Abstract
Ablation for
atrial fibrillation (AF) is an important and exciting therapy whose results
remain suboptimal. Although most
clinical trials show that ablation eliminates AF more effectively than
medications, it is disappointing that the continued single procedural success
remains ≈50% despite the substantial advances that have taken place in imaging,
catheter positioning and energy delivery. Focal impulse and rotor modulation
(FIRM), on the other hand, offers the opportunity to precisely define and then
ablate patient-specific sustaining mechanisms for AF, rather than trying to
eliminate all possible AF triggers. For
over a decade, electrophysiologists have described cases in which AF terminates
after only limited ablation – usually that cannot be explained by ‘random’
meandering wavelets. Indeed, recent
studies from several laboratories show that all forms of clinical AF are
typically ‘driven’ by stable electrical rotors and focal sources, not by
multiple meandering waves. FIRM mapping
enables an operator to place a catheter at typically 1-3 predicted sites in the
atria, and with <5-10 minutes of RF ablation, terminate AF and potentially
render it non-inducible. Several
independent laboratories have now shown that such FIRM ablation alone can
terminate or substantially slow AF in >80% of patients with persistent and
paroxysmal AF and increase the single procedure rate of AF elimination from 50%
with PV isolation alone to >80%.
Ongoing studies hint that FIRM only ablation, enabling ablation times in
the range observed for typical atrial flutter, may also achieve these high
success rates without subsequent trigger ablation. This
review summarizes the current state-of-the-art on FIRM mapping and ablation.
Credits: Ruchir Sehra MD FHRS; Sanjiv M. Narayan, MD, PHD; FHRS,John Humme, MD