Real-time T-Wave Residuum

The recent recognition of prolonged corrected QT electrocardiographic intervals (QTc intervals) in astronauts returning from long-duration space flight as well as premature ventricular contractions (PVCs) while in flight has stimulated NASA to develop software for real-time analysis of the ECGs of astronauts as they prepare for and participate in highly stressful activities. The T-wave Residuum (TWR) is a new form of T-wave morphology analysis and is one of several techniques proposed for real-time ECG analysis. It examines the repolarization heterogeneity of the individual dipoles in the heart muscles relative to each other. TWR has been cited clinically for its sensitivity and specificity in detecting conditions such as cardiomyopathy and for predicting mortality after myocardial infarction. A real-time TWR calculates the beat-by-beat T-wave residuum of an ECG and is designed to integrate into the software package, CardioSoft®, used by NASA. CardioSoft® provides the computer interface for a high frequency ECG recorder, as well as ECG record notation, storage, organization, and replay. The T-wave obtained from the 8 channel recordings (I, II, CR1-6) is sampled at 1 KHz and the DC offsets are removed. Singular value decomposition (SVD) is then performed on the array and the TWR calculated from the eigenvalues returned by SVD: