Imgaging myocardial stunning in ST-elevation myocardial infarction and Takotsubo syndrome

Abstract

This thesis longitudinally investigates the mechanics of myocardial stunning that may occur in patients with Takotsubo syndrome (TS) or ST-elevation myocardial infarction (STEMI) with timely reperfusion, using repeated transthoracic echocardiographic (TTE) examinations. All articles in this thesis are based on the Stunning in Takotsubo syndrome and Acute Myocardial Infarction (STAMI) protocol. Using repeated TTE the studies evaluate left ventricular systolic and diastolic recovery over the acute and subacute phase of TS and STEMI. Paper I: The study examined the inter- and intra-observer variability of a novel TTE approach of evaluating wall motion regionality (PrA), and also compared it to the well-established TTE method of wall motion score index (WMSI). A low inter- and intra-observer variability was found in both PrA and WMSI, indicating that PrA is at least as reliable and reproducible as WMSI. Paper II: This study evaluates the reversibility of the left ventricular myocardial dysfunction in women with TS compared to women with STEMI using PrA. Both TS and STEMI women continued to improve left ventricular function beyond 7 days of follow-up, supporting the importance of serial examinations. Paper III: This study aimed to investigate whether differences in left ventricular global and segmental strain in TS and to STEMI could account for the more favorable hemodynamic profile observed in TS compared with STEMI. Furthermore, it sought to determine whether the more favorable clinical outcome observed in men compared with women with STEMI could be explained by faster recovery of global and segmental strain. At hospital admission, global strain was reduced in both TS and STEMI. However, longitudinal strain appeared to be more impaired in TS than in STEMI, particularly in segments from the akinetic regions. No correlation was observed between global longitudinal and radial strain in TS, suggesting that TS may affect different myocardial fiber layers, whereas STEMI appears to affect all myocardial layers. Paper IV: This study evaluated left ventricular diastolic function at admission, 24 hours and 30-days after admission in women with STEMI compared to TS. At admission and 24 hours after admission differences in left ventricular diastolic function parameters were found in some diastolic function indices. At admission, there was a difference in diastolic grade between STEMI versus TS, but 24 hours later and after 30 days there was no difference in diastolic grade between the groups. Patients improved in diastolic indices and grade over the follow-up period indicating that as systolic function improves, left ventricular diastolic function improves in both conditions. Conclusion: Our studies suggest that improvement in left ventricular function over the acute and subacute phase of ST-elevation myocardial infarction and Takotsubo syndrome follow similar trajectories. These results deepen our understand in myocardial stunning and may help inform patient management.