System and method for evaluating and optimizing the contribution of particular heart chambers to the overall efficacy of cardiac pacing therapy

A method for use in delivering cardiac pacing therapy to the heart of a patient in which an implantable cardiac stimulation device is implanted, the method comprising the steps of:

• delivering cardiac pacing therapy to the heart of a patient using a pacing mode, the pacing mode specifying which chambers of the heart are paced;
• temporarily altering the pacing mode with which pacing therapy is delivered;
• detecting transient changes in the efficacy of pacing therapy following the alteration in pacing mode;
• determining the contribution of particular heart chambers to the overall efficacy of pacing therapy based on the alteration in the pacing mode and on any transient changes in the efficacy of the pacing therapy;
• and
• recording diagnostic information indicative of the contribution of particular heart chambers to the overall efficacy of pacing therapy.