Study of the dynamic relationship between T wave morphology and heart rate during ischemia

In this work the relationship between heart rate and several repolarization indices, including the QT interval and T wave morphology descriptors, has been investigated. A time-variant model has been proposed to describe the I_r to RR relationship, with I_r generically denoting one of the repolarization indices under study, and RR the running mean RR interval. The proposed methodology is applied to the analysis of stress test recordings. Three different groups of individuals are considered: ischemic patients, low-risk patients and healthy subjects. It is shown that the slope of the line fitting the I_r to RR beat series evaluated at stress peak is significantly lower in ischemic patients as compared to low-risk patients and healthy subjects, and that result is valid for any of the I_r indices. It can be concluded that loss of the T wave adaptation capability (lower slope) to heart rate changes, measured at stress test peak, is related of the presence of ischemia.