Echocardiographic assessment of patent ductus arteriosus flow pattern in preterm infants
Dear Editor: The recent article of retrospective comparison of two methods, colour Doppler ductal diameter and pulsed Doppler flow pattern, as echocardiographic indicator for patent ductus arteriosus (PDA) treatment in preterm infants by Condo' et al was well-designed and interesting. We agree the conclusions of that both methods are significantly associated, and may use as a cross check to assist in the management of preterm infants with a PDA. However, the following statement in the Discussion caused a little concern: "If, instead, treatment is indicated by a pulsatile or growing pattern, as was done in another RCT, a substantial proportion of infants may be treated despite having a ductal diameter <2.0 mm". The reference given here is our RCT. Although, as found in their study, 40 of the 83 echocardiographic traces classified as growing or pulsatile had a diameter <2.0 mm, their flow patterns did reveal a significant left to right shunting and did reflect the realistically hemodynamic status of the PDA that deserved treatment. The authors described that 82.4% of the PH pattern group having ductal diameter values >2.0 mm. However, there was no data showing the percentage of transition from PH pattern to closing or closed pattern. According to our previous reports,[3,4] about 50% of PH patterns remained to be non-significant PDA and changed to closing or closed patterns. And if a ductal diameter >2.0 mm is used as the indicator of treatment as suggested by the authors, 41.2% infants with PDA of PH pattern may be treated unnecessarily despite remaining non-significant and finally closed spontaneously. The authors indicated that a significant portion (28/197, 14.2%) of echocardiographic studies had a flow pattern could not be clearly classified. These traces appeared intermediate between the pulsatile and closing patterns. We would like to remind that the classification of PDA flow pattern depends on the profile of the pulsed Doppler wave form as well as the flow velocity, the pulsatile pattern has a left to right shunting with a pulsatile notched contour of peak flow velocity about 1.5 m/second, and closing pattern has a characteristic continuous profile with a peak flow velocity of about 2 m/second.[3,4] Finally, we would like to highlight the importance of the sequential echocardiographic assessment of the hemodynamic status of PDA rather than to depend only on a spot time measurement. What is most important is whether the echocardiographically derived index can detect prospectively the development of clinically significant PDA.
REFERENCES 1. Condo' M, Evans N, Bellu' R, Kluckow M. Echocardiographic assessment of ductal significance: retrospective comparison of two methods. Arch Dis Child Fetal Neonatal Ed on line first, published on May 5, 2011. 2. Su BH, Lin HC, Chiu HY, Hsieh HY, Chen HH, Tsai YC. Comparison of ibuprofen and indometacin for early-targeted treatment of patent ductus arteriosus in extremely premature infants: a randomised controlled trial. Arch Dis Child Fetal Neonatal Ed 2008;93:F94-F99 3. Su BH, Watanabe T, Shimitzu M, et al. Echocardiographic assessment of ductus arteriosus shunt flow pattern in premature infants. Arch Dis Child Fetal Neonatal Ed 1997;77: F36-40. 4. Su BH, Peng CT, Tsai Ch. Echocardiographic flow patterns of patent ductus arteriosus: A guide to indomethacin treatment in premature infants. Arch Dis Child Fetal Neonatal Ed 1999;81:F197-20.
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