Tuesday, December 27, 2011

How Frequently Is The Cath Lab Cancelled?

In North Carolina - a fair bit, actually.

This is a 14-hospital registry of cardiac catheterization activations for which the authors retrospectively evaluated how many were subsequently cancelled after activation.  They don't delve into a great deal of detail regarding specific findings that accounted for the cancellation - they simply observe the broad categories of cancellation.

Of all cath lab activations, it was judged that 15% were "inappropriate", with the gold standard being the consulting cardiologist opinion.  Of the cancellations, 40% were based on the EMS ECG, 31% were ED ECG, and the remainder were "not cath lab candidates".  The author's main focus in their conclusion is on the difference between EMS ECG cancellation and ED ECG cancellation due to ECG reinterpretation following activation.

What's more interesting from the paper, however, is when they break it down to the precise cohorts of activation and arrival - and note that 24.7% of EMS activations were subsequently judged inappropriate.  It is also interesting that 13% of non-PCI center activations were inappropriate vs 8% of PCI center activations.  Reading between the lines, there's probably some experiential component to the differences in activation rates, but this study doesn't specifically look at volume and training.

"Rates of Cardiac Catheterization Cancelation for ST Elevation Myocardial Infarction after Activation by Emergency Medical Services or Emergency Physicians: Results from the North Carolina Catheterization Laboratory Activation Registry (CLAR)"


  1. As a provider in one of the systems studied, I can add that there is a large degree of variation in training and protocol.

    Our current criteria for activation is:

    1. 1mm or more of ST-E in 2 or more contiguous leads
    2. New Left Bundle Branch Block
    3. Absence of frank confounders (LVH, LBBB, Paced, Pericarditis, Early Repol)

    RBBB used to be an exclusion for EMS activation, but that has since been lifted.

    At two of my services the Paramedic makes the diagnosis and they radio in the "Code STEMI Alert". It is up to the ED physician to actually activate a Code STEMI.

    At another neighboring service, the cardiac monitor must read ***ACUTE MI SUSPECTED*** and the Paramedic must agree with it's interpretation. They also transmit their ECGs.

    Those are just 3 examples of the 7+ Paramedic level services in our STEMI catchment area. My personal experience has been that LBBB was the most common inappropriate activation and LVH/Pericarditis/ER are the new sources of inappropriate activations.

    Perhaps the most interesting part of the paper was that an activation was inappropriate if they were not a cath lab candidate. I would have preferred inappropriate being "no culprit lesion or STEMI equivalent".

  2. Cath lab activation can probably be either sensitive for a lesion requiring stent, or specific, but I don't think it can be both. As we push for earlier and earlier cath lab activation we get quicker ECG reads, by less experienced personel and we sacrifice specificity for sensitivity.

    Dr. J

  3. As Dr. J points out - yes, the sacrifice is sensitivity for specificity. When you establish these all-inclusive protocols, the logical outcome is more inclusion. It ends up being a cost-benefit decision based on how much is gained by the prehospital activation vs. lost by activation of resources that is subsequently wound down.

  4. Christopher answered, in part, my first thought when I saw this paper (or an paper regarding EMS STEMI recognition). Some systems require the Marquette software to do the work, while others invest a significant amount of time into EMS education. Anybody who argues for (or against) prehospital STEMI recognition and activation has to first define what sort of EMS protocol is, or will be, in place.

    I think the conundrums of choosing an EMS-recognition strategy are well-illustrated in an old post I wrote regarding the story of 2 ECGs, one brought in by EMS:


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