Caution over use of catheter ablation for atrial fibrillation | BMJ
The British Medical Journal are running a good series at the moment entitled Too Much Medicine. They have featured investigations/tests such as CT Pulmonary Angiography or cancer screening and treatments which the authors have felt lack sufficient evidence for widespread use.
In this article, Belgian Cardiologist Hans Van Brabandt and colleagues have had a go at catheter ablation for the treatment of Atrial Fibrillation. In this procedure, cardiologists introduce a wire into the femoral/groin vein and advance it up to the heart and through a puncture of the atrial septum (dividing wall), they advance the wire tip into the left atrium or receiving chamber. The tip of the wire is then used to heat and destroy tissue around the openings of the pulmonary veins (veins draining blood from the lungs into the heart.) The reason for doing this is that these openings are where the initial burst of electrical activity occurs in patients suffering from paroxysmal atrial fibrillation. In this condition, patients experience a burst of electrical activity that makes the heart beat at a very fast and irregular rate. It is usually self terminating but causes very unpleasant palpitations. This condition frequently responds to drug treatment. In a few patients, the condition is resistant to the drugs. Other patients cannot take the drugs because of side effects. In these patients, catheter ablation is very effective at stopping the attacks and current guidelines advocate the use of this treatment in these 2 groups of patients.
The criticism of the authors in this article relates to the treatment of patients with persistent atrial fibrillation. In these patients, the electrical disturbance in the receiving chambers of the heart is not paroxysmal or episodic but permanent. This causes the patients to have a permanently irregular heart beat. Most patients in this category are not aware of the abnormality in their heart. Treatments (drugs) can be given to either slow the irregular heart beat - so called rate control treatment or to coax the heart back into a normal regular heart rhythm - so called rhythm control. Drugs are effective at the first (rate control) but not very good at the second (rhythm control). In addition rhythm control drugs tend to have some very unpleasant side - effects - hence the use of catheter ablation to acheive permanent rate control in patients with persistent atrial fibrillation.
The main criticism Van Brabant et al make in this commentary is that the evidence suggests that in patients with persistent or permanent atrial fibrillation, rhythm control (regularizing the pulse) in atrial fibrillation carries very little or no advantages when compared to rate control (slowing the pulse). A devastating complication of an irregular pulse in these patients is the formation of a clot in the left sided atrium (receiving chamber) that may embolise (or fly off) to the brain causing a stroke. This is the reason many patients in atrial fibrillation take anticoagulants or blood thinners. Rhythm control or regularizing the pulse with drugs or with catheter ablation should therefore carry a huge potential benefit of decreasing stroke risk - and yet studies suggest these treatments do NOT decrease the risk - so why do cardiologists continue to publish articles on the use of this expensive potentially harmful intervention to achieve no benefit?
As a cardiac surgeon, I have an interest in atrial fibrillation. I operate on patients with severe coronary artery disease to carry out a bypass procedure or to replace or repair damaged heart valves in patients with heart valve disease. As part of their heart condition, many of these patients have persistent atrial fibrillation. Atrial fibrillation would often be the first manifestation of their other cardiac problem. What we have discovered over the years is that the atrial fibrillation very often persists despite the otherwise successful surgical treatment of the cardiac disorder. We also know that the long term survival of these patients is not as good as those without atrial fibrillation. As described earlier, their stroke risk remain elevated. Using additional often expensive devices, it is possible for a surgeon to carry out an atrial ablation at the time of the original heart operation. This undoubtedly improves the chance of the patient regaining a normal heart rhythm or pulse after surgery. Most studies suggest performing this additional procedure does not carry any additional risk. Yet, good evidence (from randomized control studies) of long term benefit i.e. improved survival or freedom from stroke is also glaringly absent. Current NICE guidelines suggest the use of these additional procedures in patients undergoing heart surgery who are having significant symptoms relating to the atrial fibrillation - symptoms which are often indistinguishable from those caused by the original cardiac problem.
Ablation to treat atrial fibrillation at the time of so called concomitant cardiac surgery is now very common - at a significant cost to commissioners of health care. It seems extraordinary to think that in these financially straightened times, just as with catheter ablation, new expensive operative procedures are being performed without the necessary evidence behind them - too much surgery indeed.