Chronic stable angina cardiac magnetic resonance imaging

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org] Phone:617-632-7753; Associate Editor(s)-in-Chief: ; Smita Kohli, M.D.; Lakshmi Gopalakrishnan, M.B.B.S.

Overview
Cardiac magnetic resonance imaging (CMRI) is a non-invasive test that is useful in the evaluation of overall coronary anatomy and function. CMRI also helps in the identification of inflammation, neovascularization and fibrous cap, It, therefore, holds the potential for plaque characterization.

==Indications for CMR based on Consensus Panel report ==

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Class I
1. Assessment of global ventricular (left and right) function and mass

2. Detection of coronary artery disease
 * a. Coronary MRA (anomalies)

3. Acute and chronic myocardial infarction
 * a. Detection and assessment
 * b. Myocardial viability

Class II
1. Detection of coronary artery disease
 * a. Regional left ventricular function at rest and during dobutamine stress
 * b. Assessment of myocardial perfusion
 * c. Coronary MRA of bypass graft patency

2. Acute and chronic myocardial infarction
 * a. Ventricular thrombus

Class III
1. Detection of coronary artery disease
 * a. Coronary MRA (CAD)

2. Acute and chronic myocardial infarction
 * a. Ventricular septal defect
 * b. Mitral regurgitation (acute MI)

Class Inv
1. Detection of coronary artery disease
 * a. MR flow measurements in the coronary arteries
 * b. Arterial wall imaging

2. Acute and chronic myocardial infarction
 * a. Acute coronary syndromes}}

Note:
 * Class I: provides clinically relevant information and is usually appropriate; may be used as first line imaging technique; usually supported by substantial literature.


 * Class II: provides clinically relevant information and is frequently useful; other techniques may provide similar information; supported by limited literature.


 * Class III: provides clinically relevant information but is infrequently used because information from other imaging techniques is usually adequate.


 * Class Inv: potentially useful, but still investigational.

Detection of CAD using CMRI

 * Early detection of atherosclerosis and endothelial dysfunction using CMRI is possible with arterial wall imaging and assessing the reactivity of brachial artery.
 * CMRI can be used to image arteries outside the heart which are affected long before the clinical manifestations of atherosclerosis.
 * Direct endothelial function can be measured non-invasively using stimuli that causes flow mediated arterial vasodilatation . CMRI measures flow changes in response to stimuli in addition to measuring brachial dilation.


 * Alternative approaches include:
 * Visualization of the effects of induced ischemia (wall motion, perfusion)
 * Stress wall motion abnormalities: In patients with CAD, dobutamine stress CMR is helpful to identify ischemia-induced wall motion abnormalities and is considered effective is patients who are unsuitable for dobutamine echocardiography.


 * Myocardial perfusion: In patients with CAD, CMR showed improvement in myocardial perfusion after coronary angioplasty and in patients with cadiac syndrome X impaired sub-endocardial perfusion was observed.


 * Direct visualization of coronary arteries (coronary angiography and flow)
 * Coronary angiography and coronary flow evaluation: Coronary flow reserve is useful in the identification of LAD stenosis and in-stent restenosis . CMR imaging is also very accurate in the prediction of graft patency.