Atrial Fibrillation Ablation: A Coming Storm
by David A. KulwickiM
Atrial fibrillation (AF), often called "A Fib," is a cardiac rate and rhythm disturbance that afflicts 250,000 Americans each year. Though not life-threatening, AF can cause distressing symptoms such as dizziness, palpitations and loss of consciousness, and increase the risk of stroke. Because the condition can be resistant to medicines, electrophysiologists (EPs) have been developing a procedure to eradicate the electrical impulse pathways within the heart that cause AF. The procedure, called ablation, uses a specially-tipped catheter to burn deep into the atria in an effort to block these errant pathways.
AF ablation is an extremely lucrative procedure, bringing up to $90,000 per procedure into the coffers of the EPs and hospitals that perform the procedure. Often, the procedure fails and must be repeated. Despite specious benefits and significant risks, as explained below, the procedure is being aggressively promoted by health care providers who understate the risks and oversell the benefits. Patients desperate for a cure from the discomforting symptoms of AF, many elderly, are an especially easy mark for these hyped-up sales pitches. In light of the large potential patient population, the financial allure for the health care industry and the high complication rate, expect a rash of medical negligence claims arising out of this new and dangerous procedure.
MORE ABOUT AF
AF is a cardiac rate and rhythm disturbance. During AF, the heart's upper chambers beat erratically due to errant electrical impulses. There are a number of recognized causes of AF, such as underlying heart or lung disease and hypertension, but often its origin is idiopathic. The condition afflicts 250,000 Americans each year. The risk of developing AF increases with age such that 8% of adults over the age of 80 have the condition.
AF is categorized as paroxysmal, persistent and permanent. Some authors group persistent and permanent AF into a single category called "chronic AF." Other authors make a distinction between persistent and longstanding persistent AF. There are currently no consensus definitions for the various categories of AF, but the category is important since the risks and benefits of the ablation procedure vary by category. Generally, the more longstanding and persistent the AF, the more ablation is required to treat it, resulting in greater risk and lower success rates.
The first line of treatment for AF consists of medications to control the characteristically rapid heart rate along with medications or electrical cardioversion to convert the arrhythmia to a normal rhythm. If these noninvasive modalities fail, there are several surgical options: "maze" I, II and III procedures and catheter ablation. Catheter ablation involves the use of a specially-tipped catheter that is threaded into the upper chambers of the heart and then used to disassociate the errant electrical pathways that cause the atrial fibrillation.
MORE ABOUT AF ABLATION
While a complete discussion of the development of AF ablation and the various catheters, mapping systems and techniques available is beyond this paper, certain issues are worth noting. Two catheters are used to perform AF ablation. One catheter, the mapping catheter, is used to map electrical signal within the heart that must be ablated. The second catheter, the ablation catheter, is used to actually perform the ablation. The ablation catheter can modify heart tissue either through freezing (cryoablation), ultrasound, lasers or, most commonly, radiofrequency. With radiofrequency ablation, electrical impulses are delivered to the heart tissue to burn lesions that are meant to prevent errant electrical impulses from stimulating fibrillation. The most common area for these errant electrical pathways is around the pulmonary veins. Radiofrequency ablation catheters are used to burn circles around the antrum, the area where the pulmonary vein connects to the atrium. Thus, the procedure is often called pulmonary vein isolation (PVI) ablation or pulmonary vein antrum isolation (PVAI) ablation.
Originally, the procedure was performed manually with two physicians standing next to the patient. Since the patient is under constant fluoroscopy during the procedure, manual ablation results in a significant radiation exposure to the operator. A remote procedure was developed to try to solve this problem. Remote catheter ablation is performed using magnetic tipped catheters that are guided through the patient's vasculature with external magnets. Both manual and remote procedures require two operators, one to operate the mapping catheter and another to perform the ablation. In addition, due to the novelty of the procedure and equipment, representatives of device manufacturers are often present during the procedure to assist.
The risks of the procedure include stroke, perforation and pulmonary vein stenosis among others. The risk of stroke exists due to the burning that occurs in the heart, which can form char and coagulum, and as a result of cardioversion. Cardioversion is performed before, during or after the procedure to return the patient to a normal sinus rhythm. Cardioversion results in muscle lability that reduces the effectiveness of the heart's pumping mechanism thereby increasing the risk of stroke. A number of strategies have been developed to reduce the risk of stroke. First, a transesophageal echocardiogram (TEE) is performed preoperatively to determine whether there is thrombus in the atria. If so, this is an absolute contraindication to the procedure. In addition, the patient is anticoagulated perioperatively. Anticoagulation strategies vary based on case-specific facts and the institution. Generally, the patient is given therapeutic doses of heparin during the procedure and maintained on Coumadin perioperatively.
The procedure is described as technically demanding, meaning that great skill and experience is required to ensure that the appropriate areas of the heart are ablated and to make sure that good contact is made between the tip of the catheter and the tissue meant to be ablated. The complication and success rates for the procedure vary with operator experience. In 2006, the American College of Cardiology and American Heart Association published guidelines for clinical competence in performing various interventional procedures, including catheter ablation. ACC/AHA 2006 Update of the Clinical Competence Statement on Invasive Electrophysiology Studies, Catheter Ablation and Cardioversion, J Am Coll Cardiol 2006; 48: 1503-1517.
IMPLICATIONS FOR PATIENTS
Virtually every aspect of catheter ablation remains under investigation. Further, the long-term effects of the procedure are unknown. At present, there is not even a consensus definition of what constitutes success from the procedure. Making matters worse, there is vast underreporting of complications caused by the procedure. Not only is there no systematic collection of outcomes from the procedure, but device manufacturers refuse to acknowledge that complications are device-related, so there is no reporting to the Manufacturer and User Facility Device Experience (MAUDE) database administered by the FDA. Certainly, individual EPs have no incentive to report their disasters as they try to develop new business.
Professional associations have set the bar low for physicians to advise patients that the procedure is indicated. HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Personnel, Policy, Procedures and Follow-Up, Europace 2007; 9: 335-379. This opens up the population base that can be offered the procedure. However, there are many patients that would benefit from further attempts at a trial of medicine or for whom the procedure is too risky, such as the elderly who have more friable heart tissue and may be more prone to perforations, but this research has not been done.
There has been a rush to promote the procedure because it is lucrative and patients are eager to be rid of the symptoms of AF. Abuses are inevitable. As an example, ablation catheter manufacturers were recently held liable for marketing the catheters even though they had not been approved by the FDA for use in AF ablation. Further, a recent study published in the Journal of the American Medical Association, touting the benefits of AF ablation, uses questionable scientific methods. Comparison of Antiarrhythmic Drug Therapy and radiofrequency Catheter Ablation in Patients with Paroxysmal Atrial Fibrillation, JAMA, 2010; 303: 333-340. The study uses a Bayesian method that is ripe for overestimating favorable results. The study is limited to paroxysmal AF - the easiest to treat and one that generally involves a younger patient population that would be less prone to complications. The study was also set up with a guarantee of success. In it, ablation was compared to drug therapy in people who had already failed at one drug. If you fail at one drug, you are likely to fail a second. Yet, the study was released with much fanfare and, at device manufacturer's expense, posted for free online with links to a patient information page.
The dangers of AF ablation are summarized by Douglas Morrison, MD, an EP who told an FDA panel after the 2010 study was released:
I can't think of a procedure in the history of medicine where we've gone to patients and say this is very expensive, it's very dangerous, we have no idea what good it does you, but we'd like to do it, and if we talk you into a trial, we're just going to see how many of you have serious adverse events....
[The study] starts with a population of low risk, young people, no structural heart disease and predominantly paroxysmal atrial fibrillation. And to put it bluntly, as a non EP person, I'm just anxious to give you all enough rope to hang yourselves, because I think it's very hard to demonstrate, even compared to beta blockers and calcium blockers, that ablation changes life very much.
EVALUATING AF ABLATION CASES
Most AF ablation cases will be based on a failure of informed consent due to the barriers to pursuing negligence claims. Barriers to negligence claims include the fact that intraoperative imaging is routinely discarded after the procedure, there are scant consensus statements or guidelines that establish standards of care and all of the complications have been labeled "known and accepted." In terms of negligence, the most likely type of negligence would involve failure to abide by the flimsy patient selection criteria, failure to clear the patient preoperatively with a TEE or its equivalent and failure to properly manage anticoagulation perioperatively.
Informed consent claims will face the usual challenges: the patient signs an ambiguous, pro forma consent form coupled with the operating EP's remarkable memory of having the most thorough and complete informed consent discussion in the history of medicine. Potential failures in informed consent may come from representations made by the EP, hospital or their website hawking the procedure's benefits or downplaying its risks. Other failures may involve the failure to identify the personnel who will perform the procedure or their lack of experience or risk factors inherent in certain patient populations.
The stage is set for overuse of this profitable procedure: elderly, underinformed patients will be sold on the procedure based on statistics applicable to younger, less complication-prone patients who tend to have better results. EPs, who have invested time and money in training to perform the procedure, will be inclined to follow the law of the instrument as stated by Abraham Maslow: "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." When applied to most patients, AF ablation will more likely than not fail. Coupled with a 10-15% complication rate, this hammer should be used sparingly and only with due consideration from the patient.