US Patent 7894901 Apparatus and method for assessing cardiac therapy

A patient's response to therapy such as CRT is assessed by cross correlation of a patient's evoked response and physical activity surrogates. Based on the cross correlation, a determination may be made as to whether or how much the therapy is helping the patient's physical activity. For example, the degree of cross correlation index between IEGM parameters and activity threshold parameters may be used to assess whether the patient's heart condition improves the patient's physical activity. The therapy may then be modified as necessary in the event the patient is not sufficiently responding to the therapy.