2017 AF Symposium: Live Case of Ablation with FIRM Mapping System
In a live case, Dr. David Wilber from Loyola Un. Medical Center in Chicago, IL showed how he uses the Topera FIRM rotor mapping system to identify rotors in conjunction with a PVI. ‘FIRM’ stands for Focal Impulse and Rotor Modulation.
Patient background: The patient was a 54-year-old male in persistent A-Fib for 7 months, obese with a BMI of 31, hypertension, diabetes, and obstructive sleep apnea. He was symptomatic, with fatigue and decreased exercise tolerance. An MRI showed his Left Atrium was 15.5% fibrotic. (If using Dr. Nassir Marrouche’s Utah I–IV Classification System to rate the patient’s amount of fibrosis, this patient would be “Utah Stage 2”, i.e., a reasonable candidate for a catheter ablation.)
Voltage & FIRM Mapping: Rotors Ablated First
In live video streaming from Chicago, Dr. Wilber described how he first does voltage mapping while the patient is in normal sinus rhythm. He started in the right atrium, then moved to the left; he used the FIRM system to map where rotors were coming from. (In patients with persistent A-Fib, he typically finds as many as 4-8 rotors.) He mapped and ablated until there were no more rotors.
Only after using the FIRM system did he do a Pulmonary Vein ablation (PVI).
He explained that the concept of terminating A-Fib during a PVI ablation doesn’t work with the FIRM system. Instead, he looks to ablate rotational areas (which are usually 2.2 cm across). He does by with using a Contact Force sensing catheter usually at 35 watts for 30 sec.
During this ablation, he found one rotor at the base of the Left Atrial Appendage (LAA). (In the followup panel discussion, Dr. Andrea Natale commented that his colleagues now look first for A-Fib signals in the LAA.)
FIRM Rotors Hard to See
VIDEO examples: Dr. Wilber showed a video using FIRM in which [even to my untrained eye] it was easy to see a rotor. But he showed other videos where the overlapping, swirling waves made it difficult to see where exactly a rotor was coming from.
This patient was at great risk of recurrence after a catheter ablation, because of his various illnesses (comorbidities). By restoring him to normal sinus rhythm, he would be able to exercise and develop life-changing habits to reduce his obesity, diabetes, and hypertension.
Topera FIRM vs Medtronic ECGI CardioInsight: In comparison to the ECGI CardioInsight system where the rotors and focal sources are very obvious (even to untrained observers), the FIRM system display of rotors are often confusing and hard to identify. Dr. Wilber acknowledged that it takes study and experience with the FIRM system to use it effectively.
To me, the Topera FIRM system seems hard to use. In head-to-head competition with the Medtronic ECGI CardioInsight system, I predict the FIRM system will probably not survive.
The Medtronic ECGI CardioInsight system has been in limited use in Europe and in 2017 has begun a limited rollout in the U.S.
For more on the Medtronic ECGI CardioInsight, see my article: ECGI Mapping Now Available in U.S.