Comparison of Force Development of Right Atrial and Left Atrial Human Fibers

Objectives: Considering the different pressure and volume conditions in the right and left heart side, we wanted to evaluate if this is also valid for the contractile myocardial apparatus analyzed on basis of fibers taken from the right and left heart auricle.

The purpose of our study was therefore to compare calcium-induced force development between right atrial and left atrial skinned human fibers undergoing cardiac surgery.

Methods: Right and left atrial tissue from 5 patients, undergoing cardiac surgery, was collected before extracorporal circulation. Tissue was conserved and three till five fibers were prepared as “skinned fibers” for experimental examination. We exposed the dissected fibers to increasing calcium concentrations and recorded the force values.

Results: Fibers taken from the left heart side develop more force a the highest calcium concentration pCa 4.0 (3.6 mN ± 2 mN versus 2.0 ± 0.7 mN, p 0.02). This is also valid for the following calcium concentration at pCa 4.5 (1,2 ± 0.7 mN versus 1.6 ± 0.8 mN, p 0.04). At lower steps of calcium concentration the difference of force development is not significant any more (p > 0.05). Calcium sensitivity was also different: for the right heart fibers at pCa 5.0 and for the left heart fibers at pCa 4.5.

Conclusion: Contractile force is significantly reduced in isolated right heart side fibers compared with the left heart side fibers. This is significant in higher doses of calcium concentration and might reflect the adaption of left heart fibers to higher pressure volume conditions. On the other hand side calcium sensitivity was higher in the right heart side, which might balance the lower contractile force capacity.