Decreased beating rate variability of cultured cardiomyocytes by endotoxin

A decreased heart rate variability is a marker of autonomic dysfunction and indicates poor prognosis in critically ill patients. In healthy volunteers, such a decreased heart rate variability can he reversibly induced by i.v. administration of endotoxin (Crit Care Med 24 :1117-1124). It is unknown if this effect is due to a direct impact of endotoxin on the heart, or if secondary release products are responsible herefore. Using isolated, spontaneously contracting neonatal rat cardiomyocytes (CM) we investigated if endotoxin narrows beating rate variability directly.

Methods

CM from three independent preparations were cultured in serum-tree medium with endotoxin (1 μg/ml, 24 h, inducing inducible nitric oxide synthase and stimulating interleukin-6 production) or without additive. 100 consecutive contractions per cell were analysed (photo-optical system), per preparation 18 control cells and 18 cells in endotoxin-containing medium.

Results

There was a significant *P < 0.05) decrease in beating rate variability in endotoxin-treated CM (Table: data from one preparation, parameters equivalent to the measures of heart rate variability in patients).

Conclusion

Endotoxinemia (e.g. by intestinal translocation) could in vivo directly contribute to autonomic dysfunction.

Table