Higher Intra-aortic Balloon Use Fails to Help in High-Risk PCI

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While use of intra-aortic balloon pump (IABP) therapy in support of high-risk percutaneous coronary intervention (PCI) varies by as much as 40% between hospitals, mortality remains unchanged no matter the level of utilization, according to findings published online December 6, 2011, ahead of print in Circulation: Cardiovascular Quality and Outcomes. According to the authors, the findings should prompt a reevaluation of the appropriate threshold for IABP use.

Researchers led by Jeptha P. Curtis, MD, of the Yale School of Medicine (New Haven, CT), looked at 181,599 high-risk PCI procedures performed at 681 US hospitals between January 2005 and December 2007 that were entered in the National Cardiovascular Data Registry CathPCI Registry. IABP therapy was used in 10.5% (18,990) of the high-risk PCI procedures, mostly for cases involving cardiogenic shock (44.4%), unprotected left main disease (28.1%), LVEF of 30% or less (13.9%), or STEMI (10.3%).

Hospitals were grouped into quartiles according to proportion of IABP use from lowest to highest:

• Q1: 0 to 6.5%
• Q2: 6.6% to 9.2%
• Q3: 9.3% to 14.1%
• Q4: 14.2% to 40.0%

Hospital characteristics were similar across quartiles, but patients in the highest quartile of IABP use were older and generally sicker, with lower LVEF and more renal dysfunction, diabetes, prior CABG, and other comorbidities compared with patients in the lowest quartile.

The overall in-hospital death rate was 4.9%, which increased with quartile of hospital IABP use (Q1 4.2%, Q2 4.8%, Q3 5.1%, Q4 5.6%; P < 0.001). However, after multivariable adjustment for hospital and patient characteristics, in-hospital mortality did not vary across quartiles (using the lowest quartile as the reference):

• Q2: Adjusted OR 1.11; 95% CI 0.99-1.24
• Q3: Adjusted OR 1.03; 95% CI 0.92-1.15
• Q4: Adjusted OR 1.06; 95% CI 0.94-1.18

In addition, on subgroup analysis, in-hospital mortality remained unchanged regardless of increased IABP use in groups defined by STEMI, LVEF less than 30%, unprotected left main disease, and cardiogenic shock.

Vascular complications did increase with increasing IABP use, with the exception of vascular-arteriovenous fistula (table 1).

Table 1. Vascular Complications According to Hospital Quartile of IABP Use

However, as with in-hospital mortality, after multivariable analysis, the risk of vascular complications was similar regardless of increased IABP use:

• Q2: Adjusted OR 0.96; 95% CI 0.81-1.23
• Q3: Adjusted OR 1.16; 95% CI 0.99-1.36
• Q4: Adjusted OR 1.11; 95% CI 0.94-1.31

“Our findings provide no evidence to support the greater use of IABP at some hospitals and indicate a pressing need to further define the settings where this intervention provides a net benefit,” the researchers conclude.

The study, they add, highlights the fact that “much of IABP use is discretionary,” and likely influenced by factors such as physician training, clinical experience, and local practice patterns as opposed to clinical trial evidence showing improved outcomes.

‘Belt and Suspenders’

Morton J. Kern, MD, of the University of California, Irvine (Irvine, CA), noted that the results are consistent with previous studies. “Our impression is that the balloon pump is not really powerful enough to do much,” he told TCTMD in a telephone interview. “It probably has some marginal benefit in some patients, but we don’t know who those patients are as well as we should. It’s mostly for belt-and-suspenders security for the operator who wants to think that he’s actually doing some good.”

Dr. Kern explained that the mere promise of some marginal benefit “was enough to convince the operators it was better than nothing in some people, but none of the large trials really showed that this was overwhelmingly positive.”

A main problem leading to such wide variation in IABP use, he added, is the differing criteria for high risk. “The high risk patient is defined differently by different hospitals,” Dr. Kern said. “Do you wait until non-shock? Do you wait until pre-shock? Should it be anybody with a low ejection fraction? There are so many variables that a high-risk individual defined on clinical grounds could be different in different hospitals seeing the same guy. I think that’s the fundamental problem.”

Another point to consider is that IABP therapy is not without some risk. “In general, the harm is less than the potential benefit,” Dr. Kern said. “Nonetheless, there is downside if you put in a balloon pump and you don’t need it. It’s an expense, there’s potential risk of late complications, potential infection, and if you bleed it’s a big deal.”

Better Technology on the Horizon?

The bottom line, he added, is that until a better technology comes along, “clinicians are going to use balloon pumps on the basis of their own clinical judgment of perceived benefit, even though the data don’t point to that benefit very strongly.”

A candidate for such a technology is the Impella (Abiomed, Danvers, MA) percutaneous left ventricular assist device, which showed mixed results compared with IABP therapy in the PROTECT II trial. “If the Impella comes out with an easier access, smaller device at less cost, it would take over the marketplace, because that has the potential to increase cardiac output twice as much as the balloon pump,” Dr. Kern said, adding that the downside to the Impella is “larger arterial access and potential bleeding, and a cost that’s 10 times as much.”

As it stands in clinical practice, “the guys who really need support are getting the Impella, and the guys who are marginal may get a balloon pump or nothing,” Dr. Kern observed.

 

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Source:
Curtis JP, Rathore SS, Wang Y, et al. Use and effectiveness of intra-aortic balloon pumps among patients undergoing high risk percutaneous coronary intervention: Insights from the National Cardiovascular Data Registry. Circ Cardiovasc Qual Outcomes. 2011;Epub ahead of print.

 

 

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