From the Guidelines
Inferolateral ST changes on an electrocardiogram (ECG) are a significant indicator of myocardial ischemia or injury, necessitating prompt evaluation and management to prevent morbidity, mortality, and reduce the impact on quality of life. These changes are associated with the territory supplied by the right coronary artery and/or circumflex branch of the left coronary artery. The presence of ST-depression ≥0.05 mV in leads V1 through V3, or ST elevation in lead aVR, particularly when coupled with symptoms like chest pain or shortness of breath, requires immediate assessment for acute coronary syndrome 1.
Key Considerations
- The ECG is an integral part of the diagnostic work-up and should be acquired and interpreted promptly, with dynamic changes in ECG waveforms during acute myocardial ischemic episodes often requiring multiple ECGs 1.
- Serial recordings in symptomatic patients with an initial non-diagnostic ECG should be performed at 15–30 min intervals, and recurrence of symptoms after an asymptomatic interval is an indication for a repeat tracing 1.
- Acute or evolving changes in the ST-T waveforms and Q waves can help time the event, identify the infarct-related artery, estimate the amount of myocardium at risk, and determine therapeutic strategy 1.
Management Approach
- Immediate assessment for acute coronary syndrome is necessary, including obtaining serial cardiac enzymes (troponin levels), administering aspirin 325mg, and considering anticoagulation with heparin.
- Additional medications like nitroglycerin for chest pain, beta-blockers (such as metoprolol 25-50mg orally), and high-intensity statins (atorvastatin 80mg daily) may be indicated.
- Patients with these ECG findings should undergo urgent cardiac consultation for possible cardiac catheterization, especially if troponin levels are elevated or if symptoms persist despite medical therapy 1.
Prognostic Implications
- The presence of ST-segment elevation or depression, particularly when associated with reciprocal ST-segment depression, usually reflects acute coronary occlusion and results in myocardial injury with necrosis 1.
- More profound ST-segment shift or T wave inversion involving multiple leads/territories is associated with a greater degree of myocardial ischemia and a worse prognosis 1.
Given the potential for significant morbidity and mortality associated with inferolateral ST changes, prompt recognition and aggressive management are crucial to improve outcomes and quality of life.
From the Research
Implications of Inferolateral ST Segment Changes
The implications of inferolateral ST segment changes can be understood through various studies that have examined the relationship between these changes and myocardial ischemia or infarction.
- Inferolateral ST segment changes can be an indicator of acute coronary syndrome, including ST elevation myocardial infarction, non-ST elevation myocardial infarction, and unstable angina 2.
- The ST segment on the electrocardiogram is a sensitive and specific marker of myocardial ischemia and infarction, but ST segment deviation is regional, not global, thus the ECG lead must be placed over the affected region of the myocardium 2.
- Inferolateral early repolarization (ER) is associated with an increase in arrhythmic risk, particularly in the presence of myocardial ischemia, and acute myocardial ischemia can affect ER by changing the ST-segment amplitude and J-wave amplitude in ER leads 3.
- Atypical ECG patterns, such as the Aslanger pattern, can be observed in inferolateral myocardial infarction and may indicate multivessel coronary artery disease 4.
- The recognition and management of patients with acute coronary syndromes rely heavily on the standard 12-lead electrocardiogram for assessing ST-segment changes associated with ischemia, and alternative electrocardiographic leads can be optimized for detection of ischemia originating in different regions of the ventricular myocardium 5.
- The presence of Q waves and additional ST-segment depression and T-wave inversion on the admission ECG in patients with ST elevation myocardial infarction may provide information regarding the potential myocardial reserves 6.