Exercise-Induced Angina: Understanding ECG Patterns and Interpretation
Exercise-induced angina, also known as stable angina, typically occurs during physical exertion and is a sign of underlying coronary artery disease. Electrocardiogram (ECG) findings play a crucial role in diagnosing this condition and understanding its physiological impact. The following outlines the key ECG characteristics associated with exercise-induced angina.
Resting ECG Findings
At rest, approximately 50% of patients with exercise-induced angina may present with a normal ECG or only minor ST-segment changes. These subtle alterations can often be overlooked without careful evaluation. For patients with a history of prior myocardial infarction, the ECG may reveal established signs of old myocardial infarction such as Q waves or persistent ST-T wave abnormalities. These findings help clinicians determine whether the angina is due to new ischemia or related to previous cardiac damage.
ECG Changes During Exercise-Induced Angina
During episodes of angina triggered by physical activity, significant ECG changes typically emerge. One of the hallmark signs is ST-segment depression in leads with a dominant R wave. This depression is often horizontal or downsloping and reflects subendocardial ischemia.
Key ECG Features During Angina Episodes
- ST-segment changes: The ST segment becomes depressed, especially in leads with a prominent R wave. This is considered a classic indicator of myocardial ischemia.
- T-wave abnormalities: T waves may appear abnormally tall, flattened, biphasic, or even inverted in leads with a dominant R wave. These variations are closely linked to the degree of ischemia.
- U-wave inversion: In some cases, U waves may become inverted, which is an additional sign that myocardial oxygen supply is compromised.
For patients who already exhibit baseline ST-segment depression or T-wave flattening, these abnormalities tend to become more pronounced during an angina episode. Importantly, these changes are generally reversible. Once the patient stops exerting and the angina subsides, the ECG typically returns to its pre-exercise pattern. This transient nature of the ECG alterations is a distinguishing feature of stable, exercise-induced angina compared to other forms of cardiac pathology.