AF Symposium 2016
Thickening of Left Atrium and Amount of Fibrosis Predicts Outcome of A-Fib Ablation
by Steve S. Ryan, PhD
Dr. Nassir F. Marrouche, University of Utah (CARMA), is known for ground-breaking, thought-provoking research using MRI. His presentation was entitled “Atrial and Ventricular Myopathy: A Novel risk predictor for stroke and cardiovascular events.”
Amount of Fibrosis Better Predictor of Stroke Risk (and Heart Attack)
Dr. Marrouche began by showing how today’s stroke guidelines (CHADS2 or CHA2DS2-VASc) are mediocre predictive tools overall, according to most studies. Whereas atrial fibrosis detected by Delayed Enhancement-MRI (DE-MRI) is a better predictor of stroke risk.
DE-MRI stands for Delayed Enhancement Magnetic Resonant Imaging.
In Dr. Marrouche’s study, patients with more than 21% fibrosis had a 19.6% risk of stroke while those with under 8.5% fibrosis had only a 1% risk. The more fibrosis, the greater risk of clots forming in the Left Atrial Appendage (LAA).
In a study by King, higher levels of fibrosis were associated with ‘Major Adverse Cardiac Events’ (MACE), not only stroke but heart attack and deep vein thrombosis (a blood clot within a vein).
Cardiomyopathy and Fibrosis
Dr. Marrouche showed slides of normal atrial myocytes (muscle cells) vs. examples with extensive fibrosis where collagen replaced most of the red myocytes (which store oxygen until needed for muscular activity).
This is an important finding which may change the way we look at fibrosis.
This fibrosis correlated with abnormality of the atria (atrial myopathy) and deterioration of the ability of heart muscles to contract (cardiomyopathy). This is an important finding which may change the way we look at fibrosis.
(For further information on Dr. Marrouche’s work, see Higher Fibrosis at Greater Risk of Stroke and Precludes Catheter Ablation.)
Fibrosis/Myopathy Correlates with Atrial Strain
Dr. Marrouche showed slides of how the left atrium of an A-Fib patient with extensive fibrosis worked much harder to pump and had nearly three times more strain than a patient with mild fibrosis. (This may be why the left atrium often stretches and expands in remodeling.)
A-Fib Thickens Left Atrial Shape
In another ground-breaking observation, Dr. Marrouche showed slides of how the shape of the left atrium (LA) gets thicker as one progresses from no-A-Fib to paroxysmal to persistent A-Fib. In fact, in a study by Bieging, LA shape (thickness) is a strong independent predictor of outcome after AF ablation.
Left Atrial Appendage and Stroke Risk
Dr. Marrouche found that the Left Atrial Appendage (LAA) length, thickness and orientation correlate with stroke risk. These findings open up new avenues of research in A-Fib. Just looking at the LAA might produce an indication of stroke risk, which can be combined with other predictive measures.
Left Ventricular Disease Predicts Recurrence after Ablation Therapy
Some A-Fib patients also have a diseased Left Ventricle (LV) which shows up using ‘Late Gadolinium Enhancement- MRI’ (LGE-MRI). In a study by Suksaranjit, the recurrence rate after an ablation was 69% in patients with Left Ventricular LGE-MRI revealed disease, compared to 38% in patients without LV LGE-MRI. These patients also have more major adverse cardiac and cerebrovascular events.
Dr. Marrouche is now using both the amount of fibrosis and left atrial shape to stage and treat A-Fib patients. The main points we can learn from Dr. Marrouche’s research are:
Fibrosis makes the heart stiff, less flexible and weak, overworks the heart, reduces pumping efficiency and leads to other heart problems.
• Fibrosis puts you are greater risk of a stroke and other vascular problems.
• More fibrosis leads to thickened heart tissue, strains the heart and reduces the ability of the heart muscles to contract.
• A-Fib changes the thickness/shape of the left atrium.
• A-Fib can also change the length, thickness and orientation of the Left Atrial Appendage (LAA).
• Left Ventricular disease may accompany or be caused by A-Fib, be measured by MRI, and predict recurrence after catheter ablation..
What Patients Need To Know
Don’t delay! Your A-Fib leads to fibrosis! A-Fib produces fibrosis which is considered permanent and irreversible. Any treatment plan for A-Fib must try to prevent or stop remodeling and fibrosis.
Caveat: After reading Dr. Marrouche’s research and new insights that atrial fibrosis detected by DE-MRI is a better predictor of stroke risk (than CHADS2 or CHA2DS2-VASc), don’t rush into your EPs office asking about using MRI to diagnose your amount of fibrosis. Not every MRI technician and doctor has the special training and experience necessary to perform Dr. Marrouche’s testing. (And insurance companies may not want to pay for this testing. However, that may soon change.)
If you find any errors on this page, email us. Y Last updated: Monday, February 22, 2016