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We thank Dr Nigro and Dr Velez for their interest [1Nigro J.J. Velez D.A. Retrograde cardioplegia for myocardial protection during arterial switch operation (letter).Ann Thorac Surg. 2014; 97: 2233-2234Abstract Full Text Full Text PDF Scopus (1) Google Scholar] in our study [2Bojan M Peperstraete H Lilot M et al.Cold histidinetryptophan-ketoglutarate solution and repeated oxygenated warm blood cardioplegia in neonates with arterial switch operation.Ann Thorac Surg. 2013; 95: 1390-1396Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar]. The usefulness and safety of retrograde cardioplegia for the arterial switch operation in neonates has been demonstrated for a long time [3Yonenaga K. Yasui H. Kado H. et al.Myocardial protection by retrograde cardioplegia in arterial switch operation.Ann Thorac Surg. 1990; 50: 238-242Abstract Full Text PDF PubMed Scopus (13) Google Scholar], and the excellent myocardial cooling achieved by retrograde cardioplegia may account for the favorable clinical results. However, it is acknowledged that cardioplegia delivered through the retrograde route confers variable levels of protection, because of its preferential distribution to the left ventricle and the anterior septum [4Rangaraj A.T. Ghanta R.K. Umakanthan R. et al.Real-time visualization and quantification of retrograde cardioplegia delivery using near infrared fluorescent imaging.J Card Surg. 2008; 23: 701-708Crossref PubMed Scopus (9) Google Scholar], and to the higher incidence of anomalies in the venous circulation of the heart compared with the arterial circulation. An anatomic study of explanted adult hearts showed that 67% of retrograde-delivered cardioplegia was shunted through thebesian veins, thereby bypassing the microvasculature of the myocardium, whereas approximately 29% traversed the myocardium supplied by the left coronary artery, and approximately 4% traversed the myocardium supplied by the right coronary artery [5Gates R.N. Laks H. Drinkwater D.C. et al.Gross and microvascular distribution of retrograde cardioplegia in explanted human hearts.Ann Thorac Surg. 1993; 56 (discussion 417): 410-416Abstract Full Text PDF PubMed Scopus (53) Google Scholar]. A study in seven explanted pediatric human hearts identified competent coronary vein valves in five hearts requiring significant pressure gradients before opening [6Pan C. Huang A.H. Dorsey L.M. Guyton R.A. Hemodynamic significance of the coronary vein valves.Ann Thorac Surg. 1994; 57 (discussion 430–1): 424-430Abstract Full Text PDF PubMed Scopus (19) Google Scholar]. Besides, anomalies of the venous system of the myocardium are well known in the congenitally corrected transposition of the great arteries [7Bottega N.A. Kapa S. Edwards W.D. et al.The cardiac veins in congenitally corrected transposition of the great arteries: delivery options for cardiac devices.Heart Rhythm. 2009; 6: 1450-1456Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar]. Such investigations lack patients with uncorrected transposition. Finally, neonatal myocardial protection is a global approach, with respect to the adequacy between the bypass temperature, the choice and timing of the cardioplegia solution, the control of the infusion pressure [8Kronon M. Bolling K.S. Allen B.S. Halldorsson A.O. Wang T. Rahman S. The importance of cardioplegic infusion pressure in neonatal myocardial protection.Ann Thorac Surg. 1998; 66: 1358-1364Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar], the control of metabolic homeostasis, and left ventricle dilation at separation from bypass. Normothermic bypass has been the choice at our institution for several years in neonates, and cardioplegia was adjusted accordingly. However, we agree that, despite all the potential drawbacks of retrograde cardioplegia in neonates, myocardial protection may be inadequate with the decreased metabolic requirements of a hypothermic, nonworking heart. Retrograde Cardioplegia for Myocardial Protection During Arterial Switch OperationThe Annals of Thoracic SurgeryVol. 97Issue 6PreviewWe read with great interest the article by Bojan and colleagues [1] in which they described myocardial protection techniques for the neonatal arterial switch procedure. We agree that a fresh look at this population is warranted, given that care for these patients has undergone tremendous evolution. Protection strategies have evolved from one of deep hypothermic circulatory arrest to continuous systemic perfusion with intermittent blood cardioplegia and now single-dose crystalloid cardioplegia. The results of this operation have consistently improved, so there is a relatively small mortality risk; hence, the operation is now commonly deployed for more complex lesion sets. Full-Text PDF