What do ST depressions on an electrocardiogram (EKG) mean?

From the Guidelines

ST depressions on an EKG are a sign of myocardial ischemia, indicating that the heart muscle may not be receiving enough oxygen, and can be associated with coronary artery disease, exercise stress tests, certain medications, electrolyte abnormalities, or conditions like left ventricular hypertrophy. These appear as downward sloping lines on the EKG tracing where the ST segment dips below the baseline. The location, depth, and shape of ST depressions help determine their clinical significance, with horizontal or downsloping depressions greater than 1mm being more concerning than upsloping ones 1. According to the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes, ST depression, especially horizontal or downsloping, is highly suggestive of non-ST-elevation acute coronary syndrome (NSTE-ACS) 1.

When ST depressions are observed, especially with symptoms like chest pain or shortness of breath, immediate medical evaluation is necessary as they may indicate an acute coronary syndrome requiring prompt treatment with medications like aspirin, nitroglycerin, or more advanced interventions depending on the clinical context 1. The 12-lead ECG is pivotal in the decision pathway for the evaluation and management of patients presenting with symptoms suggestive of acute coronary syndrome (ACS), and transient ST changes during symptoms at rest strongly suggest ischemia and underlying severe coronary artery disease (CAD) 1.

Some key points to consider when evaluating ST depressions on an EKG include:

• The presence of ST depressions indicates myocardial ischemia, but the power to identify an ongoing myocardial infarction is poor, with only about 50% of patients with such changes eventually developing an acute myocardial infarction 1
• The location, depth, and shape of ST depressions help determine their clinical significance, with horizontal or downsloping depressions greater than 1mm being more concerning than upsloping ones 1
• ST depressions can be associated with coronary artery disease, exercise stress tests, certain medications, electrolyte abnormalities, or conditions like left ventricular hypertrophy
• Immediate medical evaluation is necessary when ST depressions are observed, especially with symptoms like chest pain or shortness of breath, as they may indicate an acute coronary syndrome requiring prompt treatment.

From the Research

ST Depressions on EKG

• ST depressions on an EKG can indicate myocardial ischemia, which occurs when the heart muscle does not receive enough oxygen-rich blood 2, 3, 4, 5, 6.
• The presence of ST depression can be associated with severe coronary lesions and a higher risk of cardiac events, such as myocardial infarction and heart failure 4, 5, 6.
• Studies have shown that patients with ST depression on their EKG are more likely to have multivessel or left main coronary artery disease, which can increase the risk of cardiac events 3, 6.
• The depth and duration of ST depression can also provide information about the severity of myocardial ischemia and the risk of cardiac events 2, 4.
• In some cases, ST depression can be a sign of unstable angina, which requires prompt medical attention to prevent further cardiac damage 4, 6.

Clinical Implications

• The presence of ST depression on an EKG can inform treatment decisions, such as the need for early invasive strategies, including coronary angiography and revascularization 6.
• Patients with ST depression may benefit from aggressive anti-ischemic therapies to reduce myocardial damage and prevent heart failure 5.
• The EKG pattern of ST depression with peaked negative T waves can identify a subgroup of high-risk patients with a poor prognosis 4.
• Early catheterization is recommended for patients with this EKG pattern to assess the extent of coronary lesions and guide treatment decisions 4.

EKG Interpretation

• ST depression can be classified as horizontal, downward-sloping, or upsloping, and the depth and duration of depression can provide information about the severity of myocardial ischemia 2, 4.
• The presence of ST depression in combination with other EKG abnormalities, such as T wave inversion, can increase the risk of cardiac events 5.
• EKG interpretation should take into account the clinical context, including the patient's symptoms, medical history, and risk factors for coronary artery disease 3, 6.