Acceleration induced voltage variations in the electrocardiogram during exhaustive simulated aerial combat maneuvering.

The high sustained +Gz acceleration of aerial combat maneuvering represents a unique cardiovascular stress. Twenty-two healthy males were subjected to exhaustive simulated aerial combat maneuvers (SACM) on a centrifuge, followed by the time course of the P, QRS, and T-wave voltage changes. Marked changes in the T-wave were noted both during and after SACM. In addition to characteristically being tall peaked T-waves with a narrow base, the maximum mean change in T-wave amplitude was 5.1 mV at 1 min post SACM. Although significant changes in the individual R and S-waves occurred, the overall QRS amplitude did not change. The normal response of apparently healthy asymptomatic individuals to maximum exhaustive G-stress includes a decrease in R-wave amplitude similar to the response to treadmill exercise seen in healthy individuals. The etiology of the electrocardiographic changes to +Gz stress has not been fully elucidated. Serum potassium levels were measured and found to be increased immediately post SACM as compared to pre-Gz stress levels. Whether or not hyperkalemia significantly contributes to the late and post SACM T-wave amplitude and configurational changes is unknown. Adrenergic stimulation and other changes undoubtedly also play a significant role in the observed changes. Documentation of the normal electrocardiographic response to +Gz stress and correlation with the known hemodynamic changes resulting from +Gz stress should increase the knowledge of what factors influence the surface electrocardiogram.