Monday, October 29, 2012

Still Overpromising Benefit of PCI After Cardiac Arrest

The folks in France have been promoting PCI universally after cardiac arrest for quite some time.  It's an appealing concept – when you look at subgroups of out-of-hospital cardiac arrest, there's a significant portion of folks who clearly have a primary cardiac cause, and clearly will benefit from emergency or early PCI.

However, this study inappropriately tries to make the case for all patients to receive PCI and therapeutic hypothermia after out-of-hospital cardiac arrest.  This is a retrospective, cohort study spanning eight years of resuscitation, coordinated between Paris, France and Seattle, Washington.  They used vital records follow-up to determine patient status for each OHCA patient surviving to hospital discharge, and then looked for associations between survival and whether they received PCI or hypothermia in-house.  The most absurd statement is as follows:
"A beneficial survival association was evident among those with and without ST-elevation MI. This finding is provocative given the current debate about whether patients without evidence of ST elevation following resuscitation can benefit from PCI and should undergo early and routine coronary catheterization."
Retrospective studies such as this suffer from substantial selection bias, in which the patients who are selected for particular therapies have interactions and confounders that simply cannot be controlled or adjusted.  Patients benefit from PCI when they have a disease process amenable to intervention – and this is clearly not every cardiac arrest patient. The patients in this study who received PCI – and hypothermia – likely had specific features that identified them to treating physicians as candidates to benefit from these therapies.

The reasonable conclusion from the data presented is exactly that – cardiac arrest patients that have specific features that make them candidate for these therapies will benefit.  PCI following cardiac arrest should not be considered to be "routine".

"Long-Term Prognosis Following Resuscitation From Out of Hospital Cardiac Arrest - Role of Percutaneous Coronary Intervention and Therapeutic Hypothermia" 

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