Advanced interatrial block (IAB) may be highly useful at detecting the presence of low voltage area (LVA), treating atrial fibrillation (AF), and predicting the outcome following ablation, according to study results published in the Journal of Electrocardiology.

In electrocardiography, prolonged P wave duration (PWD) has been defined as an IAB. Results from previous studies have revealed that prolonged PWD may accurately identify advanced LVA in AF, however, the prevalence of IAB without left atrial enlargement is reported to be significantly high among the general population. IAB with a specific morphological change of P wave has recently been found to be an independent predictor of new-onset AF and may be associated with higher risk of AF recurrence following ablation. In this study, researchers explored the possible relationship between PWD, P wave morphology, and LVA in AF.

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In this nonrandomized retrospective study, researchers divided 127 patients with AF into 2 groups based on whether they were confirmed to have LVA: LVA positive (n=35) and LVA negative (n=92). P wave morphologies were divided into 3 categories: normal, P wave duration <120 ms; partial IAB, P wave duration ≥120 ms without biphasic P waves in inferior leads; and advanced IAB, PWD ≥120 ms with biphasic P waves in any inferior leads. LVA was defined as an area with a bipolar peak-to-peak voltage amplitude of <0.5 mV and was qualitatively assessed to be categorized into 3 grades: mild (<10%), moderate (10% to 30%), and extensive (≥30%).

Results revealed that LVA was significantly prevalent among patients who were older, female, had persistent AF, and had comorbidities including hypertension with prior stroke, prior brain infarction, and left atrial enlargement. PWD was correlated with left atrial volume in the LVA negative group only. Advanced IAB was significantly higher in the LVA positive group, whereas partial IAB was found in both groups. Receiver operating characteristics curve revealed that a specific combination of IAB and biphasic P wave in any inferior lead detected the presence of LVA with 83% sensitivity and 98% specificity. Logistic regression analysis revealed that PWD and the presence of advanced IAB were independent predictors of LVA.

This study had several limitations. First, this study was nonrandomized and had a relatively small sample size; therefore, researchers could not address the impact of the location of PVA on PWD and P wave morphology. Second, researchers did not measure the left atrial conduction velocity and thus could not identify the real cause of prolonged PWD. Last, this study performed voltage map using only the criterion of LVA <0.5 mV without evaluating another voltage criterion.

The study researchers concluded that advanced IAB is a favorable parameter for estimating the presence of LVA and may be useful in AF treatment and for predicting the outcome after ablation.

Reference

Ooie T, Wakisaka O, Hujita T, et al. A specific combination of P wave duration and morphology accurately predicts the presence of left atrial low voltage area in patients with atrial fibrillation [published online October 24, 2019]. J Electrocardiol. doi:10.1016/j.jelectrocard.2019.10.002