Most years I write an update on any big developments in AF ablation.
This year’s version will be a short one. I have little new to report. But it’s worth reviewing some basic issues.
We still do not know the cause of atrial fibrillation (AF). That makes it hard to fix with ablation.
To explain why not knowing the cause of AF impairs our ability to ablate it, it’s useful to compare AF ablation to WPW ablation. Wolfe-Parkinson-White or WPW syndrome causes rapid heart rates because of an extra pathway from the top to the bottom (atria and ventricle) of the heart. You can cure WPW by ablating the extra pathway–often with one burn.
The approach to AF is to use single burns (or cryo-balloon lesions) to electrically isolate the muscle bundles surrounding the pulmonary veins. Think of that one burn (used in WPW ablation) times 60-80 to form electrical fences around the pulmonary vein orifices. This is called pulmonary vein isolation or PVI. Studies show that it is the best technique for ablating AF. It’s what we did in 2004 and it’s what we do now.
The problem is that sometimes AF is triggered by cells in the pulmonary veins, and sometimes it is not. That means we could be doing 60-80 burns in the heart and not going after the right target. There is NO way to tell. The good news, though, is that the pulmonary veins are involved often.
The other problem is that even when AF is being triggered by cells within the pulmonary veins (e.g. we are going after the right target), the lines of block from the burns are not durable, and over time, electrical activity can leak out through a gap in the line–thus causing AF. The weirder thing is that sometimes these gaps occur in patients who don’t have AF after the ablation. IOW, the burns did not completely isolate the veins and AF still stayed away. That observation suggests the burns hit something–but we don’t know what.
AF Ablation Remains Untested:
The larger problem with AF ablation is that it has never been adequately tested. In medicine, to know if a pill or surgery really works, you have to test it against a placebo in a blinded trial. Emphasis on blinded. A new medicine cannot get approved unless it works better than a placebo. Procedures should require the same proof.
AF ablation has never been tested against a placebo procedure–sometimes called a sham procedure. Every single study of AF ablation has been confounded by the patient and doctor knowing the treatment. Or, as we say, AF ablation trials are unblinded.
I know; exposing people to the risk of ablation without actually doing the ablation sounds nutty. But the list of procedures and surgeries proven useless when compared to placebo is long.
The most recent shock was stents in the heart for the relief of chest pain due to chronic and stable blockages in the coronary arteries. Millions of people worldwide have received stents, and both doctors and patients believed the metal cage relieved chest pain called angina. How could it not? The stent essentially fixes a 90% blockage to 0%.
Except … stents did not pass the placebo test!
In the ORBITA trial, a brave group of researchers from London randomized 200 patients with a single severe blockage and chest pain to either a real stent procedure or a fake procedure. The patients and the doctors taking care of them afterwards did not know which they had. To measure the effect of the stent vs the sham procedure, the researchers walked all 200 patients on a treadmill before and after the procedure, and, shockingly, there were no significant differences in exercise time, nor were there any significant differences in chest pain on questionnaires. In case you find this hard to believe, the ORBITA investigators counter the many criticisms of their trial in two worthy rebuttals.[5,6]
The message is clear– if fixing a 90% blockage does not relieve chest pain any better than a sham procedure, then it’s possible that the quality of life improvements reported after AF ablation might also be a big placebo.
A quick story: I did an ablation on a patient who had terrible AF. Terrible in that AF was causing depression, shortness of breath, dizziness and the man told me that he didn’t care if he died during the procedure, he could not live like this. I did the ablation and it went well. A year later, he told me in the office that I was a miracle worker. I had given him his life back.
Except … sit down for this... he was in AF!
I am giving a talk at the Heart Rhythm Society meeting this year on why we need a placebo-controlled trial for AF ablation. I will, of course, address the ethics of exposing a a hundred or so people to the risk of a sham procedure vs the ethics of exposing millions to a potentially worthless procedure. (For the record: I predict an AF ablation placebo control trial will show a large placebo effect, but also a real effect.)
Two new trials in AF ablation in 2018:
The CASTLE AF trial showed that for patients with heart failure and AF who have failed medicines, AF ablation reduced the rate of death and heart failure by about 12%. The trial results sound great, but it only included relatively young, mostly male patients who had moderate heart failure. Most patients with heart failure and AF are older and have multiple problems that make AF ablation unlikely to work.
Important point here: you should only apply trial results to patients like those in the clinical trials. We call this the external validity of a trial. I have written about this: Treating the Individual, Not the ‘Average’ Patient.
The CABANA trial, which is not yet published, showed that for patients with AF and risk factors for stroke, AF ablation compared with medical therapy did not significantly reduce the rate of stroke, death, bleeding or cardiac arrest. CABANA did show that AF ablation reduced AF episodes, and it improved quality of life, but, of course, CABANA was unblinded and had no placebo control. That is crucial because it was done by doctors who believe in AF ablation.
AF ablation in 2019 is about the same as in 2018.
I recommend it as an option for people who have well documented AF that…
- cannot be reversed with lifestyle measures such as weight loss, treatment of sleep disordered breathing, control of blood pressure, attainment of cardiorespiratory fitness, and reduction of alcohol intake, and
- cannot be suppressed with medicine, and
- impairs one’s quality of life enough to warrant having an invasive procedure with a risk of serious complications in the range of 1-3%. This latter point is important because once you educate people about AF, they become less frightened, and, when less frightened, the AF often becomes less burdensome.
The AHA and ACC recently published an update to the 2014 AF treatment guidelines. I wrote a few words on the new recommendations.
Here is the column: Ten Thoughts on the 2019 AF Treatment Guidelines.
- Verma A et al.Approaches to Catheter Ablation for Persistent Atrial Fibrillation. New England Journal of Medicine2015; 372(19): 1812–1822. doi:10.1056/NEJMoa1408288.
- Sauer WH, Callans DJ. The Tribulations of Atrial Fibrillation Ablation Trialists. Circulation: Arrhythmia and Electrophysiology2016; 9(1). doi:10.1161/CIRCEP.115.003738.
- Redberg RF. Sham Controls in Medical Device Trials. New England Journal of Medicine2014; 371(10): 892–893. doi:10.1056/NEJMp1406388.
- Al-Lamee R et al.Percutaneous coronary intervention in stable angina (ORBITA): a double-blind, randomised controlled trial. The Lancet. doi:10.1016/S0140-6736(17)32714-9.
- Francis DP, Al-Lamee R. Percutaneous coronary intervention for stable angina in ORBITA – Authors’ reply. The Lancet2018; 392(10141): 28–30. doi:10.1016/S0140-6736(18)31190-5.
- Al-Lamee R, Francis DP. Swimming against the tide: insights from the ORBITA trial. EuroIntervention2017; 13(12): e1373–e1375. doi:10.4244/EIJV13I12A217.
- Marrouche NF et al.Catheter Ablation for Atrial Fibrillation with Heart Failure. New England Journal of Medicine2018; 378(5): 417–427. doi:10.1056/NEJMoa1707855.
- Rothwell PM. External validity of randomised controlled trials: “To whom do the results of this trial apply?” The Lancet2005; 365(9453): 82–93. doi:10.1016/S0140-6736(04)17670-8.