May 7th, 2012
All Dressed Up and No Place to Go: False-Positive Activation of the Cath Lab for Primary PCI
Larry Husten, PHD
Primary PCI is widely recognized as the best early option for patients with ST-segment elevation myocardial infarction (STEMI). However, efforts to deliver primary PCI to the broadest possible population inevitably result in an increased number of false-positive activations of the cardiac catheterization laboratory. Now, a new study published in the Archives of Internal Medicine finds that the rate of false-positive activations is higher than expected.
James McCabe and colleagues analyzed data from 411 STEMI activations at two primary PCI centers. More than one-third — 36% — were judged to be false-positive. Patients with high BMIs or with chest pain or pressure at presentation were less likely to have a false-positive activation. The following factors were independently associated with an increased risk for a false-positive STEMI activation:
- Left ventricular hypertrophy on ECG: adjusted odds ratio (AOR) 3.15, CI 1.55- 6.40, p=0.001
- History of coronary disease: AOR 1.93, CI 1.04-3.59, p=0.04
- History of illicit drug abuse: AOR 2.67, CI 1.13-6.26, p=0.02
The authors conclude:
While a certain percentage of false-positive STEMI activations are essential to ensuring adequate diagnostic sensitivity, the point of equipoise between necessary diagnostic sensitivity and patient safety requires further investigation, particularly in light of increasing resource limitations.
In an accompanying commentary, Fouad Bachour and Richard Asinger note that the higher-than-expected rate of false-positives in the study may be partly due to “the variability of definitions.” They recommend that primary PCI programs adopt “a systematic protocol for the diagnosis and emergent treatment of STEMI including pivotal medical history for comorbid features, patient preference, continuous review of clinical experience, and direct feedback.” They suggest that an “acceptable rate of inappropriate activations … is probably in the 15% to 20% range.”
3 Responses to “All Dressed Up and No Place to Go: False-Positive Activation of the Cath Lab for Primary PCI”
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In my area, it is not variability of defintions. I think it is the fear of being criticized, peer reviewed or sued for not activating the possibly relevant emergency response protocol. We can modify the old residency cliche to read “nobody ever got the Nobel Prize for not activating the cath lab.” I am a primary care and ED doctor. Every case is scrutinized to see if I did not call a STEMI alert, trauma activation, stroke alert, or whatever the alert of the day is.
This paper is not really about false positive activation – it is about false-positive STEMI diagnosis. They define it as a false positive if there is not a culprit stenosis (they have other definitions for those not taken to the lab – but for those who are, they are making the determination based on angiography). The decision is not assessed (eg was the interpretation of the clinical and ECG information correct) – but they are asking if we can do a better job determining which patients with STEMIs have anatomy that is suitable for primary PCI – and which patients that appear to have a STEMI really do not. Their rate is much higher than previously reported – and it is really a report from 2 sites – but it raises an interesting question about whether our current criteria can be strengthened.
In some systems(ours), A STEMI diagnosis by ED physicians, who are contractually positively reinforced($) to reduce door to decision time and minimize STEMI “misses”- powerfully drives false positive cath lab activation. The sensitivity or threshold to STEMI diagnose(ROC) drives concordantly the activation of the cath lab. Unfortunately, we have no substitute marker of a thrombotically occluded epicardial coronary artery other than ST segment elevation colinked to an angiogram demonstrating such.