Superior vena cava does not seem to contribute to long-standing persistent atrial fibrillation

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The arrhythmogenicity of the superior vena cava has been rarely detected in patients with long-standing persistent atrial fibrillation, according to study from China recently published in Europace.

The superior vena cava, one of the most common non-pulmonary vein foci, “has been established as an important source of atrial fibrillation,” write Kai Xu (Shanghai Chest Hospital, Shanghai, China) and others. However, they argue, its influence in long-standing persistent atrial fibrillation has not been clear. Therefore, they set out to evaluate the role of the superior vena cava in catheter ablation of long-standing persistent atrial fibrillation.

From March 2013 to July 2013, Xu et al enrolled 102 consecutive symptomatic patients with long-standing persistent atrial fibrillation. The duration of their atrial fibrillation, before ablation, was longer than 12 months.

All patients underwent circumferential pulmonary vein isolation, complex fractionated atrial electrograms ablation and linear ablation during the index procedure. The researchers used mapping catheters (Lasso, Biosense Webster) during the procedure to detect superior vena cava-triggered atrial fibrillation and the association of the superior vena cava with the maintenance of atrial fibrillation. When the arrhythmogenicity of the superior vena cava was proved, electrical isolation of the superior vena cava was undertaken during pacing from the high right atrium.

Xu et al found that the arrhythmogenicity of the superior vena cava was confirmed in only one patient who was identified in the index ablation procedure. The patient was a 54-year-old male, with no related diseases and structural heart diseases. His left atrium diameter was 40mm and right atrium had normal size. The arrhythmogenic superior vena cava was identified with isoproterenol infusion after cardioversion.

The researchers also reported that after 12 months of follow-up, the arrhythmia-free survival rate after a single procedure was 43.1%. After the last procedure (mean 1.47±0.58 procedures), sinus rhythm was maintained in 69.6% patients (n=71), 63 patients without antiarrhythmic drugs including the patient with arrhythmogenic superior vena cava. Xu et al found that the 31 patients who had AF recurrence had higher rates of right atrium enlargement (71% vs. 34% for the non-atrial fibrillation recurrence group), higher rate of ≥2 procedures (65% vs. 34%), longer atrial fibrillation duration (84±46 vs. 45±34 months) and larger atrium diameter (50±5mm vs. 45±6mm).

There were no procedure-related deaths or pericardial tamponade, pneumothorax and phrenic nerve palsy observed. Three patients had vascular complications, including haematoma and pseudoaneurysm, which were treated with manual compression.

Xu et al conclude that this first-of-its-kind study shows “the arrhythmogenic superior vena cava is rarely detected in patients with long-standing persistent atrial fibrillation. Therefore, empiric superior vena cava electrical isolation in the stepwise approach of long-standing persistent atrial fibrillation seems unnecessary.” Nonetheless, they note that this conclusion “does not apply to general population of patients with long-standing persistent atrial fibrillation, but only those preselected for ablation.”

They also acknowledge that “important information” of superior vena cava during circumferential pulmonary vein isolation “may be missed” because the activity of the superior vena cava was not visualised and assessed during circumferential pulmonary vein isolation, but only before this procedure and during left atrial ablation. Therefore, they recommend further studies in a randomised controlled manner.

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