A Prolonged Ambulatory Electrocardiogram Recorder

Abstract

The ambulatory electrocardiogram (ECG) recorder has been in existence for more than two decades. It is used to document the transient electrocardiographic events in a patient over a protracted period. The conventional ambulatory electrocardiogram recorder, including the advanced ones, can only operate for 24 hours or so due to the memory storage constraints. In certain cases, a longer recording period is required in order to capture the symptoms that don't occur during the 24-hour recording cycle. This thesis deals with the development of a prolonged ambulatory electrocardiogram recorder that is capable of operating for three days and recording two channels of electrocardiographic data in a continuous fashion. Practicability is given first priority in design. To minimize the cost of this instrument, a tape storage technique has been employed in this project. Generally, the operating time of an ambulatory electrocardiogram recorder is restricted by the length of tape. The technology developed in this project superimposes the timing mark onto the electrocardiographic data and lets the tape move in two directions so that the track on the tape surface previously occupied by the timing mark is utilized for storage of the electrocardiographic data. In this manner, the memory size is doubled and the desired operating time can be achieved. To ensure portability and adequate power life, a switchmode dc-dc voltage converter is employed. As a result, the number of batteries needed for operation is made desirably few. To implement the design, a portable auto-reverse music player (Sony ·Walkman) was purchased and modified into an ambulatory electrocardiogram recorder. The ambulatory ECG recorder developed in this project was tested on a subject as well as on two patients at the Royal University Hospital. The results show that it is capable of operating for as long as three days and the recorded data are very close to the original ECG signal in shape.