Effects of posture and respiration on body surface electrocardiogram

Abstract

To define more fully the effects of posture and respiration on electrocardiographic (ECG) patterns, 120-lead body surface potential maps (BSPM) were recorded in 36 normal subjects (aged 21 to 48 years) during cyclic respiration in both supine and upright positions; and at static end-tidal inspiration, functional residual capacity (FRC), total lung capacity (TLC) and residual volume (RV). In addition, BSPMs were recorded at TLC and RV during the Valsalva and Müller maneuvers, respectively. P-wave, QRS and ST-segment time integrals were evaluated. From supine to upright position, there was an inferior torso shift of P-wave and QRS distributions, but no change in amplitude of their maximal or minimal values; ST-segment distributions were spatially unaltered, but there was a significant (p < 0.01) decrease in the maximal value. Relative to maps during cyclic respiration in the upright position, maps at end-tidal respiration were similar; maps at TLC, however, displayed an inferior displacement of P-wave and QRS distributions and a decrease of QRS maximal and minimal values (p < 0.01). Valsalva and Müller maneuvers were not associated with marked changes in the appearances of BSPMs. The magnitude of variability, as assessed by a root-mean-square index, was greatest between maps recorded at TLC and RV; the least variability occurred between maps recorded at end-tidal inspiration and FRC. The variability between maps recorded in the supine and upright positions was intermediate. When root-mean-square variability data of all interventions were normalized by dividing by the respective mean data range (maximum minus minimum) of each time integral, the variability of P wave > ST segment > QRS (p < 0.01). Thus, resting tidal volume respiration has little effect on body surface ECG patterns in normal adults. However, large volume respiration and posture change may substantially alter ECG body surface distributions and should be considered in states involving either factor.