Atrial fibrillation risk prediction

Risk prediction in specific conditions following stroke or TIA using modeling is helpful in targeting secondary preventive treatments that might themselves be associated with benefit and harm. Models can provide data on the risk for a specific patient, which can then more reliably inform the risk - benefit ratio for that individual and guide decision making about treatment. Risk models have been developed in symptomatic carotid disease (Ch. 27) and atrial fibrillation (Ch. 14) and these will be discussed below. 

Atrial fibrillation is a well-recognized risk factor for TIA and stroke, and many studies have identified independent prognostic factors for stroke in all patients with non-rheumatic atrial fibrillation (NRAF), irrespective of previous cerebrovascular disease (Stroke Prevention in Atrial Fibrillation Investigators 1992a, b Atrial Fibrillation Investigators 1994). The CH ADS2 score has been derived and validated to predict the risk of stroke for patients with atrial fibrillation and includes previous cerebrovascular disease as one of the independent risk factors (Gage et al. 2001) (Ch. 2). 

Development Group for the NICE national clinical guideline for management of atrial fibrillation in primary and secondary care. Risk factors for anticoagulation-related bleeding complications in patients with atrial fibrillation a systematic review. Quarterly Journal of Medicine 100 599-607 Joakimsen O, Bonaa KH, Mathiesen EB et al. (2000). Prediction of mortality by ultrasound screening of a general population for carotid stenosis the Tromso Study. Stroke 31 1871-1876... 

Tai CT, Chiang CE, Lee SH, Chen YJ, Yu WC, Feng AN, Ding YA, Chang MS, Chen SA. Persistent atrial flutter in patients treated for atrial fibrillation with amiodarone and propafenone electrophysiologic characteristics, radiofrequency catheter ablation, and risk prediction. J Cardiovasc Electrophysiol 1999 10(9) 1180-7. 

Alternatives to amiodarone include the type Ic drugs (e.g., fle-cainide and propafenone) and the type III blockers (e.g., sotalol and dofetilide). Because of the risk of pro arrhythmia, the type Ic drugs should be reserved for those without heart disease (i.e., lone atrial fibrillation). Sotalol has been shown to be at least as effective as quinidine in preventing recurrences of atrial fibrillation." However, treatment with either quinidine or sotalol is associated with a similar incidence of torsade de pointes. Since this form of proarrhythmia occurs primarily with higher doses of sotalol (quinidine usually causes torsade de pointes at low or therapeutic concentrations), it may be predicted more easily and therefore avoided. Nonetheless, it is possible that sotalol increases mortality in patients with atrial fibrillation similar to quinidine, and this requires further study." ... 

MTWA abnormahties occur at lower thresholds but at higher heart rates in patients at high risk for SCD (51). It is critical to measure MTWA at heart rates within a fixed range to maximize the predictive value with an optimal rate of 110 beats/minute. Exercise and pacing have been used for this but it can be difficult to maintain a fixed rate in the proper range especially in patients with atrial fibrillation. A recent meta-analysis estimated a negative predictive value of 91% but a positive predictive value of only 19%. The risk of an indeterminate test is high. 

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