Web site designed and maintained by Chris Cairns  © SICS EBM Group 2004                                  

MI with cardiogenic shock: Early revascularisation improves long term, survival but not hospital, survival

Citations:   Hochman JS, Sleeper LA, Webb JG et al for the SHOCK Trial Investigators. Early Revascularisation and Long-Term Survival in Cardiogenic Shock Complicating Acute Myocardial Infarction. JAMA 2006; 295: 2511-15

Lead author's name and fax: Judith Hochman, judith.hochman@mad.nyu.edu

Three-part Clinical Question:

Patients: Presenting with an acute MI complicated by clinical or haemodynamic evidence of shock.

Treatment: Early revascularisation (either Percutaneous Intervention (PCI) or Coronary Artery Bypass Grafts) vs. Initial Medical Stabilisation followed by revascularisation.

Outcomes: All cause mortality during long-term follow up

 

Search Terms:  1. exp myocardial infarction/ (36668), 2. exp shock, cardiogenic/ (1222), 3. myocardial revascularization/ (29756), 4. 1 AND 2 AND 3 (360) 5. RCT filter (194328), 6. 4  AND 5 (64 articles)

The Study: Non-blinded randomised controlled trial with intention-to-treat. (No details of allocation concealment provided).

The Study Patients: Included: ECG evidence of AMI (ST-segment elevation, a Q-wave infarction, a new left bundle-branch block, or a posterior infarction with anterior ST-segment depression) with haemodynamic (systolic BP < 90mmHg, oliguria, cardiac index > 2.2 l/min/m² + pulmonary artery occlusion pressure > 15 mmHg) or clinical (oliguria or cold extremities) evidence of shock. Shock evident within 36 hours of infarction. Excluded: severe systemic illness, mechanical or other cause of shock, severe valvular disease, dilated cardiomyopathy, the inability of care givers to gain access for catheterization, and unsuitability for revascularization.
 

Control group (N = 150; 142 analysed): Standard care. Use of thromobolytic therapy and intra-aortic balloon counter-pulsation therapy was encouraged. 63% of controls received thrombolysis and 86% had an intra-aortic balloon  pump (IABP) sited.   Delayed revascularisation > 54 h was recommended if appropriate.
 

Experimental group (N = 152; 142 analysed): Emergency coronary angiography plus proceed to PCI or CABG as dictated by coronary anatomy. Operators could choose a combination of angioplasty, coronary stents and platelet glycoprotein IIb/IIIa receptor antagonists as they saw fit. Insertion of IABP counter pulsation devices was also encouraged and achieved in 86% of patients.

The Evidence:

EBM Comments:

1) Do the methods allow accurate testing of the hypothesis? Yes.   This is follow up data published by the SHOCK group – early outcomes first published 1999.

2) Do the statistical tests correctly test the results to allow differentiation of statistically significant results? Yes 

3) Are conclusions valid in light of the results? Yes 

4) Did results get omitted, and why? Yes. 25% of eligible patients were not randomized owing to early in-hospital deaths. Most of these patients were older than the randomized patients. A further 18 patients were excluded after randomization as they were found not to meet the eligibility criteria. 

5) Did they suggest areas of further research? No 

6) Did they make any recommendations based on the results and were they appropriate? Yes. Early revascularisation should be used for patients with acute MI complicated by cardiogenic shock due to left ventricular failure. 

7) Is the study relevant to my clinical practice? Yes 

8) What level of evidence does this study represent? 1^- RCT with a high risk of bias (unblinded, 25% of eligible patients not included). 

9) What grade of recommendation can I make on this result alone? D 

10) What grade of recommendation can I make when this study is considered along with other available evidence? Grade A recommendation at the ACC guideline site (http://www.acc.org/qualityandscience/clinical/guidelines/stemi/guideline1).   This has made recommendations on role of early revascularization in STEMI based on previous publications from the SHOCK series.   The guideline also provides recommendations on level of expertise required: by persons skilled in the procedure (individuals who perform more than 75 PCI procedures per year), supported by experienced personnel in an appropriate laboratory environment (a laboratory that performs more than 200 PCI procedures per year, of which at least 36 are primary PCI for STEMI, and has cardiac surgery capability). 

11) Should I change my practice because of these results? Yes. Early coronary angiography with revascularisation improves long-term outcome in patients who develop cardiogenic shock after acute MI, even if they need to be transferred to a tertiary referral centre for the procedure. 

12) Should I audit my current practice because of these results? Yes – here is a lesson in some of the “Killer B’s” to implementation of evidence.  (Evidence-Based Medicine by D Sackett et al, Churchill Livingstone, 2000, page 179)  Burdens: how frequently do these patients present at your hospital (the study involved 30 hospitals over a 5-year period)? Barriers: location of and referral pathway for early revascularization, door-to-balloon times, experience of clinicians etc ? Benefits: do patients sustaining an AMI receive prompt thrombolysis and other therapies also known to improve long-term outcomes? Beliefs: do staff in other clinical teams know about this, what do they think? 

The survival benefit of early revascularisation was not evident in the original paper designed to investigate 30 day mortality. However, it appears by 6 months and continues to improve until 1 year post infarct. Thereafter, mortality rates are similar in the 2 groups.

Risk factors for death include advanced age, presence of shock on admission to hospital, renal insufficiency as demonstrated by serum creatinine > 170 µ/l and a previous history of hypertension. This long-term divergence of mortality is in contrast to the mortality benefit seen after revascularisation for non-shocked patients, in whom the survival curves tend to converge.

Appraised by: Stephen Harris, Department of Anaesthesia & Critical Care Medicine, Royal Cornwall Hospitals, TRURO TR1 3LJ; 20 June 2006
Email: stepharr@hotmail.com

Kill or Update By: 21 June 2010

Reviewed & Edited by Chris Cairns & Malcolm Daniel

Citation: EBM Critical Appraisals. Scottish Intensive Care Society EBM Group. 2006 & JICS 2006 Vol7(3);67-68. Harris S. Hochman JS, Sleeper LA, Webb JG et al for the SHOCK Trial Investigators. Early Revascularisation and Long-Term Survival in Cardiogenic Shock Complicating Acute Myocardial Infarction. JAMA 2006; 295: 2511-15

 Printer friendly view

 ©SICS EBM 2006