Temperature sensor based capture detection for a pacer

DETAILED DESCRIPTION In contrast to the approach taken by the prior art, the present invention utilizes a fast responsive temperature sensor located proximal to the distal end of a transvenous pacing lead to monitor the intrabeat variation of venous blood temperature due to the pumping action of the heart.
A signal indicative of the mechanical pumping action of the heart is detected and evaluated for sufficient magnitude to indicate a contraction subsequent to the occurrence of an output pacing stimulus.
Timer circuits coupled to the stimulating and detection circuits cooperate to define a capture detection window, initiated shortly after the delivery of a pacing pulse.
The cardiac signal indicative of the cardiac pumping action occurring within this time window is defined as an evoked response.
The occurrence or non-occurrence of an evoked response following a pacing pulse may be used to provoke a state transition in the pacer to alter its operation.
For example, the amplitude or pulse width of the pacing pulse may be adjusted to provide reliable pacing at the minimum appropriate pulse energy level.
Alternatively, the occurrence of the evoked response may be used for diagnostic purposes.
In a preferred embodiment of the pacer described herein, the detection of an evoked response is used to control the stimulation energy delivered by the pacer output stage.
In general, the auto threshold pacer disclosed will minimize its output energy to maximize pulse generator longevity.