Mean frontal QRS axis and pulmonary artery pressures in rheumatic mitral stenosis

The relationship between the mean frontal QRS axis calculated from the scalar 12 lead ECG, and the pulmonary artery (PA) pressures obtained by cardiac catheterisation in 64 cases of isolated rheumatic mitral stenosis (MS), was analysed. An overall trend of rightward axis shift with increasing PA pressures was observed; the best correlation was seen with systolic PA pressures (r = 0.51). It was possible to recognise 3 categories of patients: (1) With an axis of 70 degrees and below, systolic PA pressures were below 70 mm Hg in 82.4% of cases and below 80 mm Hg in 94% of cases; diastolic pressures were below 40 mm Hg in 88.2%; mean PA pressures were below 50 mm Hg in 88.2% cases. (2) With an axis of 71 degrees to 100 degrees, systolic PA pressures ranged from 30 to 120 mm Hg, diastolic PA pressures from 12 to 60 mm Hg and mean PA pressures from 19 to 80 mm Hg. (3) With an axis of above 100 degrees, systolic PA pressures were over 70 mm Hg in 95.5% of cases, diastolic PA pressures more than 30 mm Hg in 90.9%, and mean PA pressures more than 45 mm Hg in 90.9% cases. It was therefore possible to predict, with reasonable accuracy, the range of PA pressures in patients with isolated MS, except in those cases with an axis between 71 and 100 degrees.