POST-AMI: Postconditioning Not Helpful, Possibly Harmful in STEMI Patients

PARIS, France—Postconditioning does not reduce infarct size in ST-segment elevation myocardial infarction (STEMI) patients undergoing percutaneous coronary intervention (PCI) and receiving adjunctive abciximab. In fact, it may even be harmful, according to results presented Thursday, May 19 at EuroPCR 2011.

For the single-center POST-AMI (POSTconditioning during Acute Myocardial Infarction) trial, Giuseppe Tarantini, MD, PhD, of the University of Padua (Padua, Italy), and colleagues randomized 78 first-time STEMI patients within 6 hours of symptom onset to primary PCI plus abciximab with (n = 39) or without (n = 39) postconditioning, which involved 4 balloon inflations within the stent during the first minutes of reperfusion. Direct stenting was encouraged, and most subjects were implanted with BMS.

All patients had total occlusion of the infarct-related artery with poor or absent antegrade flow (TIMI flow grade 0 or 1). Baseline characteristics were similar between groups with the exception of diabetes, which was numerically more prevalent in the postconditioning group (17.0% vs. 2.6% in the control group; P = 0.066).

No Effect on Infarct Size

Cardiac magnetic resonance imaging (CMR) was performed to assess infarct size at 30 ± 10 days and 6 ± 1 months. The primary endpoint of infarct size (% of LV mass) at 30 days was slightly higher in the postconditioning group than in controls at 20.2 ± 11.9% vs. 14.3 ± 9.9% (P = 0.056). The trend favoring controls was consistent in patients with single vs. multivessel disease, LAD vs. no LAD disease, and treatment before or after 3 hours of symptom onset.

Several secondary endpoints including microvascular obstruction (MVO) on CMR and MACE at 30 days and 6 months also showed better results for the control group (table 1). On subsequent analysis, MACE risk continued to be elevated in the postconditioning group even when diabetic patients were excluded, although the difference remained nonsignificant.

Table 1. Secondary Endpoints

“Our results suggest that postconditioning did not have the expected cardioprotective effect and might even harm STEMI patients treated by primary PCI plus abciximab,” Dr. Tarantini concluded. “Larger studies, multicenter randomized clinical trials and meta-analyses [of the 8 trials published on this topic], might reach the adequate statistical power to address the impact of postconditioning on clinical outcome.”

Co-Chairs Air Concerns

Session co-chair Ran Kornowski, MD, of the Rabin Medical Center (Petach Tikva, Israel), questioned the ethical ramifications of Dr. Tarantini's conclusion. “Based on your results,” he asked, “would you be willing to participate in a larger study?”

“The answer, I think, is yes,” Dr. Tarantini replied, “because this is a small study. And if you look at the baseline characteristics, even if it's not statistically significant, everything is a little worse in the postconditioning group, so I cannot exclude [the possibility that] there is some bias.”

An audience member raised the issue of diabetes. Dr. Tarantini agreed that the cormorbidity could “in theory” still matter, even though eliminating the diabetic population did not change the MACE results, and so he suggested that future studies should stratify randomization according to diabetic status.

Safety might also be a concern, noted session co-chair Mitchell W. Krucoff, MD, of the Duke Clinical Research Institute (Durham, NC). “At a mechanical level, we tend to be conservative about [post-stenting manipulation] of a STEMI site because of the potential for 'cheese-grater effects' and any sort of post-dilation actually promoting distal embolization. Here we have an elegant physiologic concept and a very inelegant mechanical concern.”

Dr. Tarantini acknowledged the concern but stressed that POST-AMI was conducted on the heels of positive studies that used the same technique. “When we inflated the stent, at the level of the lesion we did the cycle of reinflation using 8 atmospheres just to stop the flow, and at the end we didn't see major [signs of] microscopic embolization,” he said.

“One possible suggestion,” Dr. Krucoff countered, “would be to specifically stratify patients by thrombus burden prior to the procedure.”

 

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Source:
Tarantini G. Post-conditioning during coronary angioplasty in acute myocardial infarction: The POST-AMI trial. Presented at: EuroPCR; May 19, 2011; Paris, France.

 

 

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