How is Prinzmetal's angina diagnosed?

Diagnosis of Prinzmetal's Angina

The key to diagnosing Prinzmetal's angina is documentation of transient ST-segment elevation during chest pain episodes that resolve when the pain abates, typically occurring at rest and often in the early morning hours. 1

Diagnostic Approach

Primary Diagnostic Methods

1. ECG Documentation

   • Obtain ECG during chest pain episodes to capture transient ST-segment elevation 1
   • Continuous 12-lead ECG monitoring (Holter) for 24 hours or longer to detect ST-segment elevation occurring at rest 1
   • Extended monitoring (>1 week) may be required in some cases 1

2. Coronary Angiography

   • Recommended for all patients with episodic chest pain accompanied by transient ST-segment elevation (Class I recommendation) 1
   • Helps determine extent of underlying coronary disease 1
   • Note: Spasm may develop spontaneously during angiography, aiding diagnosis 1
   • Distinguishes between normal vessels, non-obstructive disease, and significant stenoses 1

3. Provocative Testing

   • May be considered when clinical suspicion is high but spontaneous episodes not documented (Class IIb recommendation) 1
   • Intracoronary acetylcholine or ergonovine administration during angiography 1
   • Positive test requires: anginal symptoms, ischemic ECG changes, and severe vasoconstriction 1
   • Contraindicated in patients with high-grade obstructive stenosis (Class III recommendation) 1

Supplementary Diagnostic Methods

1. Exercise Stress Testing

   • Often negative or variable results in Prinzmetal's angina 1
   • One-third show ST elevation, one-third ST depression, one-third no changes 1
   • More often positive when performed in early morning hours 1

2. Imaging During Episodes

   • 2D echocardiogram or nuclear imaging during chest pain may document transmural ischemia 1

Clinical Features Supporting Diagnosis

1. Characteristic Presentation

   • Chest pain predominantly at rest, often in early morning hours 1, 2
   • Episodes often occur in clusters with asymptomatic periods lasting weeks to months 1
   • Exquisite response to nitroglycerin 1

2. Patient Demographics

   • Typically younger than patients with stable angina 1
   • Fewer coronary risk factors except for smoking 1
   • Association with other vasospastic disorders (migraine, Raynaud's phenomenon) 1, 3

Diagnostic Pitfalls and Considerations

1. Differential Diagnosis

   • Early stages of MI can also show cyclic ST elevations but lack the periodic nature of Prinzmetal's angina 1
   • Transient thrombotic occlusion on non-obstructive plaque may produce similar findings 1

2. Common Challenges

   • Capturing ECG changes during spontaneous episodes is difficult due to their transient nature 1
   • Many patients present with non-diagnostic ECGs and normal troponin levels 3
   • Symptoms may be misattributed to non-cardiac causes due to their occurrence at rest 4

3. Anatomical Considerations

   • Spasm can occur in angiographically normal vessels or those with atherosclerotic disease 1
   • Even "normal" coronary segments often have evidence of mural atherosclerosis on intravascular ultrasound 1

Management After Diagnosis

Once diagnosed, treatment with nitrates and calcium channel blockers is recommended (Class I recommendation) 1, 5. Amlodipine is specifically FDA-approved for vasospastic (Prinzmetal's) angina 5.

Risk factor modification, particularly smoking cessation, is essential, with patients having atherosclerotic lesions considered at higher risk 1.

Conclusion

The diagnosis of Prinzmetal's angina requires a high index of suspicion and systematic approach to document transient ST-segment elevation during chest pain episodes. Coronary angiography is essential, with provocative testing reserved for cases where spontaneous episodes cannot be documented.