Performing intra-aortic balloon counterpulsation (IABC) prior to PCI did not reduce myocardial infarct sizes in acute anterior STEMI patients, causing researchers to conclude that IABC should be used as a standby rather than a routine method. An accompanying editorial argued that more research to understand whether this method should be used in STEMI patients with shock is necessary, and efforts to increase the availability of primary PCI and reduce ischemia are important. The research is being presented at the European Society of Cardiology Congress in Paris and simultaneously published online Aug. 30 in the Journal of the American Medical Association.

“IABC mechanically augments coronary bloodflow, unloads the left ventricle and reduces myocardial oxygen demand,” Manesh R. Patel, MD, of the Duke Clinical Research Institute and Duke University Medical Center in Durham, N.C., and colleagues wrote. These favorable hemodynamic effects have led to demonstrated improvements in outcomes, and the recommendation that patients with acute MI and cardiogenic shock be treated with IABC support and reperfusion.”

To better understand whether adding IABC prior to PCI would benefit high-risk STEMI patients, Patel and colleagues performed the randomized CRISP-AMI (Counterpulsation to Reduce Infarct Size Pre-PCI Acute Myocardial Infarction) trial, which compared the outcomes of IABC prior to primary PCI and primary PCI alone, to understand whether the addition of IABC would reduce infarct size in acute anterior STEMI patients without cardiogenic shock.

CRISP-AMI included 337 patients with anterior STEMI without shock who were enrolled at 30 sites between June 2009 and February 2011. The researchers randomized 161 patients to receive IABC plus PCI and 176 patients to receive PCI-alone.

The median time from symptom onset to insertion of the first device was 202.5 minutes in the IABC plus PCI group and 193 minutes in the PCI alone group. Fifty-five patients received IABC for more than 24 hours and the median duration of counterpulsation in the IABC plus PCI group was 22.1 hours.

Major bleeds occurred in five patients in the IABC plus PCI arm and three patients in the PCI alone arm. Major vascular complications occurred in seven patients in the IABC plus PCI group and two patients in the PCI alone arm.

The authors reported that mean infarct sizes were comparable in both arms, 42.1 percent in the IABC plus PCI group and 37.5 percent in the PCI alone group.

“The principal finding from this study was that early planned IABC did not reduce myocardial infarct size as measured by cardiac MRI,” Patel et al wrote.

Patel and colleagues added that these findings could be due to the fact that the benefits of IABC could be offset by the increase in infarct size associated with the amount of time required to insert the aortic balloon. Additionally, the authors wrote that another explanation could be related to the timing of the cardiac MR performed three to five days after PCI.

“A third possibility is that the potential protective effect of LV unloading occurred too late in the course of the MI to salvage significant myocardium in this study,” the authors noted.

“These findings support a standby strategy (rather than routine use) of IABC during primary PCI in high-risk anterior STEMI patients.”

In an accompanying editorial, Gjin Ndrepepa, MD, of the Technische Universitat, Munich, and Adnan Kastrati, MD, of Deutsches Herzzentrum, Munich, wrote, “Explanations for failure of IABC to promote myocardial salvage and improve clinical outcome in patients with STEMI and no cardiogenic shock remain speculative.”