CRISP AMI: Balloon Pump Therapy Fails to Help STEMI Patients Without Shock

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Intra-aortic balloon pump (IABP) therapy fails to reduce infarct size or improve clinical outcomes when added prior to primary percutaneous coronary intervention (PCI) in patients with high-risk ST-segment elevation myocardial infarction (STEMI) but no cardiogenic shock. Findings from the randomized CRISP AMI trial were published online August 30, 2011, ahead of print in the Journal of the American Medical Association and presented at the European Society of Cardiology Congress 2011 in Paris, France.

Current guidelines recommend IABP therapy in conjunction with PCI for patients with cardiogenic shock, and recent observational and preclinical studies have supported the concept in patients with STEMI without shock.

For the CRISP AMI (Counterpulsation to Reduce Infarct Size Pre-PCI Acute Myocardial Infarction) trial, researchers led by Manesh R. Patel, MD, of the Duke University Medical Center (Durham, NC), studied 337 patients with anterior-wall STEMI who presented within 6 hours of chest pain symptoms and with no cardiogenic shock. Patients were randomized to PCI with (n = 161) or without (n = 176) routine IABP prior to intervention, lasting for at least 12 hours after PCI.

No Difference in MRI, Clinical Outcomes

All patients were treated quickly, with median time from first medical contact to insertion of first device roughly 9 minutes faster in PCI patients vs. IABP patients (68 min vs. 77 min; P = 0.04). Aspiration thrombectomy was used in slightly over one-third of all patients (34.8% of IABP patients and 37.4% of PCI patients), and BMS were used in 53.4% of all patients. Fifteen patients (8.5%) in the PCI group crossed over and also received IABP.

IABP therapy did not improve the primary endpoint of infarct size on cardiac MRI taken 3 to 5 days after PCI. Other MRI findings also were similar between groups (table 1).

Table 1. Cardiac MRI Findings

IABP therapy also failed to improve mean infarct size among the subset of patients at highest risk, those with proximal LAD occlusions and TIMI flow scores of 0 or 1 (46.7% vs. 42.3% with PCI alone; P = 0.11).

In terms of clinical outcomes, there were no differences between groups in rates of major bleeding or transfusion at 30 days, major vascular complications at 30 days, or death at 6 months (table 2).

Table 2. Clinical Outcomes

Dr. Manesh and colleagues offer a number of explanations as to why IABP therapy may have failed to provide any benefit, including a larger than expected infarct size due to the amount of time required to insert the intraortic balloon, and the protective effect of LV loading occurring too late in the course of the MI to salvage significant myocardium.

Balloon Pumps Should be ‘Standby Strategy’

Regardless, the strategy of routine IABP therapy in support of primary PCI “did not lead to a reduction in myocardial infarct size,” they conclude. “These findings support a standby strategy (rather than routine use) of [IABP] during primary PCI in high-risk anterior STEMI patients.”

In an accompanying editorial, Gjin Ndrepepa, MD, and Adnan Kastrati, MD, both of the Deutsches Herzzentrum (Munich, Germany), note that IABP therapy is widely used in patients with STEMI complicated by cardiogenic shock. Nevertheless, in regard to STEMI patients without shock, “use of this device should be discouraged. . . .”

Still, “Organizational efforts to increase the availability of primary PCI and reduce ischemia time remain of paramount clinical importance,” the editorial states. “Furthermore, the no-reflow phenomenon and microvascular dysfunction following primary PCI for STEMI remain prime candidates for future research due to their high incidence and strong association with mortality.”

From Mice to Men: Not So Easy

According to Gregg W. Stone, MD, of Columbia University Medical Center (New York, NY), IABP therapy represents “another in the long line” of failed strategies to reduce infarct size. “It’s very easy in mice to reduce infarct size, but it’s not so easy in humans,” he added in a telephone interview with TCTMD.

Dr. Stone noted that CRISP AMI will not impact practice. “If [the trial] was positive, it would have, but it was negative,” he said. “I think people were hopeful. On the basis of experimental data in animals, and in some uncontrolled studies in patients, there was a suggestion that balloon pumps used in that setting [of anterior STEMI without shock] might improve clinical outcomes.”

However, he called CRISP AMI “fairly definitive,” noting that the results should “close the door for the most part on balloon pumps as an adjunct to reduce infarct size.”

Despite the negative results, the search will continue for a device that can achieve the goal of unloading the left ventricle more effectively than IABP therapy. “The balloon pump is relatively modest in its afterload-reducing effects, and there will be studies started with the Impella cardiac assist device with the same sort of hypothesis,” Dr. Stone said. “The Impella device markedly increases forward cardiac output and unloads the ventricle to a much greater extent than intra-aortic balloon counterpulsation.”

Impella the Answer?

William W. O’Neill, MD, of the University of Miami (Miami, FL), was the primary investigator of the PROTECT II trial, which showed mixed results in comparing the Impella percutaneous LVAD (Abiomed, Danvers, MA) with IABP therapy in high-risk PCI patients. “It’s still an open ended question if better offloading may cause a decrease in infarct size,” he told TCTMD in a telephone interview. “The track record isn’t very good. Impella’s going to proceed with a trial, but they’ve got a challenge. I’m sure Abiomed would have loved to see balloon pump therapy do something, because that would have made for a stronger argument for looking at infarct size reduction.”

Dr. O’Neill agreed with Dr. Stone that CRISP AMI represents “a pretty definitive ‘no’ to the question as to whether balloon pumps have any more role” in high-risk STEMI patients without shock.

“I’ve spent almost 15 years looking for something to decrease infarct size,” he said. “That’s really been the holy grail and no one’s found it. I’m just not sure there’s anything that we can do in the early stages that’s going to significantly decrease infarct size. I’m pretty pessimistic right now.”

Dr. O’Neill added that for the future, “we’re switching our focus to looking at methods to augment LV function after recovery, and that’s with stem cell therapy. So our paradigm is switching to getting the artery open as well as you can; but in the end, you’re probably going to have to do something else to try to improve LV function after recuperation.”

Sources:

1. Patel MR, Smalling RW, Thiele H, et al. Intra-aortic balloon counterpulsation and infarct size in patients with acute anterior myocardial infarction without shock: The CRISP AMI randomized trial. JAMA. 2011;Epub ahead of print.

2. Ndrepepa G, Kastrati A. Need for critical reappraisal of intra-aortic balloon counterpulsation. JAMA. 2011;Epub ahead of print.

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• It is All in the Timing: Balloon Pump Prior to PCI May Help AMI and Shock Patients
• Mini-LVADs Not Ready to Supplant IABPs for Cardiogenic Shock Patients
• Study Questions Intra-Aortic Balloon Pump Use in STEMI