.01). The risk of adverse events increased with infarct extent (30%, 43%, and 71% for small [n = 10], midsized [n = 14], and large [n = 14] infarcts, P<.05). Even after infarct size was controlled for, the presence of microvascular obstruction remained a prognostic marker of postinfarction complications (chi2 = 5.17, P<.05). Among those returning for follow-up imaging, the presence of microvascular obstruction was associated with fibrous scar formation (chi2 = 10.0, P<.01) and left ventricular remodeling (P<.05). After infarction, MRI-determined microvascular obstruction predicts more frequent cardiovascular complications. In addition, infarct size determined by MRI also relates directly to long-term prognosis in patients with acute myocardial infarction. Moreover, microvascular status remains a strong prognostic marker even after control for infarct size.

Related collections

Most cited references 20

Record: found
Abstract: found
Article: not found

The "no-reflow" phenomenon after temporary coronary occlusion in the dog.

R Kloner, C E Ganote, R B Jennings (1974)

The role of microvascular damage in the genesis of the "no-reflow" phenomenon was investigated in the left ventricular myocardium of dogs subjected to temporary occlusions of a major coronary artery for 40 and 90 min. Intravenous carbon black or thioflavin S (a fluorescent vital stain for endothelium) were used to demonstrate the distribution of coronary arterial flow in control and damaged myocardium. These tracers were injected simultaneously with release of the coronary occlusion or after 5 or 20 min of reflow of coronary arterial blood. After 40 min of ischemia plus arterial reperfusion, usually the tracers were evenly distributed throughout the damaged tissue at each time of reperfusion. On the other hand, when reflow was allowed after 90 min of ischemia, portions of the inner half of damaged myocardium were not penetrated by the tracers. Electron microscopic study of this poorly perfused tissue revealed severe capillary damage; endothelial cells with large intraluminal protrusions and decreased pinocytic vesicles were common. Also, occasional intraluminal fibrin thrombi were noted, as well as extravascular fibrin deposits and erythrocytes. Myocardial cells were swollen in both poorly perfused and well-perfused irreversibly injured tissue. Contraction bands and mitochondrial Ca(2+) accumulation were prominent features of irreversible injury with reflow at 40 min but were not noted after 90 min of ischemia in areas with poor perfusion. These results suggest that 40 min of ischemia were tolerated by the capillary bed of the dog heart without serious capillary damage or perfusion defects, but that 90 min of ischemic injury was associated with the "no-reflow" phenomenon, i.e., failure to achieve uniform reperfusion. This failure of reflow was associated with extensive capillary damage and myocardial cell swelling. Death of severely ischemic myocardial cells in this model occurs before the onset of capillary damage and the no-reflow phenomenon.

0 comments Cited 183 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Ventricular dysfunction and the risk of stroke after myocardial infarction.

C Wun, M. Sutton, Lawrence Pfeffer … (1997)

In patients who have had a myocardial infarction, the long-term risk of stroke and its relation to the extent of left ventricular dysfunction have not been determined. We studied whether a reduced left ventricular ejection fraction is associated with an increased risk of stroke after myocardial infarction and whether other factors such as older age and therapy with anticoagulants, thrombolytic agents, or captopril affect long-term rates of stroke. We performed an observational analysis of prospectively collected data on 2231 patients who had left ventricular dysfunction after acute myocardial infarction who were enrolled in the Survival and Ventricular Enlargement trial. The mean follow-up was 42 months. Risk factors for stroke were assessed by both univariate and multivariate Cox proportional-hazards analysis. Among these patients, 103 (4.6 percent) had fatal or nonfatal strokes during the study (rate of stroke per year of follow-up, 1.5 percent). The estimated five-year rate of stroke in all the patients was 8.1 percent. As compared with patients without stroke, patients with stroke were older (mean [+/-SD] age, 63+/-9 years vs. 59+/-11 years; P<0.001) and had lower ejection fractions (29+/-7 percent vs. 31+/-7 percent, P=0.01). Independent risk factors for stroke included a lower ejection fraction (for every decrease of 5 percentage points in the ejection fraction there was an 18 percent increase in the risk of stroke), older age, and the absence of aspirin or anticoagulant therapy. Patients with ejection fractions of < or = 28 percent after myocardial infarction had a relative risk of stroke of 1.86, as compared with patients with ejection fractions of more than 35 percent (P=0.01). The use of thrombolytic agents and captopril had no significant effect on the risk of stroke. During the five years after myocardial infarction, patients have a substantial risk of stroke. A decreased ejection fraction and older age are both independent predictors of an increased risk of stroke. Anticoagulant therapy appears to have a protective effect against stroke after myocardial infarction.

0 comments Cited 79 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

A preliminary report comparing magnetic resonance coronary angiography with conventional angiography.

W Manning, Elazer Edelman, Weidong Li (1993)

The ability to assess the patency of coronary arteries by noninvasive means would represent an important advance. We have developed a magnetic resonance imaging (MRI) coronary angiographic technique that permits the display of areas of abnormal coronary blood flow. We have compared this method with conventional contrast angiography for the identification of coronary-artery stenoses. MRI coronary angiography was performed with an electrocardiographically gated sequence in 39 subjects, 33 to 84 years of age, who were scheduled for elective cardiac catheterization with coronary angiography. Sequential overlapping transverse and oblique sections were acquired during periods of breath-holding and were displayed as cine loops for analysis. MRI and conventional angiographic data were compared in a blinded manner. The four major epicardial coronary arteries were classified by MRI coronary angiography as being normal (or having only minimal irregularities) or as having disease that was moderately severe to severe. The sensitivity and specificity of MRI coronary angiography, as compared with conventional angiography, for correctly identifying individual vessels with > or = 50 percent angiographic stenoses were 90 percent and 92 percent, respectively. The corresponding positive and negative predictive values were 0.85 and 0.95, respectively. The sensitivity and specificity of the technique were 100 percent and 100 percent, respectively, for the left main coronary artery, 87 percent and 92 percent for the left anterior descending coronary artery, 71 percent and 90 percent for the left circumflex coronary artery, and 100 percent and 78 percent for the right coronary artery. MRI coronary angiography provides a new approach to evaluating the patency of coronary arteries. These preliminary data suggest that this technique may provide a noninvasive means of evaluating patients with known or suspected coronary artery disease. At its current stage of development, this procedure may be most helpful for excluding clinically important stenoses in patients referred for diagnostic contrast angiography.

0 comments Cited 38 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Journal

Title: Circulation

Abbreviated Title: Circulation

Publisher: Ovid Technologies (Wolters Kluwer Health)

ISSN (Print): 0009-7322

ISSN (Electronic): 1524-4539

Publication date Created: March 03 1998

Publication date (Print): March 03 1998

Volume: 97

Issue: 8

Pages: 765-772

Affiliations

[1 ]From the Division of Cardiology, Department of Medicine (K.C.W., L.A.B., S.P.S., R.S.B., J.A.C.L.) and the Division of Diagnostic Imaging, Department of Radiology (E.A.Z., C.H.L.), The Johns Hopkins University School of Medicine, Baltimore, Md, and The Feinberg Cardiovascular Research Institute (R.M.J.), Northwestern University Medical School, Chicago, Ill.