Abstract: A system and method of providing for cardiac pacing which incorporates modulation of the pacing rate in order to minimize variations in ventricular power output, e.g., variation related to patient respiratory phases. In a preferred embodiment, pacing rate is increased during inspiration relative to expiration, to restore a measure of the normal rate modulation which occurs in a normal person. Patient respiration is monitored and a respiration signal is processed to determine the timing of rate modulation. Parameters representative of respiratory changes, such as right ventricular volume and right ventricular blood pressure are also monitored and, together with respiration amplitudes changes, are used to determine an incremental rate signal for controlling the extent of rate variation.

Abstract: Apparatus and method are provided for obtaining a measure of blood flow, and more specifically cardiac output, by analyzing blood temperature variations in the arterial tract. In a first embodiment, a lead carrying two closely spaced temperature sensors is positioned so that the sensors are in the atrial tract and produce temperature signals representative of small cyclical temperature variations of the blood outputted from the heart. The two signals have substantially similar patterns for each cardiac cycle, but the signals are separated by a short time (.increment.T) representative of the distance between the two sensors. The patterns are correlated to find .increment.T, from which cardiac output is calculated. In an alternate embodiment, a single blood temperature sensor is employed along with a sensor for determining cardiac contractions, and a measure of cardiac output is obtained by comparing the time difference between a feature of the blood temperature signal with the time of cardiac contraction.

Abstract: There is provided a system and method for high rate pacing of patients for training, or revalidation of heart muscle. The system and method of this invention provide a therapy particularly directed for patients with CHF, to enable effective exercise of the cardiac muscle without requiring the patient to exercise. In another embodiment, an alternate high rate routine, or algorithm is provided for assisting a patient to exercise during at least some part of the high rate pacing routine. The high rate pacing therapy may be initiated either automatically, based upon the patient's circadian rhythm; automatically by patient data sensed by a system of sensors; or may be initiated directly by the patient by use of a simple external programmer device. The pacemaker of the invention suitably stores a plurality of algorithms which can be selected, or which can be modified or replaced by an external programmer.