This paper describes a basis for the analysis of serial electrocardiograms by a small digital computer. Two ECG interpretations from a patient can be stored on a computer disc for recall when a subsequent ECG is presented for interpretation, thereby enabling a comparison to be made between up to three serially recorded ECGs. The first ECG recorded from each patient is always retained while subsequent ECGs can be. overwritten. This allows the detection of sequential ST-T changes, and permits computer comment on differences between one ECG and another due to day-to-day variation. With the use of the presently available computing facilities, the technique allows the storage of over 25 000 ECG reports obtained from 17 000 patients.
Interest in the computer interpretation of electrocardiograms is steadily increasing :and several automated systems are now in operation (I-10). Nevertheless some cardi-,ologists are reluctant to accept this form of ECG interpretation for various reasons, including the diagnostic shortcomings of existing computer programs. In particular, the inability to utilize serial electrocardiograms for the detection of sequential ,changes, especially in suspected cases of myocardial infarction, has been regarded as a considerable drawback.
Recently, Pryor and co-workers (II) described a computer technique for reporting changes in serial ECGs with the limitation that the ECG interpretations could not be retained in the computer beyond the patient's stay in hospital. An alternative technique, which was announced previously (12), is described in detail in this paper.
METHODS AND MATERIALS
The methods used for ECG interpretation by computer have previously been discussed (7, 13). In summary, three lead ECGs derived from the modified axial lead system ( ) are analysed on a PDP8E computing system which utilizes 8196 * To whom correspondence should be sent. ,