Distractions

David Didlake

Acute Care Nurse Practitioner

Firefighter / Paramedic (Ret)

@DidlakeDW

Expert contribution by

Dr Robert Herman

@RobertHermanMD

@PowerfulMedical (Chief Medical Officer)

An adult male called 911 for new-onset epigastric burning. Fire/EMS crews found him clammy and uncomfortable. Vital signs were noted to be unremarkable with respect to any hypo-hypertensive crisis, hypoxia, etc. Breath sounds were clear in all lung fields. No appreciable skin pallor.

He denied any known medical history, specifically: coronary artery disease, hypertension, dyslipidemia, diabetes, heart failure, myocardial infarction, or any prior PCI/stent. He reported to be a social drinker, but used tobacco products daily.

Here is the time-zero 12 Lead ECG.

As crews were assessing the ECG he further elucidated that his pain was provoked during exertion with posterior radiation towards the intrascapular region, and associated with activity-limiting dyspnea. This was all very alarming because his baseline routine, otherwise, is unencumbered as he reports a usually high exertional tolerance.

Raw ECG findings

· Sinus Bradycardia

· Unusually short PR-interval

· Normal QRS axis

· Normal QRS/T angle

· Normal R-wave progression

Subtle ECG findings

· Scooped-out STD in Lead I/V5/V6

· Downsloping STD in Lead aVL (with down-up T-wave configuration)

· “Inappropriately” flattened / baseline ST in V2/V3

· Slight J-point depression in V4

The company officer on scene asked the lead paramedic, “What’s the plan?”

To which the lead paramedic replied, “Not cardiac; his symptoms are atypical. No STEMI. The shortened PR-interval is probably an accessory pathway.”

Is this OMI? There were two distracting features that crews were forced to mitigate: 1] The shortened PR-interval, and 2] “Atypical” symptoms. (But were they really?)

The shortened PR-interval, specifically, proved to be quite beguiling as it swept crews down a differential diagnosis of intermittent accessory pathway syndrome – insomuch as a “syndrome” of recurrent tachycardia to account for the patient’s symptoms.

Attached below is an excellent demonstration of the many accessory pathways found in the general population:

It’s not unreasonable to consider the shortened PR-interval as a manifestation of a “James Fiber” or “Brechenmacher Fiber” that affords accelerated conduction from the atrium to the ventricles. Another factor to be considered, according to Chou’s textbook, is that many patients have dual AVN physiology and conduction is preferential down the fast pathway. Conversely, some patient’s simply have brisk AVN conduction, which is completely benign.

Quite frankly, none of this matters acutely! The PR-interval, coupled with the perception of “atypical” symptoms, distracted the crews from seeing the bigger picture – the agonizingly subtle bigger picture. The time-zero ECG is pathognomonic for OMI.

Dr. Robert Herman, chief medical officer with @PowerfulMedical, accurately identified the problematic features on this ECG with the use of Artificial Intelligence, attached below:

The beauty of this is that Artificial Intelligence is not distracted by something exotic such as a shortened PR-interval diagnostic differential; or led astray, clinically, by strict adherence to categorization of typical versus atypical symptoms.

Set aside all clever possibilities of the shortened PR-interval and revisit the time-zero ECG with focus only on the subtle findings – appreciable to the naked eye – before application of Artificial Intelligence.

Subtle ECG findings

· Scooped-out STD in Lead I/V5/V6

· Downsloping STD in Lead aVL (with down-up T-wave configuration)

· “Inappropriately” flattened / baseline ST in V2/V3

· Slight J-point depression in V4

Until Artificial Intelligence is deployed en masse, globally, to bedside clinicians we must deliberately, methodically, and faithfully, train our eyes to identify the agonizingly subtle ECG features that support the diagnosis of Occlusive Myocardial Infarction.

A second ECG was captured with application of V4R, V8, and V9.

There is an approximate 2-minute time difference between the first ECG and this one. Notice that the previously identified subtle findings, where applicable, have discretely intensified. Moreover, V4R discloses an upward concave ST/T configuration. Anecdotally, specific to V4R, I like to think of this feature as if someone were “inflating” the ST/T with compressed air. It doesn’t meet any conventional STEMI criteria, but there is patently obvious increased area under the curve.

324mg ASA was administered, and transport was initiated. I’m told the patient initially remained “stable” within the parameter of his previously described complaint and clinical findings. But his symptoms persisted, and even repetitive Fentanyl administration could not attenuate the smoldering epigastric burn.

Then, the epigastric discomfort was replaced by beleaguering chest pressure, and his clammy skin erupted into gross diaphoresis. Alarmed, the crews captured another 12 Lead ECG.

This is now 20 minutes later, approximately. Compare the frontal plane, in isolation, from time-zero to now:

Time Zero

Now

As crews were beginning to identify the subtle changes – with now appropriate focus on the ST/T configuration rather than the PR-interval – the patient verbalized a very foreboding statement:

“Guys, I don’t feel so good.”

Anyone who has worked emergency medicine for any length of time immediately recognizes this statement as a cry for help and equally portends dire change. He became unconscious as the monitor displayed VF. Despite immediate chest compressions, and multiple rounds of defibrillation, he could not be resuscitated.

Could there have been a different outcome if the crews immediately recognized OMI – versus a shortened PR-interval – and commenced with pre-hospital Cath Lab activation? I don’t have an answer to this specific question.

Perhaps a more balanced approach is that this could equally have been a case where the patient arrives to the ED, is worked up for “non-specific” ST changes and, in the process of such a disposition, is allowed to infarct transmurally while awaiting next-day coronary angiogram where reduced LV systolic function is encountered.

Learning points

1] Acute Coronary Syndrome has many shades of clinical manifestation. "Typical" versus "Atypical" discriminators are helpful but not without limitation; and biology does not read our textbooks. Thus, a high index of suspicion is paramount.

2] Exotic ECG findings – in this case, PR-interval shortening – make for excellent academic inquiry, but should never be a point of distraction from pathognomonic occlusive coronary disease.

3] Artificial Intelligence is gaining momentum. But until its magic is available at bedside the clinician must train his/her eyes to spot the subtle features of OMI, and equally allow the bias of STEMI to fossilize.