Acute Myocardial Infarction: Serial Cardiac MR Imaging Shows a Decrease in Delayed Enhancement of the Myocardium During the 1st Week After Reperfusion

OBJECTIVES: To evaluate the time course of delayed gadolinium enhancement of infarcted myocardium by using serial contrast agent–enhanced (CE) cardiac magnetic resonance (MR) images obtained during the acute, subacute, and chronic stages of infarction.

METHODS: The study protocol was reviewed and approved by the local ethics committee, and written informed consent was obtained. Seventeen patients with reperfused acute myocardial infarction (AMI) underwent cine and CE cardiac MR a median of 1, 7, 35, and 180 days after reperfusion. Infarct size determined on the basis of delayed enhancement MR imaging at different times was compared by using nonparametric tests and Bland-Altman analysis. Extent of myocardial enhancement was compared with single photon emission computed tomographic (SPECT) measures of infarct size with Spearman correlation. Regional myocardial enhancement extent and contractility were analyzed with nonparametric tests.

RESULT: Infarct size was 18.3% of total myocardial LV volume on day 1 after AMI and decreased to 12.9% on day 7, 11.3% on day 35, and 11.6% on day 180 (all P < .001). Estimated infarct size on day 7, as compared with day 1 enhancement size, declined by 57.1% within the epicardium and by 6.3% within the endocardium (both P < .001). Infarct size on day 7 showed only minor changes at subsequent imaging and yielded a high correlation with SPECT measurements of infarct size (r = 0.84). Infarct size on day 7 inversely correlated with long-term wall thickening (P < .0001) and allowed prediction of contractile function.

CONCLUSIONS: In patients with AMI and successful coronary reperfusion, the size of delayed gadolinium enhancement at CE cardiac MR imaging significantly diminished during the 1st week after infarction. Thus, timing of CE cardiac MR imaging is crucial for accurate measurement of myocardial infarct size early after AMI. Tyrod Taylor Jersey

PMID:

Posted in * Journal Club Selections, Magnetic Resonance Imaging, Nuclear Imaging and tagged , , , , .

4 Comments

  1. Very nice study, following patients after PCI and stent placement in the setting of acute MI. This work corresponds with previous work suggesting that delayed enhancement decreases in the first week following infarction. It is also interesting that they find little change in delayed enhancement after the first week. The study suggests that when using myocardial delayed enhancement as a measure of response to therapy, one should consider the timing of the examination with respect to the initial event. It also makes clear how little we really know about the physiology underlying myocardial delayed enhancement.

  2. Very interesting findings! I personally favor the authors comments in the discussion that point that delayed gadolinium enhancement within ischemically injured myocardium is related to an increase in interstitial space and owing to the nonspecific properties of gadolinium-based contrast agents this may overestimate the true infarct size when MR is performed soon after reperfusion.
    A recent , also showed that DE-MRI overestimates when compared to First Pass perfusion imaging. It would’ve been very interesting to see if in this group of patients, the area of scar after 7 days correlated with the First Pass perfusion defect.

  3. It is important to consider the implications, of the results for scenarios where the decision for surgical revascularization is based on delayed MRI imaging.
    As described on page 92* and shown in table 3*; in particular the transmural extent of scar changed in the first 7 days.
    *To view, you must have online access/hard copy of Radiology Journal

  4. The authors evaluate the changes of delayed enhancement of infarcted myocardium by using serial MR examinations in a cohort of 17 patients. This is a relevant study clinically that sheds light into the pathophysiology of the early re-vascularized state.

    The estimation of the infarct size after coronary reperfusion is increasingly being used as a surrogate endpoint of how effective the reperfusion was.

    In the early stages after a myocardial infarction (first 48 hours) delayed enhancement of infarcted myocardium by using cardiac MRI may overestimate the infarct size, mainly due to the cellular changes that occur within the myocardium early after an event.

    Based on the myocardial enhancement images on the serial cardiac MR examinations of this cohort of 17 patients, the infarct size findings remained stable after day 7. Based on this, we would be able to determine the final infarct expansion only a week after a coronary event. This could have important implications towards the identification of patients who could potentially benefit from additional interventions such as device therapy early after a myocardial infarction (< 40 days). Some of the comments made during our discussion included: - While the significant change in the size of the area of persistent enhancement demonstrated at day 1 and day 7 may represent a change in infarct size (or a decrease in peri-infarct edema), this could have been further investigated by using heavily T2 weighted images to assess the myocardial edema and its changes. - We found very interesting that there is no mention of the obtention of first pass perfusion sequences, as they may better correlate with the areas of late enhancement as seen on the studies obtained later in time. - A recent post in this website (https://www.thepreparedminds.com/archives/614) compared an early late enhancement sequence obtained at 2 minutes after administration of the gadolinium chelate with a conventional late sequence obtained at 10 minutes and showed that the extent of extent of MVO decreased from early to late imaging. It would’ve been very interesting to see a similar approach in this group of patients, which could’ve explained their 1 case of resolved MVO.

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