Asymptomatic Hypertension = all about the follow-up

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Outpatient engagement is preferred over antihypertensive therapy in the ED.

Clinical Question: Is there an association between ED blood pressure levels and cardiovascular events in the subsequent two years?


What They Did:

Researchers performed a retrospective cohort study [1] using electronic medical records for all adults treated and discharged from the University of Alberta Hospital. The hospital system provides tertiary medical care and cares for 75,000 patients annually through the ED.

Patient visits were linked to administrative records for all health care encounters in the province two years before and after an ED visit. In addition, study investigators interrogated a national database linked to the hospital for one year (Jan. 1 – Dec. 31, 2016). The distribution of triage BPs was split into three groups based on BP: 140–159/90–99, 160–179/100–109, and ≥ 180/110.


  • Included all adult patients ≥ 18 years of age
  • Excluded patients with diagnosis:
    • Acute Stroke
    • Cerebral Contusion
    • Intracerebral Hemorrhage
    • Anaphylaxis
  • Excluded Dispositions:
    • Died in ED
    • Left against medical advice
    • Admitted
    • Transferred to another hospital
    • Only first visits for patients with multiple visits


The primary outcome was hospitalization in the subsequent two years for a composite of stroke, transient ischemic attack (TIA), heart failure, acute coronary syndrome and death. Secondary outcomes included a composite of death, stroke or TIA, in addition to acute coronary syndrome (ACS) and new heart failure.



Patient data were available for analysis on 30,278 patients. Of those, 14,717 patients (48.6%) had elevated BP readings with 10,732 patients (72.9%) not having a prior diagnosis of hypertension. Patients with a BP ≥ 140/90 were more likely to be older males with a lower acuity in the Canadian Triage and Acuity Scale (less urgent complaints). Patients were also more likely to have a prior history of hypertension, diabetes or coronary artery disease.

Among the patients with elevated BP, 70.4% were treated in outpatient follow-up within one month. Within 90 days of discharge, 31.4% were prescribed antihypertensive medications while 65.8% of patients without a history of hypertension were treated in outpatient follow-up within one month. Of that number, 13.9% were prescribed a new antihypertensive medication within 90 days of discharge.

Among patients with BP ≥160/100, 67.5% were treated in outpatient follow-up within one month. 25.0% were prescribed a new antihypertensive medication within 90 days of discharge.

From there, 26.1% were diagnosed with chronic hypertension or prescribed antihypertensive therapy in other clinical settings within two years. Additionally, these patients were more likely than the BP group 120–139/80–89 to meet the primary outcome in the subsequent one year (3.3% vs. 2.5%) and subsequent two years (5.9% vs. 3.8%). However, there was no statistically significant elevation in risk when adjusted for age, sex and comorbidities.


Patients with a history of hypertension who had elevated BPs had higher rates of death, stroke, acute coronary syndrome and heart failure in all groups compared to patients without a diagnosis of hypertension who presented in the same BP range. However, there was no statistically significant elevation in risk when adjusted for age, sex and comorbidities.


Investigators included a large heterogeneous group of ED patients. They used a reliable, comprehensive national data registry to obtain patient data. The primary and secondary outcomes were patient-oriented and inclusion criteria were broad.


Data were obtained from a single-center, urban, tertiary care ED, in Canada. Therefore, the Canadian healthcare model may not reflect all clinical practices. Researchers used a single BP reading taken at triage and may not account for false readings both high and low. The primary endpoint was a composite. All components are not equal, and the spectrum is broad. For example, death is not equal to angina or TIA.

Researchers also excluded admitted patients (17,176). Why were these patients admitted? Physicians may have admitted patients who were “really high” beyond their risk threshold or admitted those without follow-up and comorbidities. If patients at risk for a bad outcome (determined by gestalt) were admitted, this could bias the results. Additionally, the authors did not discuss the patients lost to follow-up.

We do not know how many patients who did not follow up in 30 days never followed up at all. If there was a major cardiovascular event, we assume that these patients would have been captured in the database although this does not account for patients who may have moved, died in another country or died as a “John Doe” (probably a small number, but worth mentioning). No data was included on antihypertensive data, and researchers did not assess lifestyle modification recommendations. Lastly, an observational study cannot account for all confounders.


Many factors must be considered when choosing an antihypertensive medication. Does the patient have other comorbidities, which may be best treated by a specific medication? What is the optimal dosing regimen? What is the patient’s social situation? Can they afford the medication? These questions may be beyond the scope of a single visit where the ED physician will likely never care for the patient again. Additionally, if the elevation in blood pressure was caused by pain or another medical condition, we may trigger some unwanted and unpleasant side effects.

Though this was a single-center study in Canada, the comprehensive inclusion criteria and large sample size render this study broadly applicable. In addition, we are compelled to discuss universal healthcare coverage in Canada. Access to medications and outpatient follow-up may not reflect all clinical practice. It may be easier to discharge patients with elevated blood pressure, even markedly elevated, if we believe they will have access to proper follow-up and long-term care.

We are often more cautious with patients under-insured and uninsured than with comparable groups of patients with ample insurance coverage and good outpatient follow-up. Likewise, when discharging patients with asymptomatic hypertension we must stress the importance of close follow-up and document such in the discharge instructions. This paper added to the growing body of evidence on asymptomatic hypertension and demonstrated no short-term increase risk in cardiovascular events in patients with elevated BP in the ED.

Clinical Bottom Line:

We agree with the author’s conclusion and also support the ACEP position. In patients presenting to the ED found to have asymptomatic hypertension, focus efforts on timely outpatient referral and follow-up, not on acute lowering of their blood pressure.


McAlister FA et al. Elevated Blood Pressures Are Common in the Emergency Department but Are They Important? A Retrospective Cohort Study of 30,278 Adults. Ann Emerg Med 2021. PMID: 33579586


Dr. Marco Propersi is an Assistant Professor in Clinical Emergency Medicine at Saint Joseph's Regional Medical Center in Paterson, New Jersey. He is passionate about medical education and FOAMed and contributes regularly to REBEL EM Blog. He is also currently enrolled at ALiEM's Faculty Incubator.

1 Comment

  1. In our dysfunctional systems, that elusive follow up is not always feasible. I often begin or resume anti-hypertensive treatment in the ED, even in those with asymptomatic hypertension. Just one of many things we (in the ED) have to do as the system’s safety net.

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