Differentiation of atrial tachycardia from other long RP tachycardias by electrocardiographic characteristics

BackgroundThe incidence and electrocardiographic characteristics of atrial tachycardia (AT) among long RP tachycardias have not been fully elucidated.Methods and resultsThirty-six patients with 37 long RP tachycardias were classified as having AT (n=23) or non-AT (n=14). We analyzed the electrocardiographic features, including the ratio between the RP and PR intervals (RP/PR ratio), P-wave morphology, and P-wave duration. The RP/PR ratio was higher in AT than in non-AT (2.01±0.54 vs. 1.57±0.24, P<0.001). A negative P wave in the inferior leads was less common in AT (4/23 vs. 13/14, P<0.01). The P-wave duration was longer in AT than in non-AT (105±13 ms vs. 84±10 ms, P<0.001). The fulfillment of any 2 of the following had a specificity and a positive predictive value of 100% for AT: RP/PR ratio of ≥1.65, absence of negative P wave in the inferior leads, or a P-wave duration of >96 ms.ConclusionAT accounted for nearly two thirds of long RP tachycardias in this cohort. Electrocardiographic features, including the RP/PR ratio, polarity of the P wave, and P-wave duration were useful in the differentiation of AT.