T-wave Alternans (TWA) Calculator

T-wave Alternans (TWA): Explanation and Clinical Context T-wave Alternans (TWA) refers to beat-to-beat variations in the amplitude or morphology of the T-wave on the electrocardiogram, reflecting repolarization heterogeneity. Elevated microvolt-level TWA has been validated as a non-invasive marker for increased risk of ventricular arrhythmias and sudden cardiac death, particularly in patients with structural heart disease or previous myocardial infarction. Assessment is usually performed at elevated heart rates (110–120 bpm) during exercise or pacing protocols, and results are expressed in microvolts (µV).

Standard thresholds categorize TWA as low (<47 µV), intermediate (47–60 µV), or high risk (>60 µV). TWA provides additive prognostic value beyond traditional risk factors such as ejection fraction, and helps clinicians in risk stratification for implantable cardioverter-defibrillator (ICD) therapy and closer monitoring.