Clinical evaluation of an automatic sensitivity adjustment feature in a dual chamber pacemaker

The clinical evaluation of a new automatic sensitivity adjustment feature in the Cosmos II, Model #284-05 is described. This feature, designed to maintain a 2:1 safety margin for sensing intrinsic signals, was activated by way of special programmer software in ten patients at two centers. While the feature worked satisfactorily in some cases, it did not perform as expected, and undersensing in both chambers was observed. This may have been due to biasing the adjustment toward maximum rather than minimum electrograms. This study suggested that electrograms may vary by more than 100% which underscores the importance of this feature, and reinforces the need for continued development.