Impaired regulation of cardiac function in sepsis, SIRS, and MODS

In sepsis, systemic inflammatory response syndrome (SIRS), and multiorgan dysfunction syndrome (MODS), a severe prognostically relevant cardiac autonomic dysfunction exists, as manifested by a strong attenuation of sympathetically and vagally mediated heart rate variability (HRV). The mechanisms underlying this attenuation are not limited to the nervous system. They also include alterations of the cardiac pacemaker cells on a cellular level. As shown in human atrial cardiomyocytes, endotoxin interacts with cardiac hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels, which mediate the pacemaker current If and play an important role in transmitting sympathetic and vagal signals on heart rate and HRV. Moreover, endotoxin sensitizes cardiac HCN channels to sympathetic signals. These findings identify endotoxin as a pertinent modulator of the autonomic nervous regulation of heart function. In MODS, the vagal pathway of the autonomic nervous system is particularly compromised, leading to an attenuation of the cholinergic antiinflammatory reflex. An amelioration of the blunted vagal activity appears to be a promising novel therapeutic target to achieve a suppression of the inflammatory state and thereby an improvement of prognosis in MODS patients. Preliminary data revealed therapeutic benefits (increased survival rates and improvements of the depressed vagal activity) of the administration of statins, beta-blockers, and angiotensin-converting enzyme inhibitors in patients with MODS.