Late potential analysis in Chagas disease using the vector spectral combination of orthogonal leads

Chagas disease is a major public health problem in South American countries, in the Venezuelan case, the heart is the mainly affected organ. The parasite that produces the disease invades the myocardium, causes muscle and conduction system degeneration, leading to abnormal ventricular contractility and conduction. Late potential (LP) analysis can detect abnormal electric behavior of the ventricles, which has been correlated with the presence of ventricular tachycardia episodes. Time domain methods for LP analysis are widely used but they are affected by other cardiac pathologies, i.e., branch blocks (BE), which are found simultaneously with abnormal ventricular conduction phenomena in chagasic patients. The use of an orthogonal lead vectorspectral combination using the Hartley transform has demonstrated to be a simple frequency domain method for the interpretation of abnormal ventricular potentials. This work uses the latter approach for LP analysis of high resolution ECG (HRECG) records of chagasic patients. The vectorspectral magnitude (S) was computed as the sum of the DHT spectra components of the XYZ leads in the frequency bands of 60 to 300 Hz and -300 to -60 Hz, for each chagasic patient group and a healthy subject control group in a time window at the end of QRS. Results showed that S is significantly lower in healthy subjects (63.5/spl plusmn/23.8 /spl mu/V) than in chagasic patients with abnormal electrocardiogram (89.2/spl plusmn/43.7 /spl mu/V), p<0.05. The vector spectral analysis is a simple frequency domain method for LP study, the results showed that the method can detect positive patients with generalized myocardial disease.