The invention is directed to methods and devices for optimization of biventricular pacing in subjects suffering from heart failure. The invention provides for a method for selection of optimal parameters for permanent pacing, the method comprising: positioning one or more arrays of lead wires in the posterior pericardium of a subject, wherein the arrays are connected to a multiplexing switch, wherein the switch is connected to a computer processor and a biventricular pacemaker； from the computer processor, generating a randomized sequence of: (i) pacing sites (VPS), (ii) right ventricular-left ventricular delays (RLDs), (iii) heart rates (HR)； (iv) atrioventricular delays (AVDs), (v) or any combination or permutation thereof； and determining cardiac output in real time, using aortic flow velocity, thereby allowing selection of optimal parameters for permanent pacing.
