Abstract
Since coronary artery disease (CAD) is a process characterized by segmental myocardial dysfunction, an analysis of left ventricular (LV) synchrony should be a sensitive indicator of ischemia and could be useful for quantifying small changes in LV function not reflected by global ejection fraction (EF). In the present study the LV phase histogram (PH) of the first harmonic of the Fourier analysis was used to quantitate LV synchrony at rest and at maximal supine exercise (ex) in 5 normal (N1) and 8 CAD patients (pts.). After frequency filtering the multigated data, functional maps of the phase and amplitude of the first Fourier component of the time activity curve of each pixel were created. Each LV PH was obtained by masking the phase image with an LV region, generated semi-automatically and modified if necessary to assure unambiguous LV delineation. The shape and spread of each histogram was characterized by its mean, median, mode, standard deviation (SD), skewness (SK), and kurtosis. Mean LV phase angle was linearly related to the heart rate (r = .80). N1s. had a tight resting PH with slight negative skewness (SD = 10.40 ± .52 (± sem); SK = -.66 ± .15). CAD pts. had a wider resting PH with a slightly larger SD and a significantly more positive skewness reflecting greater contractile asynchrony (SD = 16.53 ± 2.26; SK = .35 ± .22). With exercise the PH distribtion for the N1s. remained tight (SD = 9.53 ± .33) while SK changed little. (SK = -.39 ± .11). In contradistinction, with exercise CAD pts. markedly increased the spread distribution of their LV PH (SD = 27.42 ± 3.77) and increased the number of late pixels (SK = .75 ± .15). 6 pts. had an abnormal (abn.) PH response, including one pt. with a false negative EF study. In all of these pts. the abn. PH response was first seen either at submaximal exercise or at rest. 2 pts. with an abn. EF response had a N1. PH response, but these CAD pts. showed an ampltitude image abnormality which was not quantified in this study. We conclude that quantitative PH analysis is a useful adjunct for the analysis of stress RNV, and has the potential for increasing the sensitivity of this procedure.
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