Atrial fibrillation (AF) is the most

Transcription

1 ID:8644 R e v i e w Pa p e r Remote Monitoring for Atrial Fibrillation Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice. In the United States, the prevalence of AF is estimated at 2.3 million persons. 1 AF becomes more frequent as the population ages, and the prevalence is 3% to 5% in those older than 65 years. 2 With expected increases in the age of the population, the number may rise to over 5 million by Men are at somewhat higher risk for developing AF and tend to present with it at an earlier age than women. 3 The chief risk associated with AF is embolic stroke, which is increased 4- to 5-fold. 4 Strokes in AF patients tend to be severe and more likely to cause death than in patients without AF. 5 Treatment with oral anticoagulation therapy can significantly reduce the risk of stroke for many patients at moderate to high risk. Overall, AF is associated with a near doubling of mortality. 6,7 Although some AF patients are asymptomatic, many are limited by symptoms (palpitations, fatigue, shortness of breath, light-headedness, chest pain) that can have a significant impact on quality of life. Rapid or slow heart rates, irregular heartbeats, and the loss of atrial systolic contribution to ventricular filling (atrial kick ) contribute to the development of these symptoms. In addition, AF can worsen other medical conditions, especially heart failure. AF is common in heart failure, being seen in up to 50% of patients with advanced disease, 8 and AF is associated with progression of heart failure and increases in morbidity and mortality There is a complex interaction between the two disease processes; each is able to aggravate the other condition. AF exacerbates systolic heart failure by further reducing cardiac output due Remote monitoring for atrial fibrillation (AF) provides invaluable tools for diagnosis and management. Recent advances in monitoring technology have improved the ability to care for patients with AF. Wireless remote monitoring of implanted devices is revolutionizing the way health care professionals care for this subgroup of patients. Early identification and treatment of paroxysmal AF episodes has the potential to reduce the progression to persistent or permanent AF. Prompt initiation of anticoagulant therapy can reduce the rate of strokes. More thorough and realtime remote monitoring can help evaluate to improve the efficacy of rate control, antiarrhythmic drug therapy, and catheter or surgical ablation procedures. In addition to improvements in clinical care, early detection and treatment of AF could reduce health care costs associated with AF. Congest Heart Fail. 2008;14: Le Jacq Gregory Engel, MD; R. Hardwin Mead, MD From Sequoia Hospital, Redwood, CA Address correspondence to: Gregory Engel, MD, Cardiovascular Medicine and Cardiac Arrhythmias, 1950 University Avenue, Suite 160, E. Palo Alto, CA gengel@cmcadocs.com to the loss of atrial kick. A rapid ventricular response to AF reduces diastolic filling time and leads to further compromise. In some cases in which AF precedes heart failure, AF may even be the etiology of the heart failure via a tachycardia-induced cardiomyopathy. 12,13 The reason for the increased likelihood of AF in heart failure is not fully understood, but there is evidence to suggest that atrial fibrosis associated with heart failure likely plays a key role in the development of a vulnerable substrate for AF. 14 In addition to the clinical burden, AF imposes an enormous financial burden on the health care system. In the United States, the total annual cost for treatment of AF is estimated at over $6.5 billion. 15 There are over 5 million office visits and over 850,000 hospital visits (inpatient and outpatient) related to AF each year. Annual direct health care costs average $4,000 to $5,000 per patient with AF if treated with traditional therapies. Costs are considerably higher in patients with multiple AF recurrences (over $10,000 per year if there are 3 or more recurrences). 16 As simple electrocardiography (ECG) is insufficient for the diagnosis and management of AF, remote monitoring is required. Recent improvement in remote monitoring technology has greatly improved our ability to manage AF and is an important step in reducing the burden of AF on patients and the health care system. Noninvasive Monitoring Holter Monitoring. Holter monitoring, or ambulatory ECG monitoring, uses a device that continuously monitors the electrical activity of the heart for 24 hours or more. The device was named after Dr Norman J. Holter, an American biophysicist who first devised a method for recording cardiac electrical waves, storing the data, 14

2 and displaying it later. The first clinical prototypes were developed in the early 1960s. 17,18 Modern devices are generally easy to wear and can be hidden under most clothing. Data are stored, uploaded, and automatically analyzed. Technicians generally further refine the report before it is presented to the physician for review. For diagnostic purposes, AF episodes can be documented with the use of ambulatory Holter monitoring. For patients with persistent or chronic AF, Holter monitoring can be useful to evaluate rate control or to determine whether there are symptomatic episodes of rapid or slow ventricular rates. Event Monitoring. For patients having episodes that are too infrequent to be detected by Holter monitoring, an ambulatory event monitor can be worn for a month or more. Most are loop recorders and can store 2 to 5 cardiac events usually lasting 30 to 60 seconds and transmit them via telephone line. They are usually reviewed by a technician and then sent to the physician. Because the monitors are patient-triggered, they are best suited to identify symptomatic episodes of AF. Some modern event monitors are now capable of automated detection of slow or fast heart rates when worn continuously. Loop recorders with this technology store the episode until the data are downloaded. For longer-term home monitoring, transtelephonic monitors, commonly used for pacemaker followup, can be used to record and transmit a patient s rhythm at scheduled times. Mobile Cardiovascular Telemetry. Recently developed devices are capable of real-time mobile cardiovascular telemetry using devices only modestly larger than traditional loop recorders. 19 The electrogram is continuously monitored, and episodes of bradycardia or tachycardia are automatically recognized and then transmitted instantaneously. These devices have been shown to provide a higher yield in identifying arrhythmias compared with standard loop monitoring. 20 Invasive Monitoring Implantable Loop Recorders. It is hard to justify implanting an entire pacemaker system just for the purpose of monitoring. However, simple, leadless devices are a viable alternative. The Reveal (Medtronic, Inc., Minneapolis, MN) is a small, easily implantable loop recorder. It is best suited for diagnostic purposes and is primarily used in unexplained syncope. The new Reveal XT has been specifically designed to continuously and automatically monitor AF. The Sleuth implantable loop recorder (Transoma Medical, St Paul, MN) is another option and is slightly larger than the Reveal and similar in size to a pacemaker generator. The Sleuth continuously monitors electrical activity and automatically transmits data to a home monitor that sends the real-time data to a monitoring center. Although these simple and relatively low-risk devices may provide an ideal way to establish the exact AF burden and may be very useful for clinical trials of AF treatment modalities, the routine implantation of these minimally invasive devices is not justified. More research is needed to better understand how to best make use of this new technology. Pacemakers and Defibrillators. Many patients with AF also have indications for pacemakers due to associated bradyarrhythmias. AF patients with heart failure frequently have implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy (CRT) devices. Modern devices have extensive remote monitoring capabilities and provide an ideal platform for the diagnosis and management of AF. The information gathered by these devices can be downloaded at clinic visits or remotely downloaded. Advances in pacemaker technology, including improved memory, event counters, histograms, and stored electrograms, have already had a dramatic effect on the ability to monitor AF, especially asymptomatic episodes. With remote monitoring, we now have the ability to react more quickly to the information. For non-wireless devices, interrogation of the device can be performed on a schedule under clinician direction. Each of the major device manufacturers has a remote monitoring platform, and all now have wireless capabilities for devices that are compatible (usually ICD and CRT defibrillator devices). Wireless devices can be scheduled for interrogation automatically, often while the patient is asleep to minimize compliance issues. Automated alerts can be programmed to identify changes in device or physiologic parameters. For AF, wireless devices are generally capable of reporting new-onset AF or changes in AF burden. Some devices can also report high ventricular rate during AF. Data are transmitted from a home patient monitor via a standard telephone line to secure servers and are available to clinicians on a password-protected Web interface. Clinical Value of Remote Monitoring Diagnosis of AF and Stroke Prevention. Because stroke is the major risk associated with AF, improved diagnosis of AF will increase the number of patients with appropriate anticoagulation therapy and reduce the rate of stroke. In multiple randomized trials, warfarin has consistently been shown to dramatically reduce the risk of stroke in patients with AF (68% reduction in pooled analysis). 21 It has been demonstrated that AF-specific data from devices can lead to increased warfarin use. 22 Patients with sinus node dysfunction requiring pacemakers are a high-risk group for AF development. In the Mode Selection Trial (MOST), atrial tachyarrhythmia episodes were seen in over half the patients and were independent predictors of stroke and total mortality in multivariate analysis. 23 In another study of patients with pacemakers, AF episodes longer than 24 hours were independently associated with embolic events (the risk was increased 3-fold)

3 In patients who have already had a stroke, identification of AF as the cause is critical to initiating proper therapy. A systematic review of studies of noninvasive cardiac rhythm monitoring in patients with cryptogenic ischemic stroke demonstrated that new AF was detected in approximately 5% of patients who underwent Holter monitoring and 5.7% to 7.7% of patients who also had loop event monitors. 25 This review suggests that more intensive monitoring will increase the diagnostic yield. Secondary stroke prevention with oral anticoagulation therapy in patients found to have AF significantly reduces the risk of recurrent stroke (>50% reduction compared with antiplatelet therapy). 26 Monitoring of Medical Therapy. Drug therapy is still the first-line treatment for AF in the majority of patients, and strategies focused on rhythm control are often favored. An on-treatment analysis of the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) trial demonstrated that only sinus rhythm and warfarin use were associated with reduced mortality. 27 Remote monitoring can determine the frequency and duration of episodes, and treatment can be adjusted accordingly. Strategies focused on rate control can also make use of remote monitoring to identify rapid ventricular rates and help adjust dosing of nodal blocking agents. In the rate control arm of the AFFIRM trial, frequent medication changes and drug combinations were needed. 28 Identification of Asymptomatic AF. Multiple studies have demonstrated that symptoms are an unreliable tool to determine whether episodes of AF have occurred. With limited followup (30 seconds of trans-telephonic ECG recording every 2 weeks), approximately 20% of patients with known symptomatic paroxysmal AF had asymptomatic episodes as their first recurrence. 29 In the Prevention of Atrial Fibrillation After Cardioversion (PAFAC) trial, in which daily transtelephonic ECG recording was used, 70% of recurrences were asymptomatic. 30 In the Suppression of Paroxysmal Atrial Tachyarrhythmias (SOPAT) trial, symptoms were reported in only 46% of daily and symptom-triggered ECGs with AF. 31 Of interest, the majority of symptom-triggered events were sinus rhythm (only 37% showed AF), suggesting that symptoms are neither sensitive nor specific for AF. Using device-based monitoring, the majority of AF episodes were asymptomatic. 32 Even in patients receiving stable antiarrhythmic therapy, 38% of AF recurrences lasting over 48 hours were asymptomatic. 33 Monitoring After Ablation. The best way to monitor patients after AF catheter ablation and determine procedural success and follow-up treatment is still a subject of considerable discussion and debate. Symptom-based monitoring is insufficient because a high frequency of AF episodes after ablation are asymptomatic. 34,35 ECG and Holter monitoring is inferior to trans-telephonic event monitoring, 36 and even event monitoring is inferior to more prolonged monitoring that incorporates automatic arrhythmia detection. Without more intense monitoring, it is likely that cure rates of ablation are overestimated. The capability to monitor patients with implanted devices already in place has greatly improved our ability to evaluate the success of ablation procedures and enabled us to demonstrate benefits of ablation beyond simple cure rates. Device monitoring has been very useful to demonstrate significant reductions in overall atrial tachyarrhythmia burden after ablation. 37,38 Reductions in AF burden have also been shown to correlate with improvements in quality of life measures. 39 Device-based monitoring has also shown that, although there are frequent asymptomatic AF recurrences, most of these episodes are short and nonsustained. 40 For patients without implantable monitors, noninvasive devices capable of mobile cardiovascular telemetry have the potential to provide the more in-depth monitoring required after an ablation. However, patient compliance with these devices, which must be worn for extended periods, can be a problem. 41 Newer remote device monitoring technology with more real-time information adds to the ability to monitor patients and more quickly respond to recurrent AF episodes. Patient independent monitoring provides a much more reliable assessment of the result of AF ablation. Recent Advances in Remote Monitoring Remote monitoring, especially wireless monitoring, is revolutionizing the way implantable devices are followed and offers multiple advantages as an adjunct to traditional office-based device follow-up. We now have the ability to detect technical problems with devices or leads earlier. We can also identify and react to clinical changes earlier, including the development or progression of heart failure and atrial or ventricular arrhythmias. The ability to remotely monitor patients also can reduce unnecessary outpatient visits and help optimize health care resource allocation. With better AF identification, patients directly benefit from an improved quality of care. Early identification of AF episodes leads to quicker treatment and anticoagulation decisions. Patient with episodes of prolonged AF who are not receiving anticoagulation therapy can be brought in for cardioversion in a timely manner while the risk of thrombus formation is limited. Automatic arrhythmia detection allows for quicker identification of asymptomatic episodes. Follow-up of AF treatment is greatly improved. Patient compliance requirements are also significantly diminished with modern monitoring technology. In patients with ICDs, remote monitoring for AF with rapid ventricular rates provides the additional advantage of allowing device programming changes and/ 16

4 or medication modifications to avoid unnecessary antitachycardia pacing or shocks. There are limited clinical studies using the new wireless monitoring capabilities of devices, but the early reports have already documented the potential to improve AF care. The Medtronic CareLink Network (Medtronic, Inc., Minneapolis, MN) has been used for silent AF discovery and assessment of antiarrhythmic drug efficacy. 42 The Biotronik daily home monitoring system (Biotronik GmbH & Co. KG, Berlin, Germany) has also been shown to efficiently identify AF episodes and enable rapid anticoagulation decisions. 43 Using the same system in a European-based study, AF was the most common diagnosis, accounting for nearly half of the device and clinical alerts. 44 These findings frequently led to antiarrhythmic drug therapy modification, initiation of anticoagulation, or electrical cardioversion. Falsepositive findings were rare. Remote monitoring can clearly improve clinical care for AF, with the hope of reducing disease progression and diminishing symptoms. Device-based remote monitoring can also lead to improvements in patients quality of life from nonclinical factors. Remote monitoring provides peace of mind for many patients, knowing that problems can be identified quickly and that they have a direct connection from home to their physician. Patients living far away or those who have difficulty with mobility or transport can limit office visits. They also have the added convenience of avoiding time in the waiting room and limiting the burden on their caretakers, who often travel with them. Patient costs can also be reduced as they avoid transportation costs, including gas and parking fees. Health care resource utilization can also be improved with remote monitoring. Despite concerns about the potential for increased clinical workload for physicians and affiliated health professionals, the available data suggest that resource utilization can be minimized. In a recent study using the Biotronik home monitoring system, which sends daily messages, nursing time was 30 s/patient/wk and physician time was 6 s/patient/wk. 45 The mean time per patient decreased significantly over time, following a learning curve. In addition, critical alerts requiring immediate attention were uncommon. Assuming that home monitoring results in decreased office visits, overall cost savings for the clinic and patients would be seen over time. 46 Limitations of Remote Monitoring Although the evidence suggests that there are potential cost savings, there is the potential for increased workload, especially in the early stages of technology development. Changes in the way health care is organized may be needed to better handle remote monitoring. More research is required to understand the optimal health care organization model to handle the volume of data resulting from remote monitoring. Some clinical questions regarding remote monitoring also remain unanswered. Should we use current guidelines, based on limited data, to make treatment decisions when episodes of AF are identified by continuous monitoring? Can we make use of information on duration of episodes or the burden of AF (which was not readily available in the past) to make anticoagulation decisions? More studies are needed to better define potential changes in the therapeutic approach for AF. Conclusions AF is a common and costly disease associated with significant morbidity and mortality. Diagnosis and management of AF can be greatly improved with the use of remote monitoring, especially by taking advantage of recent advances in monitoring technology. Wireless remote monitoring is revolutionizing the way we care for patients with implanted devices. Early identification of AF via remote monitoring can increase anticoagulant utilization with resulting stroke reduction. Remote monitoring allows for prompt cardioversion and restoration of sinus rhythm in patients with paroxysmal AF. Improvements can be made in chronic patient management, including modifications of drug regimens for both rate and rhythm control. Remote monitoring greatly enhances our ability to monitor patients after AF ablation procedures and better define the success of these procedures. Remote monitoring also has the potential to optimize resource utilization, reduce overall costs, and improve patient quality of life. Disclosure: Medtronic, Inc. has provided grant funding for the articles in this supplement. An honoraria was declined by both authors for the writing of this article. Dr Engel receives speaking honoraria from Medtronic, Inc. References 1 Kannel WB, Benjamin EJ. Status of the epidemiology of atrial fibrillation. 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