Postconditioning in ST-elevation Myocardial Infarction (POSTEMI)

Study objectives: To assess the effects of postconditioning on infarct size in patients with ST-elevation infarction referred to PCI. Study design: Prospective, randomized, open-label study with blinded endpoint evaluation. Included patients will be randomly allocated to postconditioning or control. Patients with symptoms of acute myocardial infarction of less than 6 hours duration fulfilling ECG criteria for primary PCI are eligible. PCI follow established routines. In postconditioning patients, additional, short (1 min), intermittent balloon occlusions will be applied after initial opening of infarct related artery. After this intervention, PCI proceeds routinely with stent implantation. In the control group, stent implantation after initial opening proceeds as usual. Primary endpoint is final infarct size, determined by MRI after 4 months. 260 patients will be included. Follow-up is 1 year. Inclusion period: 18 - 24 months. Clinical implications: Reperfusion therapy, administered as early as possible after start of symptoms, has improved the prognosis in acute ST-elevation myocardial infarction. Still, however, many patients suffer large infarctions, subsequently with an increased risk of heart failure, arrhythmias, and death. In pilot studies, mechanical postconditioning has been shown to reduce infarct size and thus potentially improve prognosis. However, the effect of postconditioning must be confirmed in larger clinical trials before implemented in routine treatment.

After opening of IRA and establishment of TIMI-flow grade 2 or 3, the control group continues the procedure with stenting. In the postconditioning group 4 additional balloon inflations separated by 1 minute reperfusion are given, starting after 1 minute of reperfusion.

After opening of IRA and establishment of TIMI-flow grade 2 or 3, the control group continues the procedure with stenting.

Assesment of LV function. Comparison with CMR in the whole study population and between treatment groups.

Incidence of treated arrhythmias and heart failure during initial hospitalization Incidence of death, non-fatal myocardial infarction, unstable angina, heart failure, and cerebrovascular disease

Myocardial salvage defined as (area at risk-final infarct size)/area at risk. Area at risk measured by CMR at baseline and final infarct size by CMR at 4 months.

Inclusion Criteria: acute symptoms consistent with an acute myocardial infarction of less than 6 hours duration an occluded infarct related artery must be demonstrated (TIMI-flow 0-1) Exclusion Criteria: Prior myocardial infarction Demonstration of collaterals to the infarcted area TIMI-flow >1 before intervention or TIMI-flow <2 after initial balloon inflation Demonstration of a distal occlusion Patients given thrombolytic treatment Patients in cardiogenic shock Any contraindication to MRI (magnetic resonance imaging) Unwillingness to participate

Tollefsen IM, Shetelig C, Seljeflot I, Eritsland J, Hoffmann P, Andersen GO. High levels of interleukin-6 are associated with final infarct size and adverse clinical events in patients with STEMI. Open Heart. 2021 Dec;8(2):e001869. doi: 10.1136/openhrt-2021-001869.

Limalanathan S, Andersen GO, Klow NE, Abdelnoor M, Hoffmann P, Eritsland J. Effect of ischemic postconditioning on infarct size in patients with ST-elevation myocardial infarction treated by primary PCI results of the POSTEMI (POstconditioning in ST-Elevation Myocardial Infarction) randomized trial. J Am Heart Assoc. 2014 Apr 23;3(2):e000679. doi: 10.1161/JAHA.113.000679.