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7.
A Study of Mean Electrical Axis (QRS Axis) Among Healthy Personnel
Sir,
Electrocardiogram is a recording of electrical potential
difference at two points of heart during cardic cycle. This
current flows (depolarisation wave) from base to apex of heart
and thus throughout depolarisation phase apex of heart
remains positive in respect to the base. Average direction of
this depolarisation wave through ventricles is called QRSaxis and this mean electrical axis (QRS-axis) of normal ventrical
is +59o.1
Variation of this mean electrical axis is due to anatomical
difference in the Purkinje's system distribution in cardiac
musculature. Further certain physiological conditions also
play important role i.e. QRS-axis shift to the left occurs during
expiration, in lying posture and in obese individuals, whereas
shift to the right occurs during inspiration and standing.
Various pathological conditions e.g. ventricular hypertrophy
or bundle branch blocks after QRS-axis.1
QRS-axis in infancy (from birth to 3 months of age) is
usually between + 90o to 140o and during childhood (from 3
months to 12 or 16 years of age) is usually between +90o to
120o. Among adults, normal QRS-axis ranges between -30oto
+110o. Further, QRS-axis between +110o to ± 180o is right axis
deviation and between 0o to +90o is normal and less than 0o to
-30o is mild left axis deviation.3
To know whether QRS-axis between 0o to -30o should be
considered normal or left axis deviation (due to pathological
conditions) during annual medical examination of healthy
service personnel at 4 AFH, we conducted a study among
440 healthy personnel. Standard 12-lead electrocardiogram
was recorded in lying position during their routine medical
examination and QRS-axis was evaluated.
Personnel in this study were of age ranging from 24 to 56
years, height ranging from 158 to 186 cm and were all within
normal body weight range (weight in relation to age and
height). QRS-axis was found to be varying from -30o to +110o
(Table 1). Eighty five percent of the personnel had QRS-axis
between 0o to +90o, 13.86% had between 0o to -30o and only
1.14% had between +90o to +110o. On further analysis it was
found that among 171 personnel (38.86%) i.e. majority had
QRS-axis range +30 o to +60 o. There was no definite
relationship between QRS-axis with age or height of an
individual.
> + 1100
0
—
Among 440 personnel, 61 personnel (13.86%) were found to have 0o
to -30o of QRS axis range.
From this analysis, it is evident that about 14% healthy
population individuals QRS-axis is between 0 o to -30o,
therefore we concluded that QRS-axis between 0o to -30o
represents normal axis variation (physiological) and
pathological left axis should be considered when QRS -axis is
less than -30o.
AK Gupta*, M Noatay**
*Medical Specialist, Zonal Hospital Nahan, HP. **Medical Officer,
4 AFH, 99 APO.
Received : 3.4.2003; Accepted : 17.5.2003
REFERENCES
1.
Goldman MJ. Principles of Clinical Electrocardiography: The
Cardiac Vector. 11th ed (Asian edition). California: Drawer
L and Loss A. 1982.
2.
Guyton C, Hall JE. Electrocardiographic interpretation
of cardiac muscle abnormalities: Vector analysis. In:Text
Book of Medical Physiology. 9th ed. Bangalore: WB
Saunders, 1996;135-48.
3.
Schamorth L. The Electrical Axis. In: Schamorth C. An
Introduction to Electrocardiography. 7th ed. New Delhi:
Blackwell Science, 1990;34-48.
Table 1 : Distribution of personnel among various QRSaxis range
Sr. No.
1
2.
3.
4.
5.
6.
736
QRS-axis
No of Personnel
% of Personnel
<—30o
0o to -30o
0o to +30o
+30o to 60o
+60o to +90o
+90o to +110o
0
61
123
171
80
05
—
13.86
27.97
38.86
18.17
1.14
JAPI • VOL. 51 • JULY 2003