Assessment of intramyocardial hemorrhage by T1-weighted cardiovascular magnetic resonance in reperfused acute myocardial infarction

Abstract

Background: Intramyocardialhemorrhage (IMH) reflects severe reperfusion injury in acute myocardial infarction. Non-invasive detection of IMH by cardiovascular magnetic resonance (CMR) may serve as a surrogate marker to evaluate the effect of preventive measures to reduce reperfusion injury and hence provide additional prognostic information. We sought to investigate whether IMH could be detected by CMR exploiting the T1 shortening effect of methemoglobin in an experimental model of acute myocardial infarction. The results were compared to T2-weighthed short tau inversion recovery (T2-STIR), and T2*-weighted(T2*W) sequences.

Methods and results: IMH was induced in ten 40 kg pigs by 50-min balloon occlusion of the mid LAD followed by reperfusion. Between 4-9 days (average 4.8) post-injury, the left ventricular myocardium was assessed by T1-weigthed Inversion Recovery(T1W-IR), T2-STIR, and T2*W sequences. All CMR images were matched to histopathology and compared with the area of IMH. The difference between the size of the IMH area detected on T1W-IR images and pathology was -1.6 ± 11.3% (limits of agreement, -24%-21%), for the T2*W images the difference was -0.1 ± 18.3% (limits of agreement, -36.8%-36.6%), and for T2-STIR the difference was 8.0 ± 15.5% (limits of agreement, -23%-39%). By T1W IR the diagnostic sensitivity of IMH was 90% and specificity 70%, for T2*W imaging the sensitivity was 70% and specificity 50%, and for T2-STIR sensitivity for imaging IMH was 50% and specificity 60%.

Conclusion: T1-weigthed non-contrast enhanced CMR detects IMH with high sensitivity and specificity and may become a diagnostic tool for detection of IMH in patients with myocardial infarction.

Figure 1

Scatter plot (A) and Bland–Altman plot (D) for IMH measurements determined by T1W IR and pathology. Scatter plot (B) and Bland–Altman plot (E) for IMH measurements determined by T2-STIR and pathology. Scatter plot (C) and Bland-Altman plot (F) for IMH measurements determined by T2*W and pathology. In the Bland–Altman plots, solid lines represent the mean and dashed lines represent the upper and lower limits of agreement. LVMS = Left Ventricular Myocardial Slice.

Figure 2

Short-axis CMR images and corresponding pathology obtained four days following ischemic reperfusion injury. In the antero-septal myocardium,a distinct hyper intense core region (arrows) is present on the T1W IR image (A) while a hypointense core region (arrows) is seen on the T2-STIR (B) and T2*W images (C). Each of the observed regions corresponds to intramyocardial hemorrhage (arrows) as confirmed by pathology (D).

Figure 3

Short-axis CMR images and corresponding pathology obtained nine days following ischemic reperfusion injury. In the antero-septal myocardium a distinct hyper intense core region (arrows) is present on the T1W IR image (A), whereas only a weak hypointense region (arrows) can be detected on the T2-STIR (B) or T2*W images (C). The pathology confirms that intramyocardial hemorrhage (arrows) is present in the antero-septal myocardium.

Figure 4

Short-axis CMR images and corresponding pathology obtained five days following ischemic reperfusion injury. No hyper intense region is present on the T1W IR image (A), whereas a hypo intense core region (arrows) can be detected on the T2-STIR (B) and T2*W images (C). The LGE image (D) reveals substantial scar formation corresponding to the hypo intense T2-STIR/T2*W areas. Inside the LGE hyper intense area, a dark region is present (dashed arrow) indicative of MVO. The pathology image (E) confirms that no intramyocardial hemorrhage (arrows) is present in the antero-septal myocardium.