A 25 year old male develops acute onset chest pain, shortness of breath, and generalized urticaria shortly after receiving intravenous atropine for symptomatic bradycardia. He also reports palpitations, vomiting, and diaphoresis. On examination, he appears pale and diaphoretic, with diffuse wheezing on lung auscultation and generalized urticaria. Oxygen saturation is reduced. Electrocardiography shows ST-segment elevation in the inferolateral leads with reciprocal changes. Cardiac troponins may be mildly elevated. Emergency coronary angiography reveals normal coronary arteries, and echocardiography is normal with no regional wall motion abnormalities, consistent with transient coronary vasospasm. Symptoms and ECG changes resolve rapidly after treatment with corticosteroids, antihistamines, and supportive care. Diagnosis?
Diagnosis is Type I Kounis Syndrome triggered by atropine.
1. Definition
Kounis syndrome is an acute coronary syndrome triggered by an allergic or hypersensitivity reaction, resulting in coronary vasospasm, plaque rupture, or stent thrombosis.
2. Pathophysiology
- Allergen exposure activates mast cells, basophils, and
inflammatory pathways
- Release of mediators such as histamine,
leukotrienes, and platelet-activating factor
- These mediators cause:
- Coronary vasospasm
- Plaque rupture in patients with underlying coronary artery disease
- Stent thrombosis in previously stented patients
3. Classification
- Type I
- Occurs in patients with normal
coronary arteries
- Causes coronary vasospasm
- Troponin may be normal or
mildly elevated
- Type II
- Occurs in patients with pre-existing
atherosclerotic disease
- Leads to plaque rupture and
acute myocardial infarction
- Type III
- Occurs in patients with coronary
stents
- Leads to stent thrombosis
4. Clinical Features
4.1
Cardiac Features
- Chest pain
- Dyspnea
- Palpitations
- Nausea and vomiting
4.2
Allergic Features
- Urticaria
- Rash
- Wheezing
- Angioedema
- Hypotension or anaphylaxis
5. Diagnosis
- Clinical suspicion is key
- Acute coronary syndrome
symptoms plus allergic manifestations
- Electrocardiography
- ST elevation or depression
- Changes may be transient in
Type I
- Cardiac biomarkers
- Troponin may be normal or
mildly elevated
- Coronary angiography
- Normal coronaries in Type I
- Abnormal findings in Type II
and III
- Allergy markers
- Serum tryptase or IgE may support diagnosis
6. Key Clinical Insight
Chest pain with ECG changes in the presence of allergic features strongly suggests Kounis syndrome rather than primary acute coronary syndrome.
7. Management
7.1
Core Principle
Simultaneously treat the allergic reaction and myocardial ischemia.
7.2
Allergic Component
- Corticosteroids
- Antihistamines (H1 and H2
blockers)
- Oxygen therapy and intravenous fluids if required
7.3
Cardiac Component
Type
I
- Primary treatment is control
of the allergic reaction
- Nitrates or calcium channel
blockers may be used for vasospasm if
hemodynamically stable
Type
II and III
- Manage as acute coronary
syndrome
- Add steroids and antihistamines
7.4
Important Drug Considerations
- Epinephrine
- Remains first line for
life-threatening anaphylaxis
- Use with caution due to
risk of worsening coronary vasospasm
- Beta blockers
- Avoid in the acute phase due
to risk of unopposed alpha-mediated vasoconstriction
- Morphine
- Avoid due to histamine release and potential worsening of vasospasm
8. Prognosis
- Type I generally has a favorable prognosis with prompt
treatment
- Type II and III depend on severity of underlying coronary disease
- Early recognition reduces risk of myocardial infarction, arrhythmias, and death
9. Exam Level Pearls
- Kounis syndrome = allergic
reaction + acute coronary syndrome
- Suspect when ACS symptoms
occur with urticaria, wheeze, or anaphylaxis
- Normal coronary angiography
with ST elevation suggests Type I
- Avoid beta blockers and
morphine in acute phase
- Use epinephrine cautiously but
do not withhold in severe anaphylaxis
- ECG changes often resolve after treatment of the allergic reaction
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