The role of myocardial work in evaluating coronary microcirculation of STEMI patients after percutaneous coronary intervention

BACKGROUND: Despite of restoring epicardial infarct-related artery(IRA) patency after myocardial infarction, microvascular reperfusion were not achieved sometimes, and the deterioration of myocardial perfusion persists in a considerable number of patients. This phenomenon is known as microvascular obstruction (MVO). MVO is often observed in ST-Segment Elevation Myocardial Infarction(STEMI) patients, even if percutaneous coronary intervention (PCI) was successful. In addition, some evidence has indicated that the presence of MVO predicted poor clinical outcomes independent of myocardial infarct size. Noninvasive as well as invasive modes for assessing microvascular perfusion(MVP) are complex, time consuming, and expensive have, there is yet no simple method available at present to assess coronary microcirculation. In this research, we attempt to evaluate the usefulness of left ventricular myocardial work (LVMW), a new index of myocardial performance, for the assessment of MVP in STEMI patients after PCI. METHODS: Forty-seven patients with STEMI treated by PCI were enrolled and underwent a transthoracic doppler echocardiography (TTE) within 24-72 hours after PCI. IRA were left anterior descending (LAD) artery (29,62%), left circumflex (LCX) artery(9,19%), right coronary artery (RCA) (9,19%) respectively. Myocardial contrast echocardiography (MCE) was used to evaluate MVP after PCI, then perfusion score index (PSI) was calculated referring to whether the ultrasonic enhancing agents was replenishment or not. Patients were divided into normal MVP and impaired MVP group according to PSI. Left ventricular global longitudinal strain (GLS) was generated by speckle tracking echocardiography(STE) and pressure-strain loops (PSLs) was used to generate global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE). GLS and the MW parameters (GWI, GCW, GWW, GWE) were compared between groups. Receiver operating characteristic (ROC) curves were calculated by plotting sensitivity versus (1-specificity), allowing calculation of the area under the curve (AUC) and the identification of LVMW parameters and GLS cutoff thresholds that best identify STEMI patients with impaired MVP after PCI. RESULTS: In this study, a statistically significant difference was observed in GWI (1163±405 mm Hg% vs 1617±363 mm Hg%), GCW (1296±430 mm Hg% vs 1789±406 mm Hg%), GWE (83±8.52% vs 90±5.58%) and GLS (11.56±3.29 vs 16.65±3.59) between impaired MVP group and normal MVP group. However, there is no statistical significance difference in left ventricular ejection fraction (LVEF), and GWW. ROC analysis revealed that GCW (cut-off value: 1326 mm Hg%, AUC: .80, sensitivity: 95% and specificity: 56%), GWI (cut-off value: 1281 mm Hg%, AUC: .81, sensitivity: 90% and specificity: 70%), GWE (cut-off value: 90%, AUC: .77, sensitivity: 65% and specificity: 78%) and GLS (cut-off value: 12.5, AUC: .86, sensitivity: 90% and specificity: 67%) have appreciable AUC, sensitivity, and specificity to identify STEMI patients with impaired MVP after PCI. CONCLUSION: Measuring LVMW indices of STEMI patients after PCI may add adjuvant value for the assessment of MVP.