Intraluminal Esophageal Temperature Monitoring Using the Circa S-Cath™ Temperature Probe to Guide Left Atrial Ablation in Patients with Atrial Fibrillation
Lisa WM Leung, Zaki Akhtar, Jamal Hayat, Mark M Gallagher
Dr Lisa WM Leung St George’s Hospital,Blackshaw Road,London SW17 0QT
Bhuta S et al1 have recently published an interesting study investigating the usefulness of esophageal temperature probe monitoring to guide left atrial ablations. Avoidance of esophageal injury during left atrial ablations remains an important area of study to prevent severe thermal injury that may manifest as esophageal-pericardial or atrio-oesophageal fistulas, both potentially life-threatening conditions.
There are a wide range of commercially available esophageal temperature monitoring probes; the one investigated by Bhuta et al was the S-Cath (Circa Scientific LLC, Englewood, CO, USA), a multi-sensor probe with 12 insulated sensors placed uniformly along the length of the device. The probe’s physical profile differs from other devices: It is flexible and self-expands into an S profile, with the purpose of delivering data from the full length and width of the portion of the esophageal lumen that is exposed to thermal threat. The advantage with this design is that it may avoid the need to adjust the probe position during ablation.
The study methods involved reducing the power of the ablation by 10W if temperatures rose above 39 degrees or if the rate of temperature rise exceeded 0.2degrees per second. If temperature rise continued despite dialling down on the power, ablation would be halted and the same endoscope probe that was to be used post-procedure to evaluate for thermal lesions was used to mechanically deviate the esophagus. Temperature measurements were therefore used reactively to trigger multiple protection strategies: ablation power limitation, force limitation and mechanical deviation of the esophagus.
The timing of the endoscopy was split into 2 groups, either immediately post-ablation with the temperature probe still in situ (n=18) or to the following day (n=18). It was not clear as to why the timing of the endoscopy had to be split or how the patients were allocated to each time window. We note that in most contemporary studies of ablation-related thermal injury, endoscopy occurs at 12-72 hours post ablation. Immediate endoscopy post ablation may be less specific at identifying clinically important thermal lesions from ablation but instead identify more trivial lesions or mechanical trauma.
The study results were interesting: Lesions were observed in patients who had supposedly had the benefit of the protection of intensive temperature monitoring by the circa device, but many of these were interpreted as evidence of mechanical trauma. The manuscript did not include enough data or photographic evidence to verify this interpretation. A sceptical viewpoint would be that the study yielded 5/36 (13.9%) positive endoscopic findings, a rate of injury that is similar to most non-protected series.
A recent randomized trial investigating the efficacy of the S-Cath esophageal temperature monitoring probe compared to controls with no esophageal temperature monitoring during AF ablation found no evidence that its use reduced thermal injury- the S-Cath group had more endoscopically detected thermal lesions compared to controls (6/44, 13.6% versus 2/42, 4.76%; p=0.27).2 The study had a similar protocol to that of Bhuta et al, including the use of power titration after a significant temperature rises (>39°C). Apart from this study, only 1 other randomized trial addressed the value of esophageal temperature monitoring during AF ablation: The OPERA trial3 also which investigated the SensithermTM device (FIAB, Firenze, Italy) found no evidence that these probes reduced thermal injury.
Other methods for avoiding thermal injury to the esophagus include mechanical deviation and active thermal protection. Mechanical deviation devices suffer from the same lack of randomised trial evidence as the temperature monitoring devices. Active thermal protection, by contrast, has shown clear benefit in one substantial randomised trial,4 and supportive evidence from a meta-analysis of several earlier small studies.5 All methods are worthy of further study in this important aspect of AF ablation, but the trial evidence to date indicates a clear leader: Thermal protection rather than temperature monitoring or mechanical deviation is the most promising alternative.