2 The technology

Description of the technology

2.1 The WatchBP Home A device (Microlife) is an oscillometric blood pressure monitor. While recording blood pressure, it automatically detects pulse irregularity that may be caused by symptomatic or asymptomatic atrial fibrillation. The device measures blood pressure based on the guidelines from the European Society of Hypertension (ESH), the American Heart Association (AHA) and the British Hypertension Society (BHS). The monitor can be used for diagnosing hypertension in a clinical setting with the measurement taken under the supervision of a clinician. If hypertension is detected or suspected, the instructions for use state that the device could also be used by the person in their home for monitoring blood pressure over a longer period.

2.2 The WatchBP Home A device has an embedded algorithm that calculates the irregularity index (standard deviation divided by mean) based on interval times between heartbeats. If the irregularity index exceeds a defined threshold value, atrial fibrillation is likely to be present and an atrial fibrillation icon is displayed on the device. If atrial fibrillation is persistent, the diagnosis will be confirmed by an ECG in line with the NICE clinical guideline on atrial fibrillation. If atrial fibrillation is intermittent (paroxysmal), further ambulatory electrical monitoring tests may be needed to establish the diagnosis. To minimise the potentially misleading effect of premature beats when detecting pulse irregularity, each of the pulse beat intervals that deviates more than 25% from the average interval time is excluded from analysis.

2.3 The WatchBP Home A device can be used either in 'diagnostic' mode (4 measurements, 2 between 6 am and 9 am, and 2 between 6 pm and 9 pm, taken on 7 consecutive days) or in 'usual' mode (single measurements taken at any time). Results are stored in an internal memory or can be downloaded to a removable memory device and taken to the clinician for evaluation. In diagnostic mode, this would be after 7 days of monitoring, whereas a variable interval would be agreed with the clinician for monitoring in 'usual' mode. The device automatically displays the mean morning, evening and overall blood pressure results in a table.

2.4 The average cost of the WatchBP Home A device stated in the sponsor's submission is £75 (excluding VAT).

2.5 The claimed benefits of WatchBP Home A in the case for adoption presented by the sponsor are:

  • Provision of a convenient, portable means of measuring blood pressure while simultaneously detecting atrial fibrillation.

  • Reduced risk of stroke by earlier diagnosis of atrial fibrillation, allowing the initiation of appropriate treatment to reduce thromboembolic risk.

  • Reduced morbidity and mortality associated with stroke events.

  • Reduced need for clinic appointments for measuring blood pressure.

  • Cost savings from the reduced incidence of stroke resulting from enhanced diagnosis and treatment of atrial fibrillation.

Current management

2.6 Hypertension is diagnosed by measuring blood pressure either manually or with an automated blood pressure monitor, as outlined in NICE clinical guideline 127 on hypertension. Readings are taken initially in a clinic and can be followed by ambulatory blood pressure monitoring to confirm the diagnosis. Home blood pressure monitoring (usually using an automated monitoring device) can be undertaken for between 4 and 7 days as an alternative if ambulatory monitoring is unsuitable for the person. Treatment options for hypertension include lifestyle changes and/or antihypertensive drugs.

2.7 NICE clinical guideline 127 on hypertension recommends that blood pressure should be measured manually using direct auscultation over the brachial artery following detection of pulse irregularity.

2.8 The current care pathway for atrial fibrillation is described in the NICE clinical guideline on atrial fibrillation. Atrial fibrillation can be difficult to detect and subsequently diagnose as it is often asymptomatic and can be intermittent. The irregularity of heart rhythm caused by atrial fibrillation can be detected by pulse palpation. It may be present in people with symptoms such as palpitations, dizziness, blackouts and breathlessness but can also be found incidentally in people without symptoms during routine examination. The NICE clinical guideline on hypertension recommends that the pulse should be palpated before measuring blood pressure if using an automated monitor. The diagnosis of atrial fibrillation should be confirmed with an ECG when an irregular pulse is identified.

2.9 Current treatment options for atrial fibrillation are dependent on type (acute, persistent, paroxysmal or permanent), response to previous treatment and comorbidities. Treatment is focused on controlling heart rhythm or rate with antiarrhythmic drugs or electrical direct current cardioversion, and reducing the risk of thromboembolic complications with anticoagulant or antiplatelet drugs, according to an individual person's risk profile.

  • National Institute for Health and Care Excellence (NICE)