Aortic root replacement has evolved from the classic Bentall procedure that replaces the aorta and the aortic valve with a mechanical valve conduit to full replacement with a bioprosthetic valve – both described more than 50 years ago – to the more current valve-sparing iteration in which the patient’s aorta is replaced but their native aortic valve is preserved. It has been more than two decades since the aortic valve-sparing procedures were first developed..
Aortic root replacement has evolved from the classic Bentall procedure that replaces the aorta and the aortic valve with a mechanical valve conduit to full replacement with a bioprosthetic valve – both described more than 50 years ago – to the more current valve-sparing iteration in which the patient’s aorta is replaced but their native aortic valve is preserved. It has been more than two decades since the aortic valve-sparing procedures were first developed.
Christopher Lau, MD, Director of Endovascular Surgery in the Department of Cardiothoracic Surgery at NewYork-Presbyterian/Weill Cornell Medical Center and an Associate Professor of Cardiothoracic Surgery at Weill Cornell Medicine, and his colleagues here have been at the forefront of clinical practice and research in aortic valve replacement. In this article, Dr. Lau presents a range of research led by NewYork-Presbyterian and Weill Cornell Medicine faculty that is furthering understanding of these complex procedures, including:
- Aortic Root Replacement with and without Valve Replacements
- Valve-Sparing Root Replacement and Bicuspid Valves
- The Influence of Aneurysm Size
- When Connective Tissue Disease is Involved
- Assessing Aortic Blood Flow Following VSRR
“Several years ago, we looked at the aortic root replacement experience within our department and found that the number of mechanical root replacements had been declining while the number of bioprosthetic valve procedures and valve-sparing procedures were on the rise,” says Dr. Lau. “In reality, the basic techniques themselves are very well defined, are similarly performed by cardiac surgeons, and have undergone iterative refinements by surgeons performing the procedure. What we’re trying to do is improve the selection process for valve-sparing procedures so that we can better inform patients of the likelihood of their own valve lasting a lifetime.
Dr. Christopher Lau
Maximizing the Life of the Native Valve
Dr. Lau and his cardiovascular surgery colleagues at NewYork-Presbyterian and Weill Cornell Medicine are investigating a number of questions related to valve-sparing procedures. “The bioprosthetic valve using either bovine or porcine tissue will degenerate and wear out over time,” notes Dr. Lau. “They may last as little as eight years or as much as 15 to 20 years depending on the patient. But in general, especially in younger patients, they will wear out and need to be replaced. As the valve-sparing procedure maintains the patient’s own tissue, the valve itself usually does not degenerate. As long as it is secure in the graft the native valve can last forever.”
It’s not so much that we are trying to save everybody’s valve, but rather we’re trying to identify for each individual patient the method of replacing the root that will endure the longest with the lowest risk. Sometimes that means doing the valve-sparing root replacement and sometimes that means a valve replacement option is better.
— Dr. Christopher Lau
However, proceeding with valve sparing depends on a number of factors, including the health and characteristics of the native valve, emphasizes Dr. Lau. “We need to consider whether it is a bicuspid or tricuspid valve, will an aortic valve repair involve the leaflets, and will doing a valve leaflet repair affect the long-term durability of a valve-sparing replacement. We weigh whether the valve has any degree of stenosis or if the valve leaflets have fenestrations. If there are numerous fenestrations or if the leaflets are very damaged, then it may not be the best valve to save.”
“Additionally, we need to factor in aneurysm characteristics,” continues Dr. Lau. “Is it located at the root or in the ascending aorta? How large is the aneurysm? What is the degree of aortic insufficiency preoperatively and how is the jet of the aortic insufficiency positioned. Is it a very central jet or an eccentric jet? These are all features we evaluate to determine how likely it is that a valve will fail if we do the valve-sparing procedure. Our preoperative assessment involves 3D reconstruction images of the aorta, which provides a sense of the shape of the aorta and also the angles that it takes. CT scans only show us the axial dimension and does not give us an appreciation of these different angles or an exact perpendicular cut of the aorta. So, in order to more accurately view the aorta, we always obtain 3D reconstructions, which we can prepare for patient scans taken at our center or with scans provided from another facility.”
Aortic Root Replacement With and Without Valve Replacement
“In general, if a patient’s own valve and leaflets are of good quality, then we can save their valve and just replace the aorta,” says Dr. Lau. “If we determine on imaging that the patient’s aneurysm involves the aortic root, but we see on their echo that their valve is still functioning well with no significant aortic insufficiency, then we will usually be able to proceed with a valve-sparing root replacement. In other patients it can be more challenging. For example, if preoperative testing reveals the patient has aortic insufficiency, we may be able to perform an aortic valve repair to take care of that and still do a valve-sparing root replacement. Once the leaflet of the valve is repaired, even if it was abnormally stretched, and you remove the aneurysm and bring the valve back together into a smaller conduit, the valve can function normally again.”
Recently, Dr. Lau, along with Eilon Ram, MD, a cardiothoracic fellow; Mario F.L. Gaudino, MD, PhD, cardiothoracic surgeon, and Leonard N. Girardi, MD, Chief of Cardiothoracic Surgery at NewYork-Presbyterian/Weill Cornell Medical Center, examined the long-term outcomes of aortic root replacement with and without valve replacement for aortic root aneurysm repair. The study updates the findings that the Weill Cornell Medicine team published in 2015 in The Journal of Thoracic and Cardiovascular Surgery. That early study evaluated 890 patients who had undergone aortic root replacement between May 1997 and January 2014: 289 received a mechanical composite valved graft, 421 received a biologic composite valved graft, and 180 received a valve-sparing reconstruction. At that time, the researchers concluded, “aortic root replacement can be performed with low perioperative risk in high-volume aortic centers. The type of operation performed does not affect early or late survival. Although the mechanical composite valved graft remains the gold standard for durability, the biologic composite valved graft and valve-sparing reconstruction are excellent options for those who cannot take or want to avoid long-term anticoagulation.”
In their current study, for which publication is pending, the team reviewed 1,635 patients who had undergone aortic root replacement at NewYork-Presbyterian/Weill Cornell Medical Center between 2000 and 2021. Of these, 473 patients (29 percent) underwent valve-sparing root replacement (VSRR) and 1,162 (71 percent) underwent root replacement using a composite valve-conduit. Patients in the composite conduit group were older and had more comorbidities, including hypertension (88.4 percent vs. 66.4 percent) and Class III-IV heart failure (35 percent vs. 9.2 percent). The researchers used propensity score matching to reduce baseline differences in patient characteristics and assess similar cohorts of patients.
Characteristics of the patients and findings of the study, which compared early and long-term results of the two procedures and durability of the aortic valve, are indicated in the table below:
| Composite Conduit Group | Valve-Sparing Root Replacement Group | |
|---|---|---|
| Bicuspid aortic valves | 44.8% | 24.1% |
| Severe aortic insufficiency (AI) | 50.2% | 13.2% |
| Major postop complications | 3.6% | 1.1% |
| 10-year survival | 91.2% | 97.7% |
| Reoperations at 65±60 months | 5.8% | 5.1% |
| Operative mortality | 0.5% | 0% |
The results of the study supported the application of both valve-sparing operations and root replacement with a composite valve-conduit as they provide excellent early and long-term outcomes with low risk of reoperation out to 10 years.
Valve-Sparing Root Replacement and Bicuspid Valves
Does leaflet repair improve valve durability? This is the question that Dr. Lau and his colleagues in the Department of Cardiothoracic Surgery at NewYork-Presbyterian/Weill Cornell Medical Center sought to answer in a study in patients with bicuspid aortopathy. “Valve-sparing root replacement using the reimplantation technique is well established for treatment of trileaflet aortic valves and is increasingly being used for bicuspid aortic valves, including in those with significant aortic insufficiency,” notes Dr. Lau. “However, patients with bicuspid aortic valves are more likely to have leaflet abnormalities and long-term durability of cusp repair in this setting is not well-defined. There is some evidence that complex repairs are less durable and simple repairs may fare better. Valve-sparing root replacements are already a complex procedure and adding a cusp repair increases the operative time and may add risk to the valve due to the manipulation of the leaflets themselves. In our study, we analyzed the outcomes of our conservative cusp repair strategy, which we use in 23 percent of patients – considerably fewer when compared to studies of cusp repair reported in the literature in which the procedure is used in 67 to 100 percent of patients.”
NewYork-Presbyterian and Weill Cornell Medicine’s cardiothoracic surgery practice describes simple cusp repairs as central plication or closure of an incomplete raphe, while a complex cusp repair would require resection or patch reconstruction of cusps or reconfiguration of the commissures or the actual geometry of the leaflets.
In their study, the team reviewed the outcomes of 327 patients undergoing valve-sparing surgery with the reimplantation technique between 2006 and 2018. Of these, 66 patients were bicuspid valves with 51 who did not need cusp repair and 15 requiring cusp repair. About half of the procedures were closure of an incompletely fused raphe and the remaining were central plication to shorten the free edge. Their analysis and findings, published in the February 2021 issue of The Journal of Thoracic and Cardiovascular Surgery, showed that cusp repair coaptation height and immediate postoperative mild AI or preoperative moderate-severe AI were not predictors for the presence of mild or greater AI on follow-up and five-year survival was excellent – 100 percent for both groups.
“Our study demonstrated that valve-sparing replacement can reliably be performed with bicuspid aortic valves even when cusp repair is performed,” says Dr. Lau. “Simple cusp repairs have similar durability to valve-sparing root replacement without cusp repair in the midterm with appropriately selected patients. While preoperative moderate or severe AI are indicators that cusp repair may be necessary, few patients progress to greater than mild AI and the need for reoperation is rare at midterm follow-up after a successful repair. Cusp repair improves the durability of valves, especially those patients presenting preoperatively with moderate or severe AI.”
The Influence of Aneurysm Size
Among the many potential factors affecting the outcomes of valve-sparing root replacement is the preoperative diameter of the aneurysm. Dr. Lau and his colleagues at NewYork-Presbyterian and Weill Cornell Medicine recently undertook a study to determine whether a larger preoperative aneurysm diameter compromises operative outcomes and long-term durability. “Large aortic root aneurysms may cause stretching of the valve leaflets, potentially compromising structure and function,” says Dr. Lau. “While thinned-out leaflets with large fenestrations may not be ideal for valve-sparing, leaflets with well-preserved structure may merit preserving.”
The researchers called on the aortic database established by the Department of Cardiothoracic Surgery, identifying 487 consecutive patients undergoing valve-sparing root replacement using the reimplantation technique between 2000 and 2021. Of these:
- Patients were stratified by aneurysm size <55, 55-60 mm, and >60 mm
- Aneurysms >60 mm were more likely to have severe AI preoperatively
- Postoperatively, a majority of patients had zero or trivial aortic insufficiency
- Operative mortality was zero and the incidence of other complications was rare
Their findings indicate that when the spared valves are of adequate leaflet quality and structure, preoperative aneurysm diameter has no significant effect on the immediate operative valve outcomes or on long-term valve durability.
When Connective Tissue Disease is Involved
Many types of connective tissue disorders are associated with aortic aneurysms raising the question of valve durability, as well as safety of a valve-sparing replacement, for patients who have a connective tissue disease compared to those who do not. This concern prompted a study by Dr. Lau and his colleagues in which they evaluated the long-term outcomes of valve-sparing root replacement between 2000 and 2021 of 487 patients: 380 (78 percent) patients did not have a connective tissue disease and 107 were patients diagnosed with a connective tissue disease (22 percent). In the connective disease cohort, 97 patients had Marfan syndrome, 8 had Loeys-Dietz syndrome, and 2 had Vascular Ehlers-Danlos syndrome.
The NewYork-Presbyterian and Weill Cornell Medicine investigators found that while concomitant arch replacement was more frequent in the patients without a connective tissue disease, operative mortality and incidence of major postoperative complications did not differ between groups. At 10 years, mean freedom from moderate/severe AI was 89.6 percent, freedom from valve reoperation was 94.9 percent, and survival was 97.3 percent. With excellent operative outcomes and long-term durability of VSRR in patients both with and without connective tissue disease and survival, freedom from AI recurrence, and reoperation similar between the two groups, the findings demonstrate that valve function and durability are not affected by a connective tissue disease diagnosis.
Assessing Aortic Blood Flow Following VSRR
One of the many advantages of valve-sparing root replacement is that the aortic sinuses can be replaced at the same time. However, the differences in aortic flow dynamics when replacement involved a straight tubular prosthesis versus a prosthesis with Valsava neosinuses had not previously been evaluated. Advances in 4D flow magnetic resonance imaging technology and computational methods have made it possible to perform in vivo assessment of the effects of aortic root replacement on blood flow within a replaced aorta as well as the native distal aorta.
With the availability of this leading-edge technology, Dr. Mario Gaudino in collaboration with cardiothoracic faculty at NewYork-Presbyterian and Weill Cornell Medicine and the Department of Cardiac Surgery of the European Hospital in Rome, Italy, undertook at study of 20 patients undergoing VSSR for an aortic aneurysm with aortic insufficiency. Ten patients had the procedure with a straight tubular prosthesis and 10 with a prosthesis with Valsalva neosinuses. For each surgical group, the researchers compared the amount of rotational flow and wall shear stress (WSS) of velocity flow streamlines and estimated the occurrence of abnormal wall within the descending aorta.
This study is the first to systematically and quantitatively compare straight tube graft versus neo-SV graft versus control group. Re-creation of the sinuses of Valsalva during valve-sparing root replacement is associated with more physiologic flow and significantly lower WSS in the aortic root.
— Dr. Mario Gaudino et al, The Journal of Thoracic and Cardiovascular Surgery
“We worked with 4D flow MRI to look at the flow of blood in the new aortic root depending on what technique we used to do the valve-sparing root replacement,” explains Dr. Lau. “We found that recreating the sinuses of Valsalva with the graft led to a greater laminar blood flow similar to what is seen in the native sinuses of Valsalva and a much lower incidence of abnormal wall shear stress in the aorta.”
Specifically, the findings, published in the February 2019 issue of The Journal of Thoracic and Cardiovascular Surgery, demonstrated:
- Both the straight tube and neo-sinuses of Valsalva (neo-SV) techniques led to a well-functioning valve and trace or no aortic insufficiency
- Clinical outcomes were similarly excellent with no major complications
- Recreating neo-SV seems to lead to a pattern of blood flow that is more similar to that seen in the native SV in terms of velocities, vorticity, and trajectories during systolic flow
- Neo-SV grafts result in organized vortical flow in the sinuses, lower flow velocities, and lower WSS
While the clinical influence of these findings remains to be seen, the authors note that “4D flow imaging is a promising technique that can be used to obtain reliable in vivo findings that may help answer long-standing questions that in vitro studies alone could not answer.”
