Background— Postconditioning has been suggested to reduce myocardial damage during primary percutaneous coronary intervention (PPCI) in patients with ST-segment–elevation myocardial infarction. However, because clinical experience is limited, we examined the cardioprotective effects of postconditioning, using cardiac MRI in patients treated with PPCI.

Methods and Results— One hundred eighteen patients with ST-segment–elevation myocardial infarction referred for PPCI were randomly assigned to have either conventional PPCI or PPCI with postconditioning. Postconditioning was performed immediately after obtained reperfusion with 4 balloon occlusions, each lasting 30 seconds, followed by 30 seconds of reperfusion. The primary end point was myocardial salvage after 3 months as judged by delayed enhancement cardiac MRI. We found a 19% relative reduction of infarct size in the postconditioning group (51 16% of total area at risk versus 63 17%, P<0.01), corresponding to a 31% increase in salvage ratio. The number of patients developing heart failure was significantly fewer in the postconditioning group (27% versus 46%, P=0.048). No significant evidence of interaction between the impact of postconditioning and the location of the culprit lesion or size of the myocardium at risk was detected (P=0.21 and P=0.71).

Conclusions— Mechanical postconditioning reduces infarct size in patients with ST-segment–elevation myocardial infarction treated with PPCI. The impact of mechanical postconditioning seems to be independent of the size of myocardium at risk.

Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00507156.