Weighted average of data across all animals within each experimental group for length-dependent activation, frequency-dependent activation, and β-adrenergic stimulation measurements, testing all three cardiac output regulatory mechanisms. (A) Data from the CS group show strong correlation across all three cardiac output regulatory mechanism tests at R² = 0.997. (B) Data from the CT group show tight correlation at R² = 0.996. (C) Data from the MIS group show tight correlation, with R² = 0.997. (D) Data from the MIT group show tight linear correlation, with R² = 0.997. Linear regression and Pearson correlation coefficient are calculated as shown.