The role of implantable sensors for management of heart failure

Abstract

Heart failure is a chronic disease with significant morbidity and mortality worldwide. Drugs such as ACE-inhibitors, beta-blockers and diuretics have helped control heart failure but the incidence of hospitalizations remains high. Rigorous continuous monitoring of patients and tailored therapy based on individual clinical and hemodynamic profile has been shown to limit the symptoms of heart failure. Self-monitoring or prescribed frequent in-clinic monitoring is logistically difficult and is fraught with patient non-compliance. Consequently, implantable sensors that can monitor patient's clinical status on a continuous basis are desirable. The disadvantage with an implantable sensor is obviously that the patient has to undergo an invasive procedure, which in itself has a certain risk, although minimal, associated with it. In addition, the risk of having an implantable device has to be weighed against the benefit of monitoring the patient on a continuous basis. The risk benefit question has been answered in part by the recent success of cardiac resynchronization therapy (CRT) in treating symptoms of heart failure. A recent study has performed a meta analysis on major heart failure trials conducted to date and concluded that CRT reduces mortality and morbidity. The CRT device is a specialized pacemaker with capabilities of continuous heart monitoring and embedded therapeutic decisions. A trend of heart rates offers significant insights into the progression of heart failure and patient status. In addition, using complex algorithms, several of the heart rate variability (HRV) parameters, identified in several studies for risk stratification and prognostication, can also be calculated. Furthermore, in recent devices based on heart rate intervals, autonomic balance (critical measure of progression of heart failure) can be estimated with sophisticated algorithms. Finally, technologies that can monitor patients' activity e.g. accelerometers, can be easily incorporated into the device. Such measures may be used to evaluate the efficacy of a new therapy or simply to provide patient status. Based on advances in technology, several patient clinical features can be monitored and trended over time. The measured metrics will help form a comprehensive and objective clinical profile of the patient that the physician can act upon. Prospective studies are needed to answer the efficacy of such diagnostic measures in management of heart failure.