Improved detection of myocardial involvement in acute inflammatory cardiomyopathies using T2 mapping

Abstract

Background: T2-weighted cardiac magnetic resonance imaging is useful in diagnosing acute inflammatory myocardial diseases, such as myocarditis and tako-tsubo cardiomyopathy (TTCM). We hypothesized that quantitative T2 mapping could better delineate myocardial involvement in these disorders versus T2-weighted imaging.

Methods and results: Thirty patients with suspected myocarditis or TTCM, referred for cardiac magnetic resonance imaging, who met established diagnostic criteria underwent myocardial T2 mapping. T2 values were averaged in involved and remote myocardial segments, both defined by a reviewer blinded to T2 data. In myocarditis, T2 was 65.2±3.2 ms in the involved myocardium versus 53.5±2.1 ms in the remote myocardium (P<0.001). In TTCM, T2 was 65.6±4.0 ms in the involved myocardium versus 53.6±2.7 ms in the remote segments (P<0.001). T2 values were similar across remote myocardial segments in patients and all myocardial segments in controls (P>0.05 for all). T2 maps provided diagnostic data even in patients with difficulty breath holding. A T2 cutoff of 59 ms identified areas of myocardial involvement, with sensitivity and specificity of 94% and 97%, respectively. T2 mapping revealed regions of abnormal T2 beyond those identified by wall motion abnormalities or late gadolinium-enhancement positivity. Conventional T2-weighted short tau inversion recovery images were uninterpretable in 7 patients because of artifact and unremarkable in 2 patients who had elevated T2 values. T2-prepared steady-state-free precession images showed areas of signal hyperintensity in only 17 of 30 patients.

Conclusions: Quantitative T2 mapping reliably identifies myocardial involvement in patients with myocarditis and TTCM. T2 mapping delineated a greater extent of myocardial disease in both conditions compared with that identified by wall motion abnormalities, T2-weighted short tau inversion recovery imaging, T2-prepared steady-state-free precession, or late gadolinium enhancement. Quantitative T2 mapping warrants consideration as a robust technique to identify myocardial injury in patients with acute myocarditis or TTCM.

Figure 1

Averaged T2 values in the involved and remote segments in patients with myocarditis (N=20) and TTCM (N=10) and controls (N=30) are shown. The centerline in each box represents the median, while the lower and upper limits of each box represent 25^th and 75^th percentiles, respectively. *p<0.001 for comparison to controls (ANOVA with Bonferroni post hoc analysis), ^†p<0.001 for comparison to remote segments.

Figure 2

T2 maps, T2W-STIR, and LGE images in 3 representative patients with myocarditis. (A) A 25 year-old male presented with gastrointestinal symptoms with ST elevations and a troponin of 31.1mg/dL. Three involved and 3 remote segments are shown. (B) A 29 year-old male presented with chest pain worse with inspiration and lying flat. He had diffuse ST elevations with a peak troponin of 17.3mg/dL. Two involved and two remote segments are shown (C) A 24 year old male who presented with syncope. Peak troponin was 4.5mg/dL. All illustrated segments show elevated T2 values.

Figure 3

SSFP diastolic and systolic images, T2 maps, and LGE images in 2 patients with TTCM. (A)72 year old female presented with shortness of breath, found to have normal coronaries. (B) 49 year old female presented with chest pain, found to have normal coronaries. CMR images show apical ballooning of both left and right ventricle. In both cases, the T2 maps show elevated T2 values in the mid and/or apical segments with normal values involving the basal segments

Figure 4

ROC curves. (A) Comparison of involved myocardial segments in either myocarditis or TTCM in comparison to healthy controls. (B) Comparison of involved myocardial segments with remote segments in the same patients.

Figure 5

T2 values measured in an area of myocardium with epicardial delayed enhancement versus subendocardial myocardium in the same regions. (A) Short axis delayed enhancement image, (B) short axis T2 image from the same slice position.

Figure 6

T2 maps, T2W-STIR, and LGE images in 3 representative patients with myocarditis with no obvious edema on T2 STIR imaging. (A) 44 year old male with chest pain and a peak troponin of 33.3mg/dL. T2 values in the involved and remote segments were 65 and 54ms respectively. (B) 20 year old female with shortness of breath and chest pain with a peak troponin of 4.0mg/dL. T2 values in the involved and remote segments were 66 and 56ms respectively. (C) 39 year old male with gastrointestinal symptoms and fever with a peak troponin of 12.4mg/dL. Involved and remote segments T2 values were 67 and 45ms respectively.

Figure 7

Comparison between T2 maps and T2p-SSFP images is shown. The upper left panel shows the T2 map from a patient with tako-tsubo cardiomyopathy and negative LGE imaging; the affected region (arrow) had an abnormally elevated T2 of 65.9 ms compared to 53.0 ms in the remote myocardium. The same patient’s T2p-SSFP image (upper right panel) was visually rated as normal by two expert reviewers. The bottom left panel shows the T2 map from a patient with myocarditis whose LGE showed epicardial hyperenhancement in the inferolateral and apical segments; these segments were also abnormal by T2 mapping (T2 = 67.0 in the affected region vs. 53.0 ms in the remote myocardium). The apical region was identified as abnormal by visual assessment of the T2p-SSFP image (bottom right panel, arrow).

Figure 8

Bland-Altman plots for interobserver agreement in the measurement of T2 values for patients with myocarditis or TTCM. (A) Involved myocardial segments, (B) remote myocardial segments, and for (C) controls. LOA, level of agreement 1 standard deviation.