[Vectorcardiographic analysis of atrial activation in isolated mitral valve prolapse. Atrial vectorcardiography in prolapsed mitral valve].

The purpose of our work is to study atrial depolarization in primary mitral prolapse (MVP), since, as far as we know, such a study has never been performed. Thirty patients with MVP were studied: 23 females, aged 37,3 +/- 15,5 years and 7 males, aged 45.1 +/- 18.1 years. MVP was diagnosed by M-mode echocardiography. Atrial depolarization was analysed on photographically recorded Frank's vectorcardiograms. On PsE loops, magnitude and direction of maximum planar vector (VMax) in the frontal (F) and left sagittal (LS) planes, magnitude and direction of anterior (HV1) and posterior (HV2) vectors in the horizontal (H) plane, HV1 to HV2 amplitude ratio and total atrial activation time (T) were measured. This last value (T), measured on vectorcardiographic records, was confirmed by high-speed (200 mm/sec) electrocardiograms. These data were compared, by mean of Student's test, with those measured on records obtained from a similar group of normals. The following statistically significant (P less than 0.05) differences were detected: decreased amplitude of VMax in F (0.11 +/- 0.03 vs. 0.080 +/- 0.03) and LS (0.11 +/- 0.03 vs. 0.085 +/- 0.03), backward shift of HV2 (+65 degrees +/- 39 degrees vs. + 11 degrees +/- 35 degrees) and decreased T (98 +/- 25 vs. 85 +/- 17). The decrease of total atrial activation time, about 13% less than in normals, is the most interesting finding of our research. Such an alteration of atrial depolarization can be explained by inter- and/or intra-atrial conduction disturbance, on anatomical or functional base. Therefore, our findings are consistent either with the hypothesis that MVP is secondary to widespread pathological changes or with the one that MVP is a consequence of neurovegetative imbalance.