Systolic time interval v heart rate regression equations using atropine: reproducibility studies

Area of Science:

• Cardiology
• Physiology

Background:

• Systolic time intervals (STI) are crucial indicators of cardiac function.
• Accurate STI assessment requires accounting for heart rate (HR) variability.
• Individualized HR correction methods are needed for longitudinal STI studies.

Purpose of the Study:

• To establish reliable individual heart rate (HR) regression equations for systolic time intervals (STI).
• To assess the feasibility of using intravenous atropine for deriving these equations.
• To determine the stability of STI v HR regression equations over a 3-week period.

Main Methods:

• Six healthy males underwent weekly intravenous atropine administration to induce incremental heart rate changes.
• Systolic time intervals (STI) including LVET, QS2, and PEP were measured at varying heart rates.
• Individual STI v HR regression equations were calculated for each subject.

Main Results:

• Significant regression relationships were observed between heart rate and LVET (Left Ventricular Ejection Time) and QS2 (Total Systolic Time).
• No significant relationship was found between heart rate and PEP (Pre-ejection Period).
• Regression equations demonstrated low intra-subject variability but high inter-subject variability, proving effective for correcting daily STI fluctuations.

Conclusions:

• Intravenous atropine administration is a convenient and satisfactory method for deriving individual STI v HR regression equations.
• These individualized regression equations are stable and applicable for correcting STI measurements over several weeks.
• This method enhances the reliability of longitudinal STI monitoring in clinical and research settings.