Effect of right atrial stimulation on both atrial pressure and atrial natriuretic peptide release in essential hypertension

Several reports indicated a direct relationship between atrial pacing and atrial natriuretic peptide (ANP) blood levels, but few controlled hemodynamic studies have been reported. In particular, the relationship between increase in heart rate, release of ANP and increase in right atrial pressure (RAP) are still uncertain. Moreover, the effect of accelerated heart rate on ANP secretion in patients with essential hypertension has not yet been fully elucidated. For this, we studied 12 untreated essential hypertensive (EH; WHO stage I–II) and 10 age-matched normotensive subjects (NO) as control by right atrial stimulation (parasinusal site) in consecutive steps of 110, 130 and 150 b.p.m., each step lasting for 5 min. Both before and during stimulation at each pacing rate (after 5 min) RAP and systolic blood pressure (SBP) were measured and blood was drawn from the right atrium for ANP measurements (radioimmunoassay method). During stimulation we observed significant differences in the ANP release in comparison to the initial values: at 130 (p <0.05) and at 150 b.p.m. (p <0.01) in EH; at 150 b.p.m. (p <0.005) in NO. RAP and SBP did not differ significantly at each pacing rate from initial values both in EH and NO. No significant differences in ANP and RAP were found between EH and NO. In conclusion: (a) ANP release increases in both EH and NO, even if beginning at 130 in EH and at 150 b.p.m. in NO; (b) in both EH and NO, there is no relationship between RAP or SBP values and ANP secretion. Thus, it appears that the acceleration of heart rate through atrial pacing alone could influence the ANP secretion from atrial cells.