The following are summary points to remember about implantable hemodynamic monitoring for patients with heart failure (HF):

1. HF therapy guided by remote monitoring of signs, symptoms, weight, and biomarkers with cardiac implantable electronic devices (CIEDs) has not been shown to improve clinical outcomes, even when incorporated into remote telemedicine systems.
2. The failure of these technologies may be due to the limitations of the data assessed, rather than the concept of remote monitoring. For example, daily measurement of body weight has a sensitivity of only 9% for the development of a new HF exacerbation. Similarly, serum B-type natriuretic peptide has yet to be proven helpful in the ongoing management of patients with chronic HF.
3. The first major breakthrough in the implantable monitoring device arena was a right ventricular sensor, which, by measuring pressure during pulmonic valve opening, could estimate the pulmonary artery diastolic pressure. The Chronicle IHM (Medtronic, Inc., Minneapolis, MN) evaluated this device reported a 57% reduction (p < 0.01) in admission rate after hemodynamic data were used as an aid in patient management.
4. The COMPASS-HF (Chronicle Offers Management to Patients with Advanced Signs and Symptoms of HF) study showed that high filling pressures precede the appearance of HF symptoms and predict hospitalizations for HF. Main take-homes from this study include: a) the main hemodynamic variable that correlated with events was diastolic pulmonary artery pressure (PAP), which usually rose gradually, rather than abruptly; b) PAP-guided therapy was effective only if physicians actually modified therapy in response to PAP, even in the absence of signs and symptoms of worsening HF; c) the absence of prespecified pressure targets allowed clinicians to leave PAPs in a range high above normal in many patients; and d) New York Heart Association (NYHA) class IV patients did not benefit from PAP-guided HF management. In the latter instance, low glomerular filtration rates and/or diuretic agent resistance may have prevented effective outpatient treatment of elevated PAPs, necessitating hospitalization for intravenous therapies.
5. CHAMPION (CardioMEMS Heart Sensor Allows Monitoring of Pressure to Improve Outcomes in NYHA Class III HF Patients) is one trial showing that increases in ventricular filling pressures, in both diastolic and systolic HF patients, occur weeks before hospitalization for HF by targeting day-to-day maintenance of normal ventricular filling pressures, a HF management system using ambulatory intracardiac or PAP monitoring might succeed in keeping patients out of the hospital where other (noninvasive and CIED-based) approaches have failed—specifically devices predicting physiological parameters, such as patient activity level, heart rate variability, and intrathoracic impedance. The CHAMPION trial enrolled 550 HF patients, regardless of left ventricular ejection fraction. HF patients were randomized to two groups, one in which the clinicians used daily measurement of PAP in addition to standard of care (treatment group; n = 270) versus standard of care alone (control group; n = 280) to manage patients. There was a 28% relative risk reduction (p = 0.0002) of the primary endpoint, from a rate of 0.44 in the control group to 0.32 in the treatment group. There was a reduction of 37% in the relative risk of HF hospitalizations compared with the control group for the entire single-blinded follow-up period, which averaged >17 months. Other key findings include a significant reduction in PAP, a significant increase in the number of days alive and out of the hospital for HF, a significant reduction in the proportion of patients hospitalized for HF, and a significant improvement in quality of life in treatment versus control patients. Device complications were remarkably low, with freedom from device-related or system-related complications of 98.6%, and overall freedom from pressure-sensor failures of 100%. The reported real-world experience with this system has also been encouraging.
6. Other PAP measurement systems are in development, including a small, implanted sensor that has a battery in the capsule and talks through intrabody communication to a Reveal LINQ Insertable Cardiac Monitor device co-implanted in the patient. This Medtronic device monitors not only PAP, but also cardiac arrhythmias, patient activity, and heart rate. Another system (developed by Endotronix, Inc., Woodridge, IL) appears to be similar to the CardioMEMS HF System, except for a different external user interface.
7. Also currently under development are devices to monitor left atrial pressure (LAP) because LAP as a direct reflection of left ventricular filling pressure is the primary pressure target for the management of HF, direct measurement of LAP may potentially provide more clinical information in the management of HF than measurement of right-sided pressures or PAPs.
8. The HeartPOD (Abbott, formerly St. Jude Medical/Savacor, Inc.), a system that allowed for direct measurement of LAP in patients with ambulatory HF, was studied in a prospective randomized controlled outcomes study, the LAPTOP-HF (Left Atrial Pressure Monitoring to Optimize HF Therapy) trial. Enrollment in the LAPTOP-HF trial was stopped early, due to a perceived excess of implant-related complications. The overall result for this trial was negative, demonstrating no reduction in a combined endpoint of recurrent HF hospitalizations and complications of HF therapy. However, when the results were analyzed using the CHAMPION trial endpoint of recurrent HF hospitalizations, the results of the LAPTOP-HF trial were similar to those of the CHAMPION trial. Further evaluation of this system is required.
9. The V-LAP system (Vectorious Medical Technologies, Tel Aviv, Israel) is a next generation of implantable LAP monitoring systems, and uses advanced application-specific integrated circuit–based technologies. It is a miniature percutaneous LAP sensor that is robust, wireless, and leadless, and includes a novel drift compensation mechanism. The device is implanted permanently in the septum using a transseptal approach. The data collected can be analyzed with next-generation decision-support software systems to extract patient-specific physiological data, such as heart rate variability, the presence of valvular pathologies, early warning for arrhythmias, and diastolic and exercise hemodynamics. Another micro-electromechanical systems–based LAP monitoring system is implanted surgically, rather than transseptally (Integrated Sensing Systems, Inc., Ypsilanti, MI). The surgical implantation approach limits the use of this sensor to patients undergoing cardiac surgery; thus, it has been evaluated in first-in-man studies in patients undergoing implantation of a left ventricular assist device or other cardiac surgery.
10. Several technologically-advanced, implantable hemodynamic monitoring systems currently under development, along with novel approaches to the use of these data (including a patient self-management approach), may further advance the management of patients with HF.

Keywords: Arrhythmias, Cardiac, Atrial Pressure, Biomarkers, Cardiac Surgical Procedures, Diuretics, Electric Impedance, Geriatrics, Heart Failure, Diastolic, Heart Failure, Systolic, Heart Failure, Heart-Assist Devices, Hemodynamics, Monitoring, Physiologic, Natriuretic Peptide, Brain, Quality of Life, Standard of Care, Stroke Volume, Telemedicine, Ventricular Pressure

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