The present invention relates to targeted RNAi for the treatment of heart failure by modulating defective cardiac Ca.sup.2+ homeostasis via decreasing expression or activity of phospholamban (PLB) using adeno-associated virus (AAV) transfection of cardiomyocytes. Methods for decreasing ventricular arrhythmias, as well as methods for overall improvement of survival from heart failure in subjects are also disclosed. Further, the present invention provides methods which can be used to diagnose susceptibility to treatment by RNAi, and includes pharmaceutical compositions, kits and vectors including an RNAi sequence.
