Chest pain next best step: STEMI or aortic dissection?
Inferior ST elevation meets STEMI criteria, but the rest of the stem points somewhere else. Walk a chest pain case line by line and see why the next best step is to image the aorta.
Chapters (9)
In a chest-pain vignette, choose the next best step by applying the stability–ECG–troponin sequence, and recognise when a mimic (aortic dissection with inferior ST elevation) changes management to aortic imaging before any antithrombotic or fibrinolytic therapy.
The short version
- Climb the chest pain ladder in order, and check the stem for life threats before you treat the ECG.
- New inferior ST elevation of at least 1 mm in two or more contiguous leads meets STEMI criteria on its own, but a proximal aortic dissection extending into the right coronary artery can cause it.
- Tearing pain into the back, a pressure gap between the arms, a new aortic regurgitation murmur or a wide mediastinum means you image the aorta first: CT angiography of the chest, abdomen and pelvis.
- Suspected aortic dissection is an absolute contraindication to fibrinolysis, and the primary PCI pathway means antiplatelet and anticoagulant drugs.
- A pulse difference appears in only about 30% of dissections; with no dissection clues at all, the STEMI pathway applies.
Chest pain next best step: the case
The fastest way to get a chest pain next best step question right is to read the whole stem before you react to the ECG. Here is the case from the lesson.
A 63-year-old man with long-standing hypertension has sudden, severe chest pain that began an hour ago and tears through to his back. His blood pressure is 174/98 mm Hg in the right arm and 132/80 mm Hg in the left. His pulse is 104/min, his oxygen saturation is 97%, and there is a soft early diastolic murmur at the left sternal border. The ECG shows 2 mm of ST elevation in leads II, III and aVF, and a portable chest x-ray shows a widened mediastinum. He is in a hospital with a cath lab.
The question is the most appropriate next step. The ECG pulls you toward the cath lab. The rest of the stem pulls the other way.
The chest pain ladder: stability, ECG, troponin
The ladder from the first lesson in this series gives the order: identify life threats and stability first, then the ECG, then troponin and risk.[1]
- Rung 1: stabilityHe is hypertensive, not in shock, so he is stable enough to go for imaging.[1]
- Rung 2: the ECG and the life threatsThe ECG is obtained within 10 minutes of arrival, and it is read alongside the life-threatening causes of chest pain, not instead of them.[1][2]
- Rung 3: troponin and riskThis comes after that.[1]
Walk the stem: STEMI criteria vs aortic dissection clues
New inferior ST elevation of at least 1 mm in two or more contiguous leads: on its own, that meets the criteria for a STEMI.[2] But look at everything else.
| Finding in the stem | What it points to |
|---|---|
| Sudden, severe pain tearing into the back, in a patient with hypertension | The classic story of aortic dissection; hypertension is a major risk factor |
| Arm gap of 42 mm Hg (174 vs 132 systolic) | More than 20 mm Hg between the arms is abnormal[5] |
| Early diastolic murmur at the left sternal border | Aortic regurgitation |
| Widened mediastinum on the chest x-ray | Fits dissection |
The clues add up. Severe sudden pain, a pulse difference and a widened mediastinum together carry a probability of dissection above 80%.[1]
Aortic dissection with ST elevation: the right coronary
So why the ST elevation? A proximal dissection can extend into a coronary artery, classically the right coronary, and cause an inferior infarction.[1][3]
The next best step: CT angiography, not lysis or the cath lab
That changes every option. Taken one at a time:
- Fibrinolytic therapy is out: suspected aortic dissection is an absolute contraindication.[2]
- Emergency angiography with primary PCI would mean giving antiplatelet and anticoagulant drugs, and it delays treatment of the real problem.[2][6]
- A repeat troponin measures heart muscle injury, not the aorta, so it can't confirm or exclude a dissection, and waiting for it costs time.
- A ventilation-perfusion scan looks for pulmonary embolism, which doesn't explain the gap between the arms or the murmur.[1][4]
The answer is CT angiography of the chest, abdomen and pelvis. It is a class 1 recommendation when there is clinical concern for dissection, and CT angiography is the test of choice in stable patients. If CT is contraindicated or unavailable, the guideline names transesophageal echo or cardiac MRI instead.[1]
The branch: no arm gap, or no dissection features
What if the pressure gap between the arms were absent? A pulse difference shows up in only about 30% of dissections, so tearing pain into the back should still make you image the aorta.[1]
But if nothing pointed to dissection, the STEMI pathway would apply: primary PCI, with a goal of 90 minutes or less from first medical contact to device.[2]
- A 55-year-old woman has 2 hours of heavy chest pressure spreading to her left arm, with sweating.
- Her blood pressure is the same in both arms, her chest x-ray is normal, and her ECG shows ST elevation in leads II, III and aVF. She is at a hospital with a cath lab.
- No tearing pain, no arm gap, no murmur, no wide mediastinum: this is the classic coronary story.
- Next step: aspirin and primary PCI. The clock is about reperfusion, not imaging.[2]
Practice question
Original · USMLE styleA 63-year-old man comes to the emergency department 1 hour after the sudden onset of severe chest pain that he describes as tearing and radiating through to his back. He has a 15-year history of hypertension and takes amlodipine irregularly. He is diaphoretic and in distress but alert. Pulse is 104/min and regular, and respirations are 20/min. Blood pressure is 174/98 mm Hg in the right arm and 132/80 mm Hg in the left arm. Oxygen saturation is 97% on room air. A soft, high-pitched early diastolic murmur is heard at the left sternal border. The lungs are clear. An ECG obtained 5 minutes after arrival shows sinus tachycardia with 2-mm ST-segment elevation in leads II, III and aVF. A portable chest x-ray shows a widened mediastinum. The hospital has a cardiac catheterization laboratory.
Common questions
Can aortic dissection cause ST elevation?
Yes. A proximal dissection can extend into a coronary artery, classically the right coronary, and cause an inferior infarction with ST elevation in II, III and aVF.
What are the clinical clues to aortic dissection in a chest pain vignette?
Sudden, severe pain tearing into the back, a blood pressure gap between the arms (more than 20 mm Hg is abnormal), an aortic regurgitation murmur and a widened mediastinum. Severe sudden pain, a pulse difference and a widened mediastinum together carry a probability above 80%.
Why is fibrinolysis contraindicated in aortic dissection?
Suspected aortic dissection is listed as an absolute contraindication to fibrinolytic therapy in the 2025 ACC/AHA ACS guideline.
What imaging is used for suspected aortic dissection?
CT angiography of the chest, abdomen and pelvis, the test of choice in stable patients. If CT is contraindicated or unavailable, transesophageal echo or cardiac MRI.
Does a normal arm-to-arm blood pressure rule out dissection?
No. A pulse difference shows up in only about 30% of dissections, so tearing pain into the back should still prompt aortic imaging.
Transcript
Read the full narration, by chapter657 words
0:00The case: tearing chest pain with inferior ST elevation
Here's a case. Read it with me, and pause before the options if you want to commit to an answer. A 63-year-old man with long-standing hypertension has sudden, severe chest pain that began an hour ago and tears through to his back. His blood pressure is 174/98 in the right arm, and 132/80 in the left. His pulse is 104, his saturation is 97%, and there's a soft early diastolic murmur at the left sternal border. The ECG shows 2 mm of ST elevation in leads II, III, and aVF, and a portable chest X-ray shows a widened mediastinum. He's in a hospital with a cath lab. What's the most appropriate next step? By the end of this case, you'll apply the chest pain ladder, and spot the mimic that turns ST elevation into a reason to stop and image.
0:57The chest-pain ladder: stability, ECG, troponin
Bring back the ladder from lesson one. Rung 1, stability: he's hypertensive, not in shock, so he's stable enough to go for imaging. Rung 2, the ECG and the life threats. Rung 3, troponin and risk, comes after that.
1:13Walk the stem: STEMI criteria vs dissection clues
Now walk the stem, line by line. Inferior ST elevation, at least 1 mm in contiguous leads: on its own, that meets the criteria for a STEMI. But look at everything else. Sudden, severe pain that tears into the back is the classic story of aortic dissection, and hypertension is a major risk factor. A gap of 42 mm Hg between the arms, where more than 20 is abnormal, points the same way. The early diastolic murmur suggests aortic regurgitation, and the widened mediastinum fits too. Severe sudden pain, a pulse difference, and a widened mediastinum together carry a probability of dissection above 80%.
1:59Why the ST elevation? Dissection into the right coronary
So why the ST elevation? A proximal dissection can extend into a coronary artery, classically the right coronary, and cause an inferior infarction.
2:11The options, one at a time
That changes everything, so take the options one at a time. C, fibrinolytic therapy, is out, because suspected aortic dissection is an absolute contraindication. A, emergency angiography with primary PCI, would mean giving antiplatelet and anticoagulant drugs, and it delays treatment of the real problem. D, a repeat troponin, can't confirm or exclude a dissection, and it costs time. E, a ventilation-perfusion scan, looks for pulmonary embolism, which doesn't explain the gap between the arms or the murmur.
2:48The answer: CT angiography of the chest, abdomen and pelvis
The answer is B: CT angiography of the chest, abdomen, and pelvis. That's a class 1 recommendation when there's clinical concern for dissection, and CT angiography is the test of choice in stable patients. If CT is contraindicated or unavailable, the guideline names transesophageal echo or cardiac MRI instead.
3:12The branch: no arm gap, or no dissection features
Now the branch: what if the pressure gap between the arms were absent? A pulse difference shows up in only about 30% of dissections, so tearing pain into the back should still make you image the aorta. But if nothing pointed to dissection, the STEMI pathway would apply: primary PCI, with a goal of 90 minutes or less from first medical contact.
3:36Your turn: a classic inferior STEMI
One more, quickly. Pause if you need to. A 55-year-old woman has 2 hours of heavy chest pressure spreading to her left arm, with sweating. Her blood pressure is the same in both arms, her chest X-ray is normal, and her ECG shows ST elevation in leads II, III, and aVF. She's at a hospital with a cath lab. What's the next step? Aspirin, and primary PCI. This is the classic coronary story with no dissection clues, so the clock is about reperfusion, not imaging.
4:10High-yield recap and next lesson
Quick recap. One: climb the ladder in order, and check the stem for life threats before you treat the ECG. Two: tearing pain into the back, a pressure gap between the arms, a new aortic regurgitation murmur, or a wide mediastinum means you image the aorta first. Three: suspected dissection is an absolute contraindication to fibrinolysis. Next in the series: aortic dissection itself, and how to tell it from a heart attack in the first few minutes.
Sources
Numbers in the text, e.g. [1], point here- Gulati M, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain. Circulation 2021 (§2.3.1, §4.2.1 acute aortic syndrome, Table 4, Figure 8). ahajournals.org/doi/10.1161/CIR.0000000000001029
- Rao SV, et al. 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes. Circulation 2025 (Table 3, Table 14, §3.1, §4.3.1, §5.2.1). ahajournals.org/doi/10.1161/CIR.0000000000001309
- Farber MA, Parodi FE. Aortic Dissection. MSD Manual Professional Version (Dec 2024). msdmanuals.com/professional/cardiovascular-disorders/diseases-of-the-aorta-and-its-branches/aortic-dissection
- MSD Manual Professional Version. Chest Pain (Aug 2024). msdmanuals.com/professional/cardiovascular-disorders/symptoms-of-cardiovascular-disorders/chest-pain
- 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease (Isselbacher EM, et al. Circulation 2022). (§7.1 Table 22, §7.2; IV beta-blocker first) ahajournals.org/doi/10.1161/CIR.0000000000001106
- Hiratzka LF, et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease. Circulation 2010 (§8.6.2). ahajournals.org/doi/10.1161/CIR.0b013e3181d4739e
Guideline basis: US guidelines (2021 AHA/ACC chest pain, 2025 ACC/AHA ACS and the 2022 ACC/AHA aortic disease guideline), reviewed 22 Oct 2026. UK practice is the same: suspected dissection → CT aortogram, IV beta-blocker, no fibrinolysis.
The practice question is original and its patient is synthetic. Every fact is checked against the sources above in independent accuracy reviews. Always follow your local guidelines and your own laboratory’s ranges.
Image credits. Illustrations: Servier Medical Art (smart.servier.com), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), adapted (recoloured, outlined, labelled): "Aortic aneurysm" (aortic arch drawing, used schematically for the dissection), "Heart vascularization", "Blood pressure measurement", "scanner". Original diagrams: schematic ECG strips, the schematic chest outline (not a radiograph), the arm-pressure chart, the chest-pain ladder and the decision pathway. No AI-generated teaching images.
Corrections. None so far. Spotted an error? Email info@medservatory.com with the lesson code MS-CK-EMER-004.
For exam study only, not medical advice. Read the medical disclaimer.