Unobtrusive long-term monitoring for Atrial Fibrillation

Abstract

This master thesis project explores the use of Photoplethysmogram[PPG] technology to detect of Atrial Fibrillation[AF]. This project proposes a product-service service system for the detection and diagnosis of AF in the current healthcare system in The Netherlands. This thesis is based on interviews with cardiologists, general practitioners and literature research. One in four middle-aged adults in Europe and the US will develop Atrial Fibrillation (Kirchhof et al., 2016). Furthermore, AF is associated with a five-fold risk factor of stroke, while other cardiovascular deaths, such as sudden death and heart failure, are common in AF patients. (Kotecha et al., 2014). AF is a progressive disease, it starts with short episodes that end by themselves, paroxysmal AF, then episodes that have to be stopped in a hospital, persistent AF, and eventually permanent AF. Diagnosing AF in the first stage is difficult, the episodes are short and random, while current monitoring devices only cover up to 48 hours. Thus, the problem is that current diagnostic tools have too short a monitoring period to diagnose paroxysmal AF effectively. The proposal by Philips was to monitor over longer periods, using Philips’ HealthWatch. However, the PPG technology, integrated in the current generation HealthWatch, is too sensitive to movements on the wrist position. This could still result in an inaccurate diagnosis. PPG is a sensor technology that uses a LED to look at the reflections of the blood volume in the skin. Blood volume changes within every heartbeat in a predictable manner. From these changes, it is possible to extract information such as the heart rate. Using an algorithm, it is possible to diagnose AF from this kind of information. However, PPG is also very sensitive to the movement between the skin and the sensor. After an initial exploration of the subject the design proposal was formulated as follows: “To provide a low threshold tool to support the initial diagnosis of (paroxysmal) atrial fibrillation for the General Practitioner while collecting useful data for the further treatment and providing support for the patient.” This proposal led to the creation of Afi, which is a small diagnostic tool based on PPG, that can be deployed by the General Practitioner for unobstructed longer-term monitoring. The Afi is usually placed on the upper arm of the user. Afi was evaluated with some users and healthcare professionals [HCP], namely a GP and a leading cardiologist. The evaluation with the HCP demonstrated that Afi has excellent potential as a new way of diagnosing AF.