Superior Vena Cava as a Source of Triggers for Atrial Fibrillation: A Case Report

Authors: Marialessia Denora, MD; Domenico G. Della Rocca, MD, PhD; Carola Gianni, MD, PhD; Giovanni B. Forleo, MD, PhD; Andrea Natale, MD

 

Case Synopsis: Although pulmonary vein isolation (PVI) represents the cornerstone for catheter ablation of atrial fibrillation (AF)¹, other extrapulmonary structures [e.g., superior vena cava (SVC), coronary sinus (CS), left atrial appendage (LAA), inter-atrial septum (IAS), crista terminalis (CT)] may harbor triggers initiating AF (the so-called non-pulmonary vein (PV) triggers).

We describe the role of SVC as a non-pulmonary trigger in a patient with paroxysmal AF.

The patient was a 61-year-old male with a history of hypertension. Since the first AF diagnosis 8 months prior, he experienced several episodes of AF lasting < 24 hours and was referred to our hospital for catheter ablation.

After PV and posterior wall (PW) isolation was achieved, a pharmacologic challenge test with high-dose isoproterenol infusion (20 µg/min for 10 min) was started to assess PV/PW reconnection and elicit other potential non-PV-triggers.

Non-PV trigger mapping during the pharmacologic test was achieved via multiple catheters, as previously described^2,3: (1) a circular mapping catheter positioned in the left superior PV recording the far-field LAA activity; (2) a 20-pole linear catheter with the proximal 10 poles recording from the SVC/CT, and the distal 10 poles within the CS; (3) the ablation catheter in the right superior PV recording the far-field IAS activity (Figure 1 panel A-B).

During isoproterenol infusion, ectopic activity from the SVC was induced (earliest activation in the proximal electrodes of the 20-pole catheter within the SVC), which led to atrial fibrillation initiation (Figure 1 panel C).

SVC isolation was achieved by targeting the sites of earliest activation, which resulted in an ablation lesion starting from the septal aspect of SVC along the posterior SVC-right atrial (RA) junction and RA posterior wall, as previously described by our group⁴. No phrenic nerve capture at 20 mA was observed along the sites of ablation.

While ablating the SVC, AF terminated with restoration of sinus rhythm.  

The procedure was uncomplicated and the patient was discharged after overnight observation. No AF recurrence was documented in the following 12 months of follow-up.

The SVC is one of the most common sources (3-15%) of non-PV triggers for AF⁵; its arrhythmogenic activity is due to myocardial sleeves extending from the right atrium into the SVC, which contain cells showing enhanced automaticity and triggered activity.^3,5

Isoproterenol infusion at a high dose is pivotal to elicit SVC and other extrapulmonary triggers, especially when performing AF ablation under deep sedation or general anesthesia. If non-PV triggers are mapped, it is our standard practice to target for ablation not only those initiating AF or sustained runs of atrial tachyarrhythmias (AT), but also short runs of AT or repetitive (>10min) premature atrial contractions.⁵

Complete SVC isolation can be achieved by targeting its septal segment and sites of early activation in the SVC-RA junction and RA posterior wall; this approach allows sparing the anterior/lateral aspect, avoiding the risk of sinus node and phrenic nerve injury.⁴

In conclusion, SVC is a common source of non-PV triggers and its isolation may significantly improve outcomes.

 

References

1. Forleo GB, Di Biase L, Della Rocca DG, et al.: Exploring the Potential Role of Catheter Ablation in Patients with Asymptomatic Atrial Fibrillation: Should We Move away from Symptom Relief? J Atr Fibrillation 2013; 6:961.
2. Della Rocca DG, Mohanty S, Mohanty P, et al.: Long‐term outcomes of catheter ablation in patients with longstanding persistent atrial fibrillation lasting less than 2 years. J Cardiovasc Electrophysiol 2018; 29:1607–1615.
3. Della Rocca DG, Tarantino N, Trivedi C, et al.: Non‐pulmonary vein triggers in nonparoxysmal atrial fibrillation: Implications of pathophysiology for catheter ablation. J Cardiovasc Electrophysiol 2020; :jce.14638.
4. Gianni C, Sanchez JE, Mohanty S, et al.: Isolation of the superior vena cava from the right atrial posterior wall: a novel ablation approach. EP Europace 2018; 20:e124–e132.
5. Della Rocca DG, Di Biase L, Mohanty S, et al.: Targeting non-pulmonary vein triggers in persistent atrial fibrillation: results from a prospective, multicentre, observational registry. EP Europace 2021; 23:1939–1949.