Quantitative assessment of coarctation in infancy by Doppler spectral analysis

Abstract

The recognition of coarctation (as well as residual or recurrent coarctation) after surgical repair requires the demonstration of an abnormal pressure gradient between the central aorta and the legs. Careful physical examination, including assessment of the quality of femoral pulses by palpation, provides a rough indication concerning stenosis of the aorta at the anastomotic site. In many cases, however, the interpretation of results of this subjective quantification remains ambiguous. Measurement of systolic blood pressure in brachial and femoral arteries is a generally accepted method for quantification of recoarctation. However, the technique of noninvasive blood pressure measurements in infants and small children by the application of a cuff around upper and lower limbs is often cumbersome and in many cases unreliable. The diagnosis may be difficult, especially when the value of the pressure gradient is close to the commonly accepted 20 mm Hg, which is considered indicative of a hemodynamically significant coarctation. Direct pressure measurement by the “pull through” catheter technique is seldom performed for diagnostic reasons because of its invasive nature. To avoid this choice we performed spectral analysis of arterial Doppler signals, a technique with considerable potential for the hemodynamic assessment of proximal obstructions. 1,2 When the obstruction is hemodynamically significant, that is, producing a pressure gradient across the stenosis, characteristic changes in blood flow pattern will occur, even at a remote place of measurement. The purpose of this study was (1) to assess the clinical applicability of Doppler spectral analysis in the diagnosis of coarctation in infancy; and (2) to determine those parameters associated with the components of the waveform that correlate closest with the presence of a hemodynamically significant gradient between the right brachial and femoral arteries.