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Can Natural Anomalies Inform Surgical Design? A Reappraisal of Coronary Origins in HLHS

Monday, June 18, 2018

By

Mohammed Al-Jughiman

Al-Jughiman M. Can Natural Anomalies Inform Surgical Design? A Reappraisal of Coronary Origins in HLHS. June 2018. doi:10.25373/ctsnet.6492590

Suboptimal coronary perfusion following the Norwood procedure has been documented in multiple studies (1–5). In response to this ongoing concern, a surgical refinement was conceptualized involving the transfer of coronary arteries to the pulmonary root to potentially optimize coronary hemodynamics in hypoplastic left heart syndrome (HLHS). However, this technique is complex and may not be surgically feasible. 

Gross anatomical examination of post-Norwood HLHS specimens revealed that coronary arteries frequently originate from severely hypoplastic aortic sinuses. The neoaortic reconstruction, formed by amalgamating the hypoplastic ascending aorta and pulmonary artery, typically lies superior to the native aortic root. This configuration raises questions about the adequacy of sinusoidal flow and coronary perfusion dynamics in the reconstructed neoaorta. 

Given the physiological importance of the aortic sinuses in coronary filling, particularly in diastole, the hypothesis was proposed that transferring the coronary ostia to the pulmonary root—an anatomically larger and more favorable structure—may improve coronary flow characteristics in the Norwood circulation. This concept was investigated using computational fluid dynamics (CFD) modeling to evaluate potential differences in perfusion dynamics between the standard Norwood configuration and the proposed modification (6). 

The relevance of this investigation is further supported by recent work from Saiki et al. (7), who demonstrated persistent coronary malperfusion even when the Sano modification is used. These findings reinforce the need to explore alternative coronary configurations to optimize myocardial oxygen delivery in patients undergoing single-ventricle palliation. 

A historical case reported by Bharati et al. in 1984 describes a patient with HLHS and anomalous origin of both coronary arteries from the pulmonary trunk (8). The patient, deemed inoperable at that time, passed away on the third postnatal day. However, had the Norwood procedure been performed, the native pulmonary trunk containing both coronary arteries and the right ventricle would have been rendered systemic. This congenital configuration functionally resembles the proposed modification in reverse, raising compelling anatomical and physiological parallels. 

This conceptualized surgical refinement is not an invention but rather an anatomical and hemodynamic reassessment based on existing morphological variants and computational modeling. Surgical innovation in the current era requires rigorous simulation, physiological justification, and reproducible modeling prior to clinical application. The pulmonary root coronary transfer offers a conceptual alternative for addressing a well-documented limitation in the current Norwood approach. 

References

  1. Donnelly JP, Raffel DM, Shulkin BL, et al. Resting coronary flow and coronary flow reserve in human infants after repair or palliation of congenital heart defects as measured by positron emission tomography. J Thorac Cardiovasc Surg. 1998;115(1):103-110.
  2. Voges I, Jerosch-Herold M, Hedderich J, et al. Maladaptive aortic properties in children after palliation of hypoplastic left heart syndrome assessed by cardiovascular magnetic resonance imaging. Circulation. 2010;122(11):1068-1076.
  3. De Oliveira NC, Ashburn DA, Khalid F, et al. Prevention of early sudden circulatory collapse after the Norwood operation. Circulation. 2004;110(11 Suppl 1):II133–138.
  4. Furck AK, Hansen JH, Uebing A, Scheewe J, Jung O, Kramer HH. The impact of afterload reduction on the early postoperative course after the Norwood operation - a 12-year single-centre experience. Eur J Cardiothorac Surg. 2010;37(2):289-295.
  5. Feinstein JA, Benson DW, Dubin AM, et al. Hypoplastic left heart syndrome: current considerations and expectations. J Am Coll Cardiol. 2012;59(1 Suppl):S1-42.
  6. Al-Jughiman MK, Al-Omair MA. Modelling coronary flow after the Norwood operation: influence of a suggested novel technique for coronary transfer. Glob Cardiol Sci Pract. 2018;2018(1):7.
  7. Saiki H, Kuwata S, Kurishima C, Masutani S, Senzaki H. Vulnerability of coronary circulation after Norwood operation. Ann Thorac Surg. 2016;101(4):1544-1551.
  8. Bharati S, Szarnicki RJ, Popper R, Fryer A, Lev M. Origin of both coronary arteries from the pulmonary trunk associated with hypoplasia of the aortic tract complex: a new entity. J Am Coll Cardiol. 1984;3(2 Pt 1):437-441.
  9. Norwood WI, Lang P, Castaneda AR, Campbell DN. Experience with operations for hypoplastic left heart syndrome. J Thorac Cardiovasc Surg. 1981;82(4):511-519.
  10. Norwood WI, Lang P, Hansen DD. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med. 1983;308(1):23-26.

Comments

Submitted by Mohammed Al-Jughiman on
Donnelly and colleagues studied the rest and reserve myocardial perfusion using positron emission tomography in patients after anatomic repair of a congenital heart lesion, and after Norwood procedure for HLHS. Notably, all patients with the Norwood procedure in this study had Blalock-Taussig shunt. It is well perceived that there is a diastolic runoff through the BT shunt, creating a diminished diastolic perfusion pressure for the coronary circulation. In this study, the resting coronary flow was significantly less in the Norwood group. Although the coronary flow reserve was not significantly different between the two groups, oxygen delivery to the systemic ventricle was significantly less in the Norwood group at both rest and during adenosine hyperemia. Saiki and colleagues measured the sub-endocardial viability ratio in 29 patients with HLHS post Norwood procedure, in 27 patients with pulmonary atresia with aorto-pulmonary shunt, and in 30 control patients who had normal biventricular circulation. They selected patients with PA and AP shunt as disease controls, because the AP shunt produces diastolic runoff, which could potentially jeopardize coronary perfusion. In this study, all patients with the Norwood procedure had right ventricle to pulmonary artery shunt or the Sano shunt. In this study, the sub-endocardial viability ratio in the Norwood patients was significantly lower than the control group, and significantly lower than patients with PA and AP shunt which is the disease control group. Importantly, the authors of this study found that the stiffness index of the aorta was significantly higher in the Norwood group than in the control and disease control groups. In multivariate analysis, they identified the stiffness index of the aorta and aortic size discrepancy as independent determinants of the sub-endocardial viability ratio. This study indicated that patients post Norwood procedure even if they received Sano shunt would have a suboptimal coronary perfusion compared to normal, and compared to other congenital heart lesions even with aorto-pulmonary shunt. In other words, coronary mal-perfusion is an intrinsic to the Norwood circulation, and the diastolic runoff associated with BT shunt is only one factor influencing the coronary perfusion after the Norwood procedure. According to the authors of this study, increased aortic stiffness and aortic size discrepancy seemed to be more important patho-physiologies of the reduced sub-endocardial viability ratio post Norwood procedure. From these two and several other studies, we can conclude that coronary perfusion after the Norwood procedure is suboptimal whether BT shunt or Sano shunt was used. We believe that this makes it necessary to think of a new modification that would address this concern. As we discussed, the general goal of our study was to evaluate the hemodynamic effect of our proposed modification, the coronary transfer to the pulmonary root during the Norwood procedure. It is obviously a technically demanding modification. In our study, we could not evaluate the technical feasibility of our modification. The question that would arise, is this modification feasible in all aortic root sizes?, if not, what is the minimum aortic root size with which this modification becomes feasible?, for example is it 3 mm, less or more?. Once we finish evaluating our fourth hypothesis, we are planning to survey congenital heart surgeons’ thoughts and opinions on this modification including its technical feasibility.

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