P-wave detection by digital computer

Abstract

Rapid and accurate detection of arrhythmias in the cardiac intensive care unit is an essential requirement. Most presently operating digital systems utilize the Q-Q interval and the QRS duration or shape to detect premature ventricular contractions. Often an analog R-wave detector is employed to reduce computer time for wave recognition. Few systems are capable of multiple bed, on-line, detection of QRS complexes as well as P- and T-waves. Digital computer processing of spatial velocity or inscription speed is very attractive because it was found to give rather clear definition of the onset and offset of each of these wave times. As a consequence, a very coarse recognition strategy with a low sampling frequency could be used, a factor which reduced digital processing time considerably. A preprocessing electronic network differentiates the vectorcardiographic data and filters them to 20 decibel down at 50 Hz. These preprocessed data are then sampled at 100 Hz and digitally combined to obtain the spatial speed. The onsets and offsets of the P-wave, the QRS complex and the T-wave are found in real time. P-Q, Q-Q, Q-T intervals of 1886 beats in the records of seven patients with various arrhythmias were analyzed both by the computer and by the cardiologist. The results showed excellent agreement in five patients (average 96%) and poor detection by computer in two (average 49%) of P-Q intervals and complete agreement between both methods for Q-Q intervals. The reasons for this discrepancy in some P-Q intervals are discussed.