AMIHOT II results: MI patients treated withsuccessful angioplasty within 6 hours have greater benefit.

An infusion of supersaturated oxygen (SSO2) into the MI territory significantly reduced the infarct size in high-risk patients with acute anterior MI who had PCI within 6 hours of symptom onset.

“There really is no alternative for these patients,” said Gregg W. Stone, MD, chairman of the CardiovascularResearch Foundation.

Data from the AMIHOT II study was designed to be analyzed in conjunction with AMIHOT I findings by pooling the data via Bayesian hierarchical modeling.

Exposure to SSO2

Stone explained that after the disappointing results of AMIHOT I, investigators realized that the subset of
patients treated within 6 hours had a markedly reduced infarct size, but “you can’t look at a postoperative subset and claim success,” he said.

Excluding patients in very high-risk situations, the study randomized 301 patients with acute anterior MI to either 90 minutes of SSO2 or standard therapy on a 2.8:1 ratio. Efficacy was defined as the ability to demonstrate superiority with regard to a smaller infarct size. Safety was the ability to demonstrate noninferiority between SSO2 and standard therapy with regard to major adverse cardiac events (MACE) at 30 days.

Michael Haude, MD, of Lukaskrankkenhaus Neuss in Germany, questioned whether a longer exposure to
SSO2 would be even more beneficial for myocardial salvage and said that long-term follow-up is necessary for a complete evaluation of the therapy.

SPECT measured infarct size

Using Tc-99m Sestamibi SPECT to measure infarct size, investigators found that the SSO2 group had a
6.5% reduction in LV infarct size vs. the control group (Figure).

MACE at 30 days met the criteria for noninferiority, with a rate of 5.4% in the SSO2 group and 3.8% in ontrols.

Stone said there was a trend toward more complications at the access site within the SSO2 group compared with the standard care group (22.5% vs. 12.7%, respectively).

Haude said the event rate and other bleeding complications were of concern because they could impact
long-term outcomes and outweigh the reduction in infarct size. Stone said there was no statistical difference in transfusions between the groups.

The AMIHOT II trial had several limitations, Stone said. The study was underpowered for mortality, and
1-year follow-up will show whether the initial reduction in infarct size will have a direct impact on survival or heart failure rate, he said.

“There really is no alternative for these patients [with acute anterior MI who had PCI within 6 hours].” — Gregg W. Stone, MD