Heart failure is a condition in which the heart is unable to pump enough blood to sustain normal bodily functions. Heart failure may affect either the right side, left side, or both sides of the heart. As pumping action is lost, blood may back up into other areas of the body, including the liver, gastrointestinal tract, and extremities (right-sided heart failure), or the lungs (left-sided heart failure). Structural or functional causes of heart failure include high blood pressure (hypertension), valvular heart disease, congenital heart diseases, cardiomyopathy, heart tumor, and other heart diseases. Precipitating factors include infections with high fever or complicated infections, use of negative inotropic drugs (such as beta-blockers and calcium channel blocker), anemia, irregular heartbeats (arrhythmias), hyperthyroidism, and kidney disease.
Implantable cardiac devices, such as pacemakers and defibrillators, monitor many different parameters that may be used to determine how well a patient's heart is functioning. For instance, implantable cardiac devices can measure morphology-related parameters, impedance, intrinsic heart rate, heart rate recovery, heart rate variability, conduction delay, pressure, posture, activity, and so forth. Each of these parameters can be used evaluating the patient's heart.
The implantable cardiac devices are commonly configured to stimulate the heart with electrical pulses in response to individual or combinations of these measured parameters. Additionally, the devices can store these parameters over time and occasionally transmit the parameters to external diagnostic systems for more exhaustive analysis. The frequency of offloading data from the device is directed by a clinician or physician.
Certain parameters may be used as surrogate data for diagnosing potential heart failure. Changes in the parameters over time may suggest improvement or degradation in a patient's cardiac condition. However, it is difficult to ascertain from cursory examination of raw parameters whether the patient's condition is improving or worsening. Additionally, in some treatment environments, a clinic may routinely collect data from many patients. With increasing time demands on physicians, clinicians, and other care providers and the large amount of data parameters being collected from numerous patients, it is difficult to diagnose whether individual patients exhibit improving or deteriorating cardiac health based merely on a cursory review of the many raw parameters collected by the implantable devices.
Accordingly, there is a need to simplify parameter analysis in a way that assists care providers in quickly diagnosing the cardiac health of one or more patients. This would allow care providers to screen for patients exhibiting certain patterns that might warrant closer scrutiny, and would be particularly helpful for identifying those patients whose conditions have degenerated to a point of requiring immediate attention.