Q1. What is the current gap when it comes to identifying atrial fibrillation patients?
Atrial fibrillation is the most common sustained cardiac arrhythmia. The number of adults living with atrial fibrillation is expected to double over the next 30 to 40 years mostly due to increased longevity, increased detection, and increased prevalence of risk factors.
Atrial fibrillation is also a leading cause of morbidity and mortality worldwide with increased risk for stroke, heart failure, and death. Early detection of atrial fibrillation can enable anticoagulant therapy to reduce ischemic stroke and mortality suggesting that screening for atrial fibrillation might be beneficial to populations at risk.
The European Society of Cardiology (ESC) guidelines from 2020 recommend opportunistic screening for atrial fibrillation in patients over 65 years of age and systematic screening should be considered in individuals over 75 years of age or those with higher stroke risk. The US Preventive Services Task Force on the other hand does not recommend systematic screening and concludes that the evidence is insufficient to access the benefits and harms.
Now to answer the question as to the gap in identifying atrial fibrillation patients. We know that if we look for atrial fibrillation, we will find atrial fibrillation. As an example, Lowres et al. found that a single ECG screening resulted in a 1.4 prevalence of asymptomatic atrial fibrillation. The STROKESTOP I trial found 3% using single-lead ECG two times daily for two weeks and then in the ASSERT-II trial, 34.5% were found to have asymptomatic atrial fibrillation after about a year of using implanted cardiac monitors.
If we look for atrial fibrillation in an elderly population, we will find more cases than in a younger population as the prevalence increases with age. An ideal screening program to identify the atrial fibrillation patients has to be the combination of screening the right individuals, with validated screening modalities, at the right cost with a proven net benefit of the screening. So, this is not an easy question to answer. It is very multifaceted, but there are several ongoing randomised control trials including the STROKESTOP trials that aim to bring us closer to the answer to that question. In fact, both the STROKESTOP I trial and the LOOP study were published last year. I will talk about that a little later.
Q2. What are the guideline-recommended screening tools available in your institute and who screens?
There are many new emerging modalities that can be used for identifying atrial fibrillation and they can be roughly divided into methods that need ECG confirmation such as pulse palpation, blood pressure monitors, and photoplethysmography smartphone apps, and those that do not need 12 lead ECG confirmation from patches to handheld single-lead ECGs to continuous implantable cardiac monitors. Many of these tools are available at our institute and we use them depending on the intensity with which we want to look for atrial fibrillation.
There is no systematic screening program in Sweden, but atrial fibrillation is being diagnosed both by general practitioners as well as in hospitals. In fact, in the STROKESTOP I trial, in the control group that was not invited to screening and received standard care, the proportion with diagnosed atrial fibrillation increased gradually to more than 20% over 7 years. The group invited to screening had a higher proportion of diagnosed atrial fibrillation especially right after the screening, but the lines were quite parallel over these 7 years, so they are being diagnosed in general practice.
In Sweden, there is also quite an awareness in the general public of the different screening modalities, and it is not uncommon to meet a patient in the emergency department showing their watch or phone with atrial fibrillation warnings or single-lead ECGs. So, the patients themselves are also identifying atrial fibrillation. This will of course only become more common as the techniques evolve and become more readily available to many.
Q3. What is the suggested patient profile to screen for atrial fibrillation?
I can only repeat what I said before that we do not yet know or will we ever know the ideal patient profile for screening atrial fibrillation. But for a screening program to be successful, many factors have to be considered. We have to address the participation rate, we have to reach the participants, which individuals to screen, which age, which method to use, and also there should be a proven benefit of the screening.
The newly published STROKESTOP I trial, where they screened 75-year-olds with intermittent single lead ECGs for 2 weeks, found the benefit of screening with regards to the primary endpoint, which was the composite of ischemic or haemorrhagic stroke, systemic embolism, bleeding requiring hospitalisation, and all-cause death. On the other hand, in the also newly published LOOP study, they screened 70 to 90 olds with implantable loop recorders for over 5 years which resulted then in a three times increase in atrial fibrillation detection not surprisingly, and anticoagulation initiation between the groups. But there was no significant reduction in the risk of stroke or systemic arterial embolism. So, there are more randomised control trials ongoing, and we need them to provide us with more detailed information to answer that question.
I believe or in my opinion, the ideal patient must be an individual where we can expect to find atrial fibrillation, meaning, probably an older person or person with risk factors. Searching for atrial fibrillation in the young population reveals few cases, probably at a high cost.
It will also be important that there be an indication for intervention if atrial fibrillation was diagnosed, meaning that we would not want to screen people that would not have an indication for oral anticoagulation if we were looking at a stroke or bleeding, etc as an endpoint. On the other hand, if we are looking at other interventions, then other rules may apply – for example, we are looking for rhythm control management.
Q4. Is there a role for NT pro-BNP in atrial fibrillation screening?
NT pro-BNP is a well-known marker for heart failure. It is also the best-studied biomarker in patients with atrial fibrillation and the most recognised one to protect against incident atrial fibrillation. NT pro-BNP levels are also independently associated with an increased risk of stroke, and mortality and it improves risk stratification as it does in the ABC stroke risk score beyond the CHA2DS2-VASc score possibly being a novel tool for improved stroke prediction in atrial fibrillation.
This makes one wonder if NT pro-BNP can be a way of identifying those at the highest risk of both atrial fibrillation and stroke. Should that be the case then this could be a way of improving screening precision in the future. In my opinion, there could be a role of NT pro-BNP in atrial fibrillation screening but that is also the hypothesis of the STROKESTOP II trial which is still ongoing.
