Chapters authored
The Subcutaneous Implantable Cardioverter-Defibrillator
The subcutaneous ICD (S-ICD) represents an important advancement in defibrillation therapy that obviates the need for a transvenous lead, the most frequent complication with transvenous devices. The S-ICD has been shown similarly safe and effective as transvenous ICD therapy, but the two devices are not interchangeable. The S-ICD is only suitable for patients who do not require bradycardia or antitachycardia pacing functionality. In patients with underlying diseases associated with polymorphic ventricular tachycardia and a long life expectancy, an S-ICD may be the preferred choice. Moreover, it is advantageous in the situation of increased risk of endocarditis, i.e., previous device system infection and immunosuppression, including hemodialysis. In patients with abnormal vascular access and/or right-sided heart structural abnormalities, it may be the only option. The S-ICD is bulkier, the battery longevity is shorter, and the device cost is higher, even though remote follow-up is possible. A two- or three-incision implant procedure has been described with a lateral placement of the device and a single subcutaneous lead. The rate of inappropriate therapy for both S-ICD and transvenous systems is similar, but S-ICD inappropriate shocks are more frequently attributable to oversensing, which can often be resolved with sensing adjustments.
Part of the book: Cardiac Pacing and Monitoring
Atrial Fibrillation and the Role of Thumb ECGs
Atrial fibrillation (AF) may be underdiagnosed, and there is much that remains unknown about this prevalent and potentially life-threatening arrhythmia. AF epidemiology has been thwarted in part by the fact that about a third of patients with AF have no symptoms, those with symptoms may experience them intermittently or have vague symptoms, and it can be challenging to capture an episode on a 12-lead ECG, which is required for diagnosis. There are many significant knowledge gaps in our understanding of AF etiology and progression. A new user-friendly device that allows for frequent self-monitoring of the heart rhythm has been introduced. With the thumb ECG, patients can record a tracing multiple times a day. A smartphone app will soon allow them to interact with their healthcare providers about these ECG recordings. An ECG parser will allow for an algorithm-directed, rapid, automatic interpretation of these recordings with high specificity and sensitivity. This may help researchers learn more about the so-called silent AF, AF progression (and possible remission), and risk factors for AF. This technology holds great promise for patient care as well as for research into AF.
Part of the book: Cardiac Pacing and Monitoring
Leadless Pacemakers
Leadless or transcatheter pacemakers have recently been introduced to market with important benefits and some limitations. Implanted entirely within the right ventricle, these devices eliminate the need for transvenous pacing leads and pacemaker pockets and thus reduce the risk of infections and lead-related problems. Currently, they offer only VVI/R pacing and they cannot provide atrial sensing, antitachycardia pacing, or AV synchrony. They offer a number of features (such as rate response) and electrogram storage, albeit more limited than in a transvenous system. Real-world clinical data are needed to better comment on projected battery life, which manufacturers suggest will be at least equivalent to transvenous devices. Extracting an implanted leadless pacemaker remains a challenge, although proprietary snare and removal systems are available. However, a leadless pacemaker at end of service may be programmed to OOO and left in place; a revised device may be implanted adjacent. These innovative new devices may have important uses in special populations. Initial data on implant success and adverse events are favorable. Currently, there are two leadless pacemakers available: the Micra™ device by Medtronic and the Nanostim™ device by Abbott (formerly St. Jude Medical).
Part of the book: Cardiac Pacing and Monitoring