[Tracking Early Reperfused Myocardial Infarction using Cardiac MR]

To determine segmental myocardial changes in cardiovascular magnetic resonance feature-tracking (CMR-FT) in the early phase of reperfused myocardial infarction in patients and rats.

Ten patients receiving percutaneous coronary interventions (2-10 d) and 10 rats with 60 min induced myocardial ischemia followed by reperfusions (48 h and 7 d) were investigated by MRI. The steady state free precession cine and late gadolinium enhancement (LGE) sequences were measured to evaluate the standard short axis of the whole heart after an injection of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA, Magnevist, Bayer Health Care Pharmaceuticals) at a dose of 0.1 mmol/kg. The infarction sizes (all areas were expressed as a percentage of the whole myocardial tissues of left ventricle (LV), end-diastolic volume (EDV) and ejection fractions (EF) were calculated. The MRI cine images were analyzed using the myocardial feature tracking software CVI, estimating the peak value of radial strains (RS) and circumferential strains (CS) of the 16 AHA segments excluding apex cordis. The complete myocardial infarction (CMI) segments, partial myocardial infarction (PMI) segments and non-myocardial infarction (NMI) segments were identified and compared.

Patients: The radial strain and circumferential strain of the CMI and PMI segments were smaller than the NMI segment (both P < 0.01). However, there was no significant difference between the CMI and the PMI segment (P>0.05). Rats: No significance differences were found in EF and EDV between the two time period 48 h and 7 d (both P>0.05). The radial strain and circumferential strain of the CMI and PMI segments were smaller than the NMI segment (all P < 0.01). But there was no significance difference between the CMI segment and the PMI segment (P>0.05). No significant changes in the global radial strain and the circumferential strain were found over time (both P>0.05). But the segmental radial strain and circumferential strain became larger over time (all P < 0.05).

The systolic ability of myocardium decreases as a result of reperfusion injury in the early phase of reperfused myocardial infarction. But it can gradually recover over time with reperfusion.