Patent ID: 8241222

Claim:
A method comprising: measuring a plurality of impedance values of a path within a patient over time, wherein the path includes at least one blood vessel or cardiac chamber of the patient, and wherein the impedance values vary as a function of blood pressure within the at least one vessel or chamber; determining a plurality of values of an impedance parameter over time based on the measured impedance values, wherein each of the impedance parameter values is determined based on a respective sub-plurality of the impedance values, determining the plurality of values of the impedance parameter comprising identifying an R-wave for a current cardiac cycle, identifying a maximum impedance and a minimum impedance for the current cardiac cycle, determining a first time interval between the R-wave and the minimum impedance, determining a second time interval between the R-wave and the maximum impedance, and determining a ratio of the first time interval and the second time interval; comparing the ratio of the current cardiac cycle to a ratio of a prior cardiac cycle; and identifying a change in a cardiovascular parameter related to the blood pressure based on the comparison.