Negative inotropic and chronotropic effects on the guinea pig atrium of extracts obtained from Averrhoa carambola L. leaves.  C.M.L. Vasconcelos, M.S. Araújo, B.A. Silva and E.A. Conde-Garcia. Brazilian Journal of Medical and Biological Research, 38 (7): 1113, 2005.

Figure 5. Effect of the Averrhoa carambola aqueous extract (AEx) on the membrane calcium inward current studied by the Bowditch positive staircase phenomenon which was obtained by increasing the atrial rate from 0.2 to 1.66 Hz. A, Atrial contractile force in control solution. During the stimulus overdrive the atrial force increased from 5.25 to 9.5 mN (80.9%). B, Atrium submitted to 1.0 mg/ml AEx. In this case, during overdrive, the atrial force declined from 3.7 mN to 3.2 mN (13.5%). C, Atrial force behavior during washout. In this experimental phase, the atrial force increased from 4.1 to 8 mN (95.1%) when the preparation was in overdrive. The experiment was carried out at 27 ± 0.1ºC (stimuli: 0.2 or 1.66 Hz, 400 V, 0.5 ms).