A method and apparatus for predicting acute response to cardiac
resynchronization therapy is disclosed. The method can comprise measuring
a first interval during an intrinsic systolic cycle and measuring a
second interval during a stimulated systolic cycle. The acute response
can be predicted by comparing the percent change in duration between the
first interval and the second interval against a pre-determined threshold
value. The first and second time intervals can be measured using, for
example, a surface ECG or, alternatively, an intracardiac electrogram. In
one embodiment, the first interval can be the duration of an intrinsic
QRS complex measured during a non-stimulated systolic cycle. Similarly,
the second interval can be the duration of a stimulated QRS complex
measured during a stimulated systolic cycle.