What is the appropriate workup for suspected coronary vasospasm?

Workup for Coronary Vasospasm

For suspected coronary vasospasm, invasive coronary angiography with intracoronary acetylcholine provocation testing of BOTH the left and right coronary arteries is the gold standard diagnostic approach, and should be performed when clinical suspicion is high or when patients remain symptomatic despite medical therapy. 1

Initial Clinical Assessment

Key History Elements

• Angina at rest (particularly at night or early morning due to circadian pattern) 1, 2
• Response to nitrates/calcium channel blockers - symptoms that resolve with these medications strongly suggest vasospasm 1
• Smoking history - most consistent risk factor for coronary spasm 3
• Atypical risk profile - vasospasm often occurs with less traditional atherosclerotic risk burden compared to obstructive CAD 3

Essential Initial Testing

• 12-lead ECG during chest pain episodes - capture ST-segment elevation or depression during symptoms 1
• Ambulatory ECG monitoring (Class IIa recommendation) for suspected vasospastic angina, though notably many confirmed spasm patients do NOT show ST elevation on monitoring 4, 1
• Basic laboratory work: lipid profile, complete blood count (hemoglobin), creatinine/eGFR, HbA1c/fasting glucose, thyroid function 1
• Resting transthoracic echocardiogram to assess LVEF, regional wall motion abnormalities, and exclude other cardiac pathology 1

Non-Invasive Imaging (When Appropriate)

For patients with low-to-moderate pre-test probability of obstructive CAD:

• PET imaging preferred over SPECT - can quantify myocardial blood flow and detect both epicardial disease and microvascular dysfunction 4
• Stress CMR or transthoracic Doppler of LAD during stress echo are alternatives (Class IIb) 4
• CCTA to rule out obstructive disease in appropriate candidates 1

Definitive Diagnosis: Invasive Coronary Function Testing

When to Proceed with Invasive Testing

• Class I indication: Persistently symptomatic patients with suspected ANOCA/INOCA despite medical treatment and poor quality of life 1
• Class I indication: Suspected vasospastic angina with repetitive rest angina episodes associated with ST-segment changes that resolve with nitrates/CCBs 1
• Class I indication: Uncertain diagnosis after non-invasive testing 4

Critical Protocol Elements

Test BOTH coronary arteries - this is essential and often missed:

• Testing only the left coronary artery misses up to 35% of vasospasm cases that occur exclusively in the RCA 5
• Multivessel spasm occurs in 40-62% of cases, with higher detection when starting with the LCA 6
• RCA testing requires temporary pacing wire but is necessary for complete diagnosis 5, 7

Acetylcholine provocation protocol (most commonly used):

• Incremental intracoronary bolus doses: 25,50,100 μg in LCA; 25,50 μg in RCA 5
• Alternative agents include ergonovine or methylergonovine 2, 8
• Positive test: >90% epicardial coronary artery constriction with reproduction of chest pain and/or ECG changes 1, 6

Important Caveats

• Protocols vary significantly across institutions regarding dosage, administration time, and approach - standardization is needed 8
• Complications occur in 15-22% of cases (atrial fibrillation, ventricular arrhythmias, hemodynamic instability requiring catecholamines) but are manageable 6, 7
• Microvascular spasm can coexist with or occur independently of epicardial spasm - comprehensive functional assessment should include microvascular evaluation if epicardial spasm is negative 9, 3

Algorithmic Approach

1. High clinical suspicion (rest angina responsive to nitrates/CCBs, ST changes during pain) → Proceed directly to invasive angiography with provocation testing of both coronaries 1

2. Moderate suspicion with non-obstructive disease on CCTA/angiography → Invasive coronary function testing with acetylcholine provocation of both RCA and LCA 4, 9

3. If epicardial spasm negative → Proceed with microvascular functional assessment (coronary flow reserve, microvascular resistance) 4, 9

4. Alert the interventional cardiologist at time of referral that comprehensive functional testing is needed so the patient leaves the catheterization laboratory with a definitive diagnosis 4

The key pitfall is incomplete testing - particularly omitting the RCA or stopping after negative LCA testing, which leads to missed diagnoses and inappropriate treatment 9, 5.