An implantable stimulator and monitor measures a group of
heart failure parameters indicative of the state of
heart failure employing EGM signals, measures of
blood pressure including absolute pressure P, developed pressure (DP=systolic P-diastolic P), and / or dP / dt, and measures of
heart chamber volume (V) over one or more cardiac cycles. These parameters include: (1) relaxation or
contraction time constant tau (.tau.); (2) mechanical restitution (MR), i.e., the mechanical response of a
heart chamber to premature stimuli applied to the
heart chamber; (3) recirculation fraction (RF), i.e., the
rate of decay of PESP effects over a series of heart cycles; and (4) end systolic
elastance (E.sub.ES), i.e., the ratios of end systolic
blood pressure P to volume V. These
heart failure parameters are determined periodically regardless of patient posture and
activity level. The physician can determine whether a particular therapy is appropriate, prescribe the therapy for a period of time while again accumulating the stored
patient data for a later review and assessment to determine whether the applied therapy is beneficial or not, thereby enabling periodic changes in therapy, if appropriate.
Drug therapies and electrical stimulation therapies, including PESP stimulation, and pacing therapies including
single chamber, dual chamber and multi-chamber (bi-atrial and / or bi-ventricular) pacing can be delivered.
In patient's prone to malignant tachyarrhythmias, the assessment of heart failure state can be taken into account in setting parameters of detection or classification of tachyarrhythmias and the therapies that are delivered.