Leveraging cardiac resynchronization therapy devices to monitor patients with heart failure.

Cardiac resynchronization therapy is a standard therapy for heart failure patients with cardiac dyssynchrony. The implantable device provides a convenient and continuous platform for heart failure monitoring. Information such as heart rate variability and activity status retrieved from the device allows physicians to more comprehensively evaluate these high-risk patients. Several registries and prospective observational studies have evaluated the value of intrathoracic impedance monitoring in predicting exacerbation of heart failure. With its sensitivity and positive predictive power, the fluid index--derived from the raw intrathoracic impedance--may alert clinicians to subclinical or clinical heart failure deterioration. Uncertainty remains as to whether the additional device-derived information will translate into clinical benefit by reducing the number of hospitalizations for heart failure. An ongoing randomized controlled clinical trial is expected to clarify the role of the device-based pulmonary fluid index in the management of heart failure.