Introduction Myocardial oedema is a feature of reperfused acute myocardial infarction (AMI), and contributes to stunning of peri-infarct myocardium (the “area at risk”). Regression of oedema on T2 weighted (T2w) cardiovascular magnetic resonance (CMR) imaging is related to improved myocardial contractility post AMI in animal models, but has not been established in man. We hypothesised that resolution of tissue oedema correlates with recovery of regional contractile function.
Methods Patients after primary percutaneous coronary intervention for first ST-elevation AMI underwent CMR with T2w imaging, myocardial tagging and late gadolinium enhancement at 2, 30 and 90 days following reperfusion. Infarct size, regional circumferential strain, T2w signal intensity and volume of myocardial oedema were measured for infarct zone, peri-infarct zone and remote myocardium. Oedema and infarction were defined as zones with signal intensity 2 SDs above remote myocardium in T2w and LGE imaging respectively. T2w signal intensity was normalised to remote myocardium.
Results 30 patients had CMR imaging at all 3 time points with adequate image quality and sufficient peri-infarct oedema for quantitative analysis. Circumferential strain was significantly diminished in infarct and peri-infarct zones compared to remote myocardium (means −0.149 vs −0.184 vs −0.236, p<0.01 between groups and p<0.01 for trend). Remote myocardium showed no significant change in strain over time (F=1.44, p=0.24), while the peri-infarct zone (F=6.03, p=0.004) and infarct zone (F=20.34, p<0.001) showed a significant increase in magnitude (Abstract 089 table 1). This change closely mirrored resolution of both intensity and volume of T2w hyperenhancement (Abstract 089 figure 1). Decreased circumferential strain correlated significantly with T2w volume (r=0.30; p<0.01) and normalised T2w signal intensity (r=0.28; p<0.01). Due to the finding of recovery of function in the infarct zone, we analysed 8 patients with complete transmural infarction. The area of fully transmural infarction showed significant resolution of strain with time (means −0.103 (day 2), −0.148 (day 30) and −0.194 (day 90); p=0.04 for trend).
Conclusions Early after AMI, oedematous myocardium in the peri-infarct zone demonstrated significantly reduced strain as compared to remote myocardium. Improvement of strain in stunned myocardium closely followed the regression of myocardial oedema. Patients with larger oedema volumes and higher signal intensity on T2w imaging demonstrated greater improvement of strain within the area at risk. In addition, both transmural and subendocardial infarcts showed a degree of functional recovery after AMI. Volume and intensity of hyperenhancement on T2w CMR may give insights into functional recovery post reperfused AMI.
- Cardiovascular magnetic resonance