[The right ventricular activation in ventricular activation delays. An endocardial mapping study (author's transl)]

To investigate the right ventricular activation, filtered bipolar recordings (1 cm interelectrode distance) of Apex (RVA), Inflow tract (RVIT) and Outflow tract (RVOT) of the right ventricle were obtained in 4 groups of subjects. 1st group: 25 cases with normal QRS; 2nd group: 7 cases with left ventricular conduction disturbances (4 LBBB and 3 LAH patterns); 3rd group: 20 cases with chronic coronary heart disease (CCHD) and RBBB alone (5 cases) or combined with LAH (15 cases); 4th group: 9 young subjects without heart disease (7 cases) or ostium secundum atrial septal defect (2 cases) and RBBB pattern. The activation times were calculated from the beginning of the QRS in the first endocavitary rapid deflection. The data obtained (average +/- s.d.) for QRS duration (QRSd), RVA, RVIT and RVOT were respectively: 1st group: 97 +/- 9, 23 +/- 9, 36 +/- 9, 39 +/- 8; 2nd group: 133 +/- 43, 20 +/- 14, 25 +/- 9, 42 +/- 6; 3rd group: 152 +/- 12, 49 +/- 13, 61 +/- 18, 82 +/- 20; 4th group: 130 +/- 17, 39 +/- 12, 58 +/- 12, 55 +/- 27. Activation times as expected were similar in 1st and 2nd groups. Significant differences were noted between 1st and 3rd groups (p less than 0.001) in activation times of RVA, RVIT and RVOT. Between 1st and 4th group significant differences were noted in activation times of RVA and RVIT (p less than 0.001) while no significant differences were observed for RVOT (p greater than 0.05). In 2 cases of the third group (CCHD) and in the 2 cases of atrial septal defect the activation time of RVA was within the normal range suggesting a peripheral block. In the cases of the 3rd group with troncular RBBB activation times of RVIT and RVOT were significantly related to the QRSd (r = 0.79 and 0.65, p less than 0.001 and less than 0.01 respectively), while there was no significant correlation between the activation time of RVA and the QRSd. In accordance with other Authors our study demonstrates that: 1) the RBBB pattern in ASD has a peripheral electrogenesis; 2) the RBBB pattern in CCHD is generally due to a troncular block but our study also suggests the possibility of a distal block in these patients. In contrast with some Authors the RBBB pattern in young people without heart disease was due to a troncular and not to a peripheral block. Finally, the absence of correlation observed in the cases with troncular block of the 3rd group: 152 +/- 12, 49 +/- 13, 61 +/- 18, 82 +/- 20; 4th group: 130 +/- 17, 39 +/- 12, 58 +/- 12, 55 +/- 27. QRSd and RVIT and RVOT activation times might be explained as follows: 1) in high degree troncular block the RVA activation time is due to the time employed byt the wave front to cross the septum which is probably similar in all the cases; 2) the QRSd depends on the activation time of the peripheral areas which depends on the variable spread of activation of the right ventricle probably due to a variable participation of the specialized conduction system.