Video 4-6-7 (LR): (L) Following cardiac resynchronization therapy, the transthoracic echocardiogram in the parasternal short-axis view shows marked improvement in the patient's left ventricular systolic function. (R) Following cardiac resynchronization therapy, the transthoracic echocardiogram in the apical 4-chamber view shows marked improvement in the patient's left ventricular systolic function.