Accurate needle-free assessment of myocardial oxygenation for ischemic heart disease in canines using magnetic resonance imaging

Abstract

Myocardial oxygenation—the ability of blood vessels to supply the heart muscle (myocardium) with oxygen—is a critical determinant of cardiac function. Impairment of myocardial oxygenation is a defining feature of ischemic heart disease (IHD), which is caused by pathological conditions that affect the blood vessels supplying oxygen to the heart muscle. Detecting altered myocardial oxygenation can help guide interventions and prevent acute life-threatening events such as heart attacks (myocardial infarction); however, current diagnosis of IHD relies on surrogate metrics and exogenous contrast agents for which many patients are contraindicated. An oxygenation-sensitive cardiac magnetic resonance imaging (CMR) approach used previously to demonstrate that CMR signals can be sensitized to changes in myocardial oxygenation showed limited ability to detect small changes in signals in the heart because of physiologic and imaging noise during data acquisition. Here, we demonstrate a CMR-based approach termed cfMRI [cardiac functional magnetic resonance imaging (MRI)] that detects myocardial oxygenation. cfMRI uses carbon dioxide for repeat interrogation of the functional capacity of the heart’s blood vessels via a fast MRI approach suitable for clinical adoption without limitations of key confounders (cardiac/respiratory motion and heart rate changes). This method integrates multiple whole-heart images within a computational framework to reduce noise, producing confidence maps of alterations in myocardial oxygenation. cfMRI permits noninvasive monitoring of myocardial oxygenation without requiring ionizing radiation, contrast agents, or needles. This has the potential to broaden our ability to noninvasively identify IHD and a diverse spectrum of heart diseases related to myocardial ischemia.

Blood Oxygen Level–Dependent MRI of the Myocardium with Multiecho Gradient-Echo Spin-Echo Imaging

“…increase this feasibility. For example, signal-to-noise ratio can be improved by averaging over multiple heartbeats or breath holds (6,9,10), or can further be preserved while increasing the spatial resolution by introducing compressed sensing and subspace modeling (17). Furthermore, to improve BOLD sensitivity, mapping and increasing the field strength have been introduced (7,17,18).…”

“…breath hold is compromised, possibly because of a slower or nonexistent vascular response to the increase in CO 2 (14,25). The sensitivity of this dynamic cardiac BOLD MRI approach by using only a breath hold could be achieved by allowing analysis of the rate of T2 and T2* changes instead of static comparisons between rest and stress states (5)(6)(7)10,11,15). Interestingly, another cardiac BOLD MRI technique evaluated in participants with coronary artery disease, in whom 54% had hypertension, also showed a weaker BOLD response in the remote areas compared with healthy control participants (8), which is similar to the GESE echo-planar imaging results in our study.…”

Assessment of Myocardial Function During Blood Pressure Manipulations Using Feature Tracking Cardiovascular Magnetic Resonance

“…Multiple studies investigating myocardial oxygenation responses in healthy animal models as well as in various disease models ( 7 , 14 , 15 , 17 – 21 ) have emerged over the last decade. As we use a cine variant, it measures a cardiac phase every 40 ms, thus strain can be analyzed from the same set of images.…”

Biomedical Imaging in Experimental Models of Cardiovascular Disease

“…The principal limitation of blood oxygen level–dependent imaging lies in the relative (stress/rest ratio) nature of the measurement. The technique can detect an increase in myocardial blood flow in humans/large animals from a breath hold–induced rise in myocardial CO 2 , 88,89 but the feasibility of this in rodents is unclear.…”