Assessment of the longitudinal changes in infarct heterogeneity post myocardial infarction

Abstract

BackgroundInfarct heterogeneity, as assessed by determination of the peri-infarct zone (PIZ) by cardiac magnetic resonance imaging, has been shown to be an independent predictor for the development of cardiac arrhythmias and mortality post myocardial infarction (MI). The temporal evolution of the PIZ post MI is currently unknown. Thus, the main objective of our study was to describe the temporal evolution of the PIZ over a 6 month time period in contemporarily managed ST elevation myocardial infarction (STEMI) patients. Further, given the poor prognosis associated with microvascular obstruction (MVO) post STEMI, we sought to compare the temporal evolution of the PIZ in patients with and without MVO. We hypothesized that patients with MVO would show a relative persistence of PIZ over time when compared to those without MVO.MethodsTwenty-one patients post primary percutaneous coronary intervention were enrolled and treated with evidence based therapy. Each patient had three cardiac MRI scans at 48 h, 3 weeks and 6 months post infarction. Repeated Measures Analysis of Variance (ANOVA) was used to assess the evolution of core infarct size and peri-infarct zone size across the three time frames.ResultsThe patients in this study were predominantly male, with ~40 % LAD territory infarction and a mean LVEF of 46 ± 7 %. Core infarct size and PIZ size both decreased significantly across the three time frames. The presence of microvascular obstruction (MVO), a known adverse prognostic factor, influenced PIZ size. Both patients with and without MVO had a significant reduction in core infarct size over time. Patients with MVO did not have a significant change in PIZ size over time (11.9 ± 6.8 %, 12.2 ± 7.5 %, 10.7 ± 6.6 % p = 0.77). In contrast, non-MVO patients did have a significant decrease in PIZ size over time (7.0 ± 5.5 %, 7.1 ± 6.5 %, 2.7 ± 2.6 %, p = 0.01).ConclusionsPeri-infarct zone size, like core infarct size, varies depending upon the timing of measurement. Patients with MVO displayed a persistence of the PIZ over time.

Multi‐contrast volumetric imaging with isotropic resolution for assessing infarct heterogeneity: Initial clinical experience

“…Similarly, the maximum intensity region of the myocardium was chosen as the infarct and the peak signal intensity among all pixels in the infarct regions ( ) was determined. The signal intensity (SI) thresholds for determining the infarct core and peri‐infarct gray zone using FWHM were as follows: and , where is the signal intensity of a pixel classified as the infarct core and is the signal intensity of a pixel classified as the peri‐infarct gray zone 7,31 …”

“…The signal intensity (SI) thresholds for determining the infarct core and peri-infarct gray zone using FWHM were as follows: SI core > 0.5 * Peak infarct and Peak remote < SI grayzone < 0.5 * Peak infarct , where SI core is the signal intensity of a pixel classified as the infarct core and SI grayzone is the signal intensity of a pixel classified as the peri-infarct gray zone. 7,31 In the multi-contrast volumetric images, signal characteristics over multiple TIs for a single voxel can be represented by two tissue-dependent MR parameters including the apparent T 1 relaxation (T * 1 ) and steady-state magnetization (M ss ). 28 In this study, the two MR parameters were calculated by fitting voxel-wise signal intensities at six inversion times into a parametric exponential recovery model.…”

Myocardial viability of the peri-infarct region measured by T1 mapping post manganese-enhanced MRI correlates with LV dysfunction

“…Recent studies have revealed PIR represents the nexus for active remodeling characterized by extracellular matrix formation, angiogenesis, oxidative stress, mitochondrial energetics, apoptosis and inflammation [9,[30][31][32]. Those active and dynamic reactions could lead to its heterogeneity and arrhythmogenic substrates.…”

Sudden Cardiac Death Substrate Imaged by Magnetic Resonance Imaging

“…56 Twenty-one patients with reperfused STEMI underwent CMR-LGE at 2 days, 3 weeks and 6 months post-MI. Core infarct sizes declined significantly over time in both patients with and without microvascular obstruction (no-reflow).…”