SHOCK
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Clinical Question
Among patients who developed cardiogenic shock during acute MI, what are the benefits of early revascularization compared to initial medical stabilization on mortality?
Bottom Line
Compared to initial medical stabilization, early revascularization was associated with a nonsignificant trend towards improved survival at 30 days among patients who developed cardiogenic shock during acute MI. However, early revascularization did confer a significant benefit by 6 months.
Major Points
The role of primary PCI in cardiogenic shock was evaluated in the 1999 SHould we emergently revascularize Occluded Coronaries for Cardiogenic shocK (SHOCK) trial, which randomized 302 patients in cardiogenic shock after acute MI to a strategy of early revascularization (PCI or CABG within 12 hours of diagnosis) or to initial medical stabilization including fibrinolysis and IABP. There was a trend towards improved survival in the primary endpoint of mortality at 30 days, but this failed to achieve significance. This may be due to the fact that the trial was underpowered to detect such a difference. However, the benefit became significant at 6 months, and follow-up of the SHOCK trial cohort demonstrated the benefit or revascularization at 1 and 6 years, suggesting that the benefit of revascularization persisted for years.
Subgroup analysis found that the benefit of revascularization on survival appeared to be limited to patients <75 years, but there were too few patients ≥75 years to make any solid conclusions regarding the magnitude of benefit or harm. Indeed, subsequent studies found that the same benefit extended to patients ≥75 years old.
Guidelines
ACCF/AHA STEMI Guidelines (2013, adapted)[1]
- PCI in STEMI if <12 hours of ischemic symptoms (class I, level A)
- PCI is reasonable in STEMI if 12-24 hours since symptom onset and clinical or EKG evidence of ischemia (class IIa, level B)
- PCI in STEMI and cardiogenic shock/acute severe HF regardless of time since MI onset (class I, level B)
Design
- Multicenter, parallel-group, randomized, controlled trial
- N=302
- Early revascularization (n=152)
- Initial medical stabilization (n=150)
- Setting: 30 centers
- Enrollment: 1993-1998
- Primary outcome: 30-day mortality
- Analysis: Intention-to-treat
Population
Inclusion Criteria
- Suspected cardiogenic shock within 36 hours of acute MI
- EKG criteria for acute MI:
- ST-segment elevation
- Q-wave infarction
- New LBBB
- Posterior infarction with anterior ST-segment depression
- Cardiogenic shock by both clinical and hemodynamic criteria
- Clinical criteria:
- Hypotension (SBP <90mmHg ≥30 mins) or need for supportive measures to maintain SBP ≥90mmHg
- Evidence of end-organ hypoperfusion
- Hemodynamic criteria:
- CI ≤2.2 L/min/m2BSA
- PCWP ≥15 mmHg
Exclusion Criteria
- Severe systemic illness
- Other forms of shock
- Severe valvular disease
- Dilated cardiomyopathy
- Unsuitable for revascularization
Baseline Characteristics
- Age: 66 years
- Female: 36.8% vs. 27.3%
- White race, non-Hispanic: 72.4 vs. 78.7%
- Prior MI: 29.6% vs. 35.3%
- HTN: 49.0% vs. 43.5%
- DM: 34.2% vs. 27.9%
- CHF: 4.0% vs. 8.2%
- Renal insufficiency: 4.6% vs. 6.9%
- Prior CABG: 2.0% vs. 10.0% (P=0.003)
- Prior PCI: 6.7% vs. 7.4%
- Smoking: 52.6% vs. 56.8%
- Eligible for thrombolytic therapy: 94.4%
- Transfer admission: 55.3%
- Anterior MI: 63.6% vs. 57.4%
- Highest total CK: 3068 vs. 3464 IU/L
- Median time from MI to shock: 5.0 vs. 6.2 hrs
- Median time from MI to randomization: 11 vs. 12 hrs
- <6 hr from MI to randomization: 25.0% vs. 23.7%
- Lowest SBP: 66.4 vs. 69.8 mmHg
- SBP: 89.0 vs. 86.5 mmHg
- DBP: 53.9 vs. 55.1 mmHg
- HR: 103.3 vs. 100.1 bpm
- PCWP: 24.2 vs. 24.3 mmHg
- CI: 1.8 vs. 1.7 L/min/m2
- LVEF: 29.1% vs. 32.5%
- Number of diseased vessels:
- ≤1: 14.0% vs. 11.5%
- 2: 21.7% vs. 24.0%
- 3: 64.3% vs. 64.6%
- Left main CAD: 23.4% vs. 17.5%
Interventions
Patients randomly assigned within 12 hours after diagnosis of shock to:
- Emergency revascularization (PCI in 60% and CABG in 40%) within 6 hours of randomization. IABP recommended.
- Initial medical stabilization. Thrombolytic therapy and IABP recommended. If clinically appropriate, delayed revascularization allowed at minimum of 54 hours after randomization
Treatment
Comparisons are revascularization vs. medical therapy.
- CPR, VT, or VF before randomization: 32.7% vs. 23.9%
- Thrombolytic therapy: 49.3% vs. 63.3%
- Inotropes or vasopressors: 99.3% vs. 98.6%
- IABP: 86.2% vs. 86.0%
- Pulmonary-artery catheterization: 93.4% vs. 96.0%
- LVAD: 3.6% vs. 0.9%
- Heart transplantation: 2.0% vs. 0.7%
- Coronary angiography: 96.7% vs. 66.7%
- PCI or CABG: 86.8% vs. 25.3%
- Median time from randomization to revascularization: 1.4 vs. 102.8 hrs
Outcomes
Comparisons are revascularization vs. medical therapy.
Primary Outcomes
- 30-day mortality
- 46.7% vs. 56.0% (RR 0.83; 95% CI 0.67-1.04; P=0.11)
Secondary Outcomes
- 6-month mortality
- 50.3% vs. 63.1% (RR 0.80; 95% CI 0.65-0.98; P=0.027)
Subgroup Analysis
Out of 10 pre-specified subgroups including sex, age (<75 vs. ≥75 years), direct vs. transfer admission, early vs. late shock, eligibility vs. ineligibility for thrombolytic therapy, ± US, ± anterior infarction, ± prior infarction, ± DM, age and history of MI had a significant interaction with treatment.
Interaction between treatment group and age was significant at 30 days (P=0.01) and at 6 months (P=0.003).
- 30-day mortality for age <75 vs. ≥75 years, respectively
- 41.4% vs. 56.8% (RR 0.73; 95% CI 0.56-0.95; P=0.02)
- 75.0% vs. 53.1% (RR 1.41; 95% CI 0.95-2.11; P=0.16)
- 6-month mortality for age <75 vs. ≥75 years, respectively
- 44.9% vs. 65.0% (RR 0.70; 95% CI 0.56-0.89; P=0.002)
- 79.2% vs. 56.3% (RR 1.41; 95% CI 0.97-2.03; P=0.09)
Interaction between treatment group and history of MI was significant at 30 days (P=0.02), but not not significant at 6 months (P=0.15).
Funding
Supported by National Heart, Lung, and Blood Institute and American Heart Association