Effect of change in limb position on mean electrical axis and amplitudes of QRS complex of rat electrocardiogram.

The effect of altered fore limb alignment to trunk on mean electrical axis (MEA) and on amplitude of the QRS complex of frontal plane leads was studied in both prone and supine postures in 32 albino rats. It was found that in both postures bilateral extension of fore limbs caused a significant change in MEA to right. Unilateral change in the fore limb alignment caused a shift in MEA to right only in supine position, but was ineffective in prone position. The amplitudes of QRS complexes also changed with change in MEA. The changes in MEA with change in limb alignment and subsequent alteration in amplitude of QRS complexes can be attributed to the alteration in anatomical orientation of the heart in the chest cavity.