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Clinical introduction
During a routine ablation for paroxysmal atrial fibrillation, the right superior pulmonary vein was isolated using the cryoballoon. This was the final vein to be isolated. After the freeze, as the balloon was deflated and withdrawn, a radio-opaque structure was seen to mobilise from the vein ostium (figure 1A). This structure moved into the left atrium (figure 1B), left ventricle, aortic arch (figure 1C) and descending aorta (figure 1D) in turn (full fluoroscopic run available as online supplementary video file). The patient experienced no new symptoms and there was no change in vital signs. The procedure was carried out without interruption of the patient’s oral direct factor Xa inhibitor, and intravenous unfractionated heparin was administered after trans-septal puncture to maintain an activated clotting time of above 300 s.
Supplemental material
Question
What is the next most appropriate course of action?
Embolectomy.
Usual postprocedural care.
Thrombolytic therapy.
Start aspirin.
Answer: B
The structure seen on fluoroscopy is a mass of frozen contrast and blood. When using the cryoballoon, the aim is to achieve complete or near-complete occlusion of the pulmonary vein, thus minimising conductive warming by blood flow, which impairs the efficacy of the freeze. The adequacy of occlusion is assessed by contrast injection into the vein from the distal end of the ablation catheter. Contrast, and therefore blood, should remain static in the vein if occlusion is complete. Occasionally (reported on one other occasion in humans) this contrast/blood mixture subsequently freezes solid.1 When the balloon is withdrawn, the frozen mass detaches and enters the bloodstream. It quickly warms and disperses and therefore should not cause lasting occlusion of distal vessels. There is nothing to suggest that routine postprocedural care and anticoagulation should be altered. Embolectomy, thrombolytic therapy or antiplatelet therapy is not required as the mass will quickly melt and dissipate. The clinical relevance of this phenomenon is unknown, but there have been no reports of harm. It is likely that it occurs more frequently than is appreciated.
Footnotes
Contributors GAB wrote the manuscript and compiled the figure. He was second operator during the ablation procedure. MHT was first operator during the ablation procedure. He reviewed and approved the manuscript for submission.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.