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”