Stenosis or occlusion of one or more pulmonary veins
Initial series reported rates up to 20% of patients,
although more recent series show rates under 10%,
most less than 5%.
Mild stenosis usually requires no intervention (Fig. 1). However,
progressive or severe stenosis requires prompt intervention to avoid pulmonary vein occlusion (Fig. 2) (Fig. 3). Currently,
there are no formal recommendations to screen patients for pulmonary vein stenosis
Cardiac CT or MRI can be used to evaluate the pulmonary veins in patients with known or suspected pulmonary vein stenosis.
The pulmonary veins should be assessed by using double oblique,
multiplanar reformatted images allowing measurements of the long axis and the short axis of the pulmonary vein ostia and any area of potential narrowing.
The presence of mural thickening should also be determined.
It is important to distinguish real stenosis from pseudostenosis (especially left inferior pulmonary vein) (Fig. 4). Interlobular septal thickening,
reflecting edema in the associated lobe(s) suggests significant stenosis.
Symptomatic stenoses are typically treated with stent placement,
which has been shown to be superior to angioplasty alone,
while patients with asymptomatic high-grade (>75%) stenoses can be monitored every 3-6 months (Fig. 5).
Pericardial effusion
Pericardial effusion occurs in up to 20% of patients and can occur at time of ablation or shortly thereafter.
Most are simple and resolve spontaneously within 6 months.
Pericardial effusion and hemopericardium are associated with ablation of sites other than the pulmonary veins. Hemopericardium can develop and lead to cardiac tamponade during the procedure.
Tamponade from pericardial effusion is rare (<2%) and can also develop weeks after the ablation.
Thromboembolic
Thromboembolic events can occur in up to 7% of patients undering ablation for atrial fibrillation.
They can occur during the procedure or up to 2 weeks after.
Appropriate anticoagulation during and after the procedure can minimize risks of thromboembolism.
Esophageal perforation and atrioesophageal fistula
Esophageal perforation and atrioesophageal fistula (AEF) are rare (up to 0.25%) but life-threatening complications of ablation.
Gas,
solid debris,
and liquid are able to pass into left atrium and embolize systemically.
Because of the differences in pressure,
flow of blood from the left atrium into esophagus is limited or does not occur. Most esophageal injuries occur 1 to 6 weeks after theablation procedure.
Diagnosis of esophageal injury and AEF requires a high index of suspicion.
Patients most commonly present with fever and sepsis.
Neurologic deficits result from air embolism and stroke.
Hematemesis is rare.
Contrast-enhanced CT of the chest is the diagnostic study of choice.
Esophageal endoscopy is contraindicated because of potential for massive and fatal air embolism. Findings on CT that should raise suspicion for AEF include gas or filling defects in the left atrium,
often near the posterior wall (Fig. 6) (Fig. 7). Esophageal wall thickening with or without mural defect can also be apparent (Fig. 8).
There are limited data on the best treatment for AEF,
but surgical repair is likely better for fistula.
Despite treatment,
mortality rates are very high,
and untreated AEF is uniformly fatal.
Phrenic nerve injury
Phrenic nerve injury is a rare complication of ablative therapy (<1%) and is associated with wide area circumferential ablation.
An increased incidence (up to 11%) has been reported with the increased use of cryoablation.
The highest rate of phrenic nerve injury is associated with ablation of the right superior pulmonary vein because of its proximity of vein to phrenic nerve.
Findings on CT and radiography of phrenic nerve injury include elevation of the ipsilateral hemidiaphragm,
especially if new following ablation (Fig. 9). A fluoroscopic sniff test can confirm the finding by showing paradoxical upward motion of the affected hemidiaphragm (Fig. 10).
Most patients recover spontaneously by 12 months,
but diaphragmatic plication or phrenopexy may be required in symptomatic patients who do not recover function.
Left atrial calcification
Left atrial mural calcification is an uncommon finding following pulmonary vein ablative therapy (Fig. 11) (Fig. 12) and is not a well described phenomenon.
These calcifications do not appear to cause problems but should be clue to the radiologist that the patient had ablation and to search for other potential complications.