A method for monitoring the progression of the hemodynamic status of a patient
by tracking autonomic tone. For example, the method may be applied to patients
suffering from heart failure, diabetic neuropathy, cardiac ischemia, sleep apnea
and hypertension. An implantable or other ambulatory monitor senses a pulse amplitude
signal such as a vascular plethysmography signal. Variations of the signal amplitude
on a scale greater than the heartbeat to heartbeat scale are indicative of variations
in autonomic tone. A significant reduction in pulse amplitude and pulse amplitude
variability are indicative of a heart failure exacerbation or other disease state
change. This information may be used to warn the patient or healthcare providers
of changes in the patient's condition warranting attention.