#MedTweetorial coming!!! An Evidenced Based Medicine #EMB review of anticoagulation for #Stroke prevention in #AFib Afib A 63-year-old male presents to follow up for episodes of dizziness. He is given an implantable monitoring device. What did it show?
It was found that he had an episode of AFIB for 1 hour and 38 minutes over a 30 day period. His CHADs2Vasc is 2. He was recommended a NOAC. Should he take it?
How much time in AFIB warrants anticoagulation to lower your risk for stroke?
A brief review before we begin. Our patient’s stroke risk was calculated to be 2.2%-2.9% per year. This is based on a study of over >90,000 patients (the Swedish AFIB Cohort Study). ncbi.nlm.nih.gov/pubmed/19762550
One recommendation suggests a 0 or 1 score is deemed low risk and no anticoagulation, and score 2 or greater is “moderate-high” risk & should otherwise be an anticoagulation candidate. Our patient falls into the “high risk” group. ncbi.nlm.nih.gov/pubmed/19762550
Now, remember, CHADs2Vasc is a generalized risk score that applies to all patients and doesn’t take into account how much time they are in AFIB. You could be in AFIB for 3 hours or 24 hours per day. It doesn’t matter to this risk score.
A CHADs2Vasc of 1 (0.6-0.9% risk of an event per year does not warrant anticoagulation per guidelines). acc.org/~/media/Non-Cl…
It is well known that the tx of AFIB for stroke risk prevention involves some form of anticoagulation. What wasn’t clear to me was how long does someone have to be in AFIB (risk factors aside) in order to deem them “at-risk” for developing thromboembolism warranting anticoag tx
After doing some review I found a recent article that looks at this question and is addressed by the JAMA Cardiology article in July 2018. jamanetwork.com/journals/jamac…
Let’s first start w/a brief review. PAF is defined as AF that terminates spontaneously or with intervention in less than seven days. This classic classification applies to episodes of AFIB that last more than 30 seconds and that are unrelated to a reversible cause.
Current guidelines recommend anticoagulants for stroke prevention based on clinical risk stratification for either nonparoxysmal or paroxysmal AFIB. ncbi.nlm.nih.gov/pubmed/24685669
Given the true incidence, PAF is likely underreported, current data has found the recurrence rate of AF is high in patients who present with PAF with an incidence ranging from 70% at 1 year (without antiarrhythmic therapy) to 90% at 4 years. ajconline.org/article/S0002-…
We also know that those with high atrial high rate events (AHREs) last >5 minutes in duration are more than twice as likely to die or have a stroke. This is even without incorporating into account the afib % burden. ncbi.nlm.nih.gov/pubmed/12668495
Whether or not stroke risk varies among those with PAF vs AFIB has been an ongoing question. Compared w/ patients with non-paroxysmal AF, those with PAF may be at higher risk given intermittent organized contraction of the atria following periods of AFIB, its called “stunning.”
This “stunning” effect is known and is commonly seen after cardioversion. It is the presumed reason patients are put on anticoagulation for a month following the procedure despite them being in NSR. ncbi.nlm.nih.gov/pubmed/14659842
Some studies suggest that the risk of embolization with frequent and prolonged episodes of PAF may be similar to the risk in patients with persistent or permanent AF. However, the data is not conclusive. …w-ncbi-nlm-nih-gov.lecomlrc.lecom.edu/pubmed?term=10…
Studies have also found that a greater burden of AFIB is associated with a higher risk of ischemic stroke and arterial thromboembolism. It was concluded that PAF is an independent risk factor for stroke. But yes, time is key here! jamanetwork.com/journals/jamac…
This study found looked at patients not on anticoagulation with PAF and monitored them for 14 days. They split the time in AFIB into 3 tertiles. jamanetwork.com/journals/jamac…
Those in tertile 3 were the only tertile showing a meaningful increase in thromboembolic events, about a 215% increase in the unadjusted risk of thromboembolic events compared with tertile 1 and 2. The time spent AFIB was >%11.36 or > 158 minutes or > 2 hours 28 min.
Those in tertile 1, had 5 events over 690 person-years (0.7%) in which patients spent between 0.01%-2.03% of time in AFIB,<28 min in AFIB, while those in tertile 2 had 7 events over 639 person-years (1.09%) in which patients spent 2.05%-11.28% (30-162min) of time in AF or Flutter
They also found that the duration of the longest observed episode—was NOT significantly associated with thromboembolism but it was the greater CUMULATIVE burden of AFIB that was assoc with this risk.
With that being said, let’s address the initial question. Does our patient with PAF and a CHADsVASC of 2 with a time burden in AF of 138min warrant anticoagulation knowing his risk is now 1.09% and not the 2.2-2.9% that the CHADsVASC suggested?
I would love the feedback. Inspired by twitter Attendings @tony_breu @MedTweetorials @DxRxEdu @sargsyanz @rabihmgeha @kidney_boy @medrants @thecurbsiders
