Study will investigate & compare the left ventricular remodeling & systolic function between two groups of ST-elevation myocardial infarction undergoing primary per-cutaneous coronary intervention applying ischemic post-conditioning to one of them.

Among re-perfusion strategies for the management of ST-elevation myocardial infarction , primary per-cutaneous coronary intervention is the preferred one within 120 minutes from the first medical contact.However , restoration of the coronary blood flow can paradoxically reduce the beneficial effects of myocardial re-perfusion , a phenomenon known as myocardial re-perfusion injury.Ischemic post-conditioning has been described as a measure for myocardial salvage , performed by making cycles of briefly interrupted perfusion during the early moments of coronary re-flow.Post-conditioning may be performed immediately after the early re-flow by creating cycles of interrupted inflation & deflation of the angioplasty balloon in patients undergoing primary per-cutaneous coronary intervention.In this study investigators aim to compare the left ventricular remodeling and global systolic function immediately & 6 months after re-perfusion between two groups of 100 patients presenting with acute ST-elevation myocardial infarction, using ischemic post-conditioning in one group of patients undergoing primary per-cutaneous coronary intervention (n=50 patients) by making 4 cycles of repeated occlusion & re-perfusion 30-second each by inflation/deflation of an appropriately sized per-cutaneous trans-luminal coronary angioplasty balloon.The other group will be investigated after re-perfusion by primary per-cutaneous coronary intervention without ischemic post-conditioning (n=50 patients)

Inclusion Criteria:

1. Patients presenting with symptoms of acute myocardial ischemia with time of symptom onset < 12 hours & meeting the other following criteria of type 1 myocardial infarction according to the fouth universal definition of myocardial infarction(Thygesen, 2019):

   • Detection of a rise and/or fall of cardiac troponin values with at least one value above the 99th percentile upper reference limit.(URL)
   • Ischemic ECG changes; New or persistent ST-segment elevation with development of pathological Q waves
   • Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology.

2. Patients undergoing primary percutaneous coronary intervention as the first choice of revascularization therapy.

Exclusion Criteria:

1. Patients with transient ST segment elevation in the surface electrocardiography.
2. Patients presenting within > 12 hours from the onset of maximal symptoms.
3. Patients with evidence of pre-infarction angina.
4. Patients with evidence of collateral blood flow to the infarct region on their angiogram.
5. Patients with history of old myocardial infarction causing chronic impairment of LV systolic function.
6. Patients presenting with ST-segment elevation myocardial infarction other than type 1 according to the fouth universal definition of myocardial infarction