AAV-9 SERCA2a expression improves the ECG profile in mdx mice. A, Representative single lead II tracings from BL10, mdx and AAV SERCA2a treated mdx mice. PR, the time interval between the onset of atrial depolarization and the onset of ventricular depolarization. B, Quantitative evaluation of ECG profiles in BL10, mdx, AAV SERCA2a treated mdx mice. *, Statistically different from other groups. HR, heart rate; PR, PR interval; QRS, QRS duration; QT, QT interval; Q Amp, Q amplitude in lead I; C. Index, cardiomyopathy index.