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[Right accessory pathways with slow and decremential anterograde conduction. Electrophysiological changes during
B Cauchemez1, J S Hermida, J Bizot
1Département de cardiologie, hôpital Lariboisière, Paris.
Insights
Radiofrequency ablation successfully treated accessory pathways with slow, decremential conduction in most patients. These pathways, often atrioventricular or atrio-fascicular, were effectively targeted using M potential mapping for radiofrequency ablation.
Area of Science:
- Electrophysiology
- Cardiology
- Medical Devices
Context:
- Right-sided accessory pathways with slow, decremential anterograde conduction present unique electrophysiological characteristics.
- Distinguishing these from Mahaim’s nodo-ventricular connections is crucial for effective treatment.
- Antidromic reciprocating tachycardia can involve these pathways, necessitating targeted ablation strategies.
Purpose:
- To report on a series of patients with antidromic reciprocating tachycardia caused by accessory pathways with decremential conduction.
- To describe the radiofrequency ablation techniques and outcomes for these specific accessory pathways.
- To investigate the anatomical substrates and electrophysiological properties of these pathways.
Summary:
- Six patients with wide QRS complex tachycardia (left bundle branch block morphology) underwent radiofrequency ablation.
- Mapping focused on the proximal atrial pole, utilizing M potential recordings to identify accessory pathway activation.
- Ablation was successful in 5 out of 6 patients, with a mean follow-up of 12 months showing sustained asymptomatic status.
Impact:
- Demonstrates that accessory pathways with slow decremential conduction can be successfully ablated using radiofrequency energy.
- Highlights the utility of M potential recording for precise localization of these pathways on the tricuspid annulus.
- Provides evidence that these pathways, even when masked during sinus rhythm, are amenable to ablation, improving patient outcomes.
Abstract:
Right sided accessory pathways with slow and decremential anterograde conduction differ from the anatomical substrates of the nodo-ventricular connections described by Mahaim. The connection may also be atrio-ventricular or atrio-fascicular. The authors report a series of 6 patients (2 men, average age 31 +/- 9 years) with antidromic reciprocating tachycardia implicating accessory pathways with decremential conduction (wide QRS complexes with left bundle branch block) the radiofrequency ablation of which was centered on the proximal atrial pole. The increment of pre-excitation was 75 +/- 18 ms. No nodo-ventricular or nodo-fascicular connections were observed. One patient had an atrio-ventricular connection, the mapping and ablation (5 applications) of which were performed on the annulus, as if it were a bundle of Kent. Five patients had a nodo-fascicular connection which was masked during sinus rhythm. The localisation of the proximal atrial insertion on the tricuspid annulus was initially estimated by studying the superior junction of the circuit and by endocavitary stimulation, and then by recording the M potential (activation of the accessory pathway). This was recorded in 4 patients, either at a specific point on the annulus (lateral or postero-lateral) which was the target of ablation (3 patients, 5 +/- 3 applications) or over a wider region (2 cm) at which ablation failed (1 patient: 13 applications). The site of the increment was determined in 2 patients and was proximal to the M potential. The M potential could not be recorded on the annulus in one patient. In 2 patients, the M potential was also recorded along the side of the pathway on the antero-lateral wall of the right ventricle of the tricuspid valve at its distal pole. In 2 patients, ablation was centered on the distal pole in second intention, near to the terminal part of the right bundle where it was localised in one of the two (18 applications). Finally, ablation was obtained in 5 out of 6 patients. They remain asymptomatic after 12 +/- 7 months follow-up. These cases show that accessory pathways with slow decremential conduction usually behave like a complete conduction pathway with an accessory laterally situated atrioventricular node on the tricuspid, an accessory bundle and a distal insertion which are all accessible to ablation.