P Mitrale – Left atrial abnormality / overload

P Mitrale – Left atrial abnormality / overload

Abstract: P mitrale is the wide and notched P wave of left atrial overload (left atrial abnormality), typically seen in lead II in mitral stenosis.

P mitrale is the wide and notched P wave of left atrial overload (left atrial abnormality), typically seen in lead II in mitral stenosis. Normal P wave has a width of up to 2.5 millimeters (duration of 100 milliseconds). When the P wave widens, it is due to left atrial enlargement as the second component of the normal P wave is contributed by the left atrial activation as it spreads leftwards from the sinus node across the Bachmann’s bundle, an interatrial conduction pathway.

The change in terminology from left atrial overload to left atrial abnormality has been suggested because the same pattern can be seen in left atrial dilatation, hypertrophy or increased pressure in the left atrium or any of these in combination.^1,2,3 The terminology of left atrial abnormality was in use earlier also, but less frequently.⁴

Left atrial abnormality in the ECG has been used to predict left ventricular hypertrophy in the presence of right bundle branch block which may mask electrocardiographic evidence of left ventricular hypertrophy.

In the echocardiographic study by Mehta A and associates 92% of those with left atrial abnormality had estimated left ventricular mass diagnostic of left ventricular hypertrophy.⁵ Six commonly used criteria for left ventricular hypertrophy could detect only 5% of cases of left ventricular hypertrophy in the presence of right bundle branch block. Same group of authors have reported the utility of left atrial abnormality in the ECG for diagnosis of left ventricular hypertrophy in the presence of left bundle branch block as well.⁶

References

1. Selvaraj R. Normal and Abnormal P Wave. In: Narasimhan C, Francis J. editors. LeoSchamroth – An Introduction to Electrocardiography. Eighth Adapted Edition. New Delhi: Wiley India Pvt. Ltd. 2013. p 29.
2. Khidhir AJ, Al-Shimmery EK, Alwan MH. Are left atrial abnormalities a risk for stroke? Neurosciences (Riyadh). 2010 Jan;15(1):21-6.
3. Kohsaka S, Sciacca RR, Sugioka K, Sacco RL, Homma S, Di Tullio MR. Electrocardiographic left atrial abnormalities and risk of ischemic stroke. Stroke. 2005 Nov;36(11):2481-3.
4. Tarazi RC, Miller A, Frohlich ED, Dustan HP. Electrocardiographic changes reflecting left atrial abnormality in hypertension. Circulation. 1966 Nov;34(5):818-22.
5. Mehta A, Jain AC, Morise AP, Mehta MC, Billie M. Left atrial abnormality by electrocardiogram predicts left ventricular hypertrophy by echocardiography in the presence of right bundle-branch block. Clin Cardiol. 1998 Feb;21(2):109-14.
6. Mehta A, Jain AC, Mehta MC, Billie M. Usefulness of left atrial abnormality for predicting left ventricular hypertrophy in the presence of left bundle branch block. Am J Cardiol. 2000 Feb 1;85(3):354-9.