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[Myocardial microcirculation in humans--new approaches using MRI]
Christian M Wacker1, Wolfgang R Bauer
1Medizinische Klinik, Universität Würzburg, Germany. wacker_c@medizin.uni-wuerzburg.de
Herz
|April 2, 2003
Summary
New MRI techniques assess myocardial microcirculation without contrast agents, evaluating perfusion reserve and regional blood volume. Blood oxygen-level-dependent MRI detects capillary recruitment in coronary artery disease patients, aiding therapeutic decisions.
Area of Science:
- Cardiovascular Imaging
- Magnetic Resonance Imaging (MRI)
- Myocardial Perfusion Assessment
Background:
- Characterizing myocardial microcirculation is crucial for coronary artery disease (CAD) management, offering better insights than stenosis quantification alone.
- Existing MRI perfusion techniques often rely on contrast agents (CA), limiting reproducibility and quantitative accuracy.
- Assessing regional myocardial blood volume (RBV) and capillary recruitment is vital for understanding autoregulatory responses to stenosis.
Purpose of the Study:
- To present novel, primarily non-contrast-enhanced MRI techniques for assessing myocardial perfusion, RBV, and capillary recruitment.
- To evaluate the feasibility and reproducibility of these new techniques in volunteers and CAD patients.
- To demonstrate the utility of blood oxygen-level-dependent (BOLD) MRI for detecting post-stenotic capillary recruitment.
Main Methods:
- Developed and applied spin-labeling MRI techniques based on T1 measurements for quantitative perfusion assessment without CA.
- Utilized intravascular CA with spin-labeling to determine intra-extracapillary water proton exchange and RBV.
- Employed T2*-weighted gradient echo sequences for blood oxygen-level-dependent (BOLD) MRI to assess deoxyhemoglobin levels and capillary recruitment.
Main Results:
- Quantitative perfusion was accurately determined in volunteers (2.5 ± 0.7 ml/g/min at rest, reserve ~2.0).
- BOLD MRI demonstrated increased T2* under stress in volunteers, indicating decreased intracapillary deoxyhemoglobin.
- In CAD patients, BOLD MRI revealed significantly lower T2* in regions associated with stenosis, which increased after vasodilator administration, confirming post-stenotic capillary recruitment.
Conclusions:
- Novel MRI techniques enable noninvasive, quantitative assessment of myocardial perfusion and RBV, primarily without contrast agents.
- Myocardial BOLD MRI effectively detects capillary recruitment in response to coronary artery stenosis, providing valuable diagnostic information.
- These advancements offer improved tools for comprehensive cardiovascular assessment and therapeutic decision-making in patients with CAD.