Editor – I read with interest the case of diaphragmatic paralysis presented by Keelan at al.1 As they stated in their article, an iatrogenic cause should be considered; however, one they failed to mention, which is important for the physician to be aware of, is following pulmonary vein isolation for the treatment of atrial fibrillation.
The number of pulmonary vein isolations being performed is steadily increasing.2 At present, two main strategies exist: point by point ablation with radiofrequency energy or freezing using an expandable balloon catheter (cryoballoon). Although both are associated with phrenic nerve palsy, cryoballoon ablation has the higher complication rate reported over a number of studies (4.6–11.2% versus 0–0.3%).3 The majority of complications result in a temporary paralysis with an average recovery time of 4 months; however, permanent paralysis has been recognised.4 A right-sided unilateral palsy is the commonest reported because of the proximity of the right phrenic nerve to the right-sided pulmonary veins (especially the right superior vein). Intra-procedural phrenic nerve stimulation to monitor for complications during cryoballoon ablation has cut the rates of injury significantly5 and is routinely used at our centre.
Iatrogenic phrenic nerve palsy following pulmonary vein isolation can be easily overlooked as a potential cause both by the patient and clinician, particularly when the presentation is weeks after the procedure and our medical admissions units are frequented by breathless patients with exacerbations of chronic lung disease (personal experience). A higher index of suspicion should be employed, with earlier use of appropriate investigations.
Conflicts of interest
The author has no conflicts of interest to declare.
References
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