Changes in myocardial oxygenation and perfusion under pharmacological stress with dipyridamole: Assessment using T*2 and T1 measurements

Abstract

The aim of this pilot-study was to evaluate changes in myocar-dial oxygenation and perfusion under pharmacological stress with dipyridamole (DIP) by means of MRI. Twenty healthy volunteers were examined using a multi-echo gradient-echo sequence. The differential myocardial signal response due to the blood oxygen level dependent (BOLD) effect was studied under variable conditions of myocardial oxygen supply caused by the vasodilator DIP. Unlike contrast agents (CA) methods, which require at least two injections of CA and DIP, the presented methods require only a single infusion of DIP. To assess changes in myocardial perfusion, a saturation recovery Turbo-FLASH (SRTFL) sequence with centric reordering for T 1 measurements was used with global and slice-selective spin-preparation (five volunteers). The signal response was measured at baseline conditions and when myocardial blood flow was increased during pharmacological stress with DIP. Administration of DIP induced a 17 9% increase in T* 2. Enhanced perfusion resulted in a 15 5% decrease of T 1 after slice-selective spin preparation and a calculated increase in absolute perfusion of about 5.1 ml/(g min), which reflects coronary reserve. The study shows that DIP-induced alterations in the relationship between myocardial oxygen supply and demand are detectable in healthy volunteers using T* 2 and T 1 measurements. A combination of T* 2 and T 1 examinations could become a useful diagnostic tool for the non-invasive assessment of myocardial oxygenation and perfusion in patients with coronary artery disease (CAD). Magn Reson Med 41:686-695, 1999. 1999 Wiley-Liss, Inc.

Monitoring blood oxygen state in muscle microcirculation with transverse relaxation

“…However, Bauer et al (36,37), supported with experimental data from Atalay et al (38) and Wacker et al (39), suggested that the major contributing factor in cardiac muscle was due to perivascular field gradients. Atalay et al (38) demonstrated that blood oxygenation had a significant effect on cardiac T* 2 in isolated rat hearts, and Li et al (40) and Wacker et al (39) had similar findings in human hearts. There are some significant differences between the aforementioned studies and our approach.…”

“…Niemi et al (41), however, suggest that dipyridamole can be associated with as much as a 50% increase in blood volume in cardiac muscle, which would significantly impact the interpretation of these results. Finally, the studies of Wacker et al (39) were global measures of signal (i.e., T 2 Ј) behavior in the myocardium due to SNR restraints, and thus should be more sensitive than our ROI analysis of T 2 Ј behavior. Using the entire volume of the myocardium also has the potential for partial volume effects associated with blood in the ventricular chamber.…”

“…Second, the blood volume fraction in cardiac muscle is greater by a factor of 3-4 than in skeletal muscle (2-3% vs. 8 -10%), so the magnitude of the effect should be less in skeletal muscle compared to cardiac muscle. In addition, the studies of Li et al (40) and Wacker et al (39) in human hearts were dipyridamole studies in which increased oxygenation is assumed via the mechanism of increased blood flow due to this agent. Niemi et al (41), however, suggest that dipyridamole can be associated with as much as a 50% increase in blood volume in cardiac muscle, which would significantly impact the interpretation of these results.…”

Blood oxygen level-dependent magnetic resonance imaging in patients with stress-induced angina

“…Li et al 4 have shown that T2* reflects changes of myocardial oxygenation independent of coronary flow, and Niemi et al 5 detected significant changes of myocardial SI in T2*-weighted images after the administration of dipyridamole. Wacker et al 6 applied the method to detect perfusion-related changes of T2* relaxation time induced by dipyridamole in healthy volunteers and coronary patients. 7,8 The purpose of our study was to test the feasibility and sensitivity of BOLD-MRI to detect coronary perfusion defects.…”

Relationship of apparent myocardial T2 and oxygenation: Towards quantification of myocardial oxygen extraction fraction

“…Promising results have been shown in the assessment of oxygen change in myocardial tissue (3)(4)(5)(6)(7)(8) and coronary sinus (9) using MRI and the blood oxygen level dependent (BOLD) effect. The intravascular BOLD effect using T 2 contrast has been quantified in brain functional studies (10) and in the estimation of OEF in the brain (11).…”