Current and emerging indications for implantable cardiac monitors

Remote Monitoring of Cardiac Implantable Electronic Devices: What is the Evidence?

PURPOSE OF REVIEW

This review offers an overview of the evidence in diagnostic and therapeutic applications of remote monitoring implantable devices.

RECENT FINDINGS

Remote monitoring of cardiac implantable devices has become more and more popular in recent years as healthcare is moving towards a more patient centralized system. For heart failure patients with an ICD or pacemaker, there is controversial evidence regarding improvements in the clinical outcome, e.g., reduction of hospitalization rates or overall mortality. New developments as hemodynamic remote monitoring via measurement of the pulmonary artery pressure are promising technical achievements showing encouraging results. In cardiac remote monitoring of syncope and arrhythmias, implantable loop recorder plays an important role in diagnostic algorithms. Although there is controversial evidence according to remote monitoring of implantable devices, its use is rapidly expanding, giving healthcare providers the opportunity to react promptly to worsening of their patients. Adequate evaluation of the data created by remote monitoring systems remains an unsolved challenge of contemporary healthcare services.

The Role of Contemporary Wearable and Handheld Devices in the Diagnosis and Management of Cardiac Arrhythmias

Cardiac arrhythmias are associated with significant morbidity, mortality and economic burden on the health care system. Detection and surveillance of cardiac arrhythmias using medical grade non-invasive methods (electrocardiogram, Holter monitoring) is the accepted standard of care. Whilst their accuracy is excellent, significant limitations remain in terms of accessibility, ease of use, cost, and a suboptimal diagnostic yield (up to ∼50%) which is critically dependent on the duration of monitoring. Contemporary wearable and handheld devices that utilise photoplethysmography and the electrocardiogram present a novel opportunity for remote screening and diagnosis of arrhythmias. They have significant advantages in terms of accessibility and availability with the potential of enhancing the diagnostic yield of episodic arrhythmias. However, there is limited data on the accuracy and diagnostic utility of these devices and their role in therapeutic decision making in clinical practice remains unclear. Evidence is mounting that they may be useful in screening for atrial fibrillation, and anecdotally, for the diagnosis of other brady and tachyarrhythmias. Recently, there has been an explosion of patient uptake of such devices for self-monitoring of arrhythmias. Frequently, the clinician is presented such information for review and comment, which may influence clinical decisions about treatment. Further studies are needed before incorporation of such technologies in routine clinical practice, given the lack of systematic data on their accuracy and utility. Moreover, challenges with regulation of quality standards and privacy remain. This state-of-the-art review summarises the role of novel ambulatory, commercially available, heart rhythm monitors in the diagnosis and management of cardiac arrhythmias and their expanding role in the diagnostic and therapeutic paradigm in cardiology.

Newer Diagnostic and Cost-Effective Ways to Identify Asymptomatic Atrial Fibrillation for the Prevention of Stroke

Atrial fibrillation (Afib) is the most common and underestimated cardiac arrhythmia with a lifetime risk of >35% after the age of 55 years and the risk continues to rise exponentially. Afib leads to stasis of blood within the atria allowing clot formation and increasing the risk for systemic embolization leading to strokes. Outcomes due to Afib can improve significantly with appropriate treatment. Thus, the need for convenient, well-tolerated, cost-effective cardiac monitoring for Afib is needed. The study aims to evaluate the various newer devices and compare them with traditional Holter monitoring, keeping diagnostic yield, cost-effectiveness, and patients' convenience in mind. Though Holter monitoring is simple and non-expensive, it has major limitations including limited recording capacity, inability for real-time recordings, and inconvenience to patients. Zio Patch (iRhythm Technologies, Inc; San Francisco, CA) and other loop recording devices are patient-friendly, inexpensive, and can offer real-time data for longer days. More prospective studies are needed to evaluate the sensitivity, specificity, and the actual number of patients getting benefits from newer devices by diagnosing Afib sooner and start early prevention therapy.

Direct Powering a Real Cardiac Pacemaker by Natural Energy of a Heartbeat

Implantable medical devices are widely used for monitoring and treatment of severe diseases. In particular, an implantable cardiac pacemaker is the most effective therapeutic device for treating bradyrhythmia, however its surgical replacement is inevitable every 5-12 years due to the limited life of the built-in battery. Although several approaches of energy harvesting have been explored in this decade for powering cardiac pacemakers, the modern, commercial, and full-function pacemaker has never been powered effectively yet. Here, we report an integrated strategy for directly powering a modern and full-function cardiac pacemaker, which can pace the porcine heart in vivo by harvesting the natural energy of a heartbeat, without using any external energy storage element. The generator includes an elastic skeleton and two piezoelectric composites, which could generate a high-output current of 15 μA in vivo over state-of-the-art performance. This study makes an impressive step toward fabricating a self-powered cardiac pacemaker and resolving the power issue of implantable medical devices by piezoelectric harvesting technology.

Long-term rhythm monitoring with an implantable loop recorder in patients after the first clinical atrial fibrillation episode. Towards an individualized management

Although atrial fibrillation (AF) is an arrhythmia with a variable clinical profile (symptomatic and asymptomatic episodes), the first symptomatic episode leads to its initial diagnosis in most cases. Nowadays, continuous and remote long-term cardiac rhythm monitoring is feasible by the use of implantable loop recorders. The data concerning the AF recurrences and progression after the first electrocardiographic-documented clinical AF episode demonstrates that a high percentage of patients may not suffer any other AF recurrence, or may present a low recurrence rate of the arrhythmia in the future. The AF burden may play a key role in the management of the arrhythmia as far as the decision-making for anticoagulation, rate and/or rhythm control therapy is concerned. There is evidence that a higher AF burden is associated with a higher risk of ischemic stroke. Non-vitamin K antagonists (NOACs) anticoagulants are increasingly used in the management of AF, providing a more predictable effect with rapid onset and offset of their action. The use of these agents in combination with devices that provide a continuous remote rhythm monitoring capability has encouraged anticoagulation strategies based on the AF burden. Data from tailored anticoagulation studies in AF are in favor of the long-term rhythm monitoring, ensuring a patient-centered approach with a better evaluation and more individualized management of AF, especially in patients with intermediate thromboembolic risk and high bleeding risk. Further large randomized trials are needed, not only to evaluate such strategies but also to elucidate the long-term cardiac rhythm monitoring in the AF management.

Self-Powered, One-Stop, and Multifunctional Implantable Triboelectric Active Sensor for Real-Time Biomedical Monitoring

Operation time of implantable electronic devices is largely constrained by the lifetime of batteries, which have to be replaced periodically by surgical procedures once exhausted, causing physical and mental suffering to patients and increasing healthcare costs. Besides the efficient scavenging of the mechanical energy of internal organs, this study proposes a self-powered, flexible, and one-stop implantable triboelectric active sensor (iTEAS) that can provide continuous monitoring of multiple physiological and pathological signs. As demonstrated in human-scale animals, the device can monitor heart rates, reaching an accuracy of ∼99%. Cardiac arrhythmias such as atrial fibrillation and ventricular premature contraction can be detected in real-time. Furthermore, a novel method of monitoring respiratory rates and phases is established by analyzing variations of the output peaks of the iTEAS. Blood pressure can be independently estimated and the velocity of blood flow calculated with the aid of a separate arterial pressure catheter. With the core-shell packaging strategy, monitoring functionality remains excellent during 72 h after closure of the chest. The in vivo biocompatibility of the device is examined after 2 weeks of implantation, proving suitability for practical use. As a multifunctional biomedical monitor that is exempt from needing an external power supply, the proposed iTEAS holds great potential in the future of the healthcare industry.

Holter Monitoring and Loop Recorders: From Research to Clinical Practice

Holter monitors are tools of proven efficacy in diagnosing and monitoring cardiac arrhythmias. Despite the fact their use is widely prescribed by general practitioners, little is known about their evolving role in the management of patients with cryptogenic stroke, paroxysmal atrial fibrillation, unexplained recurrent syncope and risk stratification in implantable cardioverter defibrillator or pacemaker candidates. New Holter monitoring technologies and loop recorders allow prolonged monitoring of heart rhythm for periods from a few days to several months, making it possible to detect infrequent arrhythmias in patients of all ages. This review discusses the advances in this area of arrhythmology and how Holter monitors have improved the clinical management of patients with suspected cardiac rhythm diseases.

Left Axillary Implantation of Loop Recorder versus the Traditional Left Chest Area: A Prospective Randomized Study

BACKGROUND

Based upon the results of a previous small pilot study, we present the results of a prospective single-center randomized study comparing the performance of the implantable loop recorder (ILR) at two implanting sites.

METHODS

A group of patients whose ILRs were implanted via a left axillary approach were compared with a group who received an ILR in the traditional left site of the chest. Follow-up (FU) was scheduled every 6 months or when symptoms occurred. All patients enrolled in the study had a complete FU from implantation to explantation. R- and P-wave amplitudes were measured at implantation and during FU. Explantation of the device was programmed at the end of service life or when ILR analysis resulted in a complete and exhaustive diagnosis.

RESULTS

Sixty-three patients were enrolled (70 ± 12 years, range: 21-92, 59% male): 31 standard and 32 with axillary access. The R-wave amplitude obtained with the new technique was comparable with that obtained with the standard procedure. The diagnostic accuracy of the ILR was comparable in the two groups. The axillary implantation procedure was slightly longer but no complications were observed.

CONCLUSION

This long-term randomized study confirmed that axillary access for ILR implantation is feasible, safe, well tolerated, and reliable in terms of device performance. Moreover, it is aesthetically superior to the standard approach and carries the potential of minimizing permanent scarring after ILR extraction.

The Evolution and Application of Cardiac Monitoring for Occult Atrial Fibrillation in Cryptogenic Stroke and TIA

OPINION STATEMENT

The evaluation of the stroke and transient ischemic attack (TIA) patient has been historically predominated by the initial evaluation in the hospital setting. As the etiology of stroke has eluded us in approximately one third of all acute events, the medical community has been eager to seek the answer to this mystery. In recent years, we have seen an explosion of innovations and trends allowing for a more detailed post stroke assessment strategy aimed at the identification of occult atrial fibrillation as the etiologic cause for the cryptogenic event. This has been achieved through the evolution and aggressive application and study of prolonged and advanced cardiac monitoring. This review is aimed to clarify and elucidate the standard and novel cardiac monitoring methods that have become available for use by the medical community and expected in the higher level care of cryptogenic stroke and TIA patients. These cardiac monitoring methods and devices are as heterogeneous as our patient population and have their own advantages and disadvantages. Many factors may be taken into consideration in choosing the appropriate cardiac monitoring method and are highlighted for consideration in this review. With a judicious approach to investigating the cryptogenic stroke population, and applying a wealth of novel treatment options, we may move forward into a new era of stroke prevention.