Fehmi Keçe

Advances in Atrial Fibrillation Ablation Devices 53 2 during superior vena cava pacing with a decapolar catheter. CMAP signals were amplified using a bandpass filter between 0.5 and 100 kHz and recorded on a recording system (Prucka, GE Healthcare, Milwaukee, WI). The technique is well-described with figures by Lakhani et al. (142). The ablation is terminated after reaching a 30% reduction in CMAP, which resulted in a faster recovery of phrenic nerve injury compared to manual palpation (143). Abortion of the freeze cycle during cryoballoon ablation (‘double stop’ technique: immediately ablation termination with direct balloon deflation) is an important additional manoeuvre to prevent permanent nerve injury (143, 144). Measuring of CMAP has reduced PNP incidence to 1% compared to 4-11% with manual palpation (145). 2.8.4 Oesophageal/Vagal nerve injury Reduction of radiofrequency power to 20-25 watts aims to prevent oesophageal injury, atrial-oesophageal fistulae and vagal nerve injury causing gastric hypo-motility (146). Oesophagus and /or vagal nerve damage can be prevented by monitoring of the oesophageal temperature during ablation (147-149), with a reduction from 36% to 6% in RFCA (150) and from 18.8% to 3.2% in cryoballoon ablation (148). Temperature cut- offs may be considered safe are <38.5˚C for RFCA and >15˚C for cryoballoon procedures (148, 150). However, the use of temperature monitoring during RFCA is still under debate. Employment of temperature probes during RFCA has been associated with a higher incidence of oesophageal injury (30vs.2.5%; p<0.01) and using the temperature probe has been identified as independent predictor (151). It has been hypothesized that the probe may act as an antenna drawing RF energy to the oesophagus (152). Other methods for prevention of oesophageal damage are active cooling with saline (153), changing the oesophagus position with a deviation tool and visualization of the posterior wall and oesophagus with image-integration and electro-anatomical mapping (154-157). Whether prescription of prophylactic proton-pump inhibitors can prevent oesophageal damage needs further investigation. 2.8.5 Pulmonary vein stenosis Pulmonary vein stenosis is likely an underdiagnosed complication after AF ablation which may be due to the lack of specific symptoms (158). The most important step to reduce the risk of PV stenosis is to avoid ablation inside the PVs by careful determination of the PV ostia before ablation.