Methods for improving heart function

1. A device for treating heart failure, comprising:

a power source;

an atrial stimulation electrode;

a ventricular stimulation electrode; and

a controller that is:

operably connected to the power source and to the stimulation electrodes;

configured to receive a signal indicative of atrial electrical activity; and

programmed to:

monitor the signal to detect an atrial heart rate;

operate the device in a normal pacing mode, for which the controller is programmed to cause the atrial stimulation electrode to depolarize atrial tissue if the atrial heart rate is below a predetermined limit;

periodically transiently operate the device in a dyssynchrony-inducing mode, for which the controller is programmed to cause the ventricular stimulation electrode to depolarize ventricular tissue at a single site with a delay relative to atrial electrical activity shorter than a normal atrioventricular conduction delay;

alternate between the normal pacing mode and the dyssynchrony-inducing mode in a cycle; and

have a cycle length of at least one month.

2. The device of claim 1 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for one week of the cycle and normal pacing for the remainder of the cycle.

3. The device of claim 1 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for two weeks of the cycle and normal pacing for the remainder of the cycle.

4. The device of claim 1 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for a period of time, and then to apply normal pacing for a period of time equal to or longer than the period of the dyssynchrony-inducing mode.

5. The device of claim 4 , wherein the controller is programmed to make the dyssynchrony-inducing mode period of time one day, and the normal pacing mode period of time one or more days.

6. The device of claim 4 , wherein the controller is programmed to make the dyssynchrony-inducing mode period of time two days, and the normal pacing mode period of time two or more days.

7. A device for treating heart failure, comprising:

a power source;

an atrial stimulation electrode;

a ventricular stimulation electrode; and

a controller that is:

operably connected to the power source and to the stimulation electrodes;

configured to receive a signal indicative of atrial electrical activity; and

programmed to:

monitor the signal to detect an atrial heart rate;

operate the device in a normal pacing mode, for which the controller is programmed to cause the atrial stimulation electrode to depolarize atrial tissue if the atrial heart rate is below a predetermined limit;

operate the device in a dyssynchrony-inducing mode, for which the controller is programmed to cause the ventricular stimulation electrode to depolarize ventricular tissue at a single site with a delay relative to atrial electrical activity shorter than a normal atrioventricular conduction delay; and

periodically apply the dyssynchrony-inducing mode for a period of time of at least a few hours sufficient to stimulate molecular signaling changes that are subsequently modified by reinstating normal pacing.

8. The device of claim 7 , wherein the controller is programmed to alternate between the normal pacing mode and the dyssynchrony-inducing mode to provide repeated periods of resynchronization following induced dyssynchrony.

9. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for the period of time, and then to apply normal pacing for a period of time equal to or longer than the period of the dyssynchrony-inducing mode.

10. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for one day.

11. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for two days.

12. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for one week.

13. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode for two weeks.

14. The device of claim 7 , wherein the controller is programmed to apply the dyssynchrony-inducing mode during nighttime, and to apply the normal pacing mode for the rest of each day.