Hi, I'm Jose Hoglar, Dr. Jose Hoglar from the University of Texas Medical Center and Parkland Health in Dallas, Texas. I'm going to be speaking about latest atrial fibrillation diagnostic tools, especially anticoagulation in device-detected atrial fibrillation. I have no disclosures. I'm going to be discussing as much as possible what is recommended for device-detected atrial fibrillation management based on the 2023 atrial fibrillation guidelines. But of course, I'm going to include some data that we did not have prior to the publication of the guideline in November 2023. So the guidelines define clinical atrial fibrillation as follows. With increasing availability of wearable devices and other continuous monitoring technologies, the writing committee felt that the distinction between clinical and subclinical atrial fibrillation has become increasingly blurred. So although some might consider it a little bit less useful, it still has value. The reason is because most of the evidence from randomized trials that led to guideline recommendation for the treatment of atrial fibrillation refers to clinical atrial fibrillation. So these trials require electrocardiographic documentation of arrhythmia for inclusion, and most patients presented for clinical evaluation are therapy of the arrhythmia. So essentially, clinical atrial fibrillation means exactly that. It is patients who have atrial fibrillation documented on the EKG, and they present to the clinic for evaluation and therapy of a symptomatic arrhythmia. And then you have subclinical atrial fibrillation, which is patients, if it happens in patients who do not have symptoms attributed to atrial fibrillation, and the atrial fibrillation does identify by implantable devices, such as pacemakers, defibrillators, nerve recorders, or even wearable monitors. How prevalent is subclinical atrial fibrillation in patients with pacemakers or ICD is very prevalent. Actually, if you look at this table from this review article here, subclinical atrial fibrillation, you can see that there have been numerous studies that have shown in patients with pacemakers and implantable defibrillators that the subclinical atrial fibrillation prevalence is very high. You can see up to 70%. Of course, in patients with pacemakers for sinus node dysfunction, sick sinus syndrome, you will expect they will have more arrhythmias, atrial arrhythmias, because they have an underlying atrial myopathy. But even in patients with ICDs, for example, for all indication, the prevalence is quite high still. This is a study by Haley that they implanted loop recorders in patients over 65 attending cardiovascular or neurology clinics. This patient had no history of atrial fibrillation, but they had risk factors such as CHAS-VASc score of two or greater, sleep apnea, and obesity. They also required to have some other elements that placed them at risk for atrial arrhythmias such as enlarged atria, elevated antipro-VMP, for example. And they were looking for subclinical atrial fibrillation lasting five minutes or longer. You can see in patients with a history of stroke, systemic embolism, or TIA, the incidence of that was 39% versus 30% in patients without stroke. You can see that these patients did not have atrial fibrillation. So clinical atrial fibrillation dose is very frequently detected if you look for it in patients at high risk populations, even in the absence of atrial fibrillation. So the clinical significance of that is somewhat unclear. I also want to mention that there's still a lot of things that we don't know. For example, this is a tracing of the pacemaker. And you can see this is a ventricular signal here, and this is the atrial signal. And you can see these are very fast, irregular signals. This is just around 200 beats per minute, a little regular, maybe faster to 20, to 50 perhaps. And then you have faster atrial signals. You can see that these are much faster, 400 plus beats per minute. This is the way we think traditionally of atrial fibrillation. So we don't know whether that has different implications for treatment. But like I said, there's still a lot of things that we don't know about the signals themselves. And I have to emphasize also the importance of having to confirm the diagnosis. When the pacemaker reads atrial tachycardia or atrial fibrillation burden, they look at rapid rates, they look at what is called AMS or atrial mode switch. That means the pacemaker switches the mode because he's sensing a lot of atrial activity. But we don't know what those atrial activities are. This is an example of a false atrial mode switch, a false interpretation by the pacemaker because he was double counting the atrial signal with far field sensing of the ventricular signal. So I have to emphasize that the pacemaker did not go to medical school, so it is required that when a pacemaker reads for atrial fibrillation burden that is considered high, that we confirm the diagnosis. We loop directly to the atrial signals to see whether this is truly fast atrial fibrillation or even atrial tachycardia, flutter, or coarse AFib signals. So the first indication of the potential risk of stroke associated with device-detected atrial fibrillation was among the first important studies was the ASSERT investigators. This study included 2,500 over 2,500 patients over the age of 65, 65 or older with hypertension or prior history of AFib who had a device, arrhythmia management device. And then subclinical atrial fibrillation was defined as an atrial rate greater than 190 beats per minute for greater than six minutes. And the reason essentially six minutes was big because this is what the devices are capable of doing. There's really no other reason why six minutes is better than 10 minutes or four minutes or 15 minutes. So they were followed for a mean of two and a half years, and you can see that there was an increased incidence of stroke in patients that has subclinical atrial tachyarrhythmias. And you can see that the incidence of this based on duration, you know, the longer you monitor, the higher the incidence of this arrhythmia, and you can see that shorter duration are by far more common. These are greater than six minutes, greater than six hours here in red, but then they're greater than 24 hours. That's much, much less common, less than 10% or so. But then when you look at subgroup analysis, when it comes to the risk of stroke, most of the risk threefold increase was essentially related, observed only in the patients who have 24 hours or greater of these subclinical arrhythmias. And we know also from some similar studies that short atrial fibrillation versus long atrial fibrillation, short atrial fibrillation does not pose any risk whatsoever. And they define this short atrial fibrillation usually 15, 20 seconds, or just as long as the duration of the tracing. But you do have, very importantly, you do have to observe the patient because there is an increased risk of short atrial fibrillation to become longer durations of atrial fibrillation to progress. There's also this study, the KP arrhythm study, where the investigators, instead of looking at a single duration of an episode, they look at the total burden. That means the amount of, the percentage of time the patient had the arrhythmia during the recording period, which is in this cohort was 14-day ambulatory recording. And you can see they divide it in third aisles, a patient with a burden of less than 2%, 2% to 11% and greater than 11%. That means 11% of the entire time during the two-week recording period. And you can see that they conclude that the greater the burden of atrial fibrillation, patients with a greater burden, those were the patients who were at risk for ischemic stroke accordingly. The median burden was 4.4%, but only the patients with higher burden, there was a definitive three-fold increased risk, as you can see here, has a ratio of about three in terms of the risk of stroke thromboembolic events, including stroke TIA or venous thromboembolism. This is an observational study by Kaplan and Circulation. They look at electronic medical records from their database, and then that's intermounting health systems. And you can see that they compare patients with no atrial fibrillation according to CHAS VASCOR, and then they look at atrial fibrillation six minutes to one day and then greater than 24 hours or greater. And you can see that there is a – you can notice here an interaction between the ratio in CHAS VASCOR with patients with a CHAS VASCOR 3, 4, or 5, and higher duration had a greater risk than patients with no AFib and short duration of atrial fibrillation. Yet you can see that in the device that detected AFib, if you think historically of the risk of stroke in a patient with a CHAS VASCOR of 5, you think about 5% risk of stroke, 6% risk of stroke, and those numbers were not that. They were much less. The risk was much less. So that's something we need to cover a little bit, talk about the risk of stroke in device detected AFib. The guideline changed the way we recommend anticoagulation, and for this reason. In the prior guideline, the recommendation anticoagulation were based on CHAS VASCOR. So in this guideline, we recommend anticoagulation based on thromboembolic risk, the absolute number estimated of what is the risk of thromboembolic events per year, per 100-patient year. And when we see class 1 recommendation, when the risk is thought to be 2% or greater, then anticoagulation is recommended. And then when the risk is thought to be between 1% and 2% of thromboembolic risk per year, then the guidelines give this a 2A recommendation. And the reason we did that is so we can be a little bit more nuanced. And the reason is because, as you can see then, this is a study-level meta-analysis of the NOAA AFNET6 and Artesia trials. These are two studies that were done to study the benefit of anticoagulation in patients with device-detected atrial fibrillation. The patients with device-detected atrial fibrillation greater than six minutes, they were randomized. They had some risk factors. So in both studies, the median CHAS-VASc score was about four. But in the NOAA AFNET6, the annual rate of ischemic stroke on aspirin or placebo was 1.1%, and the annual rates of ischemic stroke in Artesia was about 1%. If you look at the annual rates of stroke that you will expect based on historical CHAS-VASc score for a CHAS-VASc of four, you will expect a risk of stroke of 4%. So we didn't see that here. So the advantage of the guideline I recommended based on absolute risk as opposed to CHAS-VASc score is because you can have populations in which the risk of stroke is not perfectly aligned with a CHAS-VASc score. So I'm glad we did it that way. So based, we didn't have the Artesia, the NOAA AFNET, but I think we got pretty close to our recommendation in the guideline, which is a 2A recommendation. And you can see that the recommendations for anticoagulation have a lower class of recommendation than in patients with clinical AFib. Because like I said, it seems to be that the risk of stroke is less in subclinical AFib, and we recommended a 2A recommendation for those with subclinical atrial fibrillation greater than 24 hours with a CHAS-VASc of two or greater, and then a 2B recommendation for those with a CHAS-VASc at three or greater with atrial fibrillation between five minutes and 24 hours. Let me remind you that in the meta-analysis, there seems to be a hinge point around the CHAS-VASc score of four, where the benefit outweighs the risk. Just a reminder that these anticoagulants have significant risk of bleeding. So in conclusion, subclinical atrial fibrillation can be highly prevalent in high-risk population in patients with implantable arrhythmia management devices, especially when they have risk factors. It is necessary to confirm the diagnosis visually. In terms of stroke risk, there seems to be an interaction between atrial fibrillation duration and risk factor, but risk of stroke seems to be lower than in patients with clinical atrial fibrillation. And the recommendation for anticoagulation in device-detected atrial fibrillation have a lower class of recommendation than for clinical atrial fibrillation. That means when we balance the risk versus benefit, then the recommendations are less robust. So thank you so much.

atrial fibrillation

subclinical AF

anticoagulation

stroke risk

ASSERT study