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AF Symposium 2016

Hot Topic: Rotors! Rotors! Rotors! Good News for Patients with Persistent A-Fib

by Steve S. Ryan, PhD

Rotors have become increasingly important in treating and ablating Atrial Fibrillation, particularly for Persistent A-Fib.

Rotors was such a hot topic, one could have called this year’s symposium the “2016 Rotor Symposium”.
If you have Persistent (or Long-standing A-Fib), you’ll want to seek out and be treated by EPs who understand rotors and recognize their importance.

Can Fibrotic Heart Tissue be Ablated?

Many EPs don’t ablate A-Fib patients with a high level of fibrosis and consider fibrotic areas as non-ablatable.

However, Dr. David Wilber of Loyola University Medical Center, Chicago, IL, found that patients with high levels of fibrosis can be successfully ablated by first examining the fibrotic areas for the presence of rotor circuits (i.e. A-Fib signal sources). Then, by ablating with both FIRM and high resolution optical mapping. This is a major new discovery.

Dr David Wilber Loyola University

Dr David Wilber Loyola University

In his presentation, “Impact of Atrial Fibrosis on Rotor Frequency and Location: Evidence from Combined Imaging and Mapping Studies,” Dr. Wilber began by examining a study by RS Oakes of 81 patients (50% had Paroxysmal A-Fib) which analyzed each patient using ‘Delayed-Enhancement Magnetic Resonant Imaging’ (DE-MRI).

Measuring Fibrotic Heart Tissue

Fibrotic heart tissue (scar tissue) is often found in patients with Atrial Fibrillation, particularly those with Persistent or Long-standing Persistent A-Fib.

DE-MRI is an MRI process which uses a metallic dye to see in 3D and identify fibrotic areas in the heart.
‘Delayed-Enhancement Magnetic Resonant Imaging’ (DE-MRI) can be used to precisely define scar tissue. As identified by DE-MRI, fibrotic heart tissue may be “low voltage”, that is, having little or no electrical activity.

In the Oakes research, “moderate” fibrosis was defined as heart tissue with 15%-35% fibrosis (low voltage) and was found in 30 patients. “Extensive’ fibrosis was defined as heart tissue with fibrosis greater than 35% and was found in 8 patients.

Fibrotic Patients and Persistent A-Fib

The Oakes study found that patients with moderate or extensive fibrosis were more frequently in Persistent A-Fib (70% vs 32%). This was true even when compared to factors such as expanded Left Atrium (LA) volume and having been in Persistent A-Fib before the ablation.

Intuitively, this makes sense. One would expect in the A-Fib remodeling process that patients with more fibrosis would be more likely to develop persistent A-Fib. (Perhaps extensive fibrosis is the reason Persistent A-Fib is harder to cure.)

Amount of Fibrosis and Recurrence Post Ablation

Dr. Wilber also discussed the DECAAF trial (see Marrouche High Fibrosis Precludes Catheter Ablation) which found fibrosis was the strongest predictor of recurrence after an ablation.

Rotors Anchored In or Located at the Edge of Fibrosis Regions

Dr. Wilber cited two additional studies. A study by BJ Hansen found that rotors are anchored to fibrotic areas of the heart. These rotor circuits can be identified and ablated by both FIRM and high resolution optical mapping. A study by McDowell found that the pattern or shape of fibrosis helps determine rotor formation.

Dr. Wilber’s Research on Left Atrium Rotors & Fibrosis

Dr. Wilber next presented his own research study. He and his colleagues used FIRM guided ablation in the examination of LA rotors and fibrosis. They first positioned the FIRM basket catheter in the right atrium and ablated rotors. They then moved to the left atrium and, after the FIRM rotor ablations, they performed a wide area circumferential Pulmonary Vein Isolation (PVI). They found more rotors (167) than focal sources (1).

Dr. Wilber and his colleagues found:

• 90% of rotor cores contained detectable fibrosis.
• The median regional fibrosis within individual rotor cores was only 13%.
• There was no relationship between the amount of fibrosis and both the number of rotors and the regional fibrosis of rotor cores.
• The mean amount of fibrosis in patients was 14.8%.

Summary and Conclusions

Summing up these research studies, Dr. Wilber concluded:

• The vast majority of rotor cores are associated with MRI detected fibrosis (90%)
• Measures of global atrial fibrosis do not predict number of identifiable rotors
• There is preferential location of rotor cores at the periphery of more dense regions of fibrosis
• Micro-anatomic distribution of fibrosis, and its impact on local electrophysiological properties, is likely to have additional influence on rotor formation, and specific sites of rotor stability.

Bottom-line for Patients with Persistent or Long-standing Persistent A-Fib

High Fibrosis Areas Can Be Ablated: While many EPs don’t ablate patients with a high level of fibrosis and consider fibrotic areas as non-ablatable, Dr. Wilber’s research shows that rotors (A-Fib signal sources) are located at or anchored in regions of fibrosis that can be ablated―particularly now that EPs know where to look for them. This may change the way mapping and ablations are done.

Good News: Patients with high fibrosis areas can be ablated.

The Amount of Fibrosis Doesn’t Predict the Number of Rotors: This is a surprising result (and needs to be confirmed by further study). This is good news for patients! Just because you have a lot of fibrosis doesn’t necessarily mean you have a lot of rotors (A-Fib signal sources). Your ablation won’t necessarily be more extensive than someone else’s.

What This Means to Patients: This fibrosis research is yet another reason for patients not to live in A-Fib! Living with A-Fib increases the risk of developing persistent A-Fib which is harder to cure. 

References for this article
Oakes RS et al. Detection and quantification of left atrial structural remodeling with delayed-enhancement magnetic resonance imaging in patients with atrial fibrillation. Circulation, 2009 April 7;119(13): 1758-67. doi: 10.1161/circulationaha.108.811877. Epub 2009 Mar 23.

DECAAF Trial: Delayed-Enhancement MRI (DE-MRI) Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation.

O’Riordan, M. DECAAF: Targeting MRI-Identified Fibrosis During Ablation Improves Outcomes. Heartwire (Conference News).  Sept. 01, 2013.

Hansen BJ et al. Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub-endocardial optical mapping in explanted human hearts. Eur Heart J 2015 Sept. 14;36(35):2390-401. doi: 10.1093/eurheartj/ehv233. Epub 2015 Jun 8

McDowell, KS. Virtual Electrophysiological Study of Atrial Fibrillation in Fibrotic Remodeling. PLOS One, February 18, 2015. DOI: 10.1371/journal.pone.0117110

Return to 2016 AF Symposium Reports by Steve Ryan, PhD

If you find any errors on this page, email us. Y Last updated: Saturday, February 16, 2019

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