Making the most of cardiac resynchronization therapy : remotely monitoring patients

October 2, 2007 By Grendel Burrell [mailto:grendel.burrell@gmail.com]

Both CRT device optimization and the use of home monitoring equipment for CRT devices were the focus of many discussions at HFSA 2007. Questions of how, and when, and what value were debated amongst the attendees and presenters. For the past 10 years, a body of evidence has accumulated to support the use of cardiac resynchronization therapy (CRT) in conjunction with optimal pharmacologic therapy (1, 2) in management of patients with heart failure (HF). Several thousand HF patients with ventricular dyssynchrony have been evaluated in randomized controlled trials comparing optimal medical therapy alone vs. medical therapy plus CRT. When CRT is added to medical therapy in symptomatic HF patients, CRT resulted in significant improvements in quality of life, functional class, exercise capacity, ejection fraction (EF), and mortality in patients randomized to CRT or to the combination of CRT and an implantable defibrillator (CRT-D).

Since approval by the US Food and Drug Administration (FDA) and market release in 2002, > 200,000 CRT devices have been implanted. Approximately 10% to 20% of the more than 20 million people with HF worldwide are potential candidates and could benefit from CRT. According to current practice guidelines, CRT should be considered for patients with severe left ventricular (LV) systolic dysfunction (LVEF ≤ 35% with LV dilation > 5.5 cm), a widened QRS interval (≥ 120 ms), and sinus rhythm who have persistent, moderate to severe HF symptoms (New York Heart Association [NYHA] functional class III or ambulatory class IV) despite receiving optimal medical therapy (http://content.onlinejacc.org/cgi/content/full/48/5/1064).

Multiple appropriately designed prospective trials have yielded concordant and consistent results showing benefit of CRT in HF patients. Patients in clinical studies for device approval had their CRT devices optimized. While CRT devices should be implanted in patients without substantial comorbid conditions and with clinical profiles similar to those enrolled in the trials that demonstrated benefit, it may be important that the devices be managed and optimized on an individual patient basis. This approach uses the best practices of evidence-based medicine serves as the basis for clinical practice guidelines addressing CRT device use and is most likely to result in acceptable benefits, risks, and cost-effectiveness.

Both atrioventricular (AV) and interventricular (V-V) delay can be optimized. AV optimization times maximal LV filling to the start of systole. VV optimization maximizes efficiency and optimizes the LV ejection function. Echo and acoustic cardiography are most frequently utilized for optimization. The increasing prevalence of heart failure is associated with numerous and protracted hospital admissions. Remote patient monitoring, the ability to record short- and long-term data from a CRT device that accurately reflects the hemodynamic and functional status of the HF patient has a number of potential implications. Implantable sensors and monitors may enable long-term, ambulatory, and frequent monitoring of hemodynamic changes in HF patients that can be used to individually adjust drug therapy and dosages. This data may provide both the patient and healthcare providers with an early warning of hemodynamic deterioration and an ongoing assessment of response to therapy. Appropriate use of these data may have systems and economic impact by prevention of hospitalizations, office visits while most importantly, improving outcomes in patients.

In current practice, CRT/CRTD devices can remotely monitor a number of physiologic parameters relevant to the HF patient, including patient weight, blood pressure, heart rate, heart rate variability reflecting the autonomic nervous system, transthoracic impedance as a measure of lung edema, and patient activity levels. The main goal of remote monitoring of such data is to reduce HF-associated morbidity by achieving a high degree of accuracy for the prediction of major clinical events, such as HF decompensation, and using these data to guide treatment-based decisions. By diminishing the frequency of clinic visits, remote monitoring may reduce health care costs and patients' inconvenience. Diagnostic data from devices such as the numbers of aborted and delivered ICD therapies are an indicator of the total incidence of tachyarrhythmia. Frequently recurring episodes of ventricular tachyarrhythmias in patients may indicate increasing instability and progression of cardiac disease (3)

Remote monitoring of CRT patients can be very useful. In a prospective, longitudinal, multicenter home monitoring trial with 123 patients having clinical indications for CRT, mean follow-up of 3 months, there were 11 unplanned re-hospitalizations for cardiovascular causes and 9 deaths. In 70% of the re-hospitalization events, the retrospective analysis of remotely acquired data through the home monitoring device, revealed an increased heart rate at rest and in mean heart rate over 24 h within 7 days preceding hospitalization. These interim findings suggested that remotely acquired data may assist in the prediction of events leading to hospitalization. (4).

"Remote monitoring may provide clinicians with information on clinical events sooner than waiting for scheduled visits, and thus, could provide the option to intervene earlier," said Marc A. Silver, M.D., Director, Heart Failure Institute, Advocate Christ Medical Center, Oak Lawn, IL. "Regular monitoring of a patient's weight and blood pressure provides critical information about response to drug therapy."

Data announced recently by Boston Scientific Corporation(http://biz.yahoo.com/prnews/070914/nef014.html?.v=21) confirmed in the community setting the success of wireless remote monitoring technology in managing cardiac patients with the LATITUDE system for monitoring CRT patients. The LATITUDE patient management system sends the clinical event data directly to the physician from the patient’s home.

Based on the first 15,000 patients monitored with the LATITUDE patient management system over the course of 106,000 monitoring months with an average follow-up of seven months, the system detected 948 patients with at least one event of sustained atrial arrhythmia for more than 24 hours. Remote monitoring between regularly scheduled follow-ups may enable clinicians to observe these events sooner in their device patients giving physicians the option to intervene before the patient’s next visit.

The LATITUDE patient management system also detected 1,516 patients who received at least one event of shock therapy for potentially life threatening arrhythmias. Currently, more than 60,000 patients are enrolled on the Boston Scientific Latitude system at more than 1,300 clinics in the US.

Health care professionals strive to understand the role of home monitoring and how to maximize its utility. Remote interrogation of CRT/CRTD provides frequent, convenient, safe and comprehensive monitoring of implantable cardiac devices. Device and patient related problems can be reliably detected, and this may reduce the frequency of outpatient visits or hospitalizations, and improve outcomes.

References:

 
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