Electrocardiogram monitoring at rest and during exercise in 31P magnetic resonance spectroscopy studies of the human heart at 1.9 tesla.

An electrocardiogram (ECG) monitoring system has been developed and evaluated in normal volunteers (n = 7) and patients with various cardiac diseases (n = 24) in a 1.9 tesla magnet during magnetic resonance spectroscopy studies. To minimize an ECG signal path, and thus to reduce motion-related artifacts on the ECG during a dynamic exercise test, one coaxial cable was used to obtain the ECG signal from two electrodes placed parallel to the longitudinal body axis on the left side of the chest. A fiber optic link and an inductor-capacitor low-pass filter were used to remove extraneous radiofrequency (RF) noise and RF pulse artifacts respectively, and the examination bed was solidly supported on the base of the magnet. The ECG monitoring system provided a useful means for continuous recording of the ECG independently of the R-R interval in the high magnetic field, and permitted reliable monitoring of the QRS complex of the subject at rest and during exercise.