The meaning of bites on the vectorcardiogram: study in adriamycin cardiomyopathy

We examined 106 VCGs of cancer patients receiving Adriamycin (ADM) to investigate the nature and meaning of bites. It is known that ADM causes patchy areas of myocardial degeneration and necrosis, the appearance of which is dose dependent. Thirty-eight cancer patients not yet receiving ADM were examined to provide controls. Patients were divided into six groups, according to total cumulative ADM dose received. The incidence of bites in the different groups was shown to be as follows: group 1 (controls, 38 patients) 13.1%; group 2 (1-100 mg/m2 of body surface ADM, 23 patients) 39.1%; group 3 (101-200 mg/m2, 33 patients) 42.2%; group 4 (201-300 mg/m2, 25 patients) 56%; group 5 (301-400 mg/m2, 15 patients) 66.6%; group 6 (greater than 400 mg/m2, 10 patients) 90%; groups 2-6 52.8%. These percentages show a trend which is highly correlated with the total cumulative dose of ADM (p=0.00005). The influence of age on the appearance of bites has been excluded by analyses of trends in patients below and over 50 years (p=0.08). In 80.35% of cases, bites appear on more than one plane and mostly close to the maximum vector (Vmax). We therefore think that these results favor the hypothesis that bites are the electrophysiologic expression of lesions, such as small fibrotic and necrotic areas, which interfere with the normal spread of the ventricular depolarization wavefront.