Maturational changes in left and right ventricular electromechanical intervals in the newborn lamb.

Electromechanical intervals of right and left ventricles were examined in newborn lambs (9 hours to 42 days). The electromechanical interval of the left ventricle did not change with maturation, while that of the right ventricle became progressively longer, resulting in an increasing ventricular mechanical asynchrony. We postulate that the pattern of developing mechanical asynchrony described may occur secondary to postnatal changes in ventricular morphology.