Influence of age on the ventricular activation and recuperation processes in the pig.

In order to establish if the electrical ventricular systole is affected by physical maturation, the electrocardiographic outline of 30 Landrace x White Belgian pigs was analyzed at ages of 1 day, 5, 20 and 45 days and 3, 4 1/2 and 6 months. Throughout the first 6 months of life the values for the parameters which represent the ventricular activation underwent an increase with physical maturation. The Q wave duration increased significantly from 45 days, and the R wave between 1 day and 45 days and from 4 1/2 months. The duration of the QRS complex and the QT interval experienced a significant increase from 5 days and between 5 and 45 days of age, respectively. The changes on the amplitude were most evident when using the lead V10 with which the R wave experienced the most significant increase during the first 20 days of life. With regard to the ventricular recuperation, the T wave duration underwent a gradual increase throughout the first six months of life. A similar evolution was experienced in the amplitude recorded in the aVF and V10 leads although in the latter the most significant increase took place between the 1st and 5th day of age. Likewise, the duration of the ST segment increased with physical maturation and more significantly between 5 and 45 days of age.