[Relation between the vectorcardiogram and mean pulmonary arterial pressure in pulmonary pathology]

Mean pulmonary artery pressure (PAP) is considered to be a valuable indicator of the severity of disease in patients with chronic lung damage. Its measurement requires minicatheterisation, an invasive technique associated with some morbidity. This study was undertaken to establish a relationship between PAP and vectorcardiography (VCG) in 76 patients with chronic lung disease. The patients were divided into three groups: Group I, PAP less than 19 mmHg; Group II, PAP between 19 and 30 mmHg; Group III, PAP greater than 30 mmHg. The patients presented with an obstructive pulmonary syndrome in 67,1% of cases, and an emphysematous syndrome in 32,9% of cases. The ECG tracing was suggestive of chronic cor pulmonale in 20 patients. The three VCG planes were analysed. The direction and amplitude of the 0,01 sec, 0,02 sec, 0,04 sec, 0,06 sec and maximum vector over each QRS loop were measured; the direction of rotation of the QRS loop and, in the horizontal plane, the duration of the terminal forces were also determined. Treatment of the angular data by Down's centre of gravity method allowed definition of the preferential direction of the vectors and of an index of precision. The statistical significance of the results was checked by the usual methods (chi-square, F test). The results confirmed the importance of the right posterior quadrant of the horizontal plane in assessing the degree of electrical overload and for evaluating the repercussions on the pulmonary circulation. In this plane, all angular positions of the 0,06 sec vector beyond -125 degrees corresponded in 9 out of 10 cases to higher than normal PAP (greater than 19 mmHg). A voltage of over 0,80 MV was always associated with higher than normal PAP. The predictive value of this method was 92%, with a specificity of 88% and a sensitivity of 39%. The VCG was also more sensitive than the ECG in assessing PAP of 19 to 30 mmHg; 25,6% of patients had deviation of the 0,06 sec vector of beyond -125 degrees in the horizontal plane whilst only 6,3% of cases had ECG criteria of chronic cor pulmonale. This study shows that simple and reliable non-invasive VCG criteria may be used to assess mean pulmonary artery pressure.