[Electrovectocardiographic manifestations of left ventricular and biventricular growth]

The basic criteria for the electrical diagnosis of left ventricular and biventricular enlargements are discussed on the basis of the myocardial depolarization and repolarization sequence. Left ventricular dilatation secondary to isolated diastolic overloading increases the manifestation of the main vectors resulting from the activation of this ventricle. These changes reflect the proximity of the left ventricular walls to the exploring electrodes. The above mentioned vectors appear as tall R waves and wide ventricular curves with counterclockwise rotation on the three planes. If the diastolic overload is a isolated phenomenon, T waves are positive and asymmetric on the left leads while the T loop, of secondary type, is concordant in its orientation with the R loop. This fact is due to a prolonged duration of the repolarization phase of the left ventricle. Global left ventricular hypertrophy produced by a sustained systolic overloading increases the magnitude and manifestation of all the vectors resulting from the depolarization of this ventricle (I, II l, III l) owing to the prolonged duration of the corresponding activation fronts. When LBBB is also present, the first septal vector is not evident. In extreme degrees of the systolic overload, the T wave is inverted and shows morphologic secondary characteristics in left leads, and the T loop opposes the R loop on frontal and horizontal planes. The directional changes of the repolarization fronts of free left ventricular walls can satisfactorily explain these features. Left ventricular hypertrophy of a segmentary type, such as that observed in idiopathic myocardiopathy, generally increases the magnitude and manifestation of septal vector I and II left. When both ventricles are hypertrophied, the electromotive forces originating in the more severely affected heart chamber predominate in electrical records.