Advances in Cardiac Pacing and Defibrillation

Dear Colleagues,

Since the first pacing system was implanted in 1958, there have been many evolutionary milestones in cardiac implantable electronic device therapy. The first implantable cardiac defibrillator was placed in 1980, and the first reported biventricular pacing in 1994. This field remains in constant evolution. The advancements have also created new challenges and drive device technology to overcome these limitations.

Lead complications account for most device complications, including acute dislodgement, lead-related vascular occlusion, infection, and lead malfunction. This has led to the development of leadless pacing through a femoral vein delivery system. This advancement has been superior to other pacing systems in patients with endocarditis, vascular occlusion, frail body habitus, and post-extraction. These systems have evolved as well now with acoustic atrial sensing to provide atrial ventricular synchrony. A clinical trial is currently utilizing a leadless device that will offer a future upgrade that will allow pacing in both atrial and ventricular. An implantable pacemaker placed at the time of cardiac surgery that fully dissolves has also been recently reported.

Implantable defibrillators can also be implanted fully subcutaneously. This provides an advantage in terms of avoiding the vascular space but is currently limited by lack of brady or anti-tachycardia pacing. The combined use of leadless pacing systems with a subcutaneous defibrillator may overcome these limitations.

Right ventricular pacing was the original ventricular pacing location; however, the risk of pacing-induced dyssynchrony and its deleterious effects has become evident. Biventricular pacing provides a viable way to mitigate dyssynchrony but primarily benefits patients with left bundle branch block and reduced ejection fraction. Recent advances have made His bundle pacing an option that may provide physiologic pacing for a wider patient population. His pacing can be utilized to provide resynchronization and has been shown to be superior to biventricular pacing in several recent studies. Implant success remains challenging, however, and has led to the development of left bundle pacing. These options should all be available to achieve cardiac resynchronization and serve as an alternative when the initial methodology is not successful.

Heart failure also remains an increasing health problem. The majority of heart failure candidates do not meet criteria for cardiac resynchronization. This important therapeutic gap of patients with reduced ejection fraction and normal or slightly widened QRS can now be treated with cardiac contractility modulation. This provides a biphasic high-voltage bipolar signal to the right ventricular septum during the absolute refractory period, eliciting an acute increase in global contractility and chronically producing improved ejection fraction exercise tolerance with improved quality of life and heart failure symptoms.

The ongoing progress in the field of cardiac device therapy is exciting. The aim of this Special Issue is to review cardiac device data more fully and discuss implant techniques, limitations, and success of current advances.

Dear colleagues, we are pleased to invite you to submit original research or reviews on these topics. We look forward to your contributions.

Dr. Kristin E. Ellison
Dr. Laura M. Gravelin
Dr. Joseph J. Souza
Guest Editors

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• implantable cardiac device, pacing, defibrillation
• leadless pacemaker
• subcutaneous defibrillator
• His bundle pacing
• left bundle pacing
• cardiac resynchronization
• cardiac contractility modulation