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). The gene discussed is MYH6; the disease is Arrhythmia.