IABP-SHOCK II
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Clinical Question
In patients with acute MI complicated by cardiogenic shock, does an intraaortic balloon pump (IABP) reduce mortality?
Bottom Line
In patients with acute MI complicated by cardiogenic shock, there was no difference in 30-day mortality with IABP placement.
Major Points
Mortality rates in patients with acute MI complicated by cardiogenic shock remain high. Given the lack of RCTs, recommendations for adjunctive therapy in this population have been based on pathophysiological assumptions and expert opinion only. An intraaortic balloon pump (IABP) is an inflatable device placed in the aorta that inflates with diastole and deflates with systole. IABPs are thought to benefit patients in cardiogenic shock by decreasing afterload during systole and increasing coronary perfusion during diastole, thereby improving overall myocardial oxygen consumption. The use of IABPs go back to the 1970s; and IABPs are the most widely used mechanical assist devices in hemodynamically unstable patients today. The 2004 ACC/AHA[1] and 2010 ESC STEMI guidelines listed class IB and IC recommendations, respectively, for the use of IABP in patients with cardiogenic shock, despite a lack of RCTs establishing its benefit.
The Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial randomized 600 patients with acute MI complicated by cardiogenic shock to either IABP or no IABP. More than 95% underwent primary PCI with stent placement in 90%. At 30 days, there was no significant difference in the primary outcome of mortality between IABP and controls. There were no differences in process-of-care outcomes, including ICU LOS, duration of catecholamines, or time to hemodynamic stability. IABP was not associated with any significant increase in adverse events, including reinfarction, stent thrombosis, bleeding, sepsis or stroke. Although there were some limitations to the study, including its relatively small size and crossover rate, these results challenge the routine use of IABP for cardiogenic shock complicating acute MI.
Guidelines
Based upon results from the IABP-SHOCK pilot trial, the 2012 ESC STEMI guidelines[2] downgraded the use of IABP in STEMI patients from 1C to 2B. The 2013 ACCF/AHA STEMI guidelines do not incorporate the outcomes of this trial.[3]
Design
- Multi-center, open-label, parallel group, randomized, control trial
- N=600 patients with acute MI complicated by cardiogenic shock
- IABP (n=301)
- Control (n=299)
- Setting: 37 centers in Germany
- Enrollment: 2009-2012
- Follow-up: 30 days
- Analysis: Intention-to-treat
- Primary end point: 30-day mortality
Population
Inclusion Criteria
- Acute STEMI or NSTEMI complicated by cardiogenic shock:
- SBP <90 mmHg for >30 mins or requiring catecholamines to maintain SBP >90 mmHg
- Clinical signs of pulmonary congestion
- Impaired end-organ perfusion (i.e. altered mental status, cold, clammy skin and extremities; UOP<30cc/hr; serum lactate >2.0 mmol/L)
Exclusion Criteria
- Age >90 years
- Coma with fixed and dilated pupils
- No intrinsic heart activity
- Cardiac resuscitation >30 minutes
- Non-cardiogenic shock or etiology of cardiogenic shock is not due to acute MI (VSD, papillary muscle rupture, etc.)
- Cardiogenic shock >12 hours before screening
- Massive pulmonary embolism
- Severe aortic regurgitation
- Severe PAD precluding IABP insertion
- Life expectancy <6 months
Baseline Characteristics
- Median age: 70 years
- Male: 68.9%
- BMI: 27.2 kg/m2
- Current smoker: 34.3%
- HTN: 69.0%
- HL: 38.3%
- DM: 32.8%
- PAD: 12.2%
- Prior MI: 23.7%
- Prior stroke: 7.4%
- Prior PCI: 19.3%
- Prior CABG: 5.4%
Clinical presentation:
- Altered mental status: 74.6%
- Cold and clammy: 83.8%
- HR 92 bpm; BP 89/55
- Creatinine: 1.28 mg/dL; oliguria (UOP<30%): 31.5%
- Serum lactate >2.0 mmol/L: 74.3%
- Resuscitation before randomization: 45%
- NSTEMI: 29.6%
- STEMI: 68.9%
- Fibrinolysis in previous 24 hours: 8%
- Use of catecholamines: 89.8%
- No. of diseased vessels:
- One: 21.4%
- Two: 26.4%
- Three: 52.3%
- Infarct-related artery:
- LAD: 43.2%
- LCx: 19.2%
- RCA: 26.0%
- LM: 9.3%
- Bypass graft: 2.6%
- LVEF: 35%
Interventions
- Randomized to intraaortic balloon counterpulsation (IABP) or control (no IABP)
- Both arms received early revascularization (primary PCI or CABG):
- Primary PCI: 95.8% (Stent implanted: 89.9%)
- CABG: 4.1%
- Both arms received optimal medical therapy:
- Aspirin: 96.7%
- Clopidogrel: 70.7%
- Prasugrel: 26.2%
- GP IIb/IIIa inhibitors: 47.1%
- UFH: 94.3%
- LMWH: 20.0%
- Statin: 71.1%
- Beta-blocker: 62.9%
- ACE-inhibitor: 60.3%
- Aldosterone-antagonist: 22.8%
- IABP was inserted before PCI or immediately after PCI.
- IABP placement: 95.7% vs. 10% (P<0.001). 4.3% of IABP arm did not undergo insertion, because patients died prior to planned insertion; 10% of control arm underwent IABP placement, mostly due to protocol violations.
Outcomes
Comparisons are IABP vs. control.
Primary Outcome
- 30-day mortality
- 39.7% vs. 41.3% (RR 0.96; 95% CI 0.79-1.17; P=0.69) Intention-to-treat
- 37.5% vs. 41.4% (RR 0.91; 95% CI 0.74-1.11; P=0.35) Per-protocol
Secondary Outcomes
- ICU LOS
- 6.0 vs. 6.0 days (P=0.34)
- Duration of catecholamines
- 3.0 vs. 3.0 days (P=0.81)
- Time to hemodynamic stabilization
- 3.0 vs. 3.0 days (P=0.50)
- LVAD placement
- 3.7% vs. 7.4% (P=0.053)
- Reinfarction in hospital
- 3.0% vs. 1.3% (RR 2.24; 95% CI 0.70-7.18; P=0.16)
- Stent thrombosis in hospital
- 1.3% vs. 1.0% (RR 1.32; 95% CI 0.30-5.87; P=0.71)
- Stroke in hospital
- 0.7% vs. 1.7% (RR 0.40; 95% CI 0.08-2.03; P=0.28)
- Peripheral ischemic complications requiring intervention in hospital
- 4.3% vs. 3.4% (RR 1.29; 95% CI 0.58-2.90; P=0.53)
- Severe bleeding in hospital by GUSTO criteria
- 3.3% vs. 4.4% (RR 0.76; 95% CI 0.34-1.72; P=0.51)
- Moderate bleeding in hospital by GUSTO criteria
- 17.3% vs. 16.4% (RR 1.05; 95% CI 0.74-1.50; P=0.77)
- Sepsis in hospital
- 15.7% vs. 20.5% (RR 0.77; 95% CI 0.54-1.08; P=0.15)
Subgroup Analysis
Results with respect to primary end point were consistent in all prespecified and post hoc subgroups, including sex, age, diabetes, HTN, type of MI, previous MI, hypothermia, and SBP.
Criticisms
- LVAD use was not controlled.
- Timing of IABP insertion was not controlled. 86.6% of IABPs went in post-PCI.
- Lower mortality rate (40%) in this trial compared to other registries and RCTs (42-48%) suggests more mild or moderately severe shock cases, precluding generalizability to severe shock.
- Small sample size [4]
- 10% cross-over rate from control group to IABP[4]
- Long-term follow-up results to follow
- High use of catecholamines and relatively low rate of systolic hypotension (many had systolic BP >90 before randomization)[5]
Funding
- German Research Foundation, German Heart Research Foundation, German Cardiac Society, Arbeitsgemeinschaft Leitende Kardiologische Krankenhausarzte, University of Leipzig-Heart Center, Maquet Cardiopulmonary and Teleflex Medical
- Authors with multiple disclosures