September 8, 2011 – Intra-aortic balloon pump (IABP) counterpulsation prior to percutaneous coronary intervention (PCI) in patients with ST segment elevation myocardial infarction (MI) does not reduce infarct size as measured by magnetic resonance imaging (MRI), according to results from the Counterpulsation Reduces Infarct Size Acute Myocardial Infarction (CRISP AMI) trial. The results were discussed during the recent European Society of Cardiology (ESC) meeting in Paris, France.
"Animal studies had suggested that inserting a balloon pump before opening the vessel would reduce the heart’s workload and, by doing so, could potentially reduce infarct size. However, having tested this observation in humans, we did not show similar results,” explained principal investigator Manesh Patel, M.D., from the Duke Clinical Research Institute of Duke University, Durham, N.C.
CRISP AMI was a multicenter, prospective, randomized trial in patients with acute ST segment elevation MI without shock. They were recruited within six hours of chest pain onset and planned primary PCI. Of the 337 patients enrolled, 161 were randomized to receive intra-aortic balloon counterpulsation (IABC) prior to primary PCI, and 176 to the standard-of-care (SOC), which includes primary PCI without IABC support.
The primary efficacy endpoint of the trial was infarct size measured by cardiac MRI at three to five days post-PCI. The secondary clinical endpoint was the composite of major adverse clinical events including death, reinfarction and heart failure at six months.
Results showed that mean infarct size was not significantly different between the IABC and SOC groups (42.1 vs. 37.5 percent, representing the percentage of left ventricle affected). At 30 days, major bleeding or transfusion had occurred in five (3.1 percent) of IABC patients and three (1.7 percent) of SOC patients. Major vascular complications occurred in seven IABC (4.3 percent) and two SOC (1.1 percent) patients. By six months, death had occurred in three (1.9 percent) of the IABC and nine (5.2 percent) of the SOC group.
While the study did not meet its primary endpoint, and was not powered to draw significant conclusions on clinical events, Patel says the results nevertheless offer an insight into the treatment of STEMI patients. “The most striking observation is the excellent overall outcome for the highest risk patients within the context of this trial,” he says. “The IABC group had less than 5 percent mortality, and it’s difficult to improve that. We’ve become very good at treating AMI patients.”
In the United States, acute mortality risk in AMI is between 6 percent and 15 percent; one-year mortality is estimated at 38 percent for women and 25 percent for men.
Patel adds that 15 of the patients in the SOC group crossed over to receive IABC, and five patients crossed over prior to PCI and ten patients after PCI. “While this trial shows that the routine use of IABC cannot be recommended in STEMI, physicians should be vigilant about identifying those patients who are at risk for rapid deterioration and may benefit from counterpulsation,” he says.
For more information: www.escardio.org