In existing academic literature published in the last two years, there is a broad consensus that existing esophageal temperature monitoring techniques do not provide sufficient visibility to reliably protect the esophagus from heat damage during atrial fibrillation ablation. The dearth of new patents in this area would seem to reinforce that existing temperature probes are a dead end. Consequently, significant research has been allocated to find better methods to protect the esophagus rather than relying on temperature readings. However, However, two imaging techniques have been recently tested that appear promising: High-resolution esophageal temperature monitoring using IRTS and ultrasound thermal imaging.
The details of our findings can be found below. Note that due to the criterion specifying emerging technologies, we have focused on techniques that have been tested or otherwise discussed in scientific literature within the last two years. Additionally, due to the highly-technical nature of this brief, we have used an unusual number of extended quotes rather than risk paraphrasing incorrectly.
Problems in Esophageal Temperature Monitoring in Ablation Therapy
While it is taken as a given that luminal esophageal temperature (LET) monitoring is crucial to avoid injury and even death as a complication of atrial fibrillation ablation therapy, the most recent evidence indicates that the traditional method of inserting a temperature probe into the esophagus is, at best, ineffective.
- A review of academic works published in the last few years finds a growing consensus that existing esophageal temperature monitoring methods fall short. For example:
- A 2018 article published in Trends in Cardiovascular Medicine notes, “Luminal esophageal temperature (LET) monitoring is one of the most commonly utilized strategies to mitigate this risk, despite little evidence that it reduces esophageal injury. The incidence of AE fistulae appears to be on the rise, despite the widespread use of LETluminal esophageal temperature monitoring.”
- At least one test showed that “multi-sensor measurement of esophageal temperature appeared to exacerbate the problem,” though whether this was an engineering problem or one of the sensors fostering over-confidence in the operator is a matter of dispute.
- A January 2020 Heart Rhythm article determined another problem in using esophageal temperature monitoring: “Significant LET increase will be undetected when lesions are >20 mm away from a temperature sensor.”
- A May 2020 article published in Heart Rhythm concurs: “Among patients undergoing AI-HP (50 W) PVI, the incidences of ablation-related endoscopic esophageal lesion in patients with and those without use of a temperature probe for LET monitoring (cutoff 39°C) were comparably low.”
- An August 2020 study found that “intraoesophageal temperature monitoring using the SensiTherm™ probe does not affect the probability of developing EDEL.”
- A search of Google’s patent database finds only a single patient that seems directly related to this brief’s criteria (see below). However, several patents note the challenges associated with esophageal temperature monitoring, including “its reactive nature” and a “recent study [that] showed that over 6% of patients exhibited evidence of esophageal ulceration after catheter ablation … despite the use of luminal esophageal temperature monitoring devices.”
- Due to the above, there have been attempts to develop alternative methods to mitigate esophageal damage during ablation procedures, such as esophageal cooling, using a balloon to deviate the esophagus away from the ablation site, electroporation, and controlled active thermal protection. Due to the lack of relevance to this project’s criteria, we did not seek more information about alternative treatments.
A Recently-Filed Patent
- Patent number US20190082969A1, labeled, “Ablation and temperature measurement devices,” includes a “temperature measurement apparatus for a patient.” This apparatus comprises a transmission conduit, an infrared fiber, a sensor assembly, and a display unit. We cannot determine from the description if there is anything novel in the approach or design of this apparatus from the barebones description in the patent.
While the traditional method of inserting a temperature sensor into the esophagus appears to be ineffective, perhaps even a dead end, imaging techniques are being developed to monitor and even map heat spikes during ablation which seem to hold more promise:
- A 2018 study published in Circulation: Arrhythmia and Electrophysiology concluded: “High-resolution esophageal temperature monitoring using IRTS allowed prediction of endoscopically detected EDEL after catheter ablation. An esophageal temperature cutoff of 50°C predicted the occurrence of EDEL with high accuracy while temperatures <50°C predicted no EDEL with high-negative predictive value of >97%. Infrared thermography seems to be a fast, accurate, and sensitive tool to monitor for esophageal temperatures during ablation and prospective studies applying specific cutoffs are needed to validate the utility of this novel temperature measurement system for prevention of EDEL, AEF, and other off-target effects of catheter ablation.”
- Another study found that “temperature monitoring with the use of ultrasound thermal imaging during the laser ablation on ex vivo porcine cardiac tissue” was feasible and could “map the spatial distribution of the tissue temperature.”
- A 2019 study published in Circulation: Arrhythmia and Electrophysiology found that LGE-MRI (late gadolinium enhancement magnetic resonance imaging) appears to be effective in the early detection of esophageal scar tissue as a result of ablation heat damage. Again, as this seemed outside of the project criteria, we did not seek additional information.