The total atrial conduction time is an independent predictor of atrial fibrillation (AF) in humans. It can be estimated by pulsed-wave tissue Doppler imaging (TDI) by measuring the time from onset of the P wave until the peak of A' velocity of the lateral left atrial wall (P-PA'). A prolongation of P-PA' identifies people at high risk of development of AF. This study investigated echocardiographic variables (including P-PA' measured with Colour TDI) which may identify dogs which developed AF within 6 months.

All dogs with AF were retrospectively reviewed. Those that developed a new-onset AF within 6 months after previous echo were included in the AF group. Dogs with underlying cardiac disease that did not develop AF within 6 months after echo were also reviewed and included in the non-AF group. The non-AF group were selected to have similar body weight (BW) and left atrial dilatation (2D LA:Ao) to the AF group. P-PA' durations were measured offline from archived colour TDI images by placing the region of interest over the interatrial septum (colour P-PA'_IAS) and lateral left atrial wall (colour P-PA'_lateral). P-PA' durations and echo variables of 2D, M-Mode and pulsed-wave TDI (S', E' and A' velocities) were compared between groups. Receiving operator characteristic curves were used to identify the best AF predictor.

Sixty-five dogs were included (22 AF; 43 non-AF). Degenerative mitral valve disease and dilated cardiomyopathy were the most frequent cardiac diseases in both groups. Risk of new-onset AF was not associated with a specific breed, gender, neutering status, or cardiac disease. BW, LA:Ao and colour P-PA'_IAS were not significantly different between groups. The AF group had significantly greater left-ventricular (LV) end-diastolic (ED) and end-systolic (ES) volumes, M-Mode LV ED and ES diameters, LV ES diameter indexed for body weight, LV ES volume indexed to body surface area (ESVi), LA maximal diameter (LA_max) and colour P-PA'_lateral. The variables with highest area under the curve (AUC) were P-PA'_lateral (0.8), LA_max (0.73), and ESVi (0.70). A colour P-PA'_lateral cut-off of 81.3 ms had a specificity of 81% and sensitivity of 65%.

Colour P-PA'_lateral duration was superior to other echo variables at predicting AF development within 6 months. LA_max had the second highest AUC despite similar LA:Ao between groups. Absolute LA size appears to play a more important role in AF than relative atrial dilation. Clinically useful cut-offs and intra/inter-observer variability need to be confirmed in a prospective study.

Disclosures

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