Cardiac pacemaker adaptive to physiological requirements

A cardiac pacemaker comprising:

• stimulus pulse generator means for applying artificial stimulus pulse signals to the heart and having an adjustable pulse repetition rate,
• means for detecting in the heart in each heart cycle the onset of a natural heart stimulus signal or an artificial stimulus pulse signal, whichever occurs first, detection of said signal coinciding with the start of the ventricular preejection period (PEP),
• means for sensing in said cycle the occurrence of the onset of ventricular ejection, which onset corresponds to the end of said PEP,
• means for measuring in each heart cycle the length of the PEP constituting the time between occurrence of the stimulus signal that is sensed by said sensing means and occurrence of the onset of ventricular ejection, and
• means coupled to said pulse generator and responding to the length of said PEP by adjusting the pulse rate of said generator as a function of the length of the PEP.

A cardiac pacemaker adaptive to physiological requirements including an adjustable rate pulse generator,

• means for delivering artificial stimulus pulses from said generator to the heart,
• means for sensing in each heart cycle the onset of a natural stimulus of the heart or an artificial stimulus, whichever is first to occur, sensing of said stimulus coinciding with the start of the preejection period (PEP),
• means for sensing the start of ejection of a heart chamber corresponding to the end of the PEP,
• means for measuring the length of time between said start of the PEP and the end of the PEP, and
• means for adjusting the rate of said pulse generator inversely with the length of the PEP.

A cardiac pacemaker adapted to respond to current physiological requirements of a patient being paced, comprising:

• adjustable rate pulse generator means having output means for coupling stimulus pulses to the heart,
• first sensing means for sensing in each heart cycle the occurrence of the onset of the QRS complex in the intrinsic heart electrical activity or an artificial pacing pulse, whichever is first to occur in the cycle, sensing of either onset of the QRS complex or the artificial stimulus pulse marking the start of a ventricular preejection period (PEP) whose length varies with said current physiological requirements and during which pressure in the ventricles increases but blood is not ejected therefrom,
• second sensing means for sensing the abrupt increase in blood flow in the arterial system resulting from ventricular ejection, which increase marks the end of the PEP,
• means for measuring the length of time between said start and said end of the PEP to yield a value representative of the length of the PEP,
• means for producing a control signal which is a function of the said value representing the length of the PEP for said signal to control the rate of said pulse generator means,
• means for adjusting the escape interval of said pacemaker in response to an extrasystole having occurred if said extrasystole produces said abrupt increase from which to measure the end of the PEP initiated by said extrasystole, and
• means for adjusting the escape interval in case of failure to detect the end point of the measurement of the PEP initiated by a natural intrinsic ECG waveform or an artificial pacing stimulus.