Taking Post-Arrest to the Cath Lab

There has been a fair bit of debate regarding the utility of taking post-arrest patients to cardiac catheterization. Clearly, ST-elevation myocardial infarction should receive intervention – although, it can sometimes be challenging to identify on post-arrest EKG. Much less has been determined regarding the treatment of those without STEMI.

This is – as is most of the relevant literature – a retrospective review of patients with cardiac arrest, as identified from a multi-center therapeutic hypothermia registry. These authors record the location of arrest, previously known coronary artery disease, the initial rhythm as shockable or unshockable, and EKG findings. They defined clinically important CAD by the presence of an intervention following cardiac catheterization, including PCI, stenting, or coronary artery bypass grafting.

Entertainingly, the authors hypothesis is “the incidence of coronary intervention would be uncommon (<5%)” – which, if it truly is their hypothesis, it is contradicted by most of their citations, including a meta-analysis citing an overall incidence of CAD in post-arrest patients ranging from 59-71%. Regardless, there were 1,396 patients with known initial rhythms, about 2/3rds of which were non-shockable. About 60% of shockable rhythms and 20% of unshockable rhythms underwent cardiac catheterization. After removing those with obvious STEMI on their EKG, there were 97 patients in their cohort of interest, 24 (24.7%) of whom underwent intervention.

This, therefore, is the “unexpectedly high” incidence of coronary intervention in this non-shockable rhythm cohort without STEMI on EKG. However, as these authors do appropriately note, these data should not specifically inform practice change. The findings in those patients undergoing catheterization are skewed by selection bias, including measured and unmeasured confounders influencing the decision to take patients for potential intervention. In an older population characteristic of a cardiac arrest cohort, some coronary disease is likely on any diagnostic test – and, in this clinical context, it seems intervention would be much more likely than not. Finally, intervention does not equate to a culprit lesion for cardiac arrest, further distancing these results as a surrogate for patient-oriented outcomes.

Despite the “surprise” these authors report, they likely overestimate any evidence for benefit in this post-arrest population, and better characterization of specific high-yield circumstances is needed.

“Incidence of coronary intervention in cardiac arrest survivors with non-shockable initial rhythms and no evidence of ST-elevation MI (STEMI)”