The document discusses indices for recognizing left atrial enlargement using chest X-ray and ECG measurements. It details the Morris index and Macruz index, including formulas for calculating atrial enlargement based on P-wave duration and PR segment length. These indices, proposed by Macruz and colleagues in 1958, have gained popularity for their effectiveness in diagnosing atrial conditions.

1. Macruz index
Left atrial enlargement

2. CRHD,SEVRE MS,LAE,RVH,PAH:Chest X-Ray
LAE:Straightned left heart border

3. CRHD,SEVRE MS,LAE,RVH,PAH:12 lead ECG

4. Morris index
A to B=0.12sec
B to C=2mm
ABXBC=0.12X2=0.24mmxsec≥0.0
4mmxsec
Multiply the length x breadth of the terminal negative portion of the P wave in lead V1 (the P terminal
force). This gives the Morris index. The area exceeds 0.04 mm-sec in left atrial enlargement. (one small
square on the ECG taken at 25 mm / sec paper speed)

5. Macruz index
A to B=widened P width=1.6mm
B to C=narrowed PR segment=0.4mm
P/PR segment ≥1.6

6. http://circ.ahajournals.org/content/27/5/935.full.pdf
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.