Clinical PaperPrognostic implication of out-of-hospital cardiac arrest in patients with cardiogenic shock and acute myocardial infarction☆
Introduction
Acute myocardial infarction (MI) complicated by cardiogenic shock (CS) is one of the most serious acute medical conditions with mortality rates of at least 40–50% in randomized clinical trials (RCT).1, 2, 3, 4, 5 The SHOCK trial assessing the effect of early aggressive revascularization showed 30-day mortality rates of 46% in patients treated with primary percutaneous coronary intervention (pPCI) or coronary artery bypass graft (CABG) and 6-month mortality of 50%.1 The recent IABP-SHOCK II study, assessing the effect of intra aortic balloon pump (IABP) counter pulsation, found 30-day and one-year mortality rates of 40% and 50%.3, 4 Mortality rates remain high today and presumably even higher in the real life clinical setting in CS patients not included in RCTs. Approximately 5% of patients with acute MI develop cardiogenic shock (CS).6, 7, 8, 9 Out-of-hospital cardiac arrest (OHCA) is estimated to occur in one in fifty MI patients, and is associated with increased early mortality in patients with ST-elevation myocardial infarction.10 Furthermore, many OHCA patients also develop CS.11 However, whether MI patients presenting with both OHCA and CS have increased mortality is not known. We therefore aimed to compare outcome in patients with acute MI and CS presenting with or without OHCA to evaluate if OHCA further increases the mortality rate in CS.
Section snippets
Inclusions
Consecutive patients presenting with CS complicating acute MI admitted to a tertiary Danish high volume PCI centre in the period from January 1st 2008 to February 1st 2013 were included. Initial registration with the diagnosis of CS was found in 517 patients. Two hundred and forty-eight patients with acute MI complicated by CS were included. The 269 excluded patients were in CS due to non-ischaemic causes (pulmonary embolism, septicaemia, hypovolemia etc.). CS was defined according to the SHOCK
Demographics
In total 248 patients were admitted with CS complicating acute MI (Fig. 1 and Table 1). In 118 patients (48%) initial presentation was OHCA with ROSC after 25 min (SD 18). Initial rhythm was ventricular fibrillation or pulseless ventricular tachycardia in 76 patients (64%), and cardiac arrest was witnessed in 84 cases (71%), with bystander cardiopulmonary resuscitation initiated in 69 (58%) of OHCA cases. Patients in the OHCA group were younger (64 years (SD 13) vs. 68 years (SD 12), p = 0.03)
Discussion
Previous studies have documented that OHCA is associated with higher mortality in STEMI patients.6, 7, 9, 10, 16 We compared patients with acute MI complicated by cardiogenic shock presenting with or without OHCA in a large contemporary unselected population, including severely haemodynamic compromised patients with severe lactate acidosis. Data suggest that although crude mortality initially was higher in the OHCA this was due to higher age and more severe metabolic acidosis and after
Conclusion
OHCA is not an independent predictor of death in acute MI complicated by cardiogenic shock. This should encourage active intensive treatment of CS patients regardless of OHCA.
Conflicts of interest
None.
Acknowledgements
The study was funded by a postgraduate research scholarship in Rigshospitalet – Copenhagen University Hospital, Department of Cardiology. The work of JK is supported by the EU Interreg IV A programme Centre for Resuscitation Science in the Oresund Region.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.11.010.