In “Bad Heartburn” – 82 y.o. female without chest pain, the paramedic had obtained an ECG on an elderly woman who only complained of mild “heartburn.” An initial ECG was obtained:
ECG interpretation :
The degree of ST elevation is significantly higher in lead II than lead II, which usually supports an RCA occlusion. Furthermore, there is mild ST depression in lead I, also typical for RCA occlusion. There is apparent sinus arrest, with a junctional escape rhythm, which suggests that the SA nodal artery (usually a branch off the RV) is involved.
The ST depression and T wave inversion in V2 and V3 suggest an acute posterior infarct.
The “classic” pattern of high R waves and upright T waves is actually not representative of acute occlusion – for more on this, read this discussion on old versus “new” teaching on recognizing posterior MIs. We do not see ST elevation in aVR or V1 that would suggest a concomitant RV infarct, however.
Although the protocols did not require a computerized interpretation to verify a STEMI, the absence of “typical” ischemic symptoms made a prehospital cath lab activation modestly more difficult to justify. Since the computer interpretation algorithms may miss a STEMI up to half of the time, the medic obtained a second tracing less than a minute later:
The ED was contacted while EMS was still on scene, and medical direction quickly agreed with alerting the cath lab, despite the atypical symptoms. As noted before, ASA was given, but NTG was withheld. Ten minutes later, during transport, the medic shot a repeat ECG with V4R.
The patient stayed in the ED for 10 minutes while the cath team was assembling, and a repeat ECG was obtained.
A complete occlusion of a LEFT-dominant circumflex was found during PCI, and was successfully stented. A transvenous pacer was placed, but was used only for a brief period. The patient recovered well.
Some discussion points:
1. You will miss STEMIs in the elderly unless you do them on practically everyone.
A study conducted in an ED found that, in patients over the age of 79, you should get an ECG on any patient with chest pain, dyspnea, altered mental status, upper extremity pain, weakness, syncope, nausea/vomiting, or abdominal pain. And even then they missed a bunch of STEMIs!
2. The computer interpretation can be falsely negative.
In a recent study using Lifepak-12 monitors, the computer only diagnosed a STEMI in 58% of the cases, while another study found that the computer got 69% of the STEMIs. Despite the high quality of the first tracing (no artifact or baseline wander), the computer missed an ECG pattern that most medic students would recognize after their first day of cardiology class!
3. Nitroglycerin probably would have been fine, but it likely isn’t worth the bother.
Aspirin therapy, fibrinolysis, and percutaneous coronary angiography have all been demonstrated to reduce mortality. Nitroglycerin, despite an appealing rationale, has not been shown save lives. Reduction of discomfort should be a goal of EMS, of course, but there isn’t much evidence that nitro does much more than that.
Okay, but what if a medic elected to give a tab or 2 of NTG to this patient – would this be harmful? Despite the standard teaching that RV MI must be ruled out before giving nitro to a patient with an inferior MI, the current data is reassuring.
I go over this in more depth in my post “Nitroglycerin – Old and New: Pt 2“, but the boiled-down version is:
- Patients with confirmed inferior and RV MI are more likely to develop hypotension after NTG administration.
- However, only 1-2% of EMS patients overall develop hypotension after NTG.
- Having an inferior STEMI (vs anterior) doesn’t seem to predict a hypotensive reaction to NTG.
- Hypotension after NTG appears to often be a vasovagal response, and can happen in people who are not having any type of ACS whatsoever.
Â The Bottom Line
Although computers are pretty good at playing chess, they aren’t always right about STEMI diagnosis. Be very suspicious of atypical symptoms, and grab an ECG. And whether or not you give NTG, this patient needs emergent reperfusion!