Abstract
Recent literature 1 , 2 , 3 , 4 contains much work on the significance of the Q-wave, and, more particularly of a large Q-3. Attempts have been made in some of these studies 1 , 4 to explain the mechanism underlying the production of a large Q-wave. Our knowledge of the mechanism of the normal Q-wave (e. g., Lewis'and Wilson's theories) has been used as a basis for discussions of the abnormal Q-waves. Conclusions have been drawn by one author 4 from pathological correlations that the large Q-wave is representative of changes in a well localized portion of the heart (the left half of the septum posteriorly). Insufficient emphasis has been placed on the fact that the names Q, R and S are entirely arbitrary and that the Q-R-S system of terminology frequently gives the same name to parts of the electrocardiogram in the 3 standard leads that do not correspond in time, and different names to parts that do so correspond. We attempted an analysis of the Q-wave in normal records and in records of the large Q-3 type (described by Pardee 1 ) to determine the relative time occupied by this deflection in the belief that this time data would throw light on the significance of the Q-wave in normal and abnormal electrocardiograms. We obtained our time data by using Einthoven's formula: i. e., when on any and every vertical line the electrocardiographic curves can be superimposed so that the height in Lead I added algebraically to that in Lead III gives the height in Lead II, the time relations are identical.
Results. In each of 25 normal ventriculograms Q-l, Q-2 and Q-3 corresponded in time with reasonable accuracy, suggesting that the Q-wave represented a more or less fixed physiological phenomenon in these instances. In ventriculograms of the large Q-3 type (fulfilling Pardee's criteria 1 ) Q-3 did not correspond in time with Q-l or Q-2. The time represented by Q-3 in 50 of these tracings (taken from 1200 consecutive electrocardiograms) was in no case identical with that occupied by Q-l and Q-2. In most of these tracings Q-3 corresponded in time with parts of R-l and R-2. In many of these tracings Q-3 corresponded more or less accurately in time with R-l or R-2.
The results given above indicate that the large Q-3 is not comparable with the normal Q-wave in that it represents a grossly varying time interval after the beginning of the Q-R-S and cannot, therefore, represent a fixed phenomenon in the heart.
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