TMEM65 and cardiomyopathy: Although APDs measured using optical mapping recordings did not differ between Tmem65 KD hearts and control in sinus rhythm after 3 weeks of Tmem65 KD, APDs were prolonged in Tmem65 KD mice when the heart was paced at 11 Hz consistent with prolonged corrected QT (QTC) intervals, as is commonly seen in cardiomyopathies and heart disease49.