"Shades of gray" in cardiac magnetic resonance images of infarcted myocardium: can they tell us what we'd like them to?

Identifying individuals at risk of sudden death continues to be a challenging problem. Subgroups classified as high risk on the basis of prior myocardial infarction, low ejection fraction, and arrhythmia-related parameters are recognized to include only a small proportion of the sudden cardiac deaths occurring annually.1 Nevertheless, as the indications for implantable cardioverter-defibrillators expand to intermediate-risk groups, issues related to cost and the potential morbidity of implantable cardioverter-defibrillator implantation take on greater significance. Article p 32 The possibility that high-resolution cardiac magnetic resonance imaging (CMR) of acute and chronic infarctions with the use of delayed gadolinium enhancement2 can improve risk stratification is now being evaluated by several groups. Bello et al3 have reported that measurements of infarct mass and surface area predict inducible monomorphic ventricular tachycardia more reliably than ejection fraction does in coronary patients referred for electrophysiological study. Because of the known limitation in positive predictive accuracy of electrophysiological testing,4 a need remains for studies of more definitive outcomes. Although CMR measurements of infarct size have also been used to forecast the extent of functional recovery after acute infarction and myocardial revascularization, studies of their predictive value for mortality are just beginning to become available. The study of Yan et al5 in this issue provides an initial look at the mortality question. It proposes a new approach for identifying a “potentially arrhythmic heterogeneous zone of viable and nonviable peri-infarct myocardium.” The authors hypothesize that the size of this zone can provide prognostic value for mortality incremental to that offered by ejection fraction and left ventricular (LV) end-systolic volume. Their study group consisted of patients with a history of coronary artery disease referred for CMR examination and found to have areas of myocardial delayed gadolinium enhancement. With the use of specialized image analysis software, the …