Atrial natriuretic factor release during rapid ventricular pacing: Interplay between autonomic and hemodynamic stimulants

Plasma levels of atrial natriuretic factor (ANF) and norepinephrine are markedly elevated during episodes of ventricular tachycardia. Although atrial distention appears to be the major stimulus for ANF release, reflex changes in autonomic tone might also contribute. Plasma ANF and norepinephrine levels, sinus node cycle length, systolic blood pressure, and mean right atrial pressure were therefore assessed during rapid right ventricular pacing at 150 beats/min for 10 minutes. In five patients (group 1) observations were made without autonomic blockade, and another five patients (group 2) had ventricular pacing after cardiac autonomic blockade. In group 1 systolic blood pressure fell during ventricular pacing from 122 ± 4 to 105 ± 5 mm Hg ( p < 0.02), norepinephrine levels increased from 195 ± 26 to 411 ± 71 pg/ml ( p < 0.02), and sinus node cycle length decreased from 936 ± 99 to 688 ± 58 msec ( p < 0.02). Right atrial pressure was elevated from 2.6 ± 0.6 to 7.4 ± 0.6 mm Hg ( p < 0.02), and ANF levels increased from 161 ± 23 to 240 ± 26 pg/ml ( p < 0.05). Whereas systolic blood pressure, norepinephrine, sinus cycle length, and right atrial pressure returned promptly to baseline levels when ventricular pacing was stopped, ANF levels continued to rise (296 ± 37 pg/ml; p < 0.05). Compared with group 1, ventricular pacing in group 2 induced a greater reduction in systolic blood pressure (19 ± 2% vs 8 ± 5%; p < 0.05) and a more marked increase in norepinephrine levels (271 ± 52% vs 111 ± 22%; p < 0.05), but because of cardiac autonomic blockade the decline in sinus cycle length was attenuated (8 ± 2% vs 33 ± 5%; p < 0.05). Inasmuch as there was no significant difference between the increase in right atrial pressure and ANF levels, it was concluded that changes in autonomic tone during ventricular tachycardia do not significantly influence ANF release.