Evaluation of restitution slopes using a quasi-stationary exercise protocol

Cardiac electrical restitution is an important tool for evaluating risk of cardiac arrhythmias. Restitution slopes are used to quantify the rates of QT and DI (diastolic) interval adaptation in response to abrupt changes in cardiac cycle or RR intervals. These slopes can be either measured experimentally using invasive stepwise pacing procedures or assessed clinically from surface ECG. However, acquiring restitution slopes from surface ECG recordings may be complicated due to the presence of significant variations in QT and DI intervals. In this paper, we suggest a novel signal processing method, which overcomes these difficulties by implementing quasi-stationary exercise testing with modulated beat-to-beat QT/DI interval variations.