EFFECT OF ACUTE BLOOD-PRESSURE CHANGES ON SIGNAL-AVERAGED ELECTROCARDIOGRAM

An acute blood pressure elevation may cause ventricular ectopic rhythm s, while its reduction may alleviate them. It is studied whether the b lood pressure exerts some effect on parameters obtained by the signal averaged electrocardiogram. In 25 patients with either hypertension (8 cases) or ventricular ectopic rhythms (10 cases) or both (7 cases) th e blood pressure was reduced by sodium nitroprusside (24 cases) and/or elevated with metaraminol (10 cases) and the signal averaging electro cardiogram was recorded under 2 or 3 pressure values on each patient. During the high pressure (193.6+/-20.1 mm Hg) the following difference s were noted compared to the low pressure (77.4+/-15.2 less) : longer QRS duration in all 25 patients (+9.92+/-10.51 ms, P<0.001); longer lo w (<40 muV) amplitude signals (LAS) in 18 patients (+6.94+/-10.93 ms, P<0.005) ; lower root mean square voltage of the terminal 40 ms of the QRS in 22 patients (-15.73+/-21.60 muV, P<0.005); and ventricular ect opic beat incidence higher in 8, lower in 1, and equal in 2 cases (wit h no arrhythmia in the other 14). The generally and focally reduced co nduction, as suggested by the QRS and LAS prolongation, might contribu te to the proarrhythmic effect of acute blood pressure elevation.