Abstract
BackgroundCurrent cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations. Novel quantitative T1-mapping techniques have the potential to further characterize the components of ischemic injury. In patients with myocardial infarction (MI) we sought to investigate whether state-of the art pre-contrast T1-mapping (1) detects acute myocardial injury, (2) allows for quantification of the severity of damage when compared to standard techniques such as LGE and T2W, and (3) has the ability to predict long term functional recovery.Methods3T CMR including T2W, T1-mapping and LGE was performed in 41 patients [of these, 78% were ST elevation MI (STEMI)] with acute MI at 12-48 hour after chest pain onset and at 6 months (6M). Patients with STEMI underwent primary PCI prior to CMR. Assessment of acute regional wall motion abnormalities, acute segmental damaged fraction by T2W and LGE and mean segmental T1 values was performed on matching short axis slices. LGE and improvement in regional wall motion at 6M were also obtained.ResultsWe found that the variability of T1 measurements was significantly lower compared to T2W and that, while the diagnostic performance of acute T1-mapping for detecting myocardial injury was at least as good as that of T2W-CMR in STEMI patients, it was superior to T2W imaging in NSTEMI. There was a significant relationship between the segmental damaged fraction assessed by either by LGE or T2W, and mean segmental T1 values (P < 0.01). The index of salvaged myocardium derived by acute T1-mapping and 6M LGE was not different to the one derived from T2W (P = 0.88). Furthermore, the likelihood of improvement of segmental function at 6M decreased progressively as acute T1 values increased (P < 0.0004).ConclusionsIn acute MI, pre-contrast T1-mapping allows assessment of the extent of myocardial damage. T1-mapping might become an important complementary technique to LGE and T2W for identification of reversible myocardial injury and prediction of functional recovery in acute MI.
Highlights
Current cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations
A total of 41 patients were scanned within 24 hours post symptoms onset; out of these, 7 patients did not undergo the 6 m follow up scan (4 were excluded following coronary artery bypass grafts (CABG) or staged percutaneous coronary intervention (PCI), and 3 refused to come back)
In order to assess the relationship between areas of injury depicted byT2W or LGE and areas of increased T1 values on T1-mapping, we investigated the correlation between absolute T1 values and the signal intensity of LGE and/orT2W on a segmental basis
Summary
Current cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations. Cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) is the current gold standard for assessing myocardial scar in chronic coronary artery disease [1,2], while T2-weighted (T2W) CMR is the accepted method for detecting oedema in acute. In the early hours post ischemia, dynamic changes of LGE were shown within the ischemic myocardium, together with a significant regression of LGE over time and full functional recovery; these findings would suggest that acute LGE does not always represent scar [6,7,8,9]. There is considerable scope for error depending on the threshold used, and secondly it remains unclear whether or not an arbitrary signal intensity threshold realistically reflects the tissue changes occurring in the myocardium [14,15]
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