**4. Evaluation of embolic risk**

All individuals who have AF are not at equally high risk for thromboembolic events, and several predisposing clinical factors can identify those patients at relatively higher or lower risk. Risk stratification for embolic events assumes added importance, since the individual's risk of embolic events needs to be carefully balanced against the risk of bleeding which is associated with anticoagulation. In patients without CKD, AF in association with any form of valvular heart disease (VHD) is considered for anticoagulation commencement as the stroke risk in this population subset is high [3, 15, 16]. Patients with nonvalvular heart disease (NVHD), however, do not necessarily require anticoagulation, and the decision to anticoagulate for stroke prevention depends on their individual risk of stroke [15–17].

bleeding risk prediction scores in patient with NVAF and CKD [28]. The seven risk predic-

, CHA2DS2

risk scores did not perform differently from each other, where the negative predictive value was not seen to be significantly different from each other. In terms of bleeding risk score,

0.66 [28]. Furthermore, the study also showed that each of the seven risk prediction scores performed significantly better for patients with normal kidney function than in patients with CKD with performance significantly worsened as severity of kidney disease increased [28]. Therefore, the study suggests that current thromboembolic and bleeding risk prediction

There is no difference in the indications for anticoagulation therapy between paroxysmal,

do not fully account for thromboembolic risk, and stroke can occur even after a sinus rhythm

As stipulated previously, no stroke risk prediction scores have been specifically developed for patients with CKD and AF. It has been shown, however, that patients with CKD and nonvalvular AF have a heightened stroke risk regardless of CHADS2DS2-VASc score, where 80% of patients having scores of ≥2 [29]. Current ACC/AHA/ESC guidelines advise that for

tion or aspirin alone should be considered in conjunction with patient specific comorbidities

anticoagulation, neither formal nor antiplatelets, is recommended [3, 9, 15, 16, 20, 22–26]. In comparison with the American guidelines, the European guidelines recommend that males

whereas those with a score of 1 should only be considered for anticoagulation, depending also on patient comorbidities and other risk factors [15, 20, 22–24]. Furthermore, for females, as female gender has been shown to be a weak risk factor for stroke in AF, guidelines advise

is 2, then anticoagulation be considered [15, 20, 22–24]. If the CHA2DS2-VASc score is 0 in men and women or is 1 in women, neither formal anticoagulation nor antiplatelet therapy is

There are few studies available that directly compare antiplatelet therapy, either single or dual agent, directly with formal anticoagulation. In a study conducted by Connely et al., it was investigated whether the addition of clopidogrel to aspirin in patients would reduce the risk of vascular events in patients with atrial fibrillation [11]. The primary end points examined included stroke, myocardial infarction, noncentral nervous system systemic embolism

[3, 9, 15, 16, 20, 22–26]. Finally, the guidelines state for patients with a CHADS2

score of ≥2 for either men or women, formal anticoagulation is recommended



persistent, or permanent AF. Clinical risk assessment tools such as the CHA2

is restored by either pharmacological or electrical cardioversion.

**5. Anticoagulation therapy in atrial fibrillation**

for patients [3, 9, 15, 16, 20, 22–26, 30]. Those with a CHADS2


Anticoagulation for Atrial Fibrillation in Patients with End-Stage Kidney Disease

HAGES and ATRIA bleed. The study showed that the thromboembolic

HAGES was the observed to be the most accurate with the highest c-statistic of

CHADS2, ATRIA stroke, HAS-

http://dx.doi.org/10.5772/intechopen.78022

DS2

score of 1, formal anticoagula-


73

score of 0, no

tion models examined included CHADS2

scores are inadequate for use in patients with CKD.

BLED, HEMORR2

HEMORR2

a CHADS2

with a CHA2

that a CHA2

**5.1. Antiplatelets**

DS2

DS2

advised or required [15, 20, 22–24].

There are several risk scores that can be used to evaluate stroke and bleeding risk in the NVHD sub-group including the HAS-BLED score, the CHADS2 and CHA2 DS2 -VASc score and the ATRIA stroke risk score [18–21]. The CHADS2 stroke risk scoring system was developed based on the analysis of 1773 patients in the National Registry for Atrial Fibrillation and in 2006 and was used in the ACC/AHA/ESC guidelines to tailor therapy for stroke prevention in AF [15]. The scoring system includes points for congestive heart failure, hypertension, age, diabetes and stroke [15, 20]. Previous stroke or TIA is the strongest predictor of stroke and equates for two points, whereas the other risk factors carry one point each. The final score measures the adjusted stroke rate per 100 patient-years [15, 18, 20]. The CHA2 DS2 -VASc score is an updated version of the CHADS2 score as not all patients with a CHADS2 score of 0 were found to be at low risk and was also noted that other risk factors that had been identified were not encompassed by this tool [18, 20, 22]. With the improvement to the CHA2 DS2 -VASc score, the 2012 ESC guidelines and 2014 ACC/AHA/HRS guidelines changed their recommendations to support the use of CHA2DS2-VASc score over the CHADS2 scoring system [18, 20, 22]. In addition to the CHADS2 , the CHA2 DS2 -VASc acknowledges that stroke risk in patients with AF is related to age as a continuous variable, the higher risk of stroke in women, and incorporates risk associated with vascular disease, prior MI, complex aortic plaque, and peripheral arterial disease [18, 20, 22]. The CHA2 DS2 -VASc score states that antithrombotic therapy may be omitted for a score of 0, either oral anticoagulants, aspirin, or no antithrombotic therapy can be considered for a score of 1, and oral anticoagulation is recommended for patients with a prior stroke, TIA, or a score of 2 or more [3, 9, 15, 16, 18, 20, 22–26]. Although CHADS2 and CHA2 DS2 -VASc scores were useful tools in the past in assisting to quantify risk of stroke in patients with NVAF, recent studies have shown that the CHA2 DS2 -VASc score is only able to correctly predict strokes in approximately 68% of cases [3, 18, 22]. The HAS-BLED scoring system was developed in 2010 as a result of the Euro Heart Survey and aims to assess the 1-year risk of major bleeding in patients with AF [18, 21]. The scoring system includes points for hypertension (Systolic >160 mmHg), abnormal renal function, liver function, stroke in past, bleeding, labile international normalized ratio (INR), age ≥65, consuming drugs and consuming alcohol [19, 21]. The scoring system is based on a maximum of nine points with each risk factor worth one point each [18, 21]. A score of 3 or more indicating an increased 1-year bleed risk on anticoagulation is sufficient to justify caution or more regular review [19–21].

While there are other more contemporary risk assessment scoring systems available, such as the ABC (age, biomarkers, clinical history) stroke risk score as devised from Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARIS-TOTLE) study, their applicability is somewhat limited, as several key risk factors included are not routinely measured, and have also yet to be widely validated in population studies [27].

Information on how to best predict stroke risk in the ESKD population is limited and precludes the ability to identify patients at high risk for stroke. No stroke risk prediction scores have been specifically developed for patients with ESRD with AF. Existing thromboembolic and bleeding risk prediction scores show good standardization of stroke risk in the general population, but performs poorly in the ESKD population. McAlister et al. conducted a retrospective large cohort study comparing the effectiveness of current thromboembolic and bleeding risk prediction scores in patient with NVAF and CKD [28]. The seven risk prediction models examined included CHADS2 , CHA2DS2 -VASc, R2 CHADS2, ATRIA stroke, HAS-BLED, HEMORR2 HAGES and ATRIA bleed. The study showed that the thromboembolic risk scores did not perform differently from each other, where the negative predictive value was not seen to be significantly different from each other. In terms of bleeding risk score, HEMORR2 HAGES was the observed to be the most accurate with the highest c-statistic of 0.66 [28]. Furthermore, the study also showed that each of the seven risk prediction scores performed significantly better for patients with normal kidney function than in patients with CKD with performance significantly worsened as severity of kidney disease increased [28]. Therefore, the study suggests that current thromboembolic and bleeding risk prediction scores are inadequate for use in patients with CKD.

There is no difference in the indications for anticoagulation therapy between paroxysmal, persistent, or permanent AF. Clinical risk assessment tools such as the CHA2 DS2 -VASc score do not fully account for thromboembolic risk, and stroke can occur even after a sinus rhythm is restored by either pharmacological or electrical cardioversion.
