The evolution of the vectorcardiogram and electrocardiogram of the normal infant: II. Transition toward adult patterns ∗

Abstract

1. 1. Vectorcardiograms and electrocardiograms were obtained in thirty-one normal infants at one month of age and in thirty-two at three months of age. These infants were members of an original group of fifty who were first studied at birth. 2. 2. The QRS sÊ loop shifted progressively to the left and less anteriorly as compared with the newborn. In addition, the QRS sÊ loop was inscribed in a counterclockwise direction in the horizontal plane at three months of age as opposed to predominantly clockwise inscription in that plane at birth. 3. 3. The electrocardiographic changes were less striking. The R S ratio in lead I was reversed from less than one at birth to greater than one at three months of age. The tall R wave in lead aVR of the newborn diminished and at three months of age the QRS complex in that lead was predominantly negative. No left axis deviation was noted. At three months of age, the height of the R wave exceeded the depth of the S wave in right precordial leads including tracings of those infants in whom a “left ventricular pattern” was seen at birth. It is theorized that the transient “left ventricular pattern” seen in precordial leads of some newborn infants is due to temporary left ventricular systolic overloading secondary to the occlusion of a previously patent ductus arteriosus. 4. 4. The vectorcardiogram oners an important advantage in the diagnosis of abnormal right ventricular hypertrophy in infants and children. It is often impossible to differentiate unequivocally the electrocardiogram of the normal child from that of a child with abnormal right ventricular hypertrophy, even up to eight years of age. However, at three months of age, the QRS sÊ loop in the horizontal plane is oriented to the left and inscribed counterclock-wise, while in abnormal right ventricular hypertrophy the loop is oriented to the right and is inscribed clockwise in that plane.