Apparatus and method for adjusting heart/pacer rate relative to ejection time to obtain a required cardiac output

An apparatus for pacing a heart in accordance with the heart/pacer rate needed to produce a required cardiac output while the person is exercising relative to ejection time of the right ventricle and changes thereof, comprising:

• a demand pacer for implantation in a human body, said pacer having a pulse generator and control circuitry, which may be realized by a microprocessor, mounted therein;
• a pacing lead for implantation in a heart, said lead including a lead body having a tip electrode adapted to engage and supply pacing pulses to a right ventricle of a heart;
• sensing means mounted on said lead body for sensing changes in the right ventricle of the heart for determining the ejection time of the right ventricle and changes in ejection time over time in the right ventricle, such sensing including measurements selected from the group consisting of measurements of changes in volume of the right ventricle, measurements of changes in pressure in the right ventricle and measurements of changes in impedance of the fluid in the right ventricle;
• and
• said control circuitry including means for determining ejection time from the sensing of changes in the right ventricle and for relating ejection time and the changes in ejection time in the right ventricle with the required pacing rate and changes in the existing pacing rate needed to supply a desired cardiac output and for causing said pacer to pace the heart at the required rate when the heart is not naturally paced.