Case reportVagus nerve injury after posterior atrial radiofrequency ablation
Introduction
Radiofrequency ablation of the posterior left atrium is required for the treatment of various arrhythmias.1 For atrial fibrillation (AF) therapy, extensive posterior atrial ablation is performed, particularly when targeting complex fractionated electrograms or for the transmural ablation of autonomic ganglia.2, 3, 4 Thermal injury resulting in atrial–esophageal fistula has been reported from collateral injury with such ablation.5, 6, 7
The vagus nerve also courses posterior to the left atrium, which also makes it vulnerable to injury (Figure 1). Vagal branches form a single cord that then runs posterior to the esophagus, enters the abdomen, and contributes to the celiac and lineal plexus, stomach, lesser omentum, and liver.8, 9 The physiology of vagus nerve injury depends on the level at which nerve damage develops and the downstream organs are innervated. For example, vagus nerve–mediated parasympathetic stimulation of the sinoatrial node, atrioventricular node, pulmonary veins, and myocardium results in slowing of the sinus and ventricular rates and can increase atrial fibrillation inducibility.2 Ablation of vagus nerve fibers above or at the regions at which they enter the heart will increase the heart rate and reduce AF inducibility.2, 3 In the gastrointestinal tract, vagus nerve fibers control peristalsis, pyloric sphincter relaxation, and gastric antrum motility.10 Injury to the vagus nerve above these organs can result in gastroparesis and pyloric spasm manifested as abdominal bloating, pain, nausea, early or easy satiety, and weight loss and has been described.11, 12, 13
We report a series of patients with postablation vagus nerve injury and discuss the utility of systematic clinical and laboratory evaluation to document and understand the level of vagus injury.
Section snippets
Patient 1
A 47-year-old woman with highly symptomatic AF refractory to flecainide and sotalol presented for left atrial catheter ablation. Radiofrequency (RF) energy at an outside institution was delivered with a 3.5-mm irrigated catheter (NaviStar ThermoCool, Biosense Webster, Diamond Bar, CA) with irrigation flow rate (17 to 30 ml/min; OIC-2) and a power setting up to 35 W. All 4 pulmonary veins were isolated using lasso and intracardiac echocardiogram (ICE) guidance with additional ablation in the
Clinical evaluation
Injury to the autonomic nervous system can be seen early after ablation for AF.14 If the vagal mediated parasympathetic nervous system is impacted, the patient may have an increased heart rate with reduced heart rate variability.14 In patients with more extensive ablation outside the pulmonary veins, the effects of injury to the autonomic nerve inputs can be seen up to 1 year later.15 Partial vagus nerve injury during ablation could be beneficial because targeted elimination of vagal inputs has
Treatment
After the diagnosis of vagus nerve injury is established, management of the gastric paresis and pyloric spasm is based on symptoms (Figure 4). Oral intake is often restricted to small, low-fat meals without foods containing indigestible fiber.23 Prokinetics in those individuals with documented paresis may enhance muscular contractility and provide some benefit.23 Patients with persistent symptoms after these initial therapies may require more aggressive options, such as botulinum toxin
Outcomes
In this case series, 1 patient completely recovered. A second patient has mild symptoms that were managed primarily by diet. The third patient continued to remain very symptomatic from inappropriate sinus tachycardia, although the gastric symptoms had largely resolved. In the prior study by Shah et al,13 the histories and outcomes of 4 patients with vagal injury after ablation for AF were reported. Two patients recovered completely, but as stated above, the other 2 required intervention because
Conclusion
Current ablative approaches along the posterior left atrium are associated with the risk of vagus nerve injury. The diagnosis of gastroparesis, pyloric spasm, and vagal injury can be made noninvasively. Early diagnosis is important to begin targeted therapy to minimize excessive weight loss and gastrointestinal symptoms. Dietary, pharmacological, and occasionally invasive therapies do relieve symptoms, with most patients reporting significant improvement over time.
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