Patent ID: 8923980

Claim:
For use with a medical device to be implanted in a patient, a method for detecting imminent lead failure in the implanted medical device comprising the steps of: (a) deriving an empirical formula by (i) selecting samples of cardiac therapy medical device leads of the model number of the medical device from the production line; (ii) subjecting the leads to destructive laboratory pull testing by (α) pulling the leads and measuring the elongation (E) and the baseline mechanical load (L B ) of the leads, (β) growing flaws in the leads, (γ) again pulling the flawed leads and measuring the elongation (E) and the baseline mechanical load (L B ) of the flawed leads, thereby obtaining test results, (iii) based upon the test results, evaluating the threshold mechanical load (L T ) and the threshold mechanical load loss (ΔL T =L B −L T ) as a function of the elongation (E), (iv) fitting the threshold test data to an empirical formula of the general form ΔL T =f T (E) to determine the best-fit function and the best-fit parameters, (v) storing the empirical formula in the cardiac therapy medical device computer; (b) for each serial number of a lead in an implanted device, (i) establishing a baseline immediately after the lead is installed into the cardiac therapy medical device during fabrication of the device, (ii) subjecting the installed lead to a nondestructive laboratory pull test, (iii) measuring the elongation (E) and the baseline mechanical load (L B ), (iv) fitting the baseline test data to a formula L B =f B (E), (v) determining the best-fit function and the best-fit parameters, (vi) storing the empirical formula in the serial number of the cardiac therapy medical device computer, (c) implanting the cardiac therapy medical device in the patient; (d) operating the cardiac therapy medical device to continuously monitor the cardiac therapy medical device computer to monitor any elongation of the lead resulting from patient movements, (i) when any elongation is sensed, measuring the elongation (E) and any corresponding mechanical load (L), (ii) determining by use of the cardiac therapy medical device computer whether the threshold for imminent structural failure has been reached by comparing the mechanical load loss (ΔL=L B (E)−L) with the threshold mechanical load loss (ΔL T (E)), (iii) should ΔL≧ΔL T (E), that is, if L≦f B (E)−f T (E), alerting the patient by use of the cardiac therapy medical device computer that structural failure of the lead is imminent, (iv) should ΔL<ΔL T (E), that is, if L>f B (E)−f T (E), continuing operation of the cardiac therapy medical device.