[The atrial vectorcardiogram at rest and during exercise. Comparison, by computerized analysis, of normal subjects and patients with mitral stenosis]. / Vettorcardioramma atriale a riposo e durante esercizio. Confronto, mediante analisi computerizzata, fra soggetti normali e pazienti con stenosi mitralica.

This study on rest and exercise atrial vectorcardiogram (Frank method) was carried out on a group of 27 healthy volunteers (Group A) and on a group of 24 patients with mitral stenosis (Group B). All 51 subjects were women. Our original program was performed using a Hewlett Packard 2100 computer. The pattern recognition of every wave was carried out by analysing a particular function obtained by translating the X, Y, Z leads on the line joining the T-P, P-Q, ST segments. In the group B on rest a significant correlation between atrial vectorcardiogram parameters and pulmonary capillary wedge pressure was not present. Between both group A and B the vectorcardiographic data were greatly superposables. It is difficult, because of the great interindividual variability of results obtained, to have very discriminant vectorcardiographic parameters between group A and group B on rest and during exercise, performed in the supine position with a bicycle ergometer. In the both groups A and B the exercise induces a significant increase of spatial magnitude of maximal P xyz vector (max P xyz) and maximal P amplitude on frontal and sagittal planes, with P loop shifting towards a vertical position. The following significant results were observed only in group B of mitral patients: 1) an increase of P wave duration; 2) an increase of the interval between the two peaks of P wave (measurable only in group B); 3) an increase in the amplitude and backward rotation of max P xyz azimuth and of the maximal vector backward directed on horizontal (H) plane; 4) an increase of P loop linear, tangential and areolar velocities. The P loop anterior and posterior area on H plane and of the spatial P xyz vectors changes during exercise were directionally similar in the normal group and in the patients with mitral stenosis. These results suggest a little diagnostic power of the P wave area changes during exercise. In both groups maximal atrial T vector increases with exertion, but only in group B migrates backward on H plane, suggesting an atrial gradient directed towards the left atrium.