Objectives: To determine sensitivity and specificity of P wave duration in the identification of left atrial enlargement in dogs.
Methods: Electrocardiograms from normal dogs and dogs with various cardiovascular diseases were evaluated. Inclusion criteria were the availability of an electrocardiogram showing a stable isoelectric line, easily recognizable P waves and good quality two-dimensional echocardiographic estimate of left atrial dimensions using the left atrial to aortic root ratio.
Using a metal caliper system, P wave duration was measured to the nearest 10 milliseconds for six consecutive heart beats; data were then averaged for each dog. The accuracy of P wave duration in predicting left atrial enlargement was determined using a receiver operating characteristic analysis.
Results: One hundred and fifty-six dogs were included in the study. Average P wave durations of 20, 30, 40 and 50 milliseconds yielded sensitivities of 100, 85, 68 and 40% and specificities of 0, 16, 64 and 93%, respectively, for the diagnosis of Left Atrial Enlargement by echocardiography. The estimated area under curve of the receiver operating characteristic curve was 0·70 (95% confidence interval: 0·60 to 0·80).
Clinical Significance: The diagnostic performance of P wave duration for identification of left atrial enlargement in dogs presents considerable limitations.