The influence of recording technique on the normal atrial vectorcardiogram

Atrial spatial vectorcardiograms (P sÊ-loops) were recorded for 20 normal individuals using high gain amplifiers with different halfpower upper frequency limits. The effects of deep inspiration and expiration were also recorded, showing that maximal respiratory movements alter the P sÊ-loop in an unpredictable fashion. Differences in the maximal frequency response of the vectorcardiograph influenced the configuration of the P sÊ-loop recorded. It is suggested that a maximal frequency response of 50 Hz is satisfactory for the recording of P sÊ-loops for clinical and some research purposes.