The Value of the Macruz Index in the Diagnosis of Atrial Enlargement

THE electrocardiographic diagnosis of atrial enlargement is a common problem. The established criteria, based on voltage, configuration, and duration of the P wave, very often fail to confirm the diagnosis even in cases of known atrial enlargement. In 1958, Macruz, Perloff, and Case1 proposed a simple formula for electrocardiographic recognition of right, left, and combined atrial enlargement. The Macruz index has been widely used in recent years. It is based on the measurement of the P-R interval, P-wave duration, and P-R segment (time between end of electric atrial systole and onset of electric ventricular systole). According to the above authors, the ratio of the P-wave duration to the P-R segment as measured in standard lead II in normal persons, is relatively constant within the limits of 1.0 and 1.6, with an average value of 1.2. In cases of right atrial enlargement the duration of the P wave hardly changes, but the