Abstract: The device for use with a catheter includes a sleeve 21 for assembly onto the shaft of a catheter 1, between the catheter shaft and a Tuohy-Borst connector 3. The internal diameter of the sleeve 21 is complementary with the external diameter of the catheter 1 so that the catheter is movable within the sleeve. The external diameter of the sleeve is such that when the Tuohy-Borst connector is closed, a seal is formed between the sleeve and the connector. A flange 24 is provided at one end of the device for engagement with the connector, to prevent movement of the sleeve with the catheter. The internal diameter of the sleeve 21 is also complementary with the external diameter of the catheter 1 so as to provide an annular space about the catheter whereby, in use, a controlled amount of backbleed of blood is allowed.

Abstract: A pacemaker and method of cardiac pacing employing the Tx mode of rate control, having means for automatically terminating the refractory period after sensing of an evoked T wave following a delivered stimulus. The pacemaker also is capable of overriding a natural rate and delivering one or more stimulus pulses so as to obtain a Tx rate determination during what would otherwise be inhibited pacer operation.

Abstract: A dual chamber pacemaker system is disclosed with means for operating in one or another of alternate rate adaptive modes. The pacemaker incorporates an atrial synchronous mode, wherein, pacing rate is determined as a function of sensed atrial signals. It also incorporates a T.sub.x mode, wherein pacing rate is controlled by a sensed QT interval, and an extra sensor mode, wherein pacing rate is controlled as a function of at least one sensed body parameter. The pacemaker comprises means for automatically testing the applicability or appropriateness of the mode currently in use, and for automatically selecting the appropriate rate control mode.

Abstract: A cardiac pacemaker is disclosed having means for automatically adjusting the rate of operation to correspond to physiological changes. Circuitry is provided for detecting the presence or absence of an evoked T wave following a delivered stimulus pulse, and for measuring the time interval between the stimulus pulse and the following T wave. The escape interval of the pacemaker pulse generator is varied in accordance with the detected stimulus-T interval and in the same direction, so as to vary the pacing rate in accordance with variations in such interval. Since this interval in turn corresponds to physiological changes, the pacemaker is adapted to automatically follow the patient's physiological changes.