Influence of detomidine on atrial fibrillation cycle length measured by intracardiac electrogram recording and by colour tissue Doppler imaging in horses.

The research article investigates how detomidine, a sedative, influences the measurement of atrial fibrillation cycle length (AFCL) in horses, by comparing invasive measurements taken through intra-atrial electrogram with noninvasive ones made through tissue Doppler imaging. The study finds that using detomidine produces a slightly longer AFCL, but improves the quality of noninvasive measurements, making them a viable alternative for examining atrial electrical remodeling and investigating the effects of anti-arrhythmic drugs.

Objective and Hypothesis

• The researchers aimed to examine the effect of detomidine, a sedative, on AFCL measurements. These measurements can be taken invasively through an intra-atrial electrogram (AFCLEGM) or noninvasively via tissue Doppler imaging (AFCLTDI).
• It was hypothesized that detomidine would not affect AFCL but would improve the ease of taking TDI measurements, enabling noninvasive determination of AFCL.

Methodology

• The investigation was a prospective clinical study examining 33 episodes of atrial fibrillation (AF) in 32 horses.
• The horses were administered detomidine, and measurements—both AFCLEGM and AFCLTDI—were undertaken before and after sedation.
• The AFCLEGM was measured from a right atrial intracardiac electrogram, while AFCLTDI was measured from atrial color tissue velocity curves in 5 different atrial wall regions.
• The researchers used a repeated-measures linear mixed model to compare the sedated and non-sedated measurements, applying the Bonferroni correction for multiple comparisons.
• Additionally, they calculated the Bland-Altman mean bias and the limits of agreement between AFCLEGM and AFCLTDI.

Results

• The findings showed that sedation increased the mean AFCL, but the increase was very small (+4 ms on average).
• For AFCLTDI measurements, sedation noticeably improved the quality of the atrial myocardial velocity curves and the number of AF cycles measurable per cardiac cycle.
• The Bland-Altman bias between AFCLEGM without sedation and AFCLTDI with sedation ranged from -18 ms to +15 ms, depending on the atrial wall region involved.
• The Bland-Altman limits of agreement were similar for AFCLEGM without sedation and AFCLTDI measurements both with and without sedation.

Conclusion

• The research indicates that while sedation increases AFCL marginally, it greatly facilitates noninvasive measurements of AFCL.
• Thus, noninvasive measurements can serve as an indicator of atrial electrical remodeling and could also be used to study AF pathophysiology and the effect of anti-arrhythmic drugs.