Despite numerous advances in heart failure management, re-hospitalization rates in patients with heart failure continue to rise, and heart failure remains the leading cause of hospitalization in the elderly. Billions of healthcare dollars are spent managing heart failure patients in the United States annually, with the majority of these costs being related to hospitalization. Thus, there is an urgent need for novel strategies to optimize outpatient management of patients with heart failure and prevent recurrent hospitalizations.
What can we do to keep patients out of the hospital? Until recently, optimal medical therapy was the only tool available for both outpatient management of heart failure patients and prevention of re-hospitalization. However, large strides in device therapy over the past two decades have given clinicians many more management options. These devices have included cardiac resynchronization devices, intracardiac defibrillators, implantable hemodynamic monitors, and combinations of these. Indeed, device therapy has been shown to be effective in reducing re-hospitalization and improving outcomes in a wide range of heart failure patients.
However, there is a large gap between device implantation and follow up (generally under the purview of electrophysiologists), and continued medical therapy and optimization of fluid status optimization (generally managed by heart failure physicians). Beyond electrophysiologic information, newer devices can provide day-to-day hemodynamic parameters that may aid physicians to detect early physiologic disturbances, optimize medical therapy and prevent hospitalization. Yet, this information has been largely under-utilized by heart failure physicians. In fact, given the rapidity of development of new devices, it has been very challenging for non-electrophysiologists to keep abreast with the latest devices.
At Massachusetts General Hospital (MGH), we propose to bridge this gap through a novel, heart failure physician-based “advanced physiologic monitoring clinic” that has been created for heart failure patients with implantable pacemaker devices. This clinic provides integrated care that combines device data with clinical data, subjective reports from the patient, and a functional assessment, to tailor heart failure therapy. Our aims are to optimize medical care and patient quality of life, reduce hospitalizations and readmissions for acute decompensated heart failure (thus reducing total cost of care), and facilitate implementation of advanced therapies when appropriate, such as cardiac resynchronization therapy, cardiac transplant evaluation, or referral for ventricular assist devices.
The MGH Heart Failure Device Monitoring Clinic
Our current strategies in managing the patient with chronic heart failure in the outpatient setting have focused on managing volume status based on daily weights and monitoring of symptoms. While these variables are essential in the management of the heart failure patient, there is evidence to suggest that these variables may not be enough to keep these patients out of the hospital. Our specialized clinic is designed to provide advanced monitoring for the heart failure patient who has an implanted device (ICD, CRT device or other implanted monitor) capable of providing diagnostic information, which can be analyzed by their heart failure clinician. ICDs and CRT devices record and provide detailed information pertaining to patient activity, heart rate, autonomic activity, and transthoracic impedance. Devices in clinical trials are capable of providing real-time hemodynamic data. This diagnostic information is downloaded from the device and medical therapy is tailored based on device data, patient symptoms and exam findings.
Services Provided at the MGH Heart Failure Device Monitoring Clinic
Patients who are at high risk for hospitalization are referred to the clinic by their primary cardiologist. At each visit, quality of life is assessed using the Minnesota Living with Heart Failure Questionnaire. Functional status is objectively evaluated using the six-minute walk test. The patient’s device is then interrogated by an EP-trained nurse practitioner, and the patient is examined and evaluated by a heart failure specialist. Using all of the data collectively, therapy is then tailored. When clinically indicated, medications are titrated and device adjustments are made such as augmentation of rate responsiveness. Patients with CRT devices may undergo device optimization using phonocardiography or are referred for echocardiographic optimization if deemed necessary. Device data in combination with clinical data, subjective reports from the patient, and a functional assessment is used to tailor therapy.
Interrogation of devices by heart failure physicians is not intended to replace routine care by the patient’s electrophysiologist, but rather, to work synergistically with the electrophysiology team that is handling the arrhythmia and lead-related issues. The goal and belief of the MGH Heart Failure Device Monitoring Clinic is that the examination of this physiological data cannot be isolated from diagnostic heart failure parameters. One method that facilitates this practice is the use of the shared electronic medical record in which the heart failure patient’s device-related information is combined in the same area as the electrophysiological reports. Staff knowledgeable in both the electrophysiological and diagnostic device parameters of monitoring is integral to the success of our patients.
Device Diagnostics Specific in Heart Failure Management
Heart Rate Variability
Heart rate variability (HRV) can be a surrogate marker for autonomic control in the heart failure patient, as it predominantly reflects parasympathetic input to the myocardium. HRV is a continuous measurement of changes in intrinsic heart rate over time, and as severity of heart failure progresses, HRV decreases. Most implantable devices will record HRV, and it is usually displayed as a 24-hour distribution of variability versus heart rate. Recent studies have demonstrated that patients with low heart rate variability correlate with high mortality and risk of hospitalization.1,2 Additionally, HRV may be useful in detecting impending decompensation. High LA pressures leading to mechanical stretch of the SA node will decrease HRV3 and since filling pressures have been shown to increase five to seven days prior to the development of symptoms severe enough to warrant hospitalization.3
Poor control of underlying cardiac arrhythmias can lead to worsening of heart failure symptoms; assessing and managing arrhythmia burden is crucial to optimal management of heart failure patients. Onset of atrial fibrillation and loss of the atrial systolic contribution to ventricular diastole can quickly lead to decompensation in patients with underlying cardiomyopathy. Patients with prophylactic, single chamber ICDs who experience frequent ventricular pacing are at increased risk of death or hospitalization for heart failure.4 In the case of cardiac resynchronization devices, percent biventricular pacing can be observed. PVC burden is another important feature that can be analyzed, as frequent PVCs may lead to myocardial dyssynchrony and worsening HF symptoms.
Most permanent pacemakers and defibrillators are equipped with an accelerometer, which detects body movement and can thus monitor general activity throughout the day. Body movement can be quantified by accelerometer signals, which are continuously collected and plotted. An “activity log index” (ALI) is then generated, which is the percentage of time the acceleration exceeds a fixed threshold, a value which corresponds to walking on a treadmill at 2.0 mph. The ALI is highly sensitive in detecting levels of physical activity, and can be used to monitor daily activity level in heart failure patients. The ALI provides objective information on a continuous basis, monitoring the patient’s activities in daily living, and is positively correlated with the six-minute walk test.5 Lower ALI scores correlate with a higher mortality risk.6
Patients will often report a subtle decrease in activity level and exercise capacity several weeks prior to heart failure decompensation or hospitalization. By routinely evaluating the ALI during device interrogation, providers may be able to detect early warning signs that can be used to predict or detect impending heart failure decompensation.
Thoracic Impedance and Fluid Index
High pulmonary and systemic venous congestion as a result of high filling pressures lead to symptoms that prompt the need for hospitalization.7 The newest device-based diagnostic modality available today has the ability to detect changes in intrathoracic fluid status, providing valuable insight into patient management. In 2004, the FDA approved a novel implantable device which can detect and record thoracic fluid status via measurement of intrathoracic impedance. The OptiVol® fluid status monitoring system (Medtronic, Inc., Minneapolis, MN) is available for use with some biventricular pacing devices and implantable defibrillators. Intrathoracic impedance decreases during periods of volume overload, and lower intrathoracic impedance has been shown to correlate with higher pulmonary capillary wedge pressures; thus, it is an added tool in determining volume status and imminent decompensation. Newer devices are currently in clinical trials that may further refine predictive accuracy of impedance monitoring.
In addition to face-to-face visits and interrogation of devices, the clinic also integrates regular remote monitoring of devices capable of transmitting physiologic data (Figure 5). We now know that recent research studies demonstrate that the use of remote monitoring dramatically decreases the response time to arrhythmia events leading to necessary medication changes and clinical evaluations. Ultimately these actions keep these patients out of the hospital. These studies had the electrophysiological device parameters as their focus. Our focus will remain primarily on the heart failure physiologic parameters.
To improve the outcomes related to close remote monitoring of physiological parameters, it is important to have involved and caring clinicians who can make any necessary pharmacological changes related to the patient’s treatment. If these are monitored on a monthly basis in patients with unstable heart failure, we can act more quickly and potentially eliminate unnecessary costly hospitalizations and emergency room visits.
A variety of implantable cardiac monitors are currently in clinical trials. As this new technology emerges, systems will need to be in place to readily manage data obtained from these devices. We live in a world where smartphones now have the ability to download entertainment in a matter of seconds. Healthcare-related information is certainly as important, and can provide a means of confirmation by allowing patients the ability to actively transmit their data to their clinicians when they detect their own clinical changes. In addition, patients will be able to view this information and can become active participants in evaluating many of these parameters.
The heart failure and electrophysiology sections at MGH work collaboratively to provide our patients with the latest available technology and care through our many research endeavors. The device monitoring program serves as a forum where implantable devices used to manage heart failure can be developed and tested. The MGH Heart Failure Device Monitoring Clinic plays a significant role in several national and international multi-center heart failure device-related studies. We were one of a few centers involved in the HOMEOSTASIS trial (St. Jude Medical), and we are actively enrolling patients in the LAPTOP-HF trial (St. Jude Medical). These trials use an implanted left atrial pressure sensor to help tailor therapy for heart failure patients with NYHA class III symptoms. We are also actively enrolling patients in the INOVATE-HF trial (BioControl Medical), which uses an implanted vagus nerve stimulator to improve heart failure symptoms. We were involved in the recent Clepsydra trial (Sorin Group), which uses novel sensors to detect changes in respiration, which are correlated with heart failure events. We are prospectively collecting data on all patients followed in the clinic. Our database will enable us to answer many questions pertinent to follow-up strategies, use of device diagnostics and remote monitoring. Endpoints such as cardiovascular events, hospitalization for heart failure, functional capacity, quality of life, and cost effectiveness are currently being evaluated.
The future of heart failure management will encompass a team of providers and active patient involvement. Through implantable technology, patients will become empowered to co-manage their heart failure. The next generation of impedance monitoring will incorporate multiple vector technology, thus increasing the precision of fluid index. Sensors will be capable of complete hemodynamic monitoring, including left atrial pressure, pulmonary artery pressures, and even PA saturation. Systems will need to be in place to appropriately manage the vast amounts of data capable of being transmitted. Implantable monitors have created a new paradigm in disease management. As treating physicians, we should embrace this technology, as it can extend our face-to-face management and better optimize care for our patients.
- La Rovere MT, Pinna GD, Maestri R, et al. Short-term heart rate variability strongly predicts sudden cardiac death in chronic heart failure patients. Circulation 2003;107:565–570.
- Adamson PB. Continuous heart rate variability from an implanted device: A practical guide for clinical use. Congest Heart Fail 2005;11:327–330.
- Horner SM, Murphy CF, Coen B, et al. Contribution to heart rate variability by mechanoelectric feedback. Stretch of the sinoatrial node reduces heart rate variability. Circulation 1996;94:1762–1767.
- Wilkoff BL, Cook JR, Epstein AE, et al. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: The Dual Chamber and VVI Implantable Defibrillator (DAVID) trial. JAMA 2002;288:3115–3123.
- Kadhresan VA, Pastore J, Auricchio A, et al. A Novel Method—The Activity Log Index—for Monitoring Physical Activity of Patients With Heart Failure. Am J Cardiol 2002;89:1435–1437.
- Singh JP, Rosenthal LS, Hranitzky PM, et al. Device diagnostics and long-term clinical outcome in patients receiving cardiac resynchronization therapy. Europace 2009; Advance access publish, 13 Sept.
- Adams KF Jr, Fonarow GC, Emerman CL, et al. Characteristics and outcomes of patients hospitalized for heart failure in the United States: Rationale, design, and preliminary observations from the first 100,000 cases in the Acute Decompensated Heart Failure National Registry (ADHERE). Am Heart J 2005;149:209–216.