Categorization and theoretical comparison of quantitative methods for assessing QT/RR hysteresis

Area of Science:

• Cardiology
• Biomedical Engineering
• Physiology

Background:

• The human electrocardiogram (ECG) exhibits a delay in QT interval adaptation to heart rate changes, known as QT/RR hysteresis (QT-hys).
• Subject-specific QT-hys quantifiers are explored as potential biomarkers, yet a consensus on the optimal method is absent.

Purpose of the Study:

• To systematically review and categorize existing quantifiers of repolarization hysteresis from surface ECG in humans.
• To evaluate the strengths and limitations of different QT-hys measurement approaches.

Main Methods:

• A comprehensive literature search identified 60 original articles reporting QT-hys quantifiers.
• Quantifiers were categorized into four groups based on their measurement principles.
• A mathematical model of the QT/RR loop illustrated method differences.

Main Results:

• Category I methods directly measure QT adaptation but require strict RR interval control.
• Category IIa/IIb methods compare QT responses during heart rate acceleration/deceleration, useful for QT/RR loops but sensitive to protocol variations.
• Category III methods model dynamic QT/RR relationships to estimate memory parameters, with promising adaptive and differentiation approaches.

Conclusions:

• Model-based approaches for QT-hys assessment are highly versatile.
• These methods enable independent quantification of QT/RR dependency and QT-hys.
• Model-based approaches are applicable across diverse experimental settings.