THM power in the spectrum of the QT interval: a refined clue to the force of ventricular contraction in man

The study has been conducted upon 13 subjects (normal volunteers or patients with normal myocardium) along 15 experimental sessions replicating ordinary activities, both sedentary and dynamic. Using newly developed software RR and QT intervals were spectrally analyzed following beat-by-beat measurement from a precordial ECG recorded in a polygraphic set-up. 1. Generally, spectral QT-Traube-Hering-Mayer power (QT-THM, 0.05 to 0.15 Hz band) was significantly increased versus baseline during interventions characterized by higher sympathetic tone. Mean QT co-varied significantly with QT-THM in a reciprocal manner. 2. Emotional stress entailed significant QT-THM increase as compared to rest. RR-THM co-varied significantly with QT-THM in a direct manner. 3. Mental concentration elicited significant QT-THM increase as compared to rest. There was no significant co-variation with mean QT or RR-THM. 4. QT-THM and RR-THM presented close sensitivity to emotional stress, while mean QT trailed them by as much as two orders of magnitude. Single QT-THM has shown comparable sensitivity to mental concentration.