Atrial Fibrillation Detection

Abstract

A trial fibrillation (AF) is present in ±3% of the general population above age 20, and its prevalence increases substantially in the ≥65-year-olds age group. 1 It is expected that AF prevalence will increase as populations get older. AF is asymptomatic in ≤40% of patients. Unfortunately, the absence of symptoms does not suggest a benign course. 2 The Framingham Heart Study found that stroke is the first manifestation of AF in at least 2% to 5% of AF patients. 3 In a hospital-based series, ≤20% of stroke patients had previously unidentified or unrecognized AF. 4 AF also increases the risk of cognitive impairment and dementia. 5 Identifying AF and reducing stroke risk in patients with AF before stroke occurs is, therefore, an important goal. Whether screening for AF in the general population is warranted is heavily debated. Opportunistic screening refers to screening offered to people as part of a routine medical checkup or when examined for another reason, whereas systematic screening entails screening in the general population (ie, mass screening) or a high-risk, target group (ie, patients with heart failure or diabetes mellitus). Opportunistic screening in patients aged >65 years with pulse palpation or ECG rhythm strip is the current recommended method by the European Society of Cardiology. 6 No recommendation is given in the US guidelines. 7 Pulse palpation is sensitive for detection of permanent AF (the sensitivity is 94%, and its specificity is 72%) but is not specific and requires confirmation with ECG. The equipment and time required to perform an ECG examination are a significant barrier to perform screening, but fortunately new methods for screening are being developed rapidly. 8 Proponents of screening cite the relatively high frequency of AF, the ease of detection and prevention of stroke with AF, and the high risk of stroke in patients with undetected AF as the main reasons for advocating systematic screening in the >65 years age group. The yield of single time-point screening for unknown AF is 1% (1.4% in those >65 years) and depends on the age and ethnicity and risk factor profile of the target population. 9 Only a minority of identified AF patients report symptoms. A significant proportion of patients with known AF who are undertreated are also identified. 10 The concerns with screening are the optimal method, frequency and setting of screenings , the lack of randomized evidence of whether screening will lead to measurable reductions in stroke incidence, and the questionable cost-efficacy of screening approaches. One randomized trial found no clear evidence of benefit of mass screening, but found opportunistic screening with pulse palpation, and found confirmation with 12-lead ECG to be probably cost-effective and superior to both mass screening and targeted screening. 11 However, this trial was performed in the warfarin era before non-vitamin K antagonists with an improved safety profile and reduced patient burden were available. Only half of the patients identified through mass screening attended a follow-up confirmation ECG. Technological advances have made screening without standard 12-lead ECG machines possible, removing at least one barrier to screening in high-risk populations. Low-cost devices attached to cell phones permitting single-lead ECG or dedicated screening devices are now available, which permit easy diagnosis of AF on the spot or allow wireless transmission to a cardiologist or technician for confirmation. 12-14 These devices provide single-lead ECGs of diagnostic quality. Studies comparing these devices head to head with standard 12-lead ECG report sensitivities of 90% to 100% and specificities between 90% and 97%. 8 Indirect methods include blood pressure measurement devices which permit simultaneous screening for AF and high BP and devices that analyze plethysmographic waveforms of cardiac activity attached to a smartphone camera with flash or a pulse oxim-eter. 15,16 False positives are possible with these indirect methods , and subsequent confirmation with ECG is still required. These methods allow screening in primary-care doctor's offices, pharmacies, or other settings where screenings are performed, for example, during influenza vaccinations. The costs are also substantially less.