Patients with atrial fibrillation who received ablation while they were already undergoing surgery to correct a leaky heart valve had fewer episodes of atrial fibrillation a year later compared to patients who had the valve surgery alone, according to a study. The patients who received ablation along with mitral valve surgery had no more deaths, adverse cardiac events or hospitalisations than patients who only received the valve surgery alone, but they were more likely to require a pacemaker.
The study, which included 260 patients within the Cardiothoracic Surgical Trials Network, a clinical research network involving 20 US and Canadian hospitals, is the first appropriately powered randomised clinical trial to assess the use of ablation in patients already undergoing mitral valve surgery. Half of the patients were randomly assigned to receive mitral valve surgery alone, while the other half also received surgical ablation. All of the study participants had persistent or long-standing persistent atrial fibrillation and were undergoing surgery to repair or replace the heart's mitral valve, which controls movement of blood from the left atrium to the left ventricle.
Of the patients who received ablation and mitral valve surgery, 63% were free from atrial fibrillation at six and 12 months after surgery, while 29% of patients who received mitral valve surgery alone were free from atrial fibrillation at those time points. Mitral valve surgery is typically performed to correct a leaking or narrowed valve. Although the procedure is unrelated to atrial fibrillation, many patients in need of valve repair also have atrial fibrillation, so surgeons have begun combining the two procedures in order to address both cardiac issues at the same time.
"Although surgeons are widely performing ablation at the time of mitral valve surgery, there is a great deal of variation with regard to when it is done, how it is done and which patients receive it," said Dr Marc Gillinov, the Judith Dion Pyle chair in heart valve research at Cleveland Clinic and the study's lead author. "We sought to conduct a well-designed randomized controlled trial to answer fundamental questions about whether this procedure is successful and how it is best done."
In the absence of strong clinical guidance regarding the use of ablation with mitral valve surgery, the decision is left largely up to physician preference, Gillinov said. About two-thirds of surgeons currently perform ablation during mitral valve surgery for patients with persistent atrial fibrillation, while one-third do not.
While the patients receiving ablation were significantly more likely to be free of atrial fibrillation six and 12 months after surgery, the study showed no significant differences in rates of death, adverse cardiac events or hospitalisation. Patients receiving the mitral valve surgery alone reported a slightly lower quality of life because more of these patients said they still experienced daily atrial fibrillation a year after the surgery.
"I think what this shows is that, in the mitral valve surgery patient who has persistent atrial fibrillation, you will achieve better rhythm control by performing ablation, without any increase in mortality or other adverse cardiac events," Gillinov said.
However, the analysis also revealed one potential downside to including ablation with mitral valve surgery. Patients receiving the ablation along with the mitral valve surgery were 2.5 times more likely to require the implantation of a pacemaker in the year following their surgery. The reason for this difference is unknown and warrants further study, Gillinov said.
Because there are several tools and techniques physicians can choose when performing surgical ablation, researchers decided to randomly assign patients receiving the ablation to either pulmonary vein isolation, in which the surgeon uses heat or cryothermy energy to destroy a small area of tissue in the heart, or a bi-atrial Maze lesion, in which the surgeon makes a complex series of lesions to correct abnormal electrical impulses. The analysis showed no significant differences in the outcomes for patients undergoing the two procedure types, though a larger study would help to elucidate any differences, Gillinov said.
Because patients have only been tracked for one year, the results do not yet provide a clear picture of the full spectrum of potential differences in cardiovascular outcomes. The researchers will continue to track patients to assess any long-term differences in survival, hospitalisation, stroke and other outcomes.
In a further study among patients with heart failure and atrial fibrillation, it was found those who underwent catheter ablation were less likely to die, be hospitalised or have recurrent atrial fibrillation than patients taking a heart rhythm regulating drug. Catheter ablation was most successful in procedures where ablation was required in other areas in addition to the pulmonary vein, researchers said.
Heart failure and atrial fibrillation often co-occur and are two of the most common heart problems in older adults. In the new study, 71% of patients treated with a surgical procedure called catheter ablation were free of atrial fibrillation, the study’s primary endpoint, after two years of follow-up, while only 34% of patients who took the anti-arrhythmic drug Amiodarone were free of symptoms at that point.
"Even when it is effective, Amiodarone often needs to be discontinued after a while due to serious long-term side effects," said Dr Luigi Di Biase, a cardiologist and electro-physiologist at St David's Medical Centre and the Albert Einstein College of Medicine at Montefiore Hospital and the study's lead author. "Our study suggests that in patients with heart failure and atrial fibrillation, catheter ablation is an effective alternative treatment that can help patients avoid or discontinue this drug to reduce the risk of these long-term side effects."
An estimated 5.6m US adults have the abnormal heart rhythm known as atrial fibrillation. Patients with both conditions are at especially high risk of serious complications and death. Amiodarone helps to regulate the heart's rhythm in these patients by relaxing the heart muscle.
"It is very important to control persistent atrial fibrillation in patients with heart failure," Di Biase said. "These patients need every bit of blood that the heart can pump, so it becomes particularly dangerous when an arrhythmia happens. People with both of these conditions frequently wind up in the hospital."
The study included just over 200 patients treated in eight European and US hospitals. All patients had heart failure, atrial fibrillation and either an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy with defibrillator (CRT-D), two medical devices that are commonly placed in patients with these conditions to control life-threatening arrhythmias or help the heart pump blood more effectively.
The researchers randomly assigned half of the patients to undergo catheter ablation, a surgical procedure in which doctors thread thin, flexible wires into the heart through blood vessels in the arm, groin or neck. These wires are used to deliver energy or heat that destroys the areas of heart tissue that cause the abnormal heart rhythm. The rest of the patients were treated with Amiodarone.
In addition to having a higher rate of freedom from atrial fibrillation, participants who underwent catheter ablation also had lower rates of hospitalisation and mortality during the two-year follow up. 31% of patients receiving ablation were subsequently hospitalised compared to 57% of patients taking Amiodarone; 8% of patients receiving ablation died during the course of the study compared to 18% of patients taking Amiodarone.
Di Biase said the type and extent of the ablation procedure had a marked impact on the procedure's success rate. "If the ablation is limited to the pulmonary vein alone, the success rate goes down – almost to the level of the Amiodarone treatment," Di Biase said. "The highest success rates were for procedures in which other areas (in addition to the pulmonary vein) were ablated."
The specific areas that benefit from additional ablation depend on each patient’s individual condition. In addition, many patients in the study required more than one ablation procedure to achieve freedom from atrial fibrillation. Di Biase said another limitation of the study is that not all hospitals have the experience and equipment necessary to properly perform catheter ablation. As a result, the advantage of ablation over Amiodarone might not be as dramatic outside of top-tier hospitals. Further research would help to track the procedure’s effectiveness in a broader variety of circumstances.
[link url="http://www.acc.org/about-acc/press-releases/2015/03/16/12/20/ablation-during-mitral-valve-surgery-reduces-atrial-fibrillation?w_nav=S"]American College of Cardiology material[/link]
[link url="http://www.nejm.org/doi/full/10.1056/NEJMoa1500528"]New England Journal of Medicine abstract[/link]
[link url="http://www.acc.org/about-acc/press-releases/2015/03/16/11/26/heart-failure-patients-fare-better-with-catheter-ablation-than-amiodarone?w_nav=S"]American College of Cardiology material[/link]
[link url="http://www.acc.org/latest-in-cardiology/clinical-trials/2015/03/15/16/52/aatac-af?w_nav=S"]ACC 2015 abstract[/link]