Actuarial survival curves

Fig. 11 The actuarial survival curves for an implantable pulse generator. The lower curve shows the pulse generator s survival as a function of batteiy depletion. Battery depletion is a normal and expected outcome so this is not considered a device failure per se. The upper curve depicts what the pulse generator s survival statistics would be if the battery s longevity were not taken into account. Thus the upper curve measures the reliability of the circuitry, hetmeticity, feed throughs, etc.

Fig. 12 Actuarial survival curves for two lead models. The upper curve for Model 4012 shows that its survival probability dropped below the trigger point of 95% after about 4.5 years. Thus this lead was put on Advisory September 26, 1991. The lower curve shows that one of its successors, Model 4024, has retained excellent rehability for nearly 10 years...

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