What are the causes of non-specific S and T wave abnormalities on an electrocardiogram (ECG)?

From the Guidelines

Non-specific S and T wave abnormalities on an ECG can be caused by a variety of conditions, including primary repolarization abnormalities due to ischemia, myocarditis, drugs, toxins, and electrolyte abnormalities, as well as secondary repolarization abnormalities resulting from changes in ventricular depolarization, such as bundle-branch blocks or ventricular preexcitation 1. These abnormalities may be localized or diffuse and can be influenced by factors such as heart rate, body position, catecholamines, and temperature changes. When interpreting these ECG findings, it is essential to consider the patient's symptoms and clinical presentation, as isolated non-specific ST changes in an asymptomatic person may not require extensive workup, while the same findings in someone with chest pain would warrant more urgent evaluation. Further evaluation, including a thorough medical history, physical examination, and possibly additional cardiac testing such as echocardiography, stress testing, or cardiac biomarkers, is typically recommended to determine the underlying cause of the abnormalities. Some key points to consider in the evaluation of non-specific S and T wave abnormalities include:

• The distinction between primary and secondary repolarization abnormalities, with primary abnormalities being due to changes in the repolarization phases of the transmembrane action potential and secondary abnormalities being due to changes in ventricular depolarization 1.
• The potential for concurrent primary and secondary repolarization abnormalities, which can make interpretation more challenging 1.
• The importance of considering alternative causes of ST-segment and T-wave changes, such as LV aneurysm, pericarditis, myocarditis, Prinzmetal’s angina, early repolarization, and Wolff-Parkinson-White syndrome 1.
• The role of electrocardiographic true posterior MI, which can present with a nondiagnostic 12-lead ECG and requires the use of posterior leads to diagnose 1.
• The prognostic information contained within the ECG pattern, which can help establish a gradient of risk of death and cardiac ischemic events 1. Overall, the evaluation and interpretation of non-specific S and T wave abnormalities on an ECG require a comprehensive approach that takes into account the patient's clinical presentation, medical history, and the results of additional diagnostic testing.

From the Research

Causes of Non-Specific S and T Wave Abnormality on ECG

• Isolated non-specific ST-segment and T-wave (NS-STT) abnormalities on electrocardiograms (ECGs) can be associated with increased risk of cardiovascular mortality and all-cause mortality in a cross-sectional United States population without known coronary artery disease 2
• T-wave abnormalities in patients with non-ST-segment elevation acute coronary syndromes are common and should not be automatically regarded as benign phenomena, as they can provide optimal risk stratification 3
• The electrocardiogram (ECG) is a crucial tool in diagnosing and managing patients with acute coronary syndromes, and ST segment elevation or depression, as well as T-wave abnormalities, can indicate acute occlusion of an epicardial artery or subendocardial ischemia 4

Clinical Significance of Abnormal T Waves

• Abnormal T waves can be a significant predictor of adverse outcomes in patients with non-ST-segment elevation acute coronary syndromes, and quantitative T-wave analysis can provide valuable prognostic information 3
• The presence of isolated minor nonspecific ST-segment and T-wave abnormalities (NSSTTAs) in older adults can be associated with significantly increased risk for coronary heart disease mortality, particularly primary arrhythmic death 5

Interpretation of ECG Abnormalities

• The Grant method of interpreting the 12-lead electrocardiogram can be a more accurate method of identifying epicardial injury and subendocardial injury than memorizing rules provided by guidelines 6
• It is essential to consider the clinical scenario, comparison to previous ECGs, and subsequent ECGs when interpreting ECG abnormalities to ensure accurate diagnosis and management 4