Published in:
01-10-2011 | Advances in Nonnuclear Imaging Technologies
Three-dimensional contrast-enhanced and non-contrast-enhanced cardiac magnetic resonance imaging for the assessment of myocardial ischemic reactions
The practice of looking deeply into the myocardium
Published in: Journal of Nuclear Cardiology | Issue 5/2011
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The assessment of regional and global myocardial function, myocardial tissue characterization, and ischemia by cardiac magnetic resonance (CMR) imaging has become an integrated part of the diagnostic armamentarium in cardiology.1 Combined scan protocols providing detailed diagnostic information on ventricular wall motion, myocardial viability, and vasodilator stress perfusion are performed during routine evaluation of patients with coronary artery disease (CAD) and deliver valuable information for accurate prognostication (Figure 1; Movie 1 in Supplementary material).2 In general, ischemia detection represents the mainstay of risk stratification and therapeutic decision making in patients with CAD. Hence, the diagnostic module “ischemia detection” is rightfully considered a key component of a comprehensive CMR examination (Figure 2; Movie 2 in Supplementary material). With CMR imaging, pharmacological stress is usually preferred and dobutamine or adenosine is used to provoke regional wall motion or perfusion abnormalities being indicative of an ischemic reaction of the myocardium. In addition, CMR imaging represents an excellent tool for the assessment of myocardial viability, since it offers the unique possibility to visualize myocardial scar tissue with high contrast and with sub-millimeter spatial resolution. The so-called late gadolinium enhancement (LGE) technique has been extensively researched and is now widely accepted as a reference standard to detect the presence and to directly quantify the extent and severity of myocardial scar in chronically injured myocardium. Regarding the CMR protocol aiming at ischemia detection, a high diagnostic performance was reported in several studies by analysis of the vasodilator stress data in combination with subsequent LGE imaging which favors a stress-only protocol.3 The diagnostic values of CMR perfusion techniques were reported in a large meta-analysis and yielded a sensitivity and specificity of 0.91 (95% CI 0.88 to 0.94) and 0.81 (95% CI 0.77 to 0.85) on a per patient level, respectively.4
Figure 1
Combined assessment of myocardial function, stress perfusion, and LGE imaging (basal short axis view). A Endsystolic still frame demonstrating hypokinetic wall motion of the anterolateral segment (white arrowhead). B Adenosine stress dynamic CMR perfusion scan (two-dimensional k-t accelerated perfusion sequence) revealed extensive inducible myocardial perfusion deficits of anterior, anterolateral, and inferolateral regions. C LGE imaging showed subendocardial scar formation of the anterolateral segment only. Note that regional myocardial contraction of the anterolateral segment was impaired resulting from subendocardial scar. The high in-plane resolution of CMR perfusion imaging facilitated by k-t-based speed-up techniques clearly identified inducible myocardial perfusion abnormalities extending the peri-infarct zone as defined by LGE
Figure 2
A Conventional multislice 2-dimensional CMR perfusion imaging during adenosine stress and at rest. Three slices of short axis geometry are usually acquired to cover 16 myocardial segments. Typical in-plane spatial resolution is in the range of 2.0 to 3.0 mm. Upper row still frame of a dynamic first-pass adenosine stress perfusion scan. A subendocardial perfusion deficit (white arrows) can be clearly delineated in inferior and inferolateral myocardial segments. Bottom row still frame of a dynamic first-pass rest perfusion scan confirming normal perfusion at rest. B Invasive x-ray angiography confirmed the presence of high grade right CAD and subtotal occlusion of the left circumflex supply territory
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