Dr Irina Savelieva, Lecturer in Cardiology, Division of Cardiac and Vascular Sciences, St George’s, University of London, talks to Cardio Debate about atrial fibrillation.
How to identify patients with AF who are at high risk of stroke?
That’s obviously the question that all physicians who face patients with atrial fibrillation for the first time should ask themselves, that’s a very important component of management of atrial fibrillation.
And of course there is the CHADS VASC score. This is a very good scheme that has been adopted by many regulatory authorities and guidelines, which is pretty simple. It incorporates major risk factors which are easily identifiable during your first interview with your patient. And it includes congestive heart failure, left ventricular dysfunction, age, hypertension, diabetes, previous stroke, advance stage – well if you can see that some aged over 75 years is advanced, so that’s your answer – and female gender.
The problem with the CHADS CASC score is that we don’t have very concrete data in patients with the CHADS VASC score 1, for example. And we don’t know exactly what the weight of separate isolated risk factors are in a patient with the CHADS VASC score of 1, and there were reports that probably these patients are not necessarily at a very high risk of stroke when anticoagulation is warranted. The ESC guidelines however do support anticoagulation in these patients and I think that physicians should follow these guidelines.
On the other hand an important thing is that patients with a CHADS VASC score of 0 are not entirely risk free of stroke. Strokes do happen in otherwise healthy persons with atrial fibrillation, with low atrial fibrillation if you will.
And this is a particular problem for us physicians, because obviously for such patients stroke is an absolutely devastating consequence of untreated atrial fibrillation that we could have prevented in this case.
And we’re trying to develop new markers for example some biomarkers such as brain natriuretic peptide (BNP), troponin, some coagulation parameters in order to assist better risk stratification in this particular patient population.
Some imaging techniques, for example MRI of the atria may indicate that certain morphologies of left atrial appendage, for example, may predispose to high risk of stroke. The extent of left atrial fibrosis also has been shown to be associated with increased risk of stroke. So that risk stratification is ongoing, it’s a moving issue.
But for the time being, for the clinician, when you first face a patient with atrial fibrillation, do CHADS VASC score and this would help you guide your management in terms of oral anticoagulation.
Anticoagulation and bleeding risk: Prevention and treatment
Bleeding as a result of oral anticoagulation is of course a dreadful consequence that was probably imposed on the patient by us, the physicians. So therefore numerous schemes have been developed in order to predict such tragic consequence of treatment with oral anticoagulants.
We advocate the use of HAS-BLED. That’s a very simple one to calculate, and again it does include factors that are easily identifiable, and most importantly they are, to some extent, modifiable at the same time. For example it helps to highlight patients with poorly controlled hypertension that predisposes to high risk of intracranial bleeding, for example, or patients who are receiving concomitant medications that may potentiate the adverse effects of oral anticoagulants for example gastro-intestinal tract, etc.
So by calculating this risk score HAS-BLED, we can identify risk factors that can change and therefore we can reduce the patient’s risk of bleeding.
But at the end of the day it is a very fine balance between the risk and benefit. And therefore here we have to exercise an individual approach to the patient.
And of course again, here, we also have some new developments. For example there is a very interesting observation that finding micro-bleeds on the MRI of the brain may actually predict the subsequent hemorrhagic stroke or even ischemic stroke, and this would help to risk stratify patients in terms of anti-coagulation. Of course it is mainly a research tool, as well as the previously mentioned imaging of the left atrium as we discussed, but it is a research tool today; tomorrow it will be part of risk stratification (protocols) in terms of bleeding.
The role of NOACs in everyday practice: Farewell to warfarin?
NOACs or warfarin – that’s a dilemma. NOACs is an acronym for new oral anticoagulants. However, these drugs are not that entirely new, and NOACs now stand for Non-Vitamin K Anti Oral Coagulants, not New or Novel.
So the actual development of these agents really revolutionized treatment of patients with AF because up until 2010-2011 warfarin was the gold standard in the majority of patients. And we know that warfarin, even if it is well managed, still does not provide 100% protection against stroke. And what does ‘well managed’ mean? It means the time and therapeutic range should be at least 70% or higher, and this is not achievable in many counties in real practice. And actually real TTR ranged somewhere between 50-60% in the majority of countries across the work, even in centres of excellence. So this is a drug that is difficult to manage.
However, the non-vitamin K oral anticoagulants offer an advantage of a more predictable, more rapid response, more rapid effect and reasonable safety compared with warfarin. Actually as a class these gents are much more effective than warfarin in terms of preventing systemic embolism and stroke – as a class; of course with some differences between the drugs. And as a class, these drugs were associated with better survival, lower mortality, which is quite a big achievement compared with the so-called gold standard, warfarin.
So I think that it’s a no brainer. If you have a patient with no contraindications to anticoagulation, who is in need of stroke prevention, with obviously no contraindications to non-vitamin K oral anticoagulants that’s probably going to be your choice.
How you select between these agents, it depends on the individual patient pattern – and I will not go into this detail at this stage.
However, warfarin will remain and will be used in our practice. And, for example, patients with valvular atrial fibrillation – specifically patients with mechanical prosthetic valves and patients with rheumatic heart disease, which still exists in certain parts of the world – they will have no option but to go on warfarin.
Of course, maybe future studies in such patients with NOACs will show different results, but for the time being warfarin is the only drug we can prescribe to these patients.
Now there are obviously some grey areas, such as treating patients with acute coronary syndrome and atrial fibrillation for the time being, until the results of large randomized clinical trials which are ongoing are available, warfarin and antiplatelet therapy is what the guidelines recommend for these patients, at least for the first year after their index event.
Then we have a subset of young patients who would require warfarin, and in young patients I mean under age 18 or 20 years, these so called new drugs or NOACs, they haven’t been tested. So for the time being we are limited to warfarin when it comes to treatment of this patient population.
In pregnancy when it is safe to give anticoagulation with warfarin, when NOACs haven’t been studied, so that’s another option. And some sub-sets such as hypertrophic cardiomyopathy, etc.
However, having said that, there are a number of studies with effectively all NOACs that are addressing these grey areas that simply could not be addressed in large randomized clinical trials such as RELY or ARISTOTLE.
A number of these studies have been instigated and we will have the results – who to manage patients in this particular scenario. But at the end of the day we are moving from warfarin to NOACs and I think this is the right direction.