CAVIAR: a tool to improve serial analysis of the 12-lead electrocardiogram

An important part of an electrocardiogram (ECG) interpretation is the comparison between the present ECG and earlier recordings. The purpose of the present study was to evaluate a combination of two computer-based methods, synthesized vectorcardiogram (VCG) and CAVIAR, in this comparison. The methods were applied to a group of 38 normal subjects and to a group of 36 patients treated with anthracyclines. A fraction of these patients are likely to develop cardiac injury during or after the treatment, since anthracyclines are known to cause heart failure and cardiomyopathy. Two ECGs were recorded on each patient, one before and one after the treatment. On each normal subject, two ECGs were recorded with an interval of 8-9 years. A synthesized VCG was calculated from each ECG and the two synthesized VCGs from each subject were analysed with the CAVIAR method. The CAVIAR analysis is a quantitative method and normal limits for four measurements were established using the normal group. Values above these limits were more frequent in the patient group than in the normal group. The conventional ECGs were also analysed visually by an experience ECG interpreter without knowledge of the result of the CAVIAR analysis. No significant serial changes were found in 10 of the patients with high CAVIAR values. Changes in the ECGs were found in two patients with normal CAVIAR values. In summary, synthesized VCG and CAVIAR could be used to highlight small serial changes that are difficult to find in a visual analysis of ECGs.