The role of AV conduction on cardiac hemodynamic has been studied for almost 30 years, highlighting the importance of a physiologic diastolic filling. Noteworthy, unnecessary atrial stimulation reproducibly increased new-onset AF both in ICD (Implantable Cardioverter-Defibrillator) and in CRTD (Cardiac Resynchronization Therapy Defibrillator) recipients. Careful analysis of unpaced and paced P wave duration and PR interval can unveil AP-induced dyssynchrony ( Figure 1).
Though easily accessible, the atrial appendage seems rarely the preferred pacing site in patients with brady-tachy syndrome, and sets the physiologic background for pacing close to the Bachmann bundle in patients with delayed interatrial conduction, as identified by a ≥ 120 ms P wave duration or markedly prolonged paced P wave/PR interval from the RAA. Bachmann bundle pacing slowed the progression from paroxysmal to chronic AF in a randomized multicenter trial. Consistently, low IAS and RAA pacing were not significantly different in absence of interatrial conduction delay. This could possibly be related to decreased interatrial conduction time. In EPASS (Electrophysiology-Guided Pacing Site Selection) trial, low interatrial septum (IAS) pacing was also superior to RAA pacing in preventing persistent or permanent AF in patients with SND and intra-atrial conduction delay. In this article, we analyze the emerging evidence in favor of the available strategies to achieve an individualized physiologic setting in bradycardia pacing. The perspective of truly physiologic pacing is the leading concept of the continued research in the past 30 years, which has made cardiac stimulation procedure more sophisticated and challenging. This has led to awareness of the concealed risks of customary cardiac pacing that can inadvertently cause atrioventricular and inter-/intra-ventricular dyssynchrony, and has promoted the development of new pacing modalities and the use of stimulation sites different from the right atrial appendage and the right ventricular apex. Cardiac stimulation nowadays aims to correct the electrophysiologic roots of mechanical inefficiency in different structural heart diseases.
Over the years, pacemakers have evolved from a life-saving tool to prevent asystole to a device to treat heart rhythm disorders and heart failure, aiming at improving both cardiac function and clinical outcomes.
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