A system and method for assessing cardiac performance through transcardiac
impedance monitoring is described. Intracardiac impedance measures are
directly collected through an implantable medical device. The
intracardiac impedance measures are correlated to cardiac dimensional
measures relative to performance of an intrathoracic pressure maneuver.
The cardiac dimensional measures are grouped into at least one measures
set corresponding to a temporal phase of the intrathoracic pressure
maneuver. The at least one cardiac dimensional measures set is evaluated
against a cardiac dimensional trend for the corresponding intrathoracic
pressure maneuver temporal phase to represent cardiac performance.