Than: A 2-hour diagnostic protocol for possible cardiac chest pain in the emergency department

Than, JAMA Internal Medicine. 2014,174(1):51-58

Clinical Question

• In patients with suspected acute coronary syndrome does a rapid diagnostic pathway allow early discharge from hospital without more adverse effects when compared with a conventional diagnostic assessment and discharge plan?

Design

• Randomised controlled trial
• Computer generated
• Block Randomisation
• Blinding of personnel determining results of primary outcome

Setting

• Single centre, Emergency Department, New Zealand
• October 2010 – July 2012

Population

• Inclusion: Adult patients with possible cardiac chest pain whose physician planned further observation/troponin testing
• Exclusion: STEMI, other clear cause for chest pain, chest pain >12 hours, persisting chest pain, pregnancy
• 3594 assessed for eligibility of whom 544 randomised

Intervention

• Low risk patients with a modified TIMI score of 0, and no new ischaemic ECG changes, underwent the rapid diagnostic pathway with a repeat Troponin 2 hours after the initial test.
  • If repeat Troponin test normal then patient discharged with outpatient stress test within 72 hours
• If TIMI score >0 or new ischaemic ECG changes, then investigated in standard fashion

(Journal watch – accessed 30th May 2014)

Control

• Repeat Troponin I assay at 6-12 hours
  • Follow up investigations at discretion of treating clinician

All Troponin tests were ARCHITECT Troponin I assay in both intervention and control group. This is not a high sensitivity troponin.

Outcome

• Primary outcome: discharge within 6 hours of arrival and without a subsequent major adverse cardiac event (MACE) within 30 days.
  • MACE:
    • death (unless clearly non-cardiac)
    • cardiac arrest
    • emergency re-vascularisation
    • cardiogenic shock
    • ventricular arrhythmia or high degree atrioventricular block requiring intervention
    • acute MI
  • Significantly more patients were successfully discharged within 6 hours in the intervention group (19.3%) vs. the control group (11%). Difference 8.3% (95% C.I. 1.8-14, P=0.009)
• Secondary outcome: Patients who had a MACE during follow-up (not including initial hospital visit)
  • 0.4% in intervention group vs. 0.0% in control group

Authors’ Conclusions

• The rapid diagnostic pathway is an effective and practical strategy to improve early discharge rates for some patients with chest pain

Strengths

• Randomised controlled trial
• Blinding of staff determining primary outcome

Weaknesses

• Not powered to compare rates of MACE between intervention and control groups
• Only 52 patients underwent the rapid diagnostic pathway.
• Patients in the intervention and control group treated differently with regard to the follow up investigations that were arranged.
• All patients that were discharged early had an outpatient stress test within 72 hours. This will limit the external validity of this trial as a number of institutions will not be able to provide this service.
• Single centre
• Only recruited between 0800 – 2200. If people who present at night are different in anyway then this trial may lack external validity.