[Hypotension during ventricular pacing. A study of the vagal reflex component].
It has been suggested that hypotension during ventricular pacing (V) could be caused by a parasympathetic vasodilating reflex. In order to evaluate this hypothesis, we studied 10 patients who had wide fluctuations of arterial pressure during V. Intra-arterial pressure, right atrial pressure, EKG and cardiac index (thermodilution) were determined in the following conditions: basal rhythm (B), V, atrioventricular pacing (A-V) and ventricular-atrial pacing (V-A). The same investigations have been carried out in the same conditions (B,V,A-V,V-A) after atropine 0.03 mg/Kg intravenously. The arterial blood pressure during V decreased markedly simultaneously with the appearance of cannon waves in the right atrial pressure tracing. During A-V the arterial pressure remained stable at the highest level observed during V. The start of V-A pacing induced a marked drop of arterial pressure, which, however, gradually increased to a level slightly lower than during A-V pacing. After atropine the arterial blood pressure during V decreased again in all patients concomitantly to the appearance of cannon waves in the atrium as before atropine. The values of arterial blood pressure during B, A-V and V-A were not different from those measured before atropine. Therefore, an increase of parasympathetic activity during V is not responsible for the wide fluctuation of arterial blood pressure. A possible role of sympathetic failure must be considered.
D000328:Adult; D000368:Aged; D001285:Atropine / Q000494:pharmacology; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007022:Hypotension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D014630:Vagus Nerve / Q000503:physiopathology*; D014664:Vasodilation
D001285:Atropine
Ipotensione durante pacing ventricolare (VVI). Studio della componente riflessa vagale.