Contractile heterogeneity of individual cardiomyocytes from HCM-patients compared to donor cardiomyocytes. Single cardiomyocytes were isolated from frozen heart tissue of HCM-patients (red) with the mutation R723G (left) or A200V (right), respectively, and from donor individuals (blue) as controls. Cardiomyocytes were permeabilized, and after adjustment of phosphorylation levels [57, 61, 80, 114, 119], they were subjected to different calcium concentrations and the respective force generation was measured. Depicted are the forces of individual left ventricular cardiomyocytes at different calcium concentrations (force-pCa-relations), normalized to maximum force. Each symbol and curve represents a different individual cell. The boxes at physiological calcium concentration highlight the much larger variance in force generation among individual cardiomyocytes from the patients compared to controls. Figure reprinted from [82] and modified, with permission from Frontiers