When Allergy Triggers a Heart Attack
🔍 Clinical Snapshot
A 56-year-old man presents with generalized urticaria, throat tightness, and chest pressure 15 minutes after a bee sting. His vitals: HR 112, BP 88/50, RR 24. ECG shows ST elevations in II, III, aVF. Troponin is mildly elevated. He receives IM epinephrine for anaphylaxis and rapidly deteriorates with worsening hypotension and bradycardia.
Was this anaphylaxis? ACS? Both?
➡️ Welcome to Kounis Syndrome.
🧠 What Is Kounis Syndrome?
Kounis Syndrome is the concomitant occurrence of acute coronary syndromes (ACS) triggered by an allergic or hypersensitivity reaction, including anaphylaxis. First described in 1991, it represents the “allergic angina” or “allergic myocardial infarction”.
It’s not a rare disease anymore—it’s a rarely diagnosed one.
🧬 Pathophysiology
Think of it as coronary vasospasm or plaque destabilization due to massive mast cell degranulation during a systemic allergic reaction.
Key mechanisms:
- Histamine, leukotrienes, platelet-activating factor, and cytokines → cause:
- Coronary vasospasm
- Plaque erosion/rupture
- In-situ thrombosis
- Eosinophils and mast cells infiltrate cardiac tissue, worsening myocardial ischemia.
- Epinephrine paradox: Standard anaphylaxis treatment can exacerbate ischemia by:
- ↑ myocardial oxygen demand
- Vasoconstriction
- Arrhythmogenic potential
🧩 Clinical Variants
Kounis syndrome has three subtypes:
| Type | Mechanism | Population | Angio Findings |
|---|---|---|---|
| Type I | Coronary spasm in normal arteries | No underlying CAD | Normal coronaries |
| Type II | Plaque rupture in existing CAD | Known CAD | Acute thrombus or ulcerated plaque |
| Type III | Stent thrombosis (eosinophil/mast-cell mediated) | Recent PCI | Stent occlusion |
⚠️ Triggers in the ED
Be suspicious when chest pain occurs with:
- Anaphylaxis or urticaria
- Drug reactions (antibiotics, NSAIDs, contrast, opioids)
- Insect bites/stings
- Shellfish or nut allergy
- Latex, anesthetics, vaccines
🩺 Clinical Presentation
Patients often present with overlapping features of:
- Anaphylaxis: Hypotension, rash, wheezing, GI symptoms
- ACS: Chest pain, ST changes, arrhythmias, troponin rise
Red Flag = Chest pain + allergic symptoms.
🧪 Diagnostics
1. ECG:
- ST-segment elevation or depression
- T-wave inversions
- Arrhythmias
2. Troponin:
- Often elevated, depending on subtype
3. Echocardiography:
- May show regional wall motion abnormalities
4. Allergy Workup:
- Serum tryptase, IgE, histamine
- Skin testing later (NOT in the acute phase)
5. Coronary Angiography:
- Type I: Normal coronaries with spasm
- Type II: Plaque rupture/thrombosis
- Type III: Stent thrombosis
🚑 ED Management: The Tightrope Walk
✅ 1. Airway, Breathing, Circulation
- Start with ABCDE
- Consider early intubation for angioedema or stridor
✅ 2. Anaphylaxis Treatment
- Epinephrine IM (0.3–0.5 mg): Still first-line, even in chest pain, unless clear ACS
- IV fluids, oxygen, antihistamines (H1 + H2), corticosteroids
- Avoid IV epinephrine unless critically hypotensive
⚠️ Pitfall: Withhold epi out of fear in hypotensive allergic ACS → worsens outcome.
✅ 3. ACS Protocols
- Aspirin if not allergic
- Avoid NSAIDs, especially if the trigger
- Nitrates & CCBs: Consider for vasospasm (esp. in Type I)
- Heparin: For Type II/III with clear thrombus
⚠️ Pitfall: Giving beta-blockers in active anaphylaxis → unopposed alpha stimulation → catastrophic hypertension or bradycardia.
🧭 Disposition and Follow-Up
- Admit ALL patients with suspected Kounis syndrome for telemetry and further cardiology workup
- Cardiology and Allergy consults
- Coronary angiography typically performed in all but the most stable Type I cases
📌 Key Takeaways
✅ Kounis = ACS + Allergy — never ignore chest pain in anaphylaxis
✅ Use IM epinephrine cautiously but do not delay it
✅ ECG + troponin in all allergic chest pain cases
✅ Avoid beta-blockers, IV epinephrine, NSAIDs
✅ Get cardiology + allergy involved early
📚 Suggested Reading
- Kounis NG. Kounis Syndrome: An Update on Epidemiology, Pathophysiology, Diagnostic Workup and Therapeutic Management. Clinical Chem Lab Med. 2016.
- UpToDate: Kounis Syndrome – Overview and Treatment
- European Heart Journal: Allergic Acute Coronary Syndrome
💬 Final Thought
In the ED, we’re trained to think fast, but Kounis demands we think wider.
That chest pain? It might not be just the peanut butter.
