What is the significance of T wave depression in electrocardiography (ECG)?

From the Guidelines

T wave depression is a significant electrocardiographic finding that requires prompt medical evaluation, as it may indicate myocardial ischemia, electrolyte disturbances, or medication effects, and initial management should include a 12-lead ECG, vital signs, cardiac enzymes, and consideration of aspirin and nitroglycerin if acute coronary syndrome is suspected. The presence of T wave depression on an ECG can be associated with various cardiac abnormalities, and its significance should be assessed in the context of the patient's clinical presentation, including symptoms such as chest pain, shortness of breath, palpitations, or dizziness. According to the 2012 ACCF/AHA focused update incorporated into the ACCF/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction 1, patients with ACS and confounding ECG patterns such as bundle-branch block, paced rhythm, or LV hypertrophy are at the highest risk for death, followed by patients with ST-segment deviation, and those with isolated T-wave inversion are at a lower risk.

Key considerations in the evaluation of T wave depression include:

• The magnitude of the ECG abnormality, as reported by Lloyd-Jones et al, who found that the diagnosis of acute non-Q-wave MI was 3 to 4 times more likely in patients with ischemic discomfort who had at least 3 ECG leads that showed ST-segment depression and maximal ST depression of greater than or equal to 0.2 mV 1
• The presence of other ECG abnormalities, such as ST-segment elevation or depression, and the distribution of these changes across the ECG leads
• The patient's clinical presentation, including symptoms and medical history
• The results of cardiac biomarker measurements, such as troponin levels

In terms of management, the initial approach should include obtaining a 12-lead ECG, checking vital signs, drawing blood for cardiac enzymes, electrolytes, and complete blood count, and providing supplemental oxygen if oxygen saturation is low. If acute coronary syndrome is suspected, administering aspirin 325mg chewed and considering nitroglycerin 0.4mg sublingually for chest pain if blood pressure allows, and consulting cardiology promptly, are recommended 1. The specific pattern and distribution of T wave changes on the ECG can help differentiate between causes and guide appropriate treatment, as discussed in the 2009 AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram 1.

From the Research

T Wave Depression

• T wave depression is a common electrocardiographic occurrence in patients with ischemic heart disease 2, 3.
• The negative T wave may be of primary or secondary type, with primary origin not being a consequence of abnormal repolarization pattern 2.
• T wave abnormalities are considered relatively benign, but can be used to guide therapies and have prognostic predictive information in the setting of unstable coronary artery disease 3.
• Quantitative T-wave analysis provides optimal risk stratification, and patients with abnormal T waves in certain categories have a significantly higher risk of death, acute myocardial infarction, and refractory angina 3.

Clinical Significance

• T wave depression can be seen in various clinical settings, including postmyocardial infarction and as a consequence of reperfusion 2.
• Acute ongoing ischemia does not cause negative T wave, but rather appears when the ongoing ischemia is vanishing or in the chronic phase 2.
• The cause of negative T wave is not located in the subepicardial area, and positive exercise testing is expressed by ST depression never by isolated negative T wave 2.

Management

• Beta-blockers and calcium channel blockers are effective in the treatment of chronic stable angina, unstable angina, and vasospastic angina 4.
• Nitrates are beneficial in acute myocardial ischemia, but the use of long-acting nitrates in stable ischemic heart disease is weakened by the development of endothelial dysfunction and tolerance 5.
• The use of long-acting nitrates has unresolved questions, including the optimal dose and potential increase in incidence of acute coronary syndromes 5.