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

BackgroundThe effects of different breath-holding positions during electrocardiographic (ECG) recording on the QRS complex are unknown.MethodsIn 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.ResultsThe mean effect of respiration in most leads was small (≥1 mm only in the S wave in V4 and in the R wave in V5), but the degree of interindividual variability was often substantial, with standard deviations of ≥1.5 mm in multiple leads.ConclusionThe 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.