Low QRS Research Articles

Clinical significance of high frequency QRS potentials in myocardial infarction: analysis based on power spectrum of lead III

Power spectrum analysis of ECG lead III QRS potentials using the Fast Fourier Transform technique was performed in 10 normal subjects and nine patients with inferior wall myocardial infarction (IWMI). A relative lowering in both low and high frequency QRS potentials was observed in the infarct group, in agreement with previous studies on power spectrum of lead II. However, contrary to earlier conclusions, the lowering was independent of a general attenuation in QRS voltages. Discriminant analysis of the frequency components showed that the high frequency components (190-310 Hz) were able to discriminate better between the two groups than the low frequency components (10-120 Hz).

Electrocardiographic alterations in diphtheria.

Electrocardiographic abnormalities in five cases of diphtheria have been described. The abnormalities found were grade I and Wanckebach’s A-V block, low voltage QRS, partial or complete left bundle branch block, premature beats and an infarction-like pattern. It is observed that the prognosis of myocarditis is not necessarily bad even in the presence of electrocardiographic abnormalities.