SPECIAL SECTION: LETTER TO THE EDITOR
Reply
Pravin M. Shah, MD, MACC
Hoag Heart and Vascular Institute, Hoag Memorial Presbyterian Hospital, One Hoag Drive, Newport Beach, California 92663, USA
pshah{at}hoaghospital.org
I thank Dr. Masaaki Uematsu for his thoughts related to my editorial comment dealing with hypertrophic cardiomyopathy and diastolic function (1).
Fleming et al. (2) first described myocardial velocity gradients detected by Doppler imaging and demonstrated Doppler velocity gradient waveforms in systole as well as in diastole. They compared these waveforms to rate of change of wall thickness both in systole and diastole and reported cyclic consistency. They showed that over 99% of systolic and 89% of early diastolic peaks in rate of change of wall thickness occurred concurrently with a peak in velocity gradient. Thus, their observations included Doppler velocity gradients during systolic thickening and diastolic thinning of the left ventricular posterior wall. They did not introduce this method "merely for the evaluation of myocardial contractility" even though they speculated on this potential.
As Dr. Uematsu, a second author on the contribution by Shimizu et al. (3), points out, their study showed a relative independence of Doppler myocardial velocity gradients to passive leg raising, which altered transmitral flow velocity profile. However, they also reported that volume-reducing therapy in congestive heart failure resulted in similar directional changes between velocity gradient and transmitral flow. This latter observation clearly indicates influence of preload on both parameters.
Dr. Uematsu considers that a robust aspect of Doppler velocity gradient is in assessment of regional rather than global diastolic function. This optimism ignores a caution expressed by Fleming et al. (2) that Doppler velocity gradient peaks may be influenced by the angle of the ultrasound beam relative to the muscle fibers. An oblique angle of the beam would yield a lower velocity gradient. The ventricular wall is composed of both circular and oblique fibers. This could have a profound effect on the noninvasive measurements of myocardial velocity gradients. Thus, in addition to physiologic and loading conditions mentioned in the editorial comment (1), the myocardial structure in terms of fiber orientation may add yet another confounding factor. We will do well to await further studies in validation and clinical application of this intriguing new Doppler technique.
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References
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1. Shah PM. Hypertrophic cardiomyopathy and diastolic dysfunction. J Am Coll Cardiol. 2003;42:286–287[Free Full Text]
2. Fleming AD, Xia X, McDicken WM, Sutherland GR, Fenn L. Myocardial velocity gradients detected by Doppler imaging. Br J Radiol. 1994;67:679–688[Abstract/Free Full Text]
3. Shimizu Y, Uematsu M, Shimizu H, et al. Peak negative myocardial velocity gradient in early diastole as a noninvasive indicator of left ventricular diastolic function. J Am Coll Cardiol. 1998;32:1418–1425[Abstract/Free Full Text]
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