Session P36.7

Effect of Heart Rate and Body Position on the Complexity of the QRS and T Wave in Healthy Subjects

VN Batchvarov, G Bortolan*, II Christov

ISIB-CNR
Padova, Italy

The effects of heart rate and body position on the complexity of the QRS and T waves have been analyzed. Principal component analysis (PCA) has been used for quantifying the complexity of the ECG waves. A group of 15 healthy subjects (8 men, 7 women, age 28.6±7.5 years) was considered. Continuous digital 12-lead ECG (500 Hz, 4.88 µV resolution) was recorded for 25 minutes in supine and standing position (5 minutes supine, 10 minutes standing, and then 10 minutes supine). Another recording was performed on same individual after approximately 1 week at the same time of the day. The first 2 minutes and the last 30 seconds of recording in each position were excluded from the study. Segments with noise or premature beats were excluded too. Principal component analysis has been applied to the intervals of QRS and T waves, and the ratio of 2nd/1st eigenvalue is the parameter used for this analysis. In the group as a whole, QRS-PCA and T-PCA did not differ significantly between standing and supine positions, despite significant increase in heart rate in standing position. However, the linear correlation coefficient between the PCA parameters and the RR interval varied widely between different subjects in the supine position (QRS-PCA: from 0.002 to 0.61; T-PCA: from 0.01 to 0.65) and even more in standing position (QRS-PCA: from -0.55 to 0.48; T-PCA: from -0.63 to 0.51). In both positions, the intra-subject variability of QRS-PCA and T-PCA was significantly smaller than the inter-subject variability.

(Abstract Control Number: 2)