Excerpt

Assessment of myocardial infarct tissue has shown to play an important role in risk-stratify patients for adverse cardiac events.1 Infarct tissue may show considerable spatial heterogeneity due to the presence of necrotic areas that are intermingled with bundles of viable cardiomyocytes. Myocardial necrosis is primarily located in the middle of the infarct region, while the regions of infarct tissue heterogeneity are primarily present in the periphery of the infarcted myocardium, which is commonly referred as infarct border zone or peri-infarct region. Peri-infarct region is an important substrate for the development of ventricular arrhythmias through the presence of reentrant circuits originating from slow-conduction pathways.2 Different imaging modalities have been used for the characterization of both infarct and peri-infarct regions. Myocardial perfusion imaging (MPI) techniques have been widely used in the evaluation of infarct tissue after myocardial infarction.3 As well, myocardial imaging with 123I-metaiodobenzylguanidine (MIBG) is a recognized imaging modality for non-invasive assessment of global and regional cardiac sympathetic innervation related to heart failure.4,5 The association of myocardial perfusion and innervation imaging has been used in patients after myocardial infarction as well in patients with hypertrophic and dilated cardiomyopathy.6,7 In particular, the combined use of these two different imaging modalities provided useful informations in identifying the presence of viable but sympathetically denervated myocardial areas, defined as trigger zone. In fact, myocardial 123I-MIBG uptake was not only reduced in the central infarct zone involved by the severe reduction of perfusion tracer uptake, but also in adjacent still viable regions as well as in areas with acute and chronic ischemia reflecting better the total extent of injured myocardium.8 These regions with impaired innervation may be viable and hypersensitive to catecholamine, resulting in increased automaticity and enhanced triggering and it has been demonstrated that the presence of trigger zone can lead to ventricular arrhythmia and sudden cardiac death.9 In this clinical context, it is important to find and quantify the regions of mismatch between infarcted and denervated myocardial region in order to provide appropriate medical or surgical intervention. …