Economic and Healthcare System Costs of Atrial Fibrillation
AF represents a costly threat to the financial stability of healthcare systems. A prevalence-based analysis of the economic burden of AF in the UK estimated the direct cost of AF to be 0.62 % (£244 million) of the total National Health Service (NHS) expenditure in 1995 and this was projected to account for 0.97 % (£459 million) of the NHS budget in 2000 − reflecting a predicted doubling in only a five-year time span. Yet, this study indicated that these costs were
probably an underestimate. Factoring in the costs of stroke care and length of stay when AF complicates another illness would further increase the expenditure.
In the US, the total annual cost (2005 US dollars) for the treatment of AF was estimated at US$6.65 billion, including US$2.93 billion for hospitalisations. 41 In the Cost of Care in AF (COCAF) survey of 671 AF patients from across France, the annual cost per patient was estimated at €3,209. 42 Furthermore, the Euro Heart Survey on AF (2003−2004) reported that the total annual cost of AF amounted to €272 million in Greece, €3,286 million in Italy, €526 million in Poland, €1,545 million in Spain and €554 million in the Netherlands. 43
The number of hospitalisations due to AF is also increasing. 44,45 In the UK alone, AF accounts for 3 to 6 % of acute hospital admissions. The Euro Heart Survey on AF suggested that inpatient care and interventional procedures account for more than 70 % of total annual costs for AF in five European countries. 43 A national costing report on AF by the National Institute for Health and Clinical Excellence (NICE) in 2006 estimated the unit cost of anticoagulation services to be an average of £565.8 per year per person and the annual cost per case of stroke was estimated to be £7,800. This report estimated the annual cost saving through stroke reduction to be £54.33 million, producing a net resource impact of £21.86 million. 48 However, this may be an underestimation because it does not include the associated comorbidities that would require proactive management in AF.
Risk Stratification for Stroke
Risk stratification for stroke is critical in the management of patients with AF to ensure that patients receive appropriate anticoagulant therapy.
Risk Stratification Schemes
The risk factors for stroke included in current stroke risk stratification schemes are mainly derived from analyses of clinical trials cohorts. The Framingham Stroke Risk Profile was one of the first risk stratification schemes for stroke to be developed. This scheme is gender-specific and includes AF, age, use of antihypertensive therapy, prior cardiovascular disease, cigarette smoking, diabetes mellitus, left ventricular hypertrophy by electrocardiogram and systolic blood pressure. Currently, the CHADS2 (one point each for congestive heart failure, hypertension, age ≥75 years and diabetes, and two points for a previous history of stroke, thromboembolism or transient ischemic attack) scheme is the most frequently used stroke risk stratification scheme (see Table 1). 52,53 Risk factors included in the CHADS2 scheme were selected from those that independently predicted the risk of stroke in AF during clinical trials. However, many risk stratification models have been found to only have a modest predictive value in identifying patients with high thromboembolic risk. In fact, a large proportion of patients are classified into the moderate/intermediate-risk category, causing uncertainty amongst clinicians as to the appropriate treatment strategy.
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Recently, additional risk factors such as female sex, age 65−74 years and vascular disease have been demonstrated to influence the risk of stroke and thromboembolism in AF patients. Consequently, the CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke, thromboembolism or transient ischaemic attack, vascular disease, age 65–74 years, female sex category; age ≥75 years and previous stroke, thromboembolism or transient ischemic attack carry doubled risk weight) scheme was developed to complement the CHADS2 scoring systems (see Table 1). The performance of the CHADS2 scheme was compared to the CHA2DS2- VASc risk scheme by applying both scoring systems to a large nationwide registry of patients admitted to hospital with AF in Denmark. 58 Although the c-statistics – a measure of the predictive value of a risk scoring scheme – were similar when the two risk schemes were tested as continuous point scales, CHA2DS2-VASc had unusually high c-statistics when applied using the traditional categories of low- (CHADS2 score of 0), intermediate- (CHADS2 score of 1–2) and high-risk groups (CHADS2 score of ≥3), which suggests that the new scheme provides improvements in predicting stroke risk
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over the CHADS2 scheme. The annual rate of thromboembolism including peripheral artery embolism, ischaemic stroke and pulmonary embolism in the CHA2DS2-VASc low risk group was 0.78 per 100 person years, compared with 1.67 per 100 person years in the CHADS2 low risk group. Only 8.7 % of the study population met the low risk CHA2DS2-VASc criteria, compared with 22.3 % when using the CHADS2 criteria (see Figure 1). This finding is similar to other assessments, including a UK study in which only 8.6 % of patients with AF in general practice were considered low risk by CHA2DS2-VASc. 59 In the Danish study, the CHA2DS2-VASc scheme performed better than CHADS2 in predicting patients at high risk; 80 % of the patients were considered high risk using CHA2DS2-VASc, however fewer than half would have met high-risk criteria if CHADS2 were used. 58 The study also found that the rate for patients in the intermediate risk group was 4.75 with CHADS2 compared with 2.01 with CHA2DS2-VASc. Thus, the newer stratification methods such as CHA2DS2-VASc appear to offer improved risk stratification, reduce the number of people classified into the intermediate-risk group, which is the category that can cause ambiguity regarding whether to treat with warfarin or aspirin.
Moreover, a recent study assessed the risk of stroke according to specific risk stratification schemes, in a cohort of 662 elderly AF patients treated with warfarin. The results indicated that the CHADS2 and CHA2DS2-VASc schemes had the best c-statistics (0.717 and 0.724, respectively) for predicting the residual thromboembolic risk despite warfarin treatment and that other risk schemes had some limitations in this setting.
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