We thank Dr Kuusela for his interest in our work and for sharing his thoughts regarding the anatomy of the right ventricular moderator band and the proposed interventricular vein.
Our original article focused specifically on the moderator band, a well-defined muscular structure of established significance in the cardiac conduction system, particularly in conveying right bundle branch fibers to the anterior papillary muscle. While the concept of associated venous structures or fetal shunting mechanisms is certainly intriguing from a developmental and physiological perspective, we respectfully consider such hypothesis to be beyond the scope and not directly relevant to the content of our publication.1
In our report, nonetheless, we showed features from an 11-week fetal heart. Since then, we have had the opportunity to examine over 20 datasets comprising serially sectioned human fetal hearts ranging from 9 to 36 weeks' gestation. This is part of an ongoing study devoted to the fate of the embryonic nodoventricular and fasciculoventricular pathways, which has not yet been submitted for publication.1
None of these specimens showed anatomical features consistent with the interventricular venous structure described by Dr Kuusela. Furthermore, no septal deficiencies were identified that would suggest a transient right-to-left channel during fetal life.
Histologically, we observed that the ventricular myocardium—both in the free walls and the septum—is composed of chains of individual cardiomyocytes arranged within a three-dimensional fibrous matrix. While small arteries and veins naturally traverse this meshwork, none have shown a consistent trajectory or configuration that supports the existence of a structured venous pathway linking the ventricles.
Scientific discussion benefits from both curiosity and critical scrutiny. While our findings do not support the presence of the proposed interventricular vein; we value the opportunity to clarify our observations and contribute to a constructive academic exchange. Continued research on fetal cardiac anatomy, supported by multidisciplinary approaches and reproducible data, remains essential to advance our understanding of this field.
Footnotes
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Reference
- 1.González-Casal D., Sánchez-Quintana D., Jiménez Restrepo A., et al. The right ventricular moderator band: from Leonardo da Vinci's drawings to current cardiac imaging. JACC Case Rep. 2024;29(21) doi: 10.1016/j.jaccas.2024.102647. [DOI] [PMC free article] [PubMed] [Google Scholar]