Predictors of Atrial Fibrillation Catheter Ablation Success — Presentations from Heart Rhythm Society
June 4, 2010 12:17 AM CT
By Christine Welniak and Mellanie True Hills
The Second Worldwide Multicenter Survey on Catheter Ablation showed a catheter ablation success rate of 70% for atrial fibrillation, but that still leaves a significant number of people who continue to have afib even after a procedure. This can be disheartening to patients and physicians alike. Why undergo an interventional procedure, such as catheter ablation, if it isn’t likely to cure AF?
That’s why doctors are trying to identify characteristics that predict which patients aren’t likely to respond to catheter ablation. That was the topic of a session we attended at the recent Heart Rhythm Society annual meeting. Factors discussed in that session that could predict whether ablation will be successful include size of the left atrium, functioning of the left ventricle, time spent in afib, and extensive atrial fibrosis. We discuss those factors in this article, with the exception of atrial fibrosis, which was discussed by Dr. Marrouche and to which we devoted an entire article, Personalized Atrial Fibrillation Treatment Using New Method to “Stage” AF.
Left Atrial Size and Volume Matter
Dr. Mauricio Arruda, of Case Western University in Ohio, began his discussion with a reminder of the relationship between left atrial size and atrial fibrillation. The landmark Framingham Heart Study, which followed 5,070 patients for 34 years, showed that the larger the size of the left atrium, the greater the chance that afib will develop. An analysis of a subset of patients in the study showed that the risk of developing atrial fibrillation rose with every 5 millimeter increase in the size of the left atrium.
Could left atrial size affect ablation outcome, too? It might. Dr. Arruda presented results from one study of 108 patients, where over 40% of the individuals had early recurrence of afib after ablation. The authors of the study concluded that an enlarged left atrium was the only variable linked to early recurrence. Non-invasive tests, such as echocardiogram, CT (computed tomography) scan, and MRI (magnetic resonance imaging), can be used to determine the size of the left atrium.
Left atrial volume may also foretell ablation outcome. Of 146 patients in a study published last year, left atrial volume predicted early recurrence of AF following ablation. The same tests—echocardiogram, CT, and MRI—can also assess left atrial volume. However, Dr. Arruda indicated that some physicians may also want to perform a transesophageal echocardiogram (TEE), where a small ultrasound probe is inserted into the throat and moved down the esophagus toward the heart.
Left Ventricle Dysfunction
The left ventricle, which pumps blood from the heart to the body, may also affect ablation outcome. Left ventricle dysfunction, which is a compromised ability to pump blood, is linked to heart failure, which in itself is associated with the onset of afib. A Framingham Health Study analysis found that 41% of patients with an initial diagnosis of heart failure later developed atrial fibrillation and that heart failure worsened the prognosis of AF.
Impaired left ventricle function often leads to changes in the anatomy of the heart. For instance, the ostia (or openings) of pulmonary veins may be larger in people with left ventricle dysfunction, making it more challenging for physicians to achieve complete isolation of the pulmonary veins, which are trigger points for AF. In addition, left ventricle dysfunction can thicken the heart muscle, making ablation more challenging.
There have only been few a trials that have studied ablation in patients with compromised left ventricle function since most studies specifically exclude these individuals from participating. However, one study showed that 73% of patients with impaired left ventricle function had freedom from afib after ablation, which is on par with results for patients without heart failure. That said, 27% of patients with left ventricle dysfunction had a recurrence of afib – more than double that experienced by patients with normal left ventricle function.
Duration of Atrial Fibrillation
How long a person has had atrial fibrillation can affect the outcome of catheter ablation. In this case, duration does not refer to the length of time a person spends in afib, known as the “afib burden”, but rather refers to the number of years the person has had AF. It doesn’t matter whether it’s paroxysmal, persistent, or long-standing persistent atrial fibrillation.
Atrial fibrillation can lead to changes in the electrophysiological properties of the heart. This is known as “remodeling” and means that afib essentially creates new pathways for it to cycle or perpetuate in the heart. Over time, this tends to make AF more severe. For instance, a patient can be diagnosed with paroxysmal afib initially and then transition to persistent, and eventually long-standing persistent, afib. This progressive nature of atrial fibrillation is why doctors say, “Afib begets Afib”.
In general, the longer an individual has atrial fibrillation, the more difficult it may become to eliminate all the afib pathways in the heart. Dr. Wyn Davies, of St. Mary’s Hospital in London, who spoke on the topic at HRS, indicated that he typically doesn’t perform ablation on a patient who has had AF for five or more years.
Age Isn’t a Factor
Doctors have also looked at whether an individual’s age can predict the outcome of catheter ablation. Some physicians don’t perform ablation on individuals who are over the age of 70-75, though recent research could change that. In one study involving over 1,500 people, 86% of the patients aged over 75 were free from afib compared to 85% of those aged 65-74, and 89% of patients less than 65. That is, people above the age 75 had comparable success rates. However, some patients remained on antiarrhythmic medication following the ablation. The researchers noted some distinctions among the age groups. People under of the age of 65 were more likely to have repeat ablations to achieve normal sinus rhythm whereas patients in the eldest group were more likely to remain on antiarrhythmic drugs following ablation.
If you’re considering catheter ablation to treat afib, you may undergo tests to assess your left atrial size and volume as well as left ventricle function in order to determine the likelihood that the procedure will be successful. If you’re healthy, your age may not be a factor, particularly if you’re willing to take antiarrhythmic drugs after the procedure.
Overall patients can’t “control” the variables that could affect ablation outcome, but this session reminded us yet again that early diagnosis and treatment is critical to optimizing your outcome.
To learn more, read:
- Temporal Relations of Atrial Fibrillation and Congestive Heart Failure and Their Joint Influence on Mortality: The Framingham Heart Study, B. Wang, et al, Circulation, 2003.
- Pulmonary Vein Isolation for the Treatment of Atrial Fibrillation in Patients with Impaired Systolic Function, M. Chen, Journal of the American College of Cardiology, 2004.
- Long-Term Clinical Efficacy and Risk of Catheter Ablation for Atrial Fibrillation in the Elderly, E. Zado, Journal of Cardiovascular Electrophysiology, 2008. “Registration Required”
Christine Welniak writes about atrial fibrillation and other heart diseases/conditions for patients, medical professionals, and investors.
Mellanie True Hills is founder and CEO of StopAfib.org and an atrial fibrillation survivor.