[Interaction between the renin system and parasympathetic nervous system in heart failure]

The increase of sympathetic activity in heart failure is accompanied by a reduced parasympathetic tone. The renin-angiotensin system has not only multiple interactions with the sympathetic nervous system, but may also influence vagal tone directly by angiotensin II. Animal studies show a reduction of parasympathetic tone by a direct action of angiotensin II in the area postrema where the blood brain barrier is absent. It is possible that, in addition to the sympathetic and renin-angiotensin system, the parasympathetic nervous system may also influence prognosis in heart failure. Therefore, baroreflex sensitivity as (CBS) an index of vagal tone was examined in 35 patients with moderate to severe heart failure (NYHA II-III). Independent of the severity of heart failure BS was the lower the higher plasma-renin-activity was. Fifty-six months after the initial examination a comparison of the surviving patients (Group 1, n = 20) with the patients who died or underwent heart transplantation (Group 2, n = 15) did not reveal significant differences in the initial hemodynamic data. However, group 2 patients showed a tendency to higher initial plasma-renin-activity and significantly lower BS 1.3 +/- 0.2 vs. 2.2 +/- 0.3 ms/mm Hg; p < 0.05).

In patients with heart failure a relation between the renin-angiotensin system and the parasympathetic nervous system is likely as there is a significant negative relationship between BS and plasma-renin-activity. Among patients with a similar degree of heart failure a low vagal tone identifies patients with a poor prognosis.