Wednesday, December 14, 2005

The importance of the electrocardiographic P wave

J. Willis Hurst of Emory University School of Medicine has written a great deal about electrocardiography, including this piece in Clinical Cardiology outlining pet peeves he terms “electrocardiographic crotchets”, or common irritating errors in interpretation. One of his crotchets is the failure to appreciate the importance of P wave abnormalities. P waves may reflect conduction abnormalities in the right or left atrium caused by atrioventricular (mitral or tricuspid) valve disorders or by disorders (hypertrophy or dilatation) of the right or left ventricle, respectively. It is important to note that the atrial conduction abnormality may or may not reflect hypertrophy or dilatation of the atrium. Thus it is proper to speak of right or left atrial abnormality as an electrocardiographic finding, but not enlargement or hypertrophy. The atrial abnormality is more telling about the corresponding valve or ventricle than the atrium itself. Regarding the importance of P waves he writes “To ignore P-wave abnormalities or to refer to them as being due to atrial enlargement or hypertrophy are crotchets.”

To the growing importance of P wave abnormalities we can now add findings from this recent paper in Stroke. Electrocardiographic left atrial abnormality (defined as dimensions of the terminal P wave component in V1 >40ms*mm) was associated with increased risk of ischemic stroke (OR 2.32) in this case-control study.

By the way---those with a scholarly interest in electrocardiography should read Hurst’s paper in the original.

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