The native T₁ in remote myocardium of patients with prior chronic infarction is not normal

Background

Global left ventricular (LV) remodeling after myocardial infarction frequently occurs. Late Gadolinium Enhancement (LGE) CMR allows imaging of focal myocardial scar with areas remote from scar having no hyperenhancement. Myocardial T₁ mapping allows quantification of interstitial fibrosis and may be a surrogate for LV remodeling. We sought to determine if there were T₁ abnormalities in remote regions (no LGE positive areas) in patients with prior myocardial infarction.

Methods

In a prospective IRB-approved study, 12 patients with a history of coronary artery disease (CAD) and chronic myocardial infarction (61 ± 9 years, 9 males) and 10 healthy subjects (52 ± 10 years, 8 males) were recruited to undergo CMR scans. All subjects were in sinus rhythm during CMR study. We assessed native T₁ mapping using the slice interleaved T₁ sequence in 5 short axis-slices (from apical to basal). The sequence was acquired in a free-breathing ECG-triggered slice-selective bSSFP. T₁ mapping of each scan was estimated by voxel-wise curve fitting using a 2-paramter fit model. All images were corrected for in-plane motion between different T₁ weighted scans. Native myocardial T₁ in healthy subjects were measured over the three mid-ventricular slices by manually drawing epicardial and endocardial contours. The native T₁ times of the remote myocardium of the CAD patients were measured by manually drawing a region of interest (ROI) on the three mid-ventricular slices and excluding the infarct area. An unpaired-samples T-test analysis was used to test for statistically significant differences between the two groups.

Results

Patient characteristics are summarized in Table 1. LGE hyperenhancement was observed in all CAD patients. The mean native T₁ time in the remote area myocardium of the CAD patients was significantly higher than the native T₁ value of the myocardium in the healthy group (1107 ± 36 ms. vs. 1061 ± 32 ms.; p = 0.005) (Figure 1).

Table 1 Subject characteristics of CAD patients and healthy cohorts with p-values of comparison.

Figure 1

boxplot with mean (line in box), interquartile range (box) and complete range (whisker) of native T1 time in remote myocardium of CAD patients and healthy cohorts (p = 0.0005).

Conclusions

Our data suggest there are diffuse changes in remote/normal myocardium resulting in abnormal/higher native T₁ times in CAD patients with prior myocardial infarction. Further studies are needed to assess the prognostic value of an abnormal native T₁ in the remote region among CAD patients.