Determination of lead III Q waves significance. Utility of deep inspiration

The relative clinical significance of lead III Q waves and the effect of inspiration has received added impetus after the finding that Q waves have predictive value for coronary artery disease and asynergy. We studied the effect of deep inspiration on Q waves in leads III and aV_Fin 31 patients and correlated it with the findings at cardiac catheterization. We found that phasic respiration can alter Q-wave duration significantly in leads III and aV_F, regardless of the presence or absence of significant associated coronary artery disease and asynergy, and is therefore of no clinical value in this regard. (Arch Intern Med137:437-439, 1977)