Effects of breath-holding position on the QRS amplitudes in the routine electrocardiogram

BACKGROUND: The effects of different breath-holding positions during electrocardiographic (ECG) recording on the QRS complex are unknown. METHODS: In 73 subjects, ECG recordings were made in 3 different breath-holding positions: normal expiration (rest), maximum inspiration, and maximum expiration. QRS wave excursions and changes in the frontal electrical heart axis were analyzed. RESULTS: The mean effect of respiration in most leads was small (>/=1 mm only in the S wave in V(4) and in the R wave in V(5)), but the degree of interindividual variability was often substantial, with standard deviations of >/=1.5 mm in multiple leads. CONCLUSION: The effect of different extreme breath-holding positions on the QRS complex is on average small but may be substantial in individuals. Lack of standardization of breathing instructions during recording of the ECG may result in differences in application of amplitude criteria and poorer reproducibility