This blog post is part of a series that will review different scoring and calculations that clinicians use to predict patient outcomes and make informed clinical decisions.
We’ll go through some background, the calculator, and example scenarios to apply it in the real world.
For each one we’ll link to a calculator that you can use. There are many options but we recommend MDcalc.com as they provide a great interface for most of the calculators that you’ll use. (Apple App or Android App).
Patients with atrial fibrillation are at a higher risk of developing clots. The score helps determine if the patient should be placed on an antiplatelet or anticoagulant therapy.
Normally, the upper halves of your heart should contract in one smooth and synchronous motion to shift blood from your atria to your ventricles. Atrial fibrillation occurs when one or both atria experience disorganized electrical signals which cause the atria to contract irregularly. Non-valvular causes of atrial fibrillation include high blood pressure, heart stimulants (alcohol, caffeine), hyperthyroidism, stress, etc.
When the normal flow of blood through the heart is disrupted by atrial fibrillation, there is an elevated chance of blood stasis in the heart, and therefore there is an increased risk for developing clots. This is most commonly seen in the left atria where clots can develop and then be sent through arterial pathways to the brain, potentially causing a stroke.
For this reason, a calculator was derived to quantify the thromboembolic risk due to non-valvular A-fib, referred to as the CHA2DS2VASC score. Below is a table that details the CHA2DS2VASC score.
|Congestive Heart Failure||1|
|Vascular disease history (prior MI, PAD, aortic plaque)||1|
|Sex Category (Female?)||1|
This table breaks down the patient’s risk of stroke (per the Swedish Atrial Fibrillation Cohort Study which included >90,000 patients) and their clinical implications (per revised 2014 guidelines from the American College of Cardiology).
|Score||Lifetime Stroke and Stroke/TIA/Systemic Embolism Risk (%/%)||Clinical Implications|
|0||0.2/0.3||Low Risk: No anticoagulation|
|1||0.6/0.9||Low-moderate risk: Consider antiplatelet or anticoagulation|
Moderate-high risk: Should otherwise be on an anticoagulant (warfarin or NOAC)
|8||10.8/15.2 (not a typo)|
Mrs. Debbie Reed is a 68 year old African American female with a PMH of moderate Alzeihmers, a-fib, and T2DM, presenting to the emergency department for acute suspected stroke. She described experiencing sudden weakness in her left leg, causing her to fall down a few hours after a neighborhood cookout including fried fish, collared greens, mac and cheese, and soft drinks. Now, Mrs. Reed has diminished consciousness and is unresponsive to questioning with left leg weakness and sensory deficits. Her NIHSS score is calculated as an 8. Mrs. Reed takes donepezil for her Alzeihmers, warfarin to decrease her risk of stroke, and metformin, GLP agonist, and insulin glargine daily for glucose control.
Applying CHA2DS2VASC scoring
Here we meet an elderly, African American female arriving for stroke workup most likely secondary to her past diagnosis of atrial fibrillation.
Her CHA2DS2VASC score is calculated at 3 (Age >65, T2DM, and Female). Because of the elevated risk of thromboembolic events, she is on oral anticoagulation as the calculator suggests…specifically warfarin.
However, warfarin is not the best option for anticoagulation for Mrs. Reed due to other factors noted in the example case. Novel Oral Anticoagulants (NOACs) are a suitable alternative when warfarin is contraindicated (such as her history of dementia).
Clinical Pearls on Oral Anticoagulation: Warfarin or NOAC?
Anticoagulant choice and dosing are outside the scope of this post, but here are a few pearls to keep in mind:
- Warfarin requires dose monitoring to be effective, which can be difficult in patients with dementia or diets varying in Vitamin K uptake.
- Warfarin is a Vitamin K antagonist. By reducing vitamin K synthesis, warfarin also reduces coagulation factor production.
- The therapeutic dosing of warfarin is tracked by measuring International Normalized Ratio (INR), a proxy for measuring coagulation times.
- Patients with dementia may forget or miss doses or not have their INR monitored routinely which can lead to their INR easily getting outside the therapeutic range.
- Differential dietary uptake of Vitamin K can impact how effective warfarin therapy is. In diets rich in vitamin K, more warfarin will be needed to maintain the therapeutic INR.
- A patient’s dietary volatility with regards to Vitamin K uptake can be a contraindication for warfarin therapy. Especially in combination with patients who do not maintain strict INR monitoring.
- Oral Factor Xa inhibitors (apixaban, rivaroxaban) have been recently shown to be comparable, if not superior, at lowering the risk of stroke and other systemic embolic events in patients with atrial fibrillation
- Discontinue warfarin and start apixaban as soon as INR is below 2.0.
- The recommended dose of apixaban for most patients is 5 mg taken orally twice daily.
- Discontinue warfarin and start rivaroxaban as soon as INR is below 3.0
- The dose of rivaroxaban for most patients is 20 mg/day orally with the evening meal
- Friberg L, Rosenqvist M, Lip GY. Evaluation of risk stratification schemes for ischaemic stroke and bleeding in 182 678 patients with atrial fibrillation: the Swedish Atrial Fibrillation cohort study. Eur Heart J. 2012 Jun;33(12):1500-10. doi: 10.1093/eurheartj/ehr488. Epub 2012 Jan 13. PMID: 22246443.
- Bruins Slot KMH, Berge E. Factor Xa Inhibitors vs Warfarin for Preventing Stroke and Thromboembolism in Patients With Atrial Fibrillation. JAMA. 2014;311(11):1150–1151. doi:10.1001/jama.2014.1403
- The Revised ACC/AHA/HRS Guidelines for the Management of Patients With Atrial Fibrillation