P2-CHA2DS2-VASc score adds additional two points to the CHA2DS2-VASc score for an abnormal P wave axis to predict risk of stroke in atrial fibrillation (AF) . The seminal study was an attempt to identify utility of P wave indices in sinus rhythm to predict the risk of stroke over and above the existing CHA2DS2-VASc score. P wave indices evaluated were prolonged P wave duration, abnormal P wave axis, advanced interatrial block and abnormal P wave terminal force in lead V1. They found that abnormal P wave axis which is an ECG correlate of left atrial abnormality improves the prediction of ischemic stroke. They concluded that P2-CHA2DS2-VASc score is a better prediction tool for AF related ischemic stroke than CHA2DS2-VASc score.
Scoring in P2-CHA2DS2-VASc gives 2 points for abnormal P wave axis, 1 point for age between 65 to 74 years and 2 points for age 75 or more, 1 point each for female sex, heart failure, hypertension, diabetes mellitus and previous myocardial infarction/peripheral artery disease, and 2 points for prevalent stroke or transient ischemic attack. The study used data from two large community based prospective cohort studies for prediction of atrial fibrillation related stroke. The hypothesis was tested in the ARIC (Atherosclerosis Risk in Communities) data  and validated in the MESA (Multi-Ethnic Study of Atherosclerosis) data .
In the study used for deriving P2-CHA2DS2-VASc score, advanced interatrial block was also independently associated with AF related stroke. But it did not improve risk prediction in their models, which they thought could be due to low prevalence in their population . Fibrotic atrial remodeling and enlargement have been considered as important components of proarrhythmic and prothrombotic substrate in the development of AF and AF related stroke . P wave indices are surrogates for detection of this substrate on the ECG .
P2-CHA2DS2-VASc score was developed as several analyses of large databases have noted the limitations of CHA2DS2-VASc score . It was thought that limitations of CHA2DS2-VASc score may be because it measures only atherosclerotic risk factors and does not directly reflect mechanisms of AF related thromboembolism. P2-CHA2DS2-VASc score was better at correctly identifying the stroke risk in low risk individuals. Authors also noted that P wave axis is automatically reported in most commercially available ECG machines so that it is easy to incorporate it into a risk score.
CHADS2 and CHA2DS2-VASc have been used to predict risk of stroke or TIA (transient ischemic attack) in patients discharged after acute coronary syndrome without known AF . Accuracy was similar to that observed in historical populations with non valvar AF and lower absolute event rates.
Stroke prediction by the CHA2DS2-VASc score in people without AF but with abnormal P wave indices was comparable to people with AF . In other words, P2-CHA2DS2-VASc score might be useful to predict stroke in persons without AF, but needs validation in further studies. P2-CHA2DS2-VASc score cannot be used in patients with persistent or permanent AF who have no ECGs in sinus rhythm, because P wave axis cannot be calculated in the presence of AF.