Is there a gender-dependent negative inotropic effect of Methylene blue on the contractile performance on the level of myofilaments?

Abstract

Objective: Methylene blue is a rescue therapy especially in patients with septic shock; the arterial blood pressure and SVR is increased, while cardiac output, oxygen delivery and oxygen consumption does not show any significant change. Therefore, we underwent the current study to observe, if MB has a direct impact on cardiac performance on level of the contractile apparatus. Methods: Right auricle tissue from 12 patients (6 male and 6 female patients) undergoing cardiac surgery was obtained prior to right atrial cannulation. The tissue was skinned with Triton-X. The fibers were exposed to a gradual increase of calcium concentration and the corresponding force was measured and recorded. We performed 3 experiments with different fibers in each cycle and each patient (n=30 in each patient with and without MB). Results: (1) Male patients without MB developed a maximal force of 2.5 mN±0.7mN, whereas samples, which were exposed to MB achieved 2.1 mN±0.2 mN. This difference was significant (p= 0.0002). (2) Female fibers with MB achieved 2.3 mN±0.2 mN whereas fibers without MB developed 2.7±0.7 mN. This was not statistical significant. (3) Focusing the different steps of calciumconcentration,male and female fiberswithMBdifferent significant to those without MB (p=0.04). Conclusions: Our data suggest, that MB has a negative inotropic effect on contractile performance of skinned human atrial fibers. We observed reduced absolute forces; additionally, there is some evidence for a gender-dependent effect on the contractile apparatus.