Noninvasive determination of atrial fibrillation cycle length by atrial colour tissue Doppler imaging in horses.

The research is about the use of tissue Doppler imaging as a noninvasive method for measuring atrial fibrillation cycle length (AFCL) in horses. The study compares this method with the traditionally invasive procedure via an intra-atrial electrogram.

Objective and Methods of the Study

• The main aim of the research was to compare AFCL as measured by an invasive intra-atrial electrogram (AFCLEGM), and noninvasively through atrial color tissue Doppler imaging (AFCLTDI).
• This is a prospective clinical study which involved 31 instances of atrial fibrillation or flutter suffered by 29 horses that were brought in for transvenous electrical cardioversion, a method to restore heart rhythm.
• The AFCLEGM was determined through a bipolar sensing/pacing electrode inserted into the right atrium of the horse, while the AFCLTDI was measured from atrial color tissue velocity curves in five specific regions of the heart.

Results and Findings

• Findings showed that the mean AFCLEGM was 161 ± 18 ms in 29 atrial fibrillation cases. In two instances of atrial flutter, the measured AFCLEGM was 244 and 324 ms.
• The mean bias between AFCLTDI and AFCLEGM ranged from -18 to +9 ms but this varied depending on the atrial wall region examined.
• The AFCLTDI was notably shorter in the left atrial free wall as viewed from the right parasternal 4-chamber and the short-axis, as compared to the other regions. The difference was statistically significant (P<0.001).

Conclusions and Applications

• The researchers concluded that tissue Doppler imaging offers an effective, noninvasive way of measuring the AFCL in horses affected by atrial fibrillation.
• Furthermore, the method was able to pinpoint spatial differences inside the equine atria, improving the precision of local assessments.
• The ability to measure AFCL – an important parameter that reflects atrial electrical remodeling – has significant connotations for studying the pathophysiology of atrial fibrillation or evaluating the effectiveness of antiarrhythmic drugs in real-time.