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May 16, 2024/Pediatrics/Cardiology

Personalized Surgical Planning for Aortic-Valve Sparing Operations in Children and Young Adults

Center uses advanced imaging techniques to optimize valve repair strategies

3D reconstruction of aortic root in congenital heart disease

By Justin T. Tretter, MD

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Congenital abnormalities of the aortic valve, such as a bicuspid aortic valve, affect up to 2% of the population. Over 10% of these patients will require surgery during childhood for significant valve dysfunction. A much larger proportion will require surgery within their young adult years.

Furthermore, aortic valve disease, or dilation of the aortic root with or without aortic valve disease, is common in those with various forms of congenital heart disease, both preceding and following repair of their defects, or in those with various forms of genetic-based aortopathies. Such conditions include tetralogy of Fallot, common arterial trunk, those with transposition of the great arteries following an arterial switch procedure, Marfan syndrome, and Loeys-Dietz syndrome, amongst others.

Unmet surgical need

Several surgical repair approaches have been attempted in this heterogeneous patient population with limited results. Various replacement options can be considered in properly selected patients, such as a mechanical or tissue valve replacement, a pulmonary autograft (Ross procedure), or aortic valve replacement with pericardium (Ozaki procedure). Each replacement option has its pros and cons related to morbidity and mortality risks, and anticipated durability.

Optimizing repair strategies to improve durability may benefit many pediatric and young adult patients in their management of this lifetime disease, avoiding the risks inherent in replacement alternatives.

Understanding the complexity of the normal and congenitally malformed aortic root

Such approaches have historically been guided by standard 2D imaging assessment and intraoperative surgical inspection. The latter is limited by assessment of the valve with the blood removed in a non-hemodynamic state. The former fails to delineate the complex, dynamic 3D anatomy of the aortic root and its valve.

With unique training as a cardiac anatomist, my initial focus was understanding and describing surgically relevant, detailed anatomy of the normal and congenitally malformed aortic root by studying autopsied heart specimens and heart development. Our collaborative research group has emphasized the aortic root can be broken down into three main components: the leaflets, the sinuses, and the interleaflet triangles. The leaflets are attached in a semi-lunar fashion, creating a crown configuration within the root in diastole. The leaflets coapt in a complex, 3D surface area, creating an intricate hemodynamic junction. There is no anatomical “annulus,” but, instead, by connecting the dots of the three lowest leaflet attachment points, we can identify a virtual basal ring. Of importance is that this virtual plane is dynamic, becoming more oval- or elliptical-shaped in diastole when the leaflets coapt. We identified marked variability in the rotational position of the normal aortic root relative to the base of the left ventricle. This determines the orientation of the three leaflets and sinuses relative to the long and short axis of the virtual basal ring. This relationship imparts an understanding of the mechanisms for valve regurgitation and how best to surgically address it.

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Establishing advanced cardiac imaging assessment for surgical personalization

As an expert in advanced 3D and 4D cardiac imaging, my focus then became how to evaluate this important dynamic anatomy in patients.

We focused our attention towards using the high spatial resolution afforded by 3D and 4D cardiac computed tomography (CT) to establish standardized and normal metrics to assess the geometry of the normal aortic root and its valve, including assessment of leaflet coaptation in diastole.

This quantitative approach is aimed not only to serve as a baseline understanding of normal but also as a benchmark for the surgeon aiming to restore aortic valve competency. In addition, we established a volume-rendering reconstruction technique called virtual dissectionto provide visualization of quantified metrics of the aortic root structure. We then turned our attention towards standardizing 4D echocardiographic assessment of the complex hemodynamic junction formed by the aortic valve leaflets, using a view we call the commissural view (Figure 1).

leaflet anatomy of heart specimen
Figure 1. The leaflet anatomy, which dictates the ventriculoarterial hemodynamic junction, is demonstrated in a heart specimen (Panel A) and compared to a 3D transesophageal echocardiographic image (Panel B). The green stars represent the leaflet commissures.

This allows us to further identify subtle leaflet pathologies that need to be addressed at the time of surgery, to complementing this CT-based surgical planning.

Clinical imaging to predict and guide avoidance of damaging the conduction system

Normal variation in the rotational position of the aortic root also correlated with variation in the underlying central fibrous body, an important group of structures that relate to the conduction system.

To further investigate its implications, I scanned autopsied heart specimens with high-resolution magnetic resonance imaging (MRI). I then cut the hearts open to visualize the detailed anatomy of the aortic root and central fibrous body and subsequently performed histology of the conduction system in a way to allow putting the histological findings of the location of the conduction system back into the 3D MRI heart datasets.

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This established important relationships between the components of the conduction system, which we cannot see with clinical imaging, towards anatomy of the aortic root and surrounding structures, which we can see with clinical imaging (Figure 2). This provided a framework for predicting the location of the conduction axis relative to the aortic root by clinical imaging.

Anatomy of left ventricular outflow tract
Figure 2. Detailed anatomy of the left ventricular outflow tract (Panel A) and structures found between the chambers of the heart (Panel B) visualized by volume-rendering reconstruction from a CT image can be used to accurately predict the location of the conduction system. The presumed location of the conduction axis is superimposed.

The risks for significantly damaging the conduction system and requiring a permanent pacemaker following surgery of the aortic valve or left ventricular outflow tract ranges between 5%-15% depending on the congenital cardiac lesion and surgery. Implementing this predictive approach, we have had no occurrence of this complication in these specific surgeries over the past two years.

Establishing the Congenital Valve Procedural Planning Program

Heart valve surgery requires a high level of understanding of the complex anatomy involved and a steep learning curve for the surgeon to master the various repair and replacement techniques. It requires a team-based approach, with experts in advanced cardiac imaging who can effectively communicate the important complexities of the involved anatomy and, together with the surgeon, create a detailed surgical blueprint.

With advanced technology, the involvement of skilled cardiovascular bioengineers to implement computational modeling with surgical simulation further complements this personalized approach.

These requirements are what led me to Cleveland Clinic, specifically to partner with Dr. Hani Najm, a skilled cardiothoracic surgeon, who has demonstrated mastery of valve repair and replacement surgeries.

Together, in February 2022, we developed the Congenital Valve Procedural Planning Program, which was built on the foundation of the described decade of translational and clinical research.

Over the past two years, we have established our program as an international center of excellence, standardizing a multimodality advanced imaging-based approach towards surgical personalization in congenital heart valve disease (Figure 3).

Imaging for valve repair
Figure 3. A multimodality imaging approach using CT with 3D and 4D reconstructions, combined with computational modeling and simulation, and 4D transthoracic and transesophageal echocardiography is used in our patients to prescribe a personalized blueprint for surgical repair or replacement.

Reference

Tretter JT, Burbano-Vera NH, Najm HK. Multi-modality imaging evaluation and pre-surgical planning for aortic valve-sparing operations in patients with aortic root aneurysm. Ann Cardiothorac Surg 2023;12:295-317.

Burbano-Vera NH, Alfirevic A, Bauer AM, Wakefield BJ, Najm HK, Roselli EE, Tretter JT. Perioperative assessment of the hemodynamic ventriculoarterial junction of the aortic root by three-dimensional echocardiography. J Am Soc Echocardiogr 2024:S0894-7317(24)00056-7.

Tretter JT, Spicer DE, Marcias Y, Talbott C, Kasten JL, Sanchez-Quintana D, Kapadia SR, Anderson RH. Vulnerability of the ventricular conduction axis during transcatheter aortic valvar implantation: a translational pathologic study. Clin Anat 2023;36:836-846.

Anderson RH, Spicer DE, Sanchez-Quintana D, Macias Y, Kapadia S, Tretter JT. Relationship between the aortic root and the atrioventricular conduction axis. Heart 2023;109:1811-1818.

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Tretter JT, Spicer DE, Franklin RCG, Beland MJ, Aiello VD, Cook AC, Crucean A, Loomba RS, Yoo SJ, Quintessenza JA, Tchervenkov CI, Jacobs JP, Najm HK, Anderson RH. Expert consensus statement: anatomy, imaging, and nomenclature of congenital aortic root malformations. Ann Thorac Surg 2023;116:6-16.

Izawa Y, Mori S, Tretter JT, Quintessenza JA, Toh H, Toba T, Watanabe Y, Kono AK, Okada K, Hirata KI. Normative aortic valvar measurements in adults using computed tomography – a potential guide to further sophisticate aortic valve-sparing surgery. Circ J 2021;85:1059-1067.

Tretter JT, Mori S, Saremi F, Chikkabyrappa S, Thomas K, Bu F, Loomba RS, Alsaied T, Spicer DE, Anderson RH. Variations in rotation of the aortic root and membranous septum with implications for transcatheter valve implantation. Heart 2018;104:999-1005.

About the author: Dr. Tretter is the Co-Director for the Congenital Valve Procedural Planning Program, Director of Advanced Cardiac Imaging and Director of Cardiac Morphology for the Pediatric and Adult Congenital Heart Center at the Cleveland Clinic. He is Professor of Pediatrics at Cleveland Clinic Lerner College of Medicine at Case Western Reserve University.

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