Noninvasive Imaging of Myocardial Viability

Abstract

Abstract-Complete knowledge of myocardial structure, metabolism, and function is crucial to understanding the response of the heart to injury such as ischemia. Increasingly, this type of knowledge is required at multiple levels, from that of the isolated myocyte to the functioning organism, to provide basic scientists and clinical investigators a common framework for translation of findings and information feedback. This article focuses on the utilization of imaging methods to assess myocardial viability in vivo. It discusses the advantages and pitfalls of different imaging techniques, with particular emphasis on available data in humans and large animal models. Because of their novelty and potential for accurate phenotyping of human pathophysiology, magnetic resonance modalities will be highlighted. (Circ Res. 2003;93:1146-1158.)Key Words: cardiac magnetic resonance imaging Ⅲ myocardial viability Ⅲ myocardial metabolism C omplete knowledge of myocardial structure, metabolism, and function is crucial to understanding the response of the heart to injury such as ischemia. Increasingly, this type of knowledge is required at multiple levels, from that of the isolated myocyte to the functioning organism, to provide basic scientists and clinical investigators a common framework for translation of findings and information feedback. This article focuses on the utilization of noninvasive imaging methods to assess myocardial viability in vivo. It discusses the advantages and pitfalls of different imaging techniques, with emphasis on available data in humans and large animal models. Because of their novelty and potential for accurate phenotyping of human pathophysiology, magnetic resonance modalities will be highlighted.The clinical recognition that myocardial dysfunction in patients with coronary artery disease was potentially reversible preceded basic science investigations into pathophysiologic mechanisms of viability. Because it was first recognized as a clinical phenomenon, the concepts of viability and functional recovery have been used interchangeably, particularly in many of the existing clinical studies. In fact, these two terms may not be synonymous. A complete assessment of viability may in truth require comprehensive evaluation of perfusion and metabolism in addition to global and regional function. This has become increasingly apparent from basic research investigations exploring potential mechanisms for viability. These pathophysiological hypotheses will be reviewed to serve as background for discussion of the relative merits of the present clinical applications of diagnostic imaging in viability assessment.

Clinical Significance of A Single Multi-Slice CT Assessment in Patients with Coronary Chronic Total Occlusion Lesions Prior to Revascularization

“…However, since the results were from post-myocardial infarction patients, it remains unclear whether the findings can be extended to all patients with a CTO lesion. Delayed hyperenhancement in a chronic collagenous myocardial scar results from an accumulation of contrast media in the interstitial space between collagen fibers, resulting in an increased volume of contrast distribution in the scar tissue compared with that of tightly packed myocytes[26]. The present study showed that the location of the early perfusion defect region identified by MSCT was corresponded to the nuclide filling defect on stressed 201 TI-SPECT perfusion imaging.…”

Evaluation of Age-Related Interstitial Myocardial Fibrosis With Cardiac Magnetic Resonance Contrast-Enhanced T1 Mapping

“…Emerging experimental and clinical investigations hold promise for the detection of myocardial fibrosis derived from noninvasive myocardial viability assessment by using contrast-enhanced magnetic resonance (MR) imaging techniques (12–14). Late gadolinium (Gd) enhancement MR protocols use a T 1 -weighted inversion recovery–prepared fast gradient echo with imaging performed 10 to 20 min after the intravenous administration of an extracellular Gd-based contrast agent (13).…”

Cardiovascular Magnetic Resonance Imaging in Experimental Models

“…On first-pass images, normal myocardium with normal perfusion would be enhanced by the contrast agent, whereas infarcted regions would appear hypoenhanced due to reduced or absent perfusion. However, the hypoenhanced region would gradually become hyperenhanced as a consequence of increased retention of contrast agent, which is thought to be caused by increased extracellular matrix within collagenous scar, and delayed washout due to reduced capillary density [56]. This method is well-validated clinically for predicting the distribution of infarcted myocardium [57] and for excluding irreversible damage where no delayed enhancement is observed [58, 59].…”