Since the advent of the Coronary Care Unit (CCU) in the early 1960’s, the field of cardiology has led in the introduction of new healthcare technology. Cardiac monitoring and resuscitation lowered the mortality rate for heart attack patients by 50 percent. This was followed by advances in cardiac imaging, prevention, monitoring techniques, and therapeutic interventions. The result has been an increase in our longevity.
However, with that longevity, comes a price to pay in terms of the diseases of aging. The most obvious is dementia, but heart disease, particularly heart failure, has been on the rise in recent decades. Today, there are an estimated 6 million Americans with clinical heart failure. It is the most common cause of hospitalization under the Medicare program as well as the largest expenditure. The result has been an attempt to shift the management of heart failure to the outpatient setting to improve cost effectiveness. The creation of programs for remote patient monitoring coupled with efforts at patient and caregiver education has been a challenge because reimbursement for these services has lagged behind even though they have proven to save money. Using the parameter of 30 day rehospitalization rates, successful monitoring programs have achieved a 30 percent reduction in rehospitalization with significant cost savings, but, at the same time, other programs using similar technology have failed to demonstrate benefit. What can explain the disparity in the results?
Let’s start with the technology. The measurement of daily weight with a scale has long been the surrogate for the fluid retention that is the hallmark of worsening heart failure. Keeping in mind that a gallon of water weighs a little more than 8 pounds, a sudden change in weight signals the onset of fluid retention which is followed by the development of the congestive symptoms.
Anyone, however, who has worked in a hospital knows how unreliable this measurement can be. Variability of the equipment, standardization of the sensor, observer variability and recording of results are all sources of error. To address this problem, recent technology employing impedance devices, radar devices and pressure sensors has been introduced.
Impedance measurement was first attempted using surface electrodes to measure changes in electrical impedance as a reflection of thoracic fluid content.