Supporting evidence includes (a) that beta-blocker therapy in DCM patients can increase MYH6 mRNA levels while downregulating MYH7, and this shift in the MYH6/MYH7 ratio is associated with an improvement in left ventricular ejection fraction [11,12]; (b) in failing hearts, not only is MYH6 mRNA significantly downregulated, but its expression variability is also markedly reduced [2,3], suggesting a “response window” that may be critical for cardiac adaptability. This evidence concerns the gene MYH7 and familial dilated cardiomyopathy.