The Role of Cardiac Resynchronization Devices in Monitoring Patients with Chronic Heart Failure
Philip B. Adamson
Emilio Vanoli
Management of patients with chronic heart failure initially focuses on determining an etiology for left ventricular dysfunction followed by establishing life-saving medication and device therapies intended to reduce the chances of progressive pump dysfunction and sudden cardiac death.1 Beta-blockers, angiotensin, antagonism with ACE-inhibitors, or angiotensin receptor blockers, and aldosterone blockade form the basis for neurohormonal intervention for selected heart failure patients, and many times result in significant improvement in quality of life and pump function, along with reduced mortality.1 Coupled with neurohormonal inhibition, device therapies further reduce mortality1,2,3,4,5 and, in the case of cardiac resynchronization therapy (CRT),4,5,6 improve morbidities of this chronic disease syndrome.
Patients with persistent left ventricular systolic dysfunction and symptomatic heart failure, after adequate neurohormonal intervention, complicated with interventricular conduction delays, have a consensus recommendation for correction of ventricular electromechanical dyssynchrony (QRS > 120 msec) using cardiac resynchronization therapy (CRT) achieved with atrioventricular sequential biventricular pacing.1,4,5,6 It is clear that CRT, with or without implantable cardioverter defibrillator (ICD) therapy, reduces symptoms and hospitalizations due to worsening of heart failure. It also improves ventricular function in over 70% of patients and significantly reduces risk of death.1,4,5,6 Despite significant advances in heart failure disease management from optimal medical and device therapies, frequent hospitalizations remain a significant problem with very important clinical, economic, and social consequences. The most common reason for patients to require hospitalization is worsening congestion resulting from excessive volume accumulation.7 In this context, the next and most involved step in long-term heart failure management is monitoring patients to avoid volume congestion in hopes of reducing the need for hospitalization. To prevent volume congestion, follow-up of patients with heart failure still relies mostly on traditional methods, such as frequent physical examination, daily weight monitoring, and reporting of symptoms. These tools have marginal predictive value when estimating volume or hospitalization risks,8,9,10,11 providing the rationale for incorporating new data in long-term heart failure disease management.
The focus of this chapter is to review diagnostic information available from implanted CRT devices with consideration for how these parameters may help assess ambulatory patients with heart failure. A suggested means to coordinate information processing is provided to achieve optimal outcomes with an emphasis on developing a strategy for triaging follow-up in hopes of reducing the need for hospitalization to achieve normal volume status. Several important lessons can be learned about monitoring heart failure patients by reviewing studies examining heart failure disease management strategies.
HEART FAILURE DISEASE MANAGEMENT: MONITORING STRATEGY TRIALS
Several approaches to heart failure disease management have been evaluated in clinical studies and include a variety of frequent encounter strategies designed to reduce the need for hospitalization, as summarized in Table 15.1.12,13,14,15,16,17,18 Among several excellent studies, one very interesting trial was the Specialized Primary and Networked Care in Heart Failure (SPAN-CHF) trial, which prospectively randomized heart failure patients from a mix of academic and community practice sites to usual care or an intervention arm.14 Patients were enrolled during an index heart failure hospitalization and were randomly assigned to groups that received follow-up care that normally occurred at the site or to a second group that had a nurse case manager, who visited the patient’s home with education materials and home situation assessment. In the intervention arm, nurses telephoned patients once or twice a week to reinforce the home visit information and to make sure that patients were taking their medications, adhering to dietary restrictions, and weighing in daily. With the intervention outlined in SPAN-CHF, there was a significant 52% reduction in heart failure hospitalizations during the 90-day intervention, but the effect on this end-point was lost once the nurse calls stopped, even though patients had telephone numbers to call any time for help.14 Interestingly, total hospitalizations for any cause were no different between the
intervention and control group. Neurohormonal intervention in SPAN-CHF was similar between the control and intervention groups throughout the trial. Therefore, the reduction in heart failure hospitalizations was likely due to better volume management in the intervention group, rather than from maximizing life-saving medications.14
intervention and control group. Neurohormonal intervention in SPAN-CHF was similar between the control and intervention groups throughout the trial. Therefore, the reduction in heart failure hospitalizations was likely due to better volume management in the intervention group, rather than from maximizing life-saving medications.14
TABLE 15.1 Summary of Key Disease Management Studies and Their Basic Results | ||||||||||||||||||||||||||||||||||||||||
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SPAN-CHF demonstrated that nurse calls are very effective in reducing heart failure hospitalizations, but, in most health care systems, this intervention is not reimbursable and requires funding from sources other than pay-for-service billing, which seriously limits widespread application. However, the SPAN-CHF and other trials clearly demonstrate that intensive focus on volume management in patients with heart failure reduces episodes of heart failure decompensation.
Another similarly designed trial, the Trans-European Network-Home-Care Management System (TEN-HMS), was conducted in three countries characterized by nationalized health care systems (Germany, the Netherlands, and the United Kingdom).15 Patients with a recent heart failure hospitalization were randomly assigned to one of three groups intended to implement long-term heart failure management strategies, including institution and uptitration of life-saving medical therapies to appropriate dosing. The first of the three groups consisted of a transtelephonic information management system in which the patient’s blood pressure, pulse, cardiac rhythm, and weight were transmitted twice daily to a centralized data management server via Internet access and then transmitted to the patient’s responsible study site.15 Automated monitoring of the physiologic information allowed preset parameters of weight change, blood pressure values, or rhythm changes to alert nurses at each study center of a change in patient status. Then providers contacted patients for assessment with final medical decision-making determined by combining information gained from monitored physiologic parameters and from direct patient contact.
The second randomized group consisted of telephone calls monthly from a specially trained heart failure nurse provider, who assessed the patient’s symptoms and current medication dosing and adherence. The nurse contacts were intended to ensure that the long-term plan for the patient’s heart failure management initially instituted during the index hospitalization was successfully implemented during the follow-up period. Additionally, it was thought that nurse contact might provide opportunities to identify volume changes earlier in hopes to avoid congestion leading to acute care hospitalization. The automated monitoring group and nurse contact group were initially hypothesized for comparison, and the third group was added as a control.15
The third randomization group was considered “usual care,” in which the patient’s long-term heart failure management plan, again established in the index hospitalization, became the responsibility of the patient’s primary care provider. Interestingly, the primary end-point of the trial, which was days lost because of death or hospitalization in acute care hospitalizations for any reason during 450 days of follow-up, was not significantly different in any of the groups, but mortality
(which was a component of the primary end-point) was markedly higher in the usual care group compared with nurse telephone management or automated information monitoring.15 As a matter of fact, those patients randomized to nursing care or automated telephone care were three times more likely to survive the 12-month follow-up period than those who received their post-hospitalization management from primary care providers.15 No significant difference in mortality or the primary end-point was found between the nurse care group and the automatic telemonitoring group.
(which was a component of the primary end-point) was markedly higher in the usual care group compared with nurse telephone management or automated information monitoring.15 As a matter of fact, those patients randomized to nursing care or automated telephone care were three times more likely to survive the 12-month follow-up period than those who received their post-hospitalization management from primary care providers.15 No significant difference in mortality or the primary end-point was found between the nurse care group and the automatic telemonitoring group.
To further understand the effect in TEN-HMS, a subsequent analysis found that monitoring daily weight measurements, using two rule of thumb approaches including either a 3 pound weight gain in one day or 5 pounds in three days, or a moving average convergence divergence algorithm, had neither adequate sensitivity nor specificity to be clinically useful in remote monitoring of patients with heart failure, at least in preventing heart failure decompensation leading to hospitalization.19
A more recent trial, The Home or Hospital in Heart failure (HHH), was a European Community-funded, multinational, randomized, controlled clinical trial, conducted in the UK, Poland, and Italy, to assess the feasibility of a new system of home telemonitoring of clinical and physiological parameters, which was compared to usual care in reducing cardiac events in 461 patients with chronic systolic heart failure.18 Home telemonitoring was administered with the following three randomized strategies: (1) monthly telephone contact; (2) phone contact plus weekly transmission of vital signs; and (3) phone contact, weekly transmission of vital signs, and monthly 24-hour recording of cardiorespiratory activity. Patients completed 81% of vital signs transmissions, as well as 92% of cardiorespiratory recordings, but after 12 months, there was no significant effect of home telemonitoring in reducing bed-days occupancy for heart failure or cardiac death plus heart failure hospitalization. A trend toward a reduction of cardiac events was, however, observed in the Italian cohort.18
SUMMARY
Several important lessons can be learned from monitoring strategy trials. Primarily frequent (more than once a month) contact with patients with chronic heart failure in most studies results in a significant reduction in the need for hospitalization to manage volume exacerbations. In addition, frequent nurse calls to this population may favorably impact mortality. Patient contact has several goals, but generally assesses patient volume (congestion symptoms, weight, etc.), perfusion (blood pressure, symptoms), and adherence to recommended medical and lifestyle recommendations (diet, medications, activity, etc.) Although daily weight assessment was a component of most management strategy trials, the performance of this measurement in predicting hospitalization is consistently poor.10,11, 19
Furthermore, the exact operational details in an individual remote patient encounter tend to be unique to the patient and are difficult to quantify and generalize. It is probable that weekly telephone contacts require spending time evaluating several patients who are very stable in order to discover patients whose heart failure status is changing. What is needed is a means to remotely identify unstable patients to focus nurse calls only on those patients with changing volume. This approach may be more practical in actual clinical practice, if the information about clinical status is accurate, precise, routinely available by remote monitoring, and specific enough to guide clinical decision making.
Diagnostic information from CRT devices may meet these criteria and may form the basis for a more efficient means to guide clinical contact between patients and health care providers in an out-patient environment. In fact, it is possible that device-based information may provide earlier signs of impending heart failure decompensation and may provide earlier warning compared to traditional tools, such as history, physical examination, and daily weight assessments.
CARDIAC RESYNCHRONIZATION THERAPY DEVICES AS MONITORS
Information from implanted devices, such as cardiac resynchronization therapy delivery systems, are generally classified as direct, easily understood physiologic parameters, or calculated data derived from sensed or induced impulses (Table 15.2 and Table 15.3). Monitoring heart rate, atrial or ventricular arrhythmias, ventricular response to atrial arrhythmias, and amount of atrial or ventricular pacing has direct clinical application and can be viewed as continuously measured vital signs. Derived data include heart rate variability, intrathoracic impedance, and hourly activity counts. These data require testing in clinical trials to determine how the parameter should influence decision making. Each of these monitoring features will now be reviewed including the evidence justifying their clinical utility.
TABLE 15.2 Continuously Measured Device-Based Diagnostic Information Available Remotely or by Direct Interrogation | ||||
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TABLE 15.3 Implanted Device Components from Which Direct Physiologic Information Is Sensed or Derived Information Is Computed | ||||||||||
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Direct Physiologic Information from Implanted Devices
Heart Rate
Resting heart rates may have prognostic value in patients with chronic heart failure.20,21 Traditional simple heart rate measurements are influenced by both clinical and environmental factors, which may limit understanding of how heart rate may be associated with clinical interventions or prognosis. In contrast, device-based heart rate calculation can provide continuous monitoring over very long periods. Routine heart rate assessment during daytime and nighttime may help determine the efficacy of beta-blocker therapy, as the reduction in heart rate before and after therapy initiation relates to adequate dosing and mortality reduction.21 Heart rate may also predict hospitalization risk. In one trial, nighttime heart rate increased slightly but significantly from 75±11 bpm to 78±11 bpm comparing the period starting 3 weeks before hospitalization to the day of hospitalization (p >0.01). Using an automatic change detection algorithm, the change in nighttime heart rate was 45% sensitive with 2.8 false positives per patient year of follow-up to predict impending decompensation (Fig. 15.1
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