HE-MACS Calculator

About History and Electrocardiogram-only Manchester Acute Coronary Syndromes (HE-MACS)

In the case of patients presenting to the emergency department with cardiac symptoms compatible with an acute coronary syndrome (ACS), biomarker testing enables earlier triage and reassurance with serial cardiac troponin testing can help clinicians to rule out ACS over as little as 2 h with a contemporary assay and 1 h with a high sensitivity assay.

Validated decision aids such as the Troponin-only MACS (T-MACS) can ‘rule in’ ACS, ‘rule out’ ACS and risk stratify remaining patients after a single troponin blood test.

However, biomarker testing may not be readily available in all emergency settings so another decision aid, the History and Electrocardiogram-only Manchester Acute Coronary Syndromes (HE-MACS) was derived and validated to aid triage and risk stratification using only the history, physical examination and ECG.

Probability of ACS = 1 / (1 + ex)

Where:

• x = - [(1.426 x sweating) + (1.838 x EKG) + (0.734 x pain) + (0.996 x vomiting) + (1.353 x systolic BP) + (0.675 x tobacco) + (0.024 x age) + (0.462 x sex) − 4.416]
• and the variables are as 0 for female and 1 for male, and 1 where the sign or symptom is present and 0 where absent.

The result is then interpreted and grouped in the appropriate risk category as follows:

If the patient is in the very low risk group of ACS or MACE in 30 days, discharge without biomarker testing may be possible with caution, but perhaps testing in ambulatory setting could be appropriate. As always, with decision aid tools clinical judgment should trump any results and all patient cases treated on their individual merit.

The “<4.0%” threshold for “ruling out” risk of ACS or MACE achieved 99.5% sensitivity (95% CI 97.1-100) in validation cohorts. 30-day major adverse cardiac event (MACE) was defined as acute MI, all-cause death, or coronary revascularization.

If the patient is in the other three risk groups, further investigation is required.

HE-MACS was derived by logistic regression in one cohort of 796 patients and validated in two similar prospective studies (of 474 and 659 patients). Patients underwent serial troponin sampling and 30-day follow-up for the primary outcome of ACS.

On validation, 5.5 and 12.1% (pooled total 9.4%) patients were identified as 'very low risk' with a pooled sensitivity of 99.5% (95% confidence interval: 97.1-100.0%).

HE-MACS may be used not only in triage and resource allocation in emergency departments but also in prehospital environments where biomarker concentration testing is not available. Often primary care settings are the first medical contact for patients with chest pain who are then referred to the emergency departments. HE-MACS could help rule out ACS risk in some patients and avoid unnecessary referrals.

The HE-MACS requires further validation in paramedic, primary care and other healthcare settings.

References

Original reference

Alghamdi A, Howard L, Reynard C, et al. Enhanced triage for patients with suspected cardiac chest pain: the History and Electrocardiogram-only Manchester Acute Coronary Syndromes (HE-MACS) decision aid. Eur J Emerg Med. 2018.

Validation

Todd F, Duff J, Carlton E. Identifying low-risk chest pain in the emergency department without troponin testing: a validation study of the HE-MACS and HEAR risk scores. Emergency Medicine Journal 2022; 39:515-518.

Other references

Body R, Carley S, McDowell G, Pemberton P, Burrows G, Cook G, et al. The Manchester Acute Coronary Syndromes (MACS) decision rule for suspected cardiac chest pain: derivation and external validation. Heart. 2014.