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Potential role of remote monitoring for scheduled and unscheduled evaluations of patients with an implantable defibrillator

Hein Heidbüchel, Pieter Lioen, Stefaan Foulon, Wim Huybrechts, Joris Ector, Rik Willems, Hugo Ector
DOI: http://dx.doi.org/10.1093/europace/eun010 351-357 First published online: 2 February 2008


Aims Follow-up of implantable cardioverter defibrillator (ICD) patients, with regular in-office visits every 3–6 months, puts a significant burden on specialized electrophysiology clinics. New technology allows for remote monitoring of device function. We wanted to investigate its potential reliability and to which extent its use can reduce in-office visits.

Methods and results We retrospectively analysed data from 1739 prospectively coded ICD visits in a random set of 169 patients (followed between 2 month and 10.4 year in an academic centre). We defined (i) whether the visit was planned or not, (ii) what were the reasons for unplanned visits, (iii) whether any relevant finding was made, (iv) whether a remote monitoring system with the ability or not to detect pacing threshold would have been able to capture the problem, and (v) what actions were taken. The standard follow-up scheme consisted of in-office visits 1 month after implantation and then every 6 months, unless approaching battery depletion. From the 1739 visits, 1530 were performed according to clinical schedule (88%) and in 1197 of those (78.2%), no relevant finding was made. In 0.52% (n = 8) early post-implant pacing threshold increases would not have been detected by remote monitoring without the ability to determine thresholds (although two patients showed a high impedance). Moreover, in 6% of the planned visits, reprogramming would require a consecutive in-office visit (4%) or hospitalization (2%). Only 175 visits (9.6% of all) were conducted prior to the planned follow-up date due to patient symptoms [another 42 (2.4%) were due to planned surgery or safety warnings]. The proportion of relevant findings during unscheduled visits was significantly higher than during scheduled visits (80.6 vs. 21.8%; P < 0.0001) and a higher proportion of those was arrhythmia- and/or device-related (85.1 vs. 55.3%, P < 0.0001). Reprogramming was required more often (33.1 vs. 4%; P < 0.0001) and hospitalization rate was higher (18.3 vs. 2%; P < 0.0001), so that 51.4% of unscheduled visits would require in-office evaluation. Overall, remote follow-up would correctly exclude device function abnormalities or arrhythmic problems in 1402 (82.2%), identify an arrhythmic problem in 262 (15.3%), correctly identify a device-related problem in 35 (2.1%), but potentially miss an isolated pacing problem in 6 (0.46%). Clinical evaluation would diagnose a relevant clinical problem in the absence of any device interrogation abnormality in 170 patients (10%).

Conclusion ICD remote monitoring can potentially diagnose >99.5% of arrhythmia- or device-related problems if combined with clinical follow-up by the local general practitioner and/or referring cardiologist. It may provide a way to significantly reduce in-office follow-up visits that are a burden for both hospitals and patients.

  • Telemedicine
  • Remote visit
  • Implantable defibrillators
  • Pacemaker
  • Telemetry


The implementation of large randomized trials showing the effectiveness of implantable cardioverter defibrillators (ICD) in both secondary and primary prophylaxis of sudden cardiac death has led to an exponential rise in the number of implanted ICDs. Moreover, the complexity of ICDs has increased, with more diagnostic information (e.g. on atrial arrhythmias, functional capacity, and volume status), more complex algorithms for differentiating supraventricular from ventricular arrhythmias, and refined therapeutic capabilities (e.g. for atrial arrhythmias or including cardiac resynchronization therapy). ICD follow-up requires thorough electrophysiological expertise.1 The growing number of ICD recipients and their more complex devices are leading to rapidly increasing workload for the follow-up of these patients in specialized centres. And although clinicians were inclined to lengthen the time-interval between follow-up visits from 3 to 6 months, some recent warnings concerning potential device malfunction have required to further intensify follow-up in a number of patients.2

Remote monitoring of implanted devices may allow for earlier detection of device malfunction or clinical problems than during the scheduled routine follow-up visit.35 It is also attractive from a patient’s perspective since it may lead to greater reassurance and obviates the need to be physically present for a routine check-up often requiring long and timely trips to the hospital. More recent technology even does not require active participation of the patient anymore, with automatic and wireless transmissions by the device, and pre-specified methods of notification of the follow-up physician.5,6 More intense follow-up as is possible with remote monitoring may help to stabilize the underlying disease process (through early detection and management of heart failure) and has the potential to better prevent inappropriate ICD interventions which is of even greater concern in primary prophylaxis patients.3

Although most modern remote monitoring systems allow for extensive data retrieval, most lack the possibility to evaluate pacing thresholds (although newer devices will include automatic capture management, both in the RV, atrium, and LV) and the potential to remotely reprogram the device. Together with the fact that a physical examination of the patient is not possible, these technical limitations make that remote follow-up is not fully equivalent to an intra-muros follow-up visit.

Currently, scheduled regular in-office follow-up is the standard and remote monitoring is regarded as a supplementary option. However, since many of the scheduled visits do not require any change of therapy and are therefore time and cost-consuming, a possible expansion of the role of remote monitoring has to be investigated.6,7 The aims of this study were: (i) to assess the proportion of current in-office ICD visits, without any relevant finding and not needing any action, with only minor findings and/or action, or with relevant findings requiring immediate action (reprogramming, drug adjustments, hospitalization); (ii) to evaluate whether these events would be detected or missed by remote follow-up (i.e. its effectiveness and safety); and (iii) to evaluate to which extent remote monitoring in combination with clinical follow-up by the referring physician can reduce visits that require the physical presence of the patient in the electrophysiology centre.


We conducted a retrospective analysis based on the prospectively coded relational database of all ICD visits at the University Hospital Leuven since 1994. A study group was chosen by selecting all patients who had an in-office ICD evaluation during a randomly chosen 12-week period (n = 169). All their electronic visit records were reviewed and recoded if required for this analysis. A single-chamber ICD, DDD-ICD, and CRT-ICD was implanted in 120, 24, and 25 of these patients, respectively. A total of 1739 ICD visits were analysed, with an average visit number of 10.3 per patient (range 1 till 31) over an average follow-up period of 5.3 year (range 2 month to 10.4 year). Average patient age at implantation was 56.3 year, and 143 were men (85%). Most implantations were performed for secondary prophylaxis, with only 9% (n = 15) receiving an ICD for primary prevention (10 with ischaemic heart disease and Madit-1 criteria; 5 with primary electrical disease). At implantation, pacing output was programmed to at least three times the measured pacing threshold to accommodate for anticipated pacing threshold rises during the first week. Pacing output was reduced later to optimize device longevity.

All the electronic visit records were reviewed and recoded if required for this analysis. The database from its inception prospectively logged the reason for each ICD visit, the patient history, and physical examination, all device data (settings and episode information), and any changes to medical or device treatment that were made during the visit. Each visit was classified as scheduled or not, i.e. whether or not the visit was made according to a previously arranged appointment for routine follow-up or as the result of an intercurring event. Visits according to an elective appointment change (e.g. due to change of availability of patient or physician) were still regarded as ‘scheduled’. Regular follow-up in our centre since 1994 constitutes of a post-implant visit 1 to 2 month after initial implantation, and 6-monthly visits thereafter, unless indication of battery depletion. All patients are also routinely seen by their referring cardiologist twice per year (i.e. intermediate between 6-monthly ICD visits) or once per year in those without major cardiological problems (e.g. stable ischaemic heart disease, primary electrical disease, etc.). Moreover, depending on their cardiac status, patients are advised to be regularly followed by their family physician. During every in-office visit, compliance with these instructions to see the referring cardiologist and/or family physician is verified. Moreover, referring physicians receive a report about every in-office visit, including the instructions given to their patient. With ICD end-of-life approaching, in-office inter-visit intervals were progressively shortened to 4, 3, or 2 m to maximize device longevity. According to product advisories or warnings, some patients were notified for earlier than anticipated follow-up: also these visits were classified as unscheduled. In most of these patients, a 3-month follow-up was instituted thereafter, visits that were considered as ‘scheduled’.

We recorded which was the main reason for an unscheduled visit (Table 1). Moreover, all relevant findings that were present or detected during ICD visits (clinically or device-related) were categorized according to the classification in Table 2. A ‘relevant finding’ was defined as any finding that explained a clinical problem (e.g. the cause of a shock) or could have led to a clinical problem if undetected (e.g. lead or device malfunctioning), or that constituted a change in the health status of the patient. ‘Non-relevant findings’ were any other findings not falling into the above categories and that did not cause an imminent threat to the patients health (e.g. inappropriate drug dosing interval, possibility for uptitrating of ACE-inhibitors or beta-blockers, too high pacing output programmed compared to the actual thresholds). When more than one finding was made in a patient during an ICD visit, the main relevant finding, i.e. the one prompting a therapeutic intervention, is listed. Since it was the goal of this study to evaluate whether remote monitoring of the device and/or clinical evaluation by a referring physician would have been able to detect any problem, the categorization of relevant findings was made accordingly. For example, since many remote monitoring systems cannot evaluate pacing thresholds, lead problems were categorized into those that could be detected only via threshold determination or also due to impedance and/or sensing problems. If a lead problem resulted in inappropriate shocks, it was categorized into that section.

View this table:
Table 1

Reasons for unscheduled implantable cardioverter defibrillators visits (n = 209)

View this table:
Table 2

Relevant findings (clinical or device-related) during implantable cardioverter defibrillators visits

Any therapeutic action that was undertaken as the result of an ICD visit was classified following the categorization scheme of Table 3.

View this table:
Table 3

Actions undertaken during implantable cardioverter defibrillators visits

Summary data are given as mean±SD. Comparisons between groups for categorical variables were based on χ2 tests. Results were considered to be significant at P < 0.05.


Of the 1739 analysed visits, 1530 (88%) were performed according to their prior scheduled appointment, whereas 209 (12%) were unscheduled, i.e. earlier than planned (Figure 1).

Figure 1

Flow chart of all 1739 implantable cardioverter defibrillators visits analysed in this study, of which 1530 (88%) were performed according to the routine follow-up schedule and 209 were performed earlier than anticipated. The number and type of relevant findings for each group are indicated.

Scheduled visits

During the vast majority of scheduled visits, no relevant clinical or device-related findings were made (n = 1197, 78.2%; Figure 1 and Table 2), and in 90% of these patients (n = 1075; 70% of all scheduled visits) not even one change was made to medical treatment or device programming. In the other 122 patients without relevant findings, small drug dose changes (n = 104) and/or minor adjustments in programming were performed (n = 22) that could have been postponed, none of those being urgent.

During 21.8% of the routinely scheduled visits (n = 333) a relevant finding was made, arrhythmia- and/or device-related in 184 (55.3%; 12% of all scheduled visits) and a clinical problem in 149 (44.7%; 9.7% of all scheduled visits) (Table 2).

All the clinical problems could have been recognized and treated by the general practitioner or referring cardiologist. Three patients with diaphragmatic stimulation would also have been recognized in this way and referred for a consecutive in-office ICD visit to deal with it.

In eight cases (0.52% of all scheduled visits), remote-monitoring without the ability to determine pacing thresholds would not have been able to effectively detect or define a device-related problem. In 6 of the 169 patients, the ventricular pacing threshold at the first post-discharge visit (an average of 24 days after implantation) was ≥3 times higher than threshold at implantation, without any abnormality in sensing or pacing lead impedance (in four of these six patients, pacing threshold normalized after 3–6 months, whereas in two the threshold remained elevated; in none however, revision of the lead was required). In two more patients, there was a significant rise in pacing lead impedance to >2× implant values (noted after 15 and 27 months), in one associated with a rise in pacing threshold, and in the other without a pacing or sensing problem. Since all the patients in the present study had a primary ICD indication, none of them was pacemaker-dependent at implant. Three of 169 became pacing-dependent in the years during follow-up; in none of them there was a rise in pacing threshold. In three patients, early dislocation of the atrial or ventricular lead resulted in loss of pacing after 1–42 days, but this also resulted in undersensing and would have permitted remote identification of the problem. In case the remote system was able to detect pacing thresholds, all arrhythmia or device-related issues would have been correctly diagnosed.

For 4% of all scheduled ICD follow-ups, patients would need an additional in-office visit for ICD reprogramming since current remote systems do not allow programming (i.e. they are pure monitoring systems). In addition, 32 more patients (2%) would have been advised hospitalization (urgently in 3). As a result, in 94% of the scheduled visits remote follow-up could suffice.

Unscheduled visits

Most of the 209 unscheduled ICD visits were performed because the patient (thought) he/she had experienced an ICD intervention (n = 98; 46.9%), or had felt palpitations or other possible arrhythmia-related symptoms without subjective impression of ICD intervention (n = 37; 17.7%). The frequency of less common reasons is listed in Table 1. Overall, when 34 unscheduled ICD visits due to elective surgery (n = 16), safety warnings (n = 14), or clinical studies (n = 4) are excluded, only 175 ICD visits (10% of all visits in this population) were conducted prior to the planned follow-up due to an unexpected clinical event (Figure 1). This study group was used for further analysis (Tables 2 and 3).

As expected, the proportion of relevant findings during unscheduled visits was much higher than during scheduled visits (n = 141; 80.6 vs. 21.7%; P < 0.0001, Figure 2). In 120 of those 141 visits (85.1%; 68.6% of the 175 unscheduled visits) this finding was arrhythmia- and/or device-related (significantly higher than for scheduled visits with relevant findings, P < 0.0001), and in 21 (14.9%; 12% of all scheduled visits) it was a clinical problem, not significantly different from the routine visits (Table 2 and Figure 2). The group of clinical problems also comprised two patients with diaphragmatic stimulation.

Figure 2

Proportion of relevant findings during scheduled vs. unscheduled implantable cardioverter defibrillators evaluations. Unscheduled visits detected significantly more arrhythmia- or device-related problems, but the proportion with clinically relevant findings was similar.

Even a remote-monitoring system without the ability to determine pacing thresholds would have detected all relevant arrhythmia- and/or device-related problems in none of the unscheduled visits, an isolated pacing problem was found.

During 33.1% of all unscheduled remote ICD follow-ups (n = 58) reprogramming of the device was deemed necessary which would require an additional in-office visit (P < 0.0001 vs. scheduled visits, Figure 3). In addition, 12.6% patients needed hospitalization (n = 22, of whom 12 immediate) (P < 0.0001 vs. scheduled visits). Therefore, in 45.7% of the unscheduled visits, a subsequent in-office visit or hospital admission would be required after initial remote interrogation, significantly more than for scheduled visits (where this constituted 6%; P < 0.0001).

Figure 3

Type of action required when a relevant finding was made during scheduled or unscheduled implantable cardioverter defibrillators evaluations. Reprogramming (requiring an in-office visit) or hospitalization was significantly more often needed during patient-initiated, unscheduled, visits.

When a patient consulted because of a device intervention or arrhythmia-related symptom, remote monitoring of the device could have elucidated the problem or reassured the patient in 94.8% (128 of 135). In seven patients (5.2%), device interrogation did not show any specific findings, but heart failure or another clinical problem was diagnosed.

In two patients, potentially life-threatening situations were detected early, i.e. an infinite shock lead impedance and ineffective shock delivery due to shock lead fracture for a ventricular tachycardia that stopped spontaneously, and battery depletion as the result of repetitive shocks in another patient.

ICD follow-up in general

When considering all 1739 ICD evaluations excluding the 34 for elective surgery, safety warnings, or clinical studies (total n = 1705), remote follow-up would correctly exclude device function abnormalities or arrhythmic problem in 1402 (82.2%), identify an arrhythmic problem, or cause for inappropriate therapy in 262 (15.3%), correctly identify a device-related problem in 35 (2.1%), but potentially miss an isolated pacing problem in 6 (0.4%; Figure 4). Clinical evaluation would diagnose a relevant clinical problem in the absence of any device interrogation abnormality in 170 patients (10%).

Figure 4

Performance of remote monitoring (without the ability to detect isolated pacing threshold increases) regarding the detection or exclusion of device-related or clinical problems. Only a minority of situations (0.4%), i.e. with an isolated pacing problem was present, would have incorrectly been classified as ‘no problem’. More advanced systems that will also allow pacing threshold determination could circumvent this limitation.


Our results indicate that remote monitoring of ICD function can potentially diagnose >99.5% of arrhythmia- or device-related issues, provided that the technology works seamlessly and transfers the same information as during in-office device interrogation. Most current remote systems do not allow determination of pacing threshold. Somewhat surprisingly, our analysis showed that this was only of relevance in 0.4% of the evaluations and ±3% of the patients (6 of 169, all during the first month). For this reason, other authors have suggested to always perform the first visit as an in-office visit when current remote monitoring systems are used.7 This also allows decreasing pacing outputs in other patients, increasing device longevity. Larger studies will be needed to determine with more certainty the proportion of patients with early unexpected pacing threshold increase and its magnitude in order to better assess the risks of relying on remote monitoring during this period. Moreover, auto-capture features will soon supplement remotely monitored data, further decreasing the relevance of this issue. This will also be important for the follow-up of more complex (DDD- or CRT-) devices, which comprised only a small proportion of our study (29%) but are known to be associated with more lead-related problems. Moreover, two patients in our series had a pacing lead impedance rise >1 year after implantation, and in one this was associated with a pacing threshold increase. Assuming that both impedance findings would trigger a subsequent in-office device check, no patient would have been at risk, even in the rare ICD patient who is pacemaker-dependent. On the contrary, the remote finding of unexpected pacing impedance rise could have led to earlier diagnosis of a lead-related problem.

The potential to reduce in-office follow-ups is clearly the highest for routinely planned visits. Also Lazarus has shown that for about half of the ICD patients not any preset event is automatically transmitted during an average follow-up of 1 year.5 Moreover, we showed that only in 6% of the planned visits, reprogramming or hospitalization was considered necessary. Although a consecutive in-office visit after the remote evaluation would add to the costs and time-investment for these patients, their small proportion certainly does not counterbalance the important time-savings for patients and physicians that could be achieved for the group as a whole. Moreover, if the remote system automatically transmits diagnostics after fixed time intervals or specifically alerts after detection of a relevant event (like an asymptomatic intervention or device problem) this can allow a more rapid adjustment of therapy which would otherwise be delayed until the next scheduled follow-up visit.3,4,811 Autocapture features will become widely available on new ICDs released in 2008, both on a ventricular level (RV and LV, for most manufacturers) and on an atrial level (for some manufacturers). The values will be available via remote monitoring. This will enhance the early detection benefit, especially for patients with more complex devices. Prospective health-economical studies however will be needed to correctly determine the medical and economic benefits of systematic remote monitoring as first-line approach in routine ICD follow-up. Checking daily reports will require investments in infrastructure, personnel, and training. Moreover, the economical benefits will be highly dependent on the national health-care system. A multinational European study, the EuroEco trial, is currently underway to investigate these aspects. A French study showed that remote monitoring can avoid two follow-up visits per year and would become cost-saving after an average follow-up of 34 months.12

Our data show that the medical and economic benefit is clearly less in patients who consult for an unforeseen event. Although remote monitoring significantly more often detected an arrhythmia- or device-related problem in these visits, a clinical evaluation may be necessary to rule out any medically relevant triggering circumstance (ischaemia, heart failure, etc.) or cause of complaints, and in about half of the patient-initiated ICD evaluations ensuing reprogramming (during a consecutive in-office visit) or hospitalization is required. Remote monitoring therefore may not be very much time- or cost-saving in this situation. It may however serve as a triage system (e.g. for patients to whom can be confirmed that they received appropriate therapy) and as a rapid response system that is of major psychological importance for the patient (through self-check via a personalized website and/or by telephonic contact with the follow-up centre).13,14 Moreover, since patient-initiated visits only constituted ∼10% of all ICD evaluations, the overall economic and workload impact of remote monitoring may still be considerable. Finally, remote programming of the ICD could be of help to prevent inappropriate therapy when a relevant cause is detected. Although the technical issues for remote programming can easily be overcome, it will require a legal framework and thorough clinical evaluation before such bi-directional remote interaction becomes reality.

An important limitation of our study (from a scientific viewpoint) is the fact that our centre has since the beginning of the ICD era advised the patients to see their referring cardiologists and general practitioner on a routine basis, in addition to their follow-up in our centre. As mentioned, compliance with these instructions to see the referring cardiologist and/or family physician was verified during every in-office visit. This additional follow-up may have led to an underestimation of the clinically relevant findings compared to arrhythmia- and device-related findings during the in-office ICD visits in this retrospective study, since they may have been diagnosed and treated before. At the other hand, we are convinced that systematic local clinical follow-up on pre-specified intervals according to a patient-dependent scheme will be a prerequisite for efficient and clinically sound remote follow-up. The fact that even in our study there was a relevant clinical finding during 9.7% of the routine follow-up visits supports such an approach. Further research will undoubtedly be necessary to define the optimal follow-up scheme in different types of patients (primary vs. secondary ICD indication; electrical heart disease vs. structural heart disease; stratified along NYHA and/or LV ejection fraction; etc.), and which type of physician is best suited for the interim clinical evaluation (general practitioner or cardiologist). Also further extensions to remote monitoring, like collection of haemodynamic and other physiological parameters may help to predict deterioration of the clinical status which could prompt notification for a visit or hospital admission.14 Remote monitoring may never replace completely the follow-up visits in a specialized electrophysiology clinic, but it certainly has the potential to safely lengthen the time interval between those visits.

To conclude, our analysis has shown that remote monitoring of ICD patients can potentially diagnose >99.5% of arrhythmia- or device-related issues by itself, and >99.5% of all problems if combined with clinical follow-up by the local general practitioner and/or referring cardiologist. Even with currently available technology, it can significantly reduce scheduled follow-ups, for which reprogramming or hospitalization is needed in only 6% of the visits. For unscheduled evaluations, it can help to reassure about half of the patients, although an ensuing in-office visit or hospitalization will be required in the other half. Remote monitoring definitely can alleviate the burden of in-office visits for both hospitals and patients alike.

Conflict of interest: H.H. and R.W. receive unconditional research grants from Medtronic Inc. and Boston Scientific. H.H. is a member of the Physician Advisory Board of St Jude Medical, and is Coordinating Clinical Investigator of the Biotronik-sponsored EuroEco trial.


Funding to pay the Open Access publication charges for this article was provided by the authors.


  • Presented in part at the Europace meeting, Lisbon, June 2007.

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