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Figure 4 Force generation by isolated right ventricular trabeculae from non-failing, failing, and left ventricular assist device (LVAD)-supported hearts. (A) Representative force transients at low stimulation frequency (0.5 Hz) showing higher developed force in failing and LVAD-supported trabeculae than in non-failing muscles. *p < 0.05 NF versus HF and HF-LVAD. (B) Representative force transients at high stimulation frequencies (2.5 Hz) showing higher developed force in non-failing and LVAD-supported trabeculae compared with unsupported failing trabeculae. p < 0.05 NF versus HF. (C) Averaged data (± SEM) in which developed force is plotted as a function of stimulation frequency in each of the three groups. A clearly positive force-frequency relationship is seen in non-failing myocardium, a clearly negative force-frequency relationship is seen in unsupported failing myocardium, and a flat force-frequency relationship is seen after LVAD support.