Time Is Muscle: Avoiding NSTEMI and STEMI Misdiagnoses with Fast, Accurate ECG Interpretation

In the case of a cardiac event, every minute that passes is precious, and any amount of time that is wasted — whether due to a delayed diagnostic workup or faulty ECG interpretation — can risk lasting damage to muscles and organs.

Yet many cardiologists spend those initial minutes pursuing diagnoses that end up being wrong, according to a cohort study conducted by the Myocardial Ischaemia National Audit Project using data from more than half a million patients. In the Editor's Choice study, published in the European Heart Journal: Acute Cardiovascular Care, investigators found that nearly a third of all patients with acute myocardial infarction had their diagnoses changed during their care.

The changes included shifts from NSTEMI to STEMI and vice versa, as well as adjustments to NSTEMI/STEMI from angina of unknown causes. Due to those initial NSTEMI and STEMI misdiagnoses, patients were less likely to receive guideline-based care and experienced elevated mortality rates. According to the study's authors, if STEMI and NSTEMI patients had received correct diagnoses from the outset, 251 lives could have been saved annually.

The Importance of Taking Faster ECGs

It is not difficult to imagine how prompt use of ECG could have affected these numbers, yet only 24.3% and 21.5% of patients received prehospital ECG for diagnoses that turned out to be STEMI and NSTEMI, respectively. These rates are concerning, given that suspected ACS in any setting — hospital or not — should be evaluated within 10 minutes of first medical contact with a 12-lead ECG, as guidelines from the Journal of the American College of Cardiology (JACC) recommend.

That 10-minute mark matters due to the urgency of the intervention windows: ACC/AHA guidelines dictate that patients with STEMI should receive treatment via thrombolytic or emergency cath within 30 and 90 minutes, respectively.

Still, some settings facilitate timely diagnostics better than others. Notably, EDs commonly struggle with obtaining prompt ECG readings given all the registration, triage, and other administrative matters involved in an emergency room check-in. One study from the Journal of the American Heart Association found that nearly 13% of STEMI patients did not receive an ECG within 15 minutes, and one case even involved an 80-minute wait.

Researchers attribute these variances to complexities in ECG screening criteria and called for more widespread and actionable recommendations for ECG evaluation of suspected ACS. In the meantime, physicians in any setting should remember this guidance from the American Heart Association: if a patient experiences chest pain, pressure, heartburn, or other cardiac symptoms, run the ECG immediately. It's fast, easy, and widely accessible at the point-of-care, so there's no reason not to do so.


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Ensuring Accurate ECG Interpretation

Even with prompt ECGs, providers need to interpret the results correctly. Ensuring proper and adequate training for all practitioners on the waveforms most indicative of NSTEMI and STEMI can help significantly.

Many ECG platforms now feature computerized components that can support diagnostic decision-making at rates on par with, or even exceeding, human electrocardiographer capabilities. One such program, GE Healthcare's Marquette 12SL, was found to have an adequate predictive value in STEMI diagnoses, according to a study in the Canadian Journal of Emergency Medicine. By employing computer-assisted ECG interpretation, clinicians could minimize analysis time by up to 28%, as a JACC study found, which would better position them to meet that critical 10-minute window amid high-volume times, such as during the COVID-19 pandemic.

Understanding the Full Picture

Though advanced solutions can augment human capabilities, it's important to underscore that they cannot replace them. An ACS diagnosis should factor in ECG findings, but it should not entirely depend on them, as not all cases of MI will present with abnormal ECG. One JAMA study, for example, found that more than 1 in 5 ACS patients with normal or nonspecific initial ECGs went on to have a confirmed STEMI diagnosis.

Diagnoses should be informed by technologies and other clinical indications, including personal history, family history, presentation of symptoms, access to previous ECG readings, and — with certain caveats — the results of laboratory testing as advised by the care team, such as high-sensitivity troponin testing.

Together, these tools can support a broader picture of underlying mechanisms behind cardiac events and inform correct diagnoses the first time around. After all, with every minute risking precious blood flow and tissue viability, time is not just muscle; it's life. We cannot waste one bit of it.