Effects of acute autonomic modulation on atrial conduction delay and local electrograms duration in paroxysmal atrial fibrillation

Abstract

Slowed atrial conduction may contribute to reentry circuits and vulnerability for atrial fibrillation (AF). The autonomic nervous system (ANS) has modulating effects on electrophysiological properties. However, complex interactions of the ANS with the arrhythmogenic substrate make it difficult to understand the mechanisms underlying induction and maintenance of AF. Aim: To determine the effect of acute ANS modulation in atrial activation times in patients (P) with paroxysmal AF (PAF). Methods and results: 16P (9 men; 59 ± 14 years) with PAF, who underwent electrophysiological study before AF ablation, and 15P (7 men; 58 ± 11 years) with atrioventricular nodal reentry tachycardia, without documentation or induction of AF (control group). Each group included 7P with arterial hypertension but without underlying structural heart disease. The study was performed while off drugs. Multipolar catheters were placed at the high right atrium (HRA), right atrial appendage (RAA), coronary sinus (CS) and His bundle area (His). At baseline and with HRA pacing (600 ms, shortest propagated S2) we measured: i) intraatrial conduction time (IACT, between RAA and atrial deflection in the distal His), ii) inter-atrial conduction time (interACT, between RAA and distal CS), iii) left atrial activation time (LAAT, between atrial deflection in the distal His and distal CS), iv) bipolar electrogram duration at four atrial sites (RAA, His, proximal and distal CS). In the PAF group, measurements were also determined during handgrip and carotid sinus massage (CSM), and after pharmacological blockade of the ANS (ANSB). AF was induced by HRA programmed stimulation in 56% (self-limited -6; sustained -3), 68.8% (self-limited -6; sustained -5), and 50% (selflimited -5; sustained -3) of the P, in basal, during ANS maneuvers, and after ANSB, respectively (p = NS). IACT, interACT and LAAT significantly lengthened during HRA pacing in both groups (600 ms, S2). P with PAF have longer IACT (p b 0.05), a higher increase in both IACT, interACT (p b 0.01) and electrograms duration (p b 0.05) with S2, and more fragmented activity, compared with the control group. Atrial conduction times and electrograms duration were not significantly changed during ANS stimulation. Nevertheless, ANS maneuvers increased heterogeneity of the local electrograms duration. Also, P with sustained AF showed longer interACT and LAAT during CSM. Conclusion: Atrial conduction times, electrograms duration and fractionated activity are increased in PAF, suggesting a role for conduction delays in the arrhythmogenic substrate. Acute vagal stimulation is associated with prolonged interACT and LAAT in P with inducible sustained AF and ANS modulation may influence the heterogeneity of atrial electrograms duration.

Beat to beat wavelet variability in atrial fibrillation

“…PAF constitutes a situation that has often unknown causes and is also quite often unsuccessfully treated. It exhibits a very complex and difficult to understand pathophysiology, since various triggers and substrates interacting through different ways, leading to the development of reentrant circuits [2]. Its prevalence, the low regulation success, as well as the risks for stroke and cardiac diseases when the arrhythmia is unregulated, raise the need for new approaches towards a sophisticated treatment planning on a personalised basis.…”

Looking for new frontiers in atrial fibrillation ablation. A remaining challenge for health care

“…6,7 More advanced AF is, therefore, more difficult to treat with simple catheter ablation. Nevertheless, around 40% of the procedures performed are reported to be for patients with persistent type of AF.…”

Looking for new frontiers in atrial fibrillation ablation. A remaining challenge for health care

“…5 Differences in the success rates are likely E-mail address: m.martinsoliveira@gmail.com related to a more complex substrate in persistent (and long-standing persistent) AF, and with the fact that the electrical, autonomic and structural changes related to the atrial remodeling phenomena promote the maintenance of AF, contributing to the resistance to sinus rhythm conversion and to AF recurrences. 6,7 More advanced AF is, therefore, more difficult to treat with simple catheter ablation. Nevertheless, around 40% of the procedures performed are reported to be for patients with persistent type of AF.…”