Implanted cardiac devices with remote monitoring capacity: “it’s like having a physician follow me on a daily basis”

A little over 50 years ago, Furman and Schwedel reported the first implantation of a permanent pacemaker for a patient who presented Stokes–Adams seizures [1]. Since those pioneering times, pacing technology has evolved from very rudimentary devices that could only stimulate the heart at a fixed rate with a fixed output voltage to highly sophisticated computer-based devices that allows programming variable rates; tracking atrial activity; monitoring and self-adjustment of output voltages (auto threshold); the collection of an incredible amount of information and even transmission of patient alerts. This evolution was driven by three different factors:

• • Patient needs as dictated by the evolution of standard of care in cardiology

• • The continual forward march of technological innovation

• • The more recent revolution of information transmission

The patients’ needs

Owing to general improvements in social conditions and medical care, human longevity has increased significantly to reach more than 80 years in most of the Western world. Paradoxically, this sometimes means that patients who survive to such an age may have more health problems than those in previous generations. One explanation for this is that in the past, only the fittest would attain a venerable age. In addition to this, ongoing developments in pharmacologic and interventional management of patients means that there is an explosion of cardiac rhythm disorders (including atrial fibrillation (AF), bradycardia, atrioventricular (AV) block and sudden cardiac death) that could be treated with implanted devices such as pacemakers and defibrillators.

The first patients who benefited from a pacemaker were those with the most severe manifestation of AV block and sinus node disease who were at risk of dying or who suffered from recurrent syncope. Dying of ‘old age’, in many instances from bradycardia, was something that was not considered unexpected or unacceptable in those days. The concepts of ‘aging’ and ‘dying naturally’ have changed dramatically over the last 50 years: hence the explosion of new clinical indications for device therapy. These have become so complex that regular revisions of clinical guidelines are needed and one can hardly practice now without these [2].

An example of this is the epidemic of AF: its increased incidence is only partially explained by the aging of the population. Other factors such as co-existing diseases and the capacity to identify asymptomatic episodes (usually with the aforementioned diagnostic capabilities of pacemakers and defibrillators) have to be taken into consideration. AF is associated with a significant mortality risk and potentially disabling morbidity. For instance, in patients over the age of 80 years, AF may be responsible for up to one-third of strokes. AF is also part of the broader ‘sinus node disease’, which is usually associated which bradycardia. One can therefore appreciate the dual usefulness of pacemakers in this context: to treat and to prevent (by early diagnosis) the complications of AF [2,3].

Another area where great progress has been made to alter the concept of ‘dying naturally’ is in the prevention of sudden death. Major advances in the treatment of coronary artery disease and heart failure have increased patients’ safety; but at the same time, they have also allowed more patients to survive the initial insult to their hearts (whether acute myocardial infarction or other damage to the left ventricular myocardium) leaving them at higher risk for sudden arrhythmic death. Consequently, we have observed over the same period of time an explosion in the number of cardiac defibrillators implanted for a primary prevention indication. Initially, these were simple devices that could only identify ventricular arrhythmias according to a cut-off rate and treat with internal shocks. Because ischemic coronary disease, heart failure and arrhythmic troubles are inter-related, the defibrillators have evolved into devices that can discriminate different arrhythmias and deliver tailored therapies more effectively, and even diagnose conditions that could impact negatively on the well-being or the survival of the patients such as silent ischemia with S-T segment monitoring, volume overload with thoracic impedance measurements or ominous adverse arrhythmic events with heart rate variability.

Finally, with older age and more debilitating medical conditions come increased difficulties with mobility. It is therefore expected and desirable to modify our methods of collecting information from pacemakers and defibrillators while reducing patients’ need to travel or visit the doctor’s office.

The forward march of technological innovation

Pacemakers were initially used in patients with either no underlying heart rhythm or a very slow escape rhythm (which was often incompatible with life). Once these devices started to be implanted in patients with more intermittent rhythm disorders, sensing was rapidly introduced to allow pacing to be delivered only when needed. Shortly thereafter, the need for ‘physiologic pacing’ appeared: either with the introduction of activity sensors that could adjust the pacing rate to the patients’ metabolic needs or the development of dual-chamber pacing, which restored AV synchrony. The latest, but certainly not the least technological improvement came with the introduction of triple-chamber (A-V-V) pacing to achieve a better synchronous electrical activation of both right and left ventricles (at the inter- and intraventricular levels). Implantable cardiac defibrillators were developed in parallel with the regular pacemakers; however, this development was somewhat slower, and it took the advent of miniaturization for defibrillators to enter into the mainstream of cardiac rhythm management.

The miniaturization for pacemakers and defibrillators meant that both the actual devices (‘cans’) and their leads (or electrodes) that establish the link between them and the heart were greatly reduced in size over the years. This has been driven by the development of smaller batteries and capacitors, combined with the evolution of microchip technology. Although the race towards miniaturization and producing more sophisticated devices was driven both by practical and cosmetic reasons, there are some potential setbacks. In recent years, the number of medical advisories and recalls related to pacemakers, defibrillators and leads have increased. On average, physicians are implanting more devices that are smaller, have more leads and perform more tasks. These conditions increase the likelihood of developing many types of device malfunction.

The revolution of information transmission

Over the last two decades, information transmission has been revolutionized by the development of the internet, digital communications and wireless transmissions. Before long, these capacities were associated with and integrated into implantable devices: first with the cardiac defibrillators and more recently with pacemakers.

Standard of care requires that the patients and their devices be followed up regularly for the purposes evaluating both the clinical condition of the patient and the functioning of the device (with the associated need for adjusting medications and device programming accordingly). Usually, it is recommended to perform these follow-ups as clinically indicated – between one and four times per year [4]. This can be challenging, particularly in large clinics or in remote areas. Some important recent developments in device technology are helping to improve patient and device safety in this respect. First, certain devices can monitor their own performance (sensing, pacing threshold, lead impedance and battery status) and store this information for easy access at the next appointment. Second, they can self-adjust some features (sensing and output values) to assure near-perfect patients’ safety. Third, they can generate alerts whenever a ‘dangerous’ condition is met (medical, arrhythmic or device related). Fourth, the information from all of the above can be stored within the device and be transmitted rapidly over traditional telephone line or through the internet for ‘on-line’ interpretation (and action) [5–7].

Therefore, it has now become possible to have information travel to the physician rather than depending on the patient to travel. This type of monitoring and information transmission can now be performed as often as needed, allowing for ‘tailored’ follow-up both for some aspects of the medical condition of the patient as well as for the functioning of the implanted devices, even beyond the usual clinical guidelines.

The modern ‘deluge’ & the needle in the haystack

In its 27 February 2010 issue, The Economist published a 14-page special report on the benefits and the dangers of the “deluge of information” to which we are submitted [101]. Too much of a good thing can be as bad as not enough: although it is clearly desirable that as much information as possible be collected by the implanted devices and that it should be transmitted as early as possible for analysis and interpretation, there is a risk that with the flood of information that will be available per unit of time (being seconds, days or years) the important part of it may go unnoticed for too long (if not completely overlooked): the needle lost in the haystack. This is even more true considering that implanted devices are only one of the players in the game and that other ‘health parameters’ such as bodyweight, blood pressure and heart rate, blood sugar, or INR could likewise be measured, monitored and transmitted (adding more hay to the stack). Not all measurements need to be addressed immediately or generate rapid intervention, but at the same time failure to recognize serious problems when they occur can lead to dangerous situations. This is the challenge of the 21st Century: infrastructures to collect and treat all the information need to be developed, systems that can collect the information, perform a triage and select what needs to be reviewed and evaluated, and then transferred to the appropriate resources for appropriate action. As always, the issues of sensitivity and specificity need also to be addressed: unnecessary false alerts can create as much harm as failure to recognize serious conditions.

Conclusion

Our patient demographics and the technology available to treat them have evolved tremendously over the last decades: more patients who are sicker, older, and with more limited mobility capacity receive smaller and more complex devices that can both provide more useful information and can be subject to more failures. Having the information travel as often as needed instead of the patients is a desirable objective both for the patients as well as for the physicians and allied professionals who are running device clinics. The paradigm for follow-up of patients with implanted devices is being redefined with the advent of new technologies and communication capabilities, and the infrastructures to gather, store, analyze and filter the information needs to be further developed in response to these changes in order to permit us to use this information to appropriately and rapidly treat our patients.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.