Remote Monitoring in Heart Failure: the Current State

Abstract

The treatment of congestive heart failure is an expensive undertaking with much of this cost occurring as a result of hospitalization. It is not surprising that many remote monitoring strategies have been developed to help patients maintain clinical stability by avoiding congestion. Most of these have failed. It seems very unlikely that these failures were the result of any one underlying false assumption but rather from the fact that heart failure is a progressive, deadly disease and that human behavior is hard to modify. One lesson that does stand out from the myriad of methods to detect congestion is that surrogates of congestion, such as weight and impedance, are not reliable or actionable enough to influence outcomes. Too many factors influence these surrogates to successfully and confidently use them to affect HF hospitalization. Surrogates are often attractive because they can be inexpensively measured and followed. They are, however, indirect estimations of congestion, and due to the lack specificity, the time and expense expended affecting the surrogate do not provide enough benefit to warrant its use. We know that high filling pressures cause transudation of fluid into tissues and that pulmonary edema and peripheral edema drive patients to seek medical assistance. Direct measurement of these filling pressures appears to be the sole remote monitoring modality that shows a benefit in altering the course of the disease in these patients. Congestive heart failure is such a serious problem and the consequences of hospitalization so onerous in terms of patient well-being and costs to society that actual hemodynamic monitoring, despite its costs, is beneficial in carefully selected high-risk patients. Those patients who benefit are ones with a prior hospitalization and ongoing New York Heart Association (NYHA) class III symptoms. Patients with NYHA class I and II symptoms do not require hemodynamic monitoring because they largely have normal hemodynamics. Those with NYHA class IV symptoms do not benefit because their hemodynamics are so deranged that they cannot be substantially altered except by mechanical circulatory support or heart transplantation. Finally, hemodynamic monitoring offers substantial hope to those patients with normal ejection fraction (EF) heart failure, a large group for whom medical therapy has largely been a failure. These patients have not benefited from the neurohormonal revolution that improved the lives of their brothers and sisters with reduced ejection fractions. Hemodynamic stabilization improves the condition of both but more so of the normal EF cohort. This is an important observation that will help us design future trials for the 50% of heart failure patients with normal systolic function.

Invasive Validation of the Echocardiographic Assessment of Left Ventricular Filling Pressures Using the 2016 Diastolic Guidelines: Head-to-Head Comparison with the 2009 Guidelines

“…Projections estimate that >8 million people will have heart failure by 2030 and that health care costs could exceed ≥50 billion. 1,2 Determining left ventricular (LV) filling pressure is clinically important for the management of patients with congestive heart failure, as elevated LV filling pressure results in increased risk for hospitalization and poor outcomes. 2,3 …”

Correlation of Limb Bioimpedance to Echocardiographic Indicators of Congestion in Patients with NYHA Class II/III Heart Failure

“…We were impressed by the significant correlations seen between the BIS measurements obtained with the SOZO system and traditional TTE measures of congestion. Previous impedance studies using conventional measurement methods have failed to demonstrate effectiveness in detecting decompensation due to study limitations [4]. However, the new design of SOZO has eliminated some of the issues previously resulting in conflicting data.…”

“…However, challenges including variability in electrode placement, body positioning, and time constraints have been documented [3]. Both single and multi-frequency bioimpedance have previously been investigated as a means to detect early congestion, but early results did not shown these to be reliable indicators [4]. Single-frequency bioimpedance analysis (SF-BIA) relies on the information from a single frequency reading, typically 50 kHz.…”

Utilization of Bioimpedance Spectroscopy in lieu of Invasive Monitoring for Monitoring Fluid Overload (Preprint)

“…Bioimpedance, both single and multi-frequency, has been investigated as a means to detect early congestion but has not consistently been shown to be a reliable indicator. [6] Single-frequency bioimpedance analysis (SF-BIA) relies on the information from a single frequency reading, typically 50 kHz with population-specific algorithms (based on gender, ethnicity, height, weight, and age) used to estimate the composition of body compartments. Multi-frequency bioimpedance (MF-BIA) uses 2 or more frequencies but is still limited in its ability to detect total body fluid, particularly in patients with fluid imbalances due to the use of calculations based on normalized fluid distributions.…”