Assessment of the diagnostic value of 24-hour ambulatory electrocardiographic monitoring.

During the 1st year of operation of a national 24-hour ambulatory ECG-monitoring service, 531 recordings were collected. The information from these recordings and accompanying patient diaries were classified according to the indication for monitoring, the presence or absence of the 'indicated' sympton or other symptom in the diary and the presence or absence of correlating arrhythmias on the tape. On the basis of this categorization 7.5% of recordings were considered completely diagnostic (indicated symptom noted in diary with correlating arrhythmias). An additional 26.6% or recordings, although not completely diagnostic, were considered clinically useful in that they provided information regarding the relationship of symptoms to arrhythmias or the presence or absence of arrhythmias. Major causes of loss of information were poorly completed diaries or no diary, lack of precise definition of the indication for monitoring and technical faults resulting in uninterpretable recordings. Rectification of these deficiences could improve the efficiency of data collection and analysis.