Post-Arrest Catheterization Delusions

We have, yet again, another favorable publication espousing the benefit of cardiac catheterization after cardiac arrest.  There is not a great deal of ambiguity regarding the management of post-arrest STEMI.  However, the cohort these authors examine – those without obvious cardiac cause for arrest – is harder to to judge.

Unfortunately, this article is the same level of evidence as the prior publications in this field – by which I mean, practice change followed by retrospective, observational case-series.  These authors look back at their cohort cohort of VT/VF that was not STEMI – a reasonable initial stratification based on presenting rhythm and likely association with acute coronary syndrome.  Of 269 patients meeting this definition, 122 underwent early catheterization and 147 did not.  The outcomes were more favorable in the cohort that underwent catheterization, and thus, the conclusion:

“In comatose survivors of cardiac arrest without STEMI who are treated with TH, early CC is associated with significantly decreased mortality.”

But, these authors are unable to pin down exactly what element of post-arrest care in the catheterization lab leads to this decreased mortality.  Only 26.2% of patients undergoing early catheterization had a lesion amenable to intervention (the authors call this level of incidence “high” – hum), and intervening on a coronary lesion conferred no specific survival advantage.  Therefore, it’s not the PCI that benefited these patients.  There was an increased incidence of post-resuscitation shock in the catheterization cohort, and these underwent left-ventricular support more frequently – which may or may not have resulted in improved outcomes.  Furthermore, the median time to therapeutic hypothermia in the catheterization cohort was an hour faster as well – suggesting this baseline difference in treatment may have influenced cognitive outcomes.

Unfortunately, retrospective studies like this suffer critically from selection bias – patients in the arm receiving cardiac catheterization may have had other unreported features favorable for cognitively intact outcomes, leading clinicians to treat them differently/more aggressively.  It would be inappropriate to generalize this observational association with causation and send all post-arrest to catheterization.  Certainly, some subset of VT/VF arrest benefits from early cardiac catheterization, but this study unfortunately does little to delineate which.

“Early cardiac catheterization is associated with improved survival in comatose survivors of cardiac arrest without STEMI”
www.ncbi.nlm.nih.gov/pubmed/23927955‎