Remote Monitoring Via Implanted Devices in Heart Failure: Rising Star or Lame Duck? (2011)

This editorial refers to ‘Potential value of automated daily screening of cardiac resynchronization therapy defibrillator diagnostics for prediction of major cardiovascular events: results from Home-CARE (Home Monitoring in Cardiac Resynchronization Therapy) study’ by S. Sack et al., published in this issue on pages 1019–1027. Implantable cardioverter–defibrillators (ICDs) have become standard therapy for patients with poor systolic function and low left ventricular ejection fraction, most often due to ischaemic heart disease, and also non-ischaemic cardiomyopathy. These patients are thus protected from life-threatening arrhythmias but remain at risk of deterioration of cardiac function leading to decompensation. Cardiac resynchronization therapy can improve symptoms of heart failure and mortality in advanced heart failure but has more recently been shown to also reduce mortality in milder heart failure patients with broad QRS complexes.1 Implantation rates have been shown to be increasing steadily in Europe2,3 and it is expected that they will increase further after the recent updated guidelines on device therapy in heart failure.4 These devices can increasingly be connected to remote monitoring to assess device function but also heart failure-related parameters. Prospective data on the use of remote monitoring is scarce but is being increasingly used also in the light of recent device-related malfunctions. The use of parameters that can predict heart failure-related complications can be an important add-on to these remote technical device check-ups. As mentioned, prospective data are few but there are numerous trials currently recruiting or in the follow-up phase that should be available within the next few years and these should aid in answering important questions such as if heart failure hospitalizations can be prevented by remote monitoring of cardiac devices. A lot of study designs are not published in peer-reviewed journals but can be looked up at www.clinicaltrials.gov. A comprehensive review was recently published summarizing available systems and reviewing ongoing trials.5 In this issue of the European Journal of Heart Failure, Sack et al.6 present data from the Home-CARE study comparing seven different parameters possibly related to worsening of heart failure with regard to their prospective value in predicting heart failure hospitalization. These parameters, however, did not include changes in thoracic impedance measurements, which are possibly the most sensitive markers of pulmonary fluid accumulation.7,8 The authors found that combination of several predictors showed higher sensitivity and even higher specificity than using a single parameter. The downside is that even if all seven parameters are included, the specificity of alerts was not >65%. One could speculate that in a follow-up study the best parameters could be tested with inclusion of thoracic impedance. Patient activity seemed to have a low predictive value whereas mean and resting heart rates as well as heart rate variability appeared to be more important. The upside of the presented results is, however, that the specificity of combined parameters was very high which cannot be expected from thoracic impedance measurements alone.9 Remote monitoring of ICDs can aid in early detection of technical problems. This includes lead problems such as fracture, but also device problems such as early battery depletion. Even though the event rate is low early after implantation10 this can increase during the lifespan of an implanted device. The occurrence of frequent non-sustained ventricular tachycardias or successful anti-tachycardia pacing can precede shock therapy, which might be prevented by changes in therapy such as intensifying antiarrhythmic treatment. The occurrence of atrial fibrillation (AF) with fast ventricular conduction or other supraventricular tachycardias as well as intermittent T-top oversensing are typical examples of situations where early detection could prevent inadequate ICD therapies. What is the evidence for remote monitoring in the prevention of heart failure events? Non-device telemonitoring of patient parameters such as symptoms and weight showed no benefit over conventional therapy.11,12 Registry data, which can obviously not replace prospective analyses, suggest that mortality is lower in patients with remote monitoring than in a group receiving standard face-to-face follow-up.13 For the use of intrathoracic impedance we eagerly await the report of prospective randomized studies such as DOT-HF (Diagnostic Outcome Trial in Heart Failure)14 and OptiLink HF.15 It is, however, to be expected that in real life specificity will not be higher than suggested by earlier studies. Sack et al. can be heralded to try to combine several parameters to overcome this caveat. If future studies can combine promising parameters with intrathoracic impedance it might be possible to find a combination with reasonable sensitivity and specificity. Cardiac resynchronization devices are actually the theoretical prototype for remote monitoring. Most patients have an ICD function and may benefit from early detection of technical problems and ventricular tachyarrhythmias as discussed in the previous paragraph. New-onset AF may be a marker of worsening heart failure. In patients with cardiac resynchronization it is especially deleterious because of loss of biventricular stimulation especially during exercise16 and it has been demonstrated to be an independent predictor of non-response to CRT17 as well as mortality.18 The effecT study (NCT00811382) was started to prospectively study the early treatment of AF episodes detected via home monitoring. What are the future possibilities for remote monitoring? Patients at high risk of device malfunctions will continue to receive remote monitoring devices. As we await the results from additional randomized trials, prevention of heart failure events is a reasonable target. This might have to be restricted to certain populations until we find additional parameters or technical advances that will improve sensitivity and specificity. Cost effectiveness is an important issue that cannot be left unmentioned. Remote monitoring can be used to reduce face-to-face contacts that could save health-care expenditure as well as costs to the individual patient (travel expenses) and to society (missing time at work). For the issue of cost, prospective trials are also missing but ongoing. Finally, we must not forget patient satisfaction and quality of life. Implantable cardioverter–defibrillators shocks and heart failure hospitalizations can impact on patients’ lives. Heart failure is associated with reduced quality of life. Remote monitoring can aid in patient satisfaction providing an additional sense of security and acceptance of their cardiac device with as a possible downside the continuous reminder of their illness. Conflicts of interest: D.J.V. has received consultancy fees from Medtronic and Biotronik, and is the Principal (Co-) Investigator of the DOT-HF Study. A.H.M. has received lecture fees from Medtronic, Biotronik, Boston Scientific, and Sorin.