MYH6 and cardiac arrhythmia: Echocardiography revealed a profound dilated cardiomyopathy and heart failure in Ptpmt1fl/fl/Myh6-Cre+ mice, including both systolic and diastolic LV dilation, thinning of ventricular walls, depression of EF and FS, arrhythmias, and impaired myocardial contraction (Figure 5D–J, Figure 5—video 1, and Figure 5—video 2).