A patient monitoring system including an implantable medical device for monitoring a plurality of physiological factors contributing to physiological conditions of a patient's heart by measuring a first impedance affected by the plurality of physiological factors, across one of a plurality of vectors, and a second impedance affected by the plurality of physiological factors, across a second one of the plurality of vectors subsequent to determining the first impedance. A change in impedance is determined based upon the first impedance and the second impedance measurements. Using an equation .DELTA.Z.sub.VX=.alpha..sub.AVX*Q.sub.A+.alpha..sub.BVX*Q.sub.B, where Q.sub.A is a fractional resistivity change of a first contributing physiological impedance factor, Q.sub.B is a fractional resistivity change of a second physiological impedance factor, .alpha..sub.AVX is an impedance sensitivity factor for physiological impedance factor Q.sub.A, and .alpha..sub.BVX is an impedance sensitivity factor for physiological impedance factor Q.sub.B, the value of one of the contributing physiological impedance factors is determined. The contributing physiological impedance factors may include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume.