Prinzmetal Angina EKG Findings
The hallmark EKG finding in Prinzmetal angina is transient ST-segment elevation during episodes of chest pain that resolves spontaneously or with nitroglycerin administration, distinguishing it from evolving myocardial infarction. 1
Primary EKG Characteristics During Active Spasm
ST-segment elevation is the defining feature and indicates transmural ischemia from complete or near-complete coronary occlusion during vasospasm 1:
- Transient ST-elevation occurs in the leads corresponding to the territory of the spastic coronary artery and resolves when chest pain abates 1
- The ST-elevation reflects focal transmural ischemia in the absence of collateral circulation 1
- In approximately 50% of cases, a peaked and symmetrical T wave appears first, followed by progressive ST-segment elevation if spasm persists 2
Associated EKG Changes During Episodes
Beyond ST-elevation, several concurrent findings occur during active coronary spasm 2:
- Increased R wave height in affected leads
- Coincident S-wave diminution
- Upsloping TQ segment in many cases
- ST-T wave alternans (alternating ST-segment elevation and negative T wave depth) in approximately 20% of cases 2
The presence of ST-T wave alternans and >25% increase in R wave height are particularly important as they correlate with higher risk of ventricular arrhythmias 2.
Arrhythmic Complications on EKG
Ventricular arrhythmias are very frequent during Prinzmetal angina episodes 2:
- The prevalence and severity of ventricular arrhythmias correlate with: duration of episodes, degree of ST-segment elevation, presence of ST-T wave alternans, and >25% increase in R wave 2
- Transient bundle branch block occasionally occurs during ischemic attacks 1
- Complete atrioventricular block can occur during severe episodes 3
EKG Findings Between Episodes
A completely normal EKG between episodes does not exclude Prinzmetal angina 1:
- The resting EKG when asymptomatic may be entirely normal
- Comparison of symptomatic versus asymptomatic tracings is extremely valuable for diagnosis 1
- Previous Q waves from prior infarction may be present but do not indicate current instability 1
Exercise Testing Variability
Exercise stress testing shows unpredictable and non-reproducible results in Prinzmetal angina 1:
- One-third of patients show ST-segment elevation
- One-third show ST-segment depression
- One-third show no ST-segment changes
- Results may vary within the same patient and are more often positive when performed in early morning hours 1
Critical Diagnostic Pitfall
A completely normal EKG during an episode of significant chest pain should direct attention to other possible causes for the patient's symptoms 1. The key to diagnosis is documentation of ST-segment elevation specifically during transient chest discomfort that resolves when pain abates 1.