The Failing Ottawa Heart

Canada! So many rules! The true north strong and free, indeed.

This latest innovation is the Ottawa Heart Failure Risk Scale – which, if you treat it explicitly as titled, is accurate and clinically interesting. However, it also masquerades as a decision rule – upon which it is of lesser standing.

This is a prospective observational derivation of a risk score for “serious adverse events” in an ED population diagnosed with acute heart failure and potential candidates for discharge. Of these 1,100 patients, 170 (15.5%) suffered an SAE – death, myocardial infarction, hospitalization. They used the differences between the groups with and without SAEs to derive a predictive risk score, the elements of which are:

• History of stroke or TIA (1)
• History of intubation for respiratory distress (2)
• Heart rate on ED arrival ≥110 (2)
• Room are SaO2 <90% on EMS or ED arrival (1)
• ECG with acute ischemic changes (2)
• Urea ≥12 mmol/L (1)

This scoring system ultimately provided a prognostic range from 2.8% for a score of zero, up to 89.0% at the top of the scale. This information is – at least within the bounds of generalizability from their study population – interesting from an informational standpoint. However, they then take it to the next level and use this as a potential decision instrument for admission versus discharge – projecting a score ≥2 would decrease admission rates while still maintaining a similar sensitivity for SAEs.

However, the foundational flaw here is the presumption admission is protective against SAEs – both here in this study and in our usual practice. Without a true, prospective validation, we have no evidence this change in and its potential decrease in admissions improves any of many potential outcome measures. Many of their SAEs may not be preventable, nor would the protections from admission be likely durable out to the end of their 14-day follow-up period. Patients were also managed for up to 12 hours in their Emergency Department before disposition, a difficult prospect for many EDs.

Finally, regardless, the complexity of care management and illness trajectory for heart failure is not a terribly ideal candidate for simplification into a dichotomous rule with just a handful of criteria. There were many univariate differences between the two groups – and that’s simply on the variables they chose to collect The decision to admit a patient for heart failure is not appropriately distilled into a “rule” – but this prognostic information may yet be of some value.

“Prospective and Explicit Clinical Validation of the Ottawa Heart Failure Risk Scale, With and Without Use of Quantitative NT-proBNP”

http://onlinelibrary.wiley.com/doi/10.1111/acem.13141/abstract

5 thoughts on “The Failing Ottawa Heart”

  1. Dr Radecki
    Not surprisingly I see things differently.
    This paper is step 2 of a multistep program to make better decisions for AHF patients in the ED. We have now derived and validated the scale on more than 1,600 patients assessed prospectively. We now have a scale that is validated and ready for Step 3, an implementation trial to see if patients are better off when OHFRS is used.
    Please note this is not a dichotomous rule for a simple problem like ankle injuries, but a Scale with a range of scores as is appropriate for a complex problem like AHF. The scale is intended to be used with clinical judgement, and other admission factors such as opportunity to optimize medical, rapid follow-up, and strong home support. We are not telling clinicians who to admit.
    Rather we are providing an estimate of medical risk for these patients. There are no other prospectively validated risk scales for ED patients with AHF. So, after this second study, we can now provided ED physicians with more information than they had previously.
    In addition we provide strong data on the potential value of NT-proBNP in assessing risk for AHF patients.
    We know that many AHF patients can be safely sent home from the ED and this scale helps a bit with decision making.
    No, we have not cured cancer in one study but we are making progress.
    Please be patient
    With respect
    Ian Stiell
    U Ottawa

    1. Hi Ian –

      I don’t think we’re actually in a terrible much of disagreement. I think the prognostic information you provide, as a result of the process you used, is very interesting. I expect it will experience the typical issues from overfitting as you validate it prospectively. Translating this “information” into “practice recommendation”, I think, is the really hard part. Clinicians would really value is a tool that helps them parse out those whose disease trajectory can be durably altered for some period of time – but then, again, care after leaving the ED/subsequent hospitalization is so heterogeneous it’s hard to rely on the effects from the initial ED disposition decision, either.

      Greatly appreciate all you do for the specialty and our practice.

      – Ryan

      1. Thanks for the kind words Ryan. One small point of clarification is that this was a prospective validation of the scale that we derived and published in Acad EM in 2013. We will be moving onto implementation soon and welcome feedback from one all.
        Thanks for your interest!
        Ian

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