Ischemic Conditioning After PCI Shows No Benefit in STEMI Patients

Reed Miller

October 29, 2012

MIAMI — Ischemic postconditioning following PCI of ST-segment-elevation MI patients did not improve outcomes compared with PCI without this extra procedure in the 700-patient randomized POST trial [1].

Thirty-day follow-up results from POST, presented by Dr Joo-Yong Hahn (Samsung Medical Center, Seoul, Korea) here at TCT 2012, showed that ischemic postconditioning of the target vessel with four one-minute balloon occlusions after primary PCI did not improve myocardial reperfusion compared with conventional primary PCI and that the clinical outcomes one month after the procedure were not significantly different between the 350 patients randomized to postconditioning and the 350 randomized to standard PCI. Also, no cardioprotective effects of ischemic postconditioning appeared in any of the prespecified subgroups, he said.

A 2005 study by Staat et al in 30 patients showed that postconditioning reduced enzymatic infarct size in STEMI patients undergoing primary PCI [2]. Previous research suggested that postconditioning inhibits opening of the mitochondrial permeability transition pore, which is involved in reperfusion injury after ischemia reperfusion.

However, subsequent postconditioning studies using contrast-enhanced MRI to examine infarct size have shown inconsistent results. "Previous studies showing the cardioprotective effects of preconditioning have several limitations--they did not reflect current standard practice patterns of primary PCI," Hahn said. "They performed only direct stenting and thrombus aspiration, and glycoprotein IIb/IIIa inhibitors were either not used or used seldom."

The postconditioning procedure specified for the POST trial included four episodes of one-minute balloon occlusion and one-minute deflation within one minute after restoration of coronary flow after PCI. The patients in the study were on aspirin and clopidogrel. Thrombus aspiration, predilation before stenting, or use of glycoprotein IIb/IIIa inhibitors were left to the operators' discretion, which "reflects the current practice pattern of primary PCI."

Hahn acknowledged several possible limitations of the POST trial. The sample size may have been too small to make definite conclusions on clinical outcomes, and the study was not double-blinded. He also pointed out that the prespecified postconditioning protocol was not followed in 8% of patients randomized to postconditioning and the ECGs taken before and 30 minutes after the procedure are not available for 3.5% of patients in the study. Also, the study excluded patients with hemodynamic instability, cardiogenic shock, or left main lesion, and these patients might have reperfusion injury and therefore benefit from postconditioning, he said.

The study was supported by grants from the Korean Society of Interventional Cardiology, the Sungkyunkwan University Foundation for Corporate Collaboration, and Medtronic Korea. Hahn has no conflicts of interest.