IABP Therapy May Benefit Patients With Large STEMI, Persistent Ischemia Post-PCI

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Hemodynamic support reduces 6-month mortality in patients with large ST-segment elevation myocardial infarction (STEMI) complicated by persistent ischemia after percutaneous coronary intervention (PCI), according to a substudy of the CRISP-AMI trial published online September 26, 2014, ahead of print in EuroIntervention.

As a whole, the CRISP-AMI trial, published in 2011 in the Journal of the American Medical Association, found that intraaortic balloon pump (IABP) therapy fails to reduce infarct size or improve clinical outcomes when deployed prior to primary PCI in patients with high-risk STEMI but no cardiogenic shock.

Methods
The current substudy, by Nico H.J. Pijls, MD, PhD, of Catharina Hospital Eindhoven (Eindhoven, the Netherlands), and colleagues, looked at patients with ECG evidence of large STEMI (defined as summed ST-deviation ≥ 15 mm) at the time of admission and poor ST-segment resolution (< 50%) post-PCI. In all, 149 out of the 323 patients in CRISP-AMI with baseline ECG and 6-month follow-up data had large STEMI, with 36 patients (n = 15 IABP and 21 control) also showing poor ST-segment resolution.
Within the control group, 5 patients (24%) crossed over to IABP therapy due to progression of hemodynamic deterioration.
Mean patient age was 55 years, and 89% were men. Systolic and diastolic blood pressures were 135 ± 31 mm Hg and 83 ± 22 mm Hg, respectively. In all cases, the infarct-related artery was the LAD, and primary PCI was successful 94% of the time. Patients receiving IABP support did so for 22 ± 9 hours. Baseline characteristics, apart from the time from first hospital contact to device use in the infarct-related artery, all were similar between the IABP and control groups.

At 6 months, none of the patients in the IABP group had died, compared with 5 in the control group (0 vs 24%; P = .046). The mortality curves diverged early after PCI, with 4 of the nonsurviving control patients dying before hospital discharge due to refractory cardiogenic shock (n = 1) or unsuccessful resuscitation and/or defibrillation (n = 3).

Estimated survival at 6 months was consistent across different subpopulations of patients randomized to IABP in CRISP-AMI. Within the control group, however, survival decreased in patients with large MI and even more so in those with large MI coupled with poor ST resolution (table 1). In patients with large MI, the presence of poor ST-segment resolution—irrespective of IABP use—was associated with increased risk of death (OR 17.419; 95% CI 2.0-154.7; P = .01).

Table 1. Estimated 6-Month Survival

 

Small MI

(n = 180)

Large MI

(n = 149)

Large MI +

Poor ST Resolution

(n = 36)

IABP Group

97.8%

98.5%

100%

Control Group

96.7%

92.7%

76.2%

 

A trend favoring IABP use also was seen for the composite endpoint of death, cardiogenic shock, or new/worsening heart failure (7% vs 33%; log-rank P = .06).

Important to Target the Right Patients

In an email to TCTMD, study investigator Lokien X. van Nunen, MD, also of Catharina Hospital Eindhoven, commented that the subgroup analysis “sheds light on the discrepancy between trial and practice—why many clinicians on one hand experience benefit of IABP therapy in patients, while trial results on the other hand do not corroborate these findings. IABP therapy is indeed useful in a specific patient population—ie, those with persistent ischemia after acute myocardial infarction, whether or not associated with (pre)shock.

“This underlines the importance of coronary autoregulation in IABP efficacy, a factor which is not accounted for in the large randomized trials, like CRISP-AMI and IABP-SHOCK II,” he continued, suggesting that it might be one reason the trials failed to prove benefit. In short, he said, “the wrong patients were included.”

IABP use is not always well tailored in clinical practice, Dr. van Nunen said. “When using IABP therapy, clinicians should always keep in mind the status of coronary autoregulation in the patient and its effect on IABP efficacy. Large amounts of ischemic but viable myocardium are reasons for IABP insertion, while in cardiogenic shock due to older myocardial infarction with already necrotic myocardium, patients are probably better off with other mechanical support devices, like Impella [Abiomed; Danvers, MA].”

Dr. van Nunen reported that at his center, IABP therapy is used regularly in patients with persistent ischemia after successful PCI. He and his colleagues have also recently initiated the randomized SEMPER FI trial in this patient subset.

Subgroup Findings Make Sense

Acute MI patients who undergo successful PCI but still experience ischemia, or no reflow, are at the highest risk for future cardiovascular events, Dr. van Nunen said. “Due to the ongoing ischemia, coronary autoregulation is exhausted and coronary blood flow is directly dependent on coronary perfusion pressure, which is augmented by IABP,” he explained. “The combination of improving coronary circulation and decreasing [the] workload of the heart results in a significant decrease of ischemic burden of the myocardium and limits infarct size, thereby improving outcome.”

E. Magnus Ohman, MD, of Duke University Medical Center (Durham, NC), who served as study chair of CRISP-AMI but was not involved with the current analysis, said that the current results are consistent with the trend toward better survival seen in the overall trial.

Many physicians are already using IABP in patients with large anterior MIs and ongoing ischemia, he told TCTMD in an email. As to why the therapy seems most beneficial in this subset, Dr. Ohman commented: “This is unclear and it may be a chance finding, as it is a small subgroup of an overall neutral study, so we have to be cautious and not over-interpret these findings.”

 


Source:
van Nunen LX, van’t Veer M, Schampaert S, et al. Intra-aortic balloon counterpulsation reduces mortality in large anterior myocardial infarction complicated by persistent ischaemia: a CRISP-AMI substudy. EuroIntervention. 2014;Epub ahead of print.

 

Disclosures:

 

  • The CRISP-AMI trial was funded by Maquet.
  • Dr. Pijls reports receiving an unrestricted institutional research grant, reimbursements for travel expenses, and speaker’s fees from Maquet.

 

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