We present an in-depth review article that tackles a topic of growing interest for cardiac surgeons: cardiac reoperations, specifically valve reoperations. This article is structured into two clearly defined sections. The first section focuses on the preoperative evaluation of patients in this context, emphasizing the importance of surgical risk assessment and interpretation with the help of a multidisciplinary team to facilitate informed decision-making. Additionally, the importance of recommended complementary imaging tests before performing reoperations on these patients is directly addressed. To conclude this first section, an overview is provided of various surgical strategies that must be planned in advance to maximize successful outcomes.

The second section of the review specifically addresses reoperations on the aortic, mitral, and tricuspid valves. It offers recommendations on surgical approaches and techniques based on individual circumstances, providing valuable information to optimize overall outcomes in valve reoperations.

The number of cardiac valve reoperations is experiencing exponential growth, mainly due to the aging population and the increase in bioprosthetic implant procedures, both surgical and percutaneous. This rise leads to a correlating increase in cases of endocarditis and structural deterioration of these bioprostheses. This trend is expected to continue in the near future, especially with the imminent introduction of percutaneous aortic valve implants (TAVI) in low-risk patient groups. In this context, possessing the necessary knowledge and technical skills to perform successful reoperations in these patients has taken on unprecedented importance in the modern era of cardiac surgery.

Cardiac reoperations demand an even higher level of expertise than the first intervention. Technical complexity is largely influenced by the presence of pericardial and mediastinal adhesions, which become more pronounced with more recent surgeries and an increased number of prior interventions. Additionally, patients requiring reoperations often present with a higher burden of comorbidities and frailty, factors that inevitably influence a less favorable prognosis.

Screening and surgical risk assessment
The Heart Team approach is central to the evaluation of patients anticipated to require a reoperation. In decision-making, both clinical and anatomical considerations of the patients are given equal weight.

Although traditional surgical risk scores, such as EuroSCORE II or the STS scale, continue to be useful in predicting outcomes for reoperated patients, controversy remains regarding which scale is most appropriate for mortality prediction. Individual risk factors, like the NYHA functional classification, remain pertinent, demonstrating a mortality rate of 1.6% in functional class I and 20.8% in functional class IV. Scheduled procedures reflect a mortality rate of 1.4%, while urgent and emergency cases increase this figure to 8% and 37.5%, respectively, underscoring the critical importance of performing surgery before clinical deterioration occurs.

In the context of valve reoperations, concomitant procedures, such as additional coronary surgery, have shown a negative impact on outcomes. Therefore, current trends lean towards percutaneous revascularization whenever possible. All recognized comorbidity parameters that increase surgical risk in a first operation, such as low ejection fraction, liver or renal dysfunction, also impact reoperations.

The complexity of surgery is also influenced by other specific surgical factors. These include the number of previous operations, the degree of paravalvular or infected tissue calcification, the presence and location of patent grafts, and the proximity of mediastinal structures to the sternum in anticipation of a re-sternotomy.

Lastly, but no less importantly, the surgeon’s skill and experience play a critical role in achieving successful outcomes in these procedures. Multiple studies have shown a volume-dependent correlation between surgical experience and outcomes in high-complexity surgeries.

Preoperative assessment
Today, two imaging tests are essential for thorough preoperative evaluation in any patient undergoing a valve reoperation: transesophageal echocardiography (TEE) and electrocardiography-synchronized computed tomography (CT).

TEE provides a detailed visualization of valve morphology and dysfunction mechanisms, which is crucial for decision-making. For instance, it allows determining if a cardiac reoperation is necessary for significant paravalvular leakage or if a transcatheter valve-in-valve procedure is more suitable in cases of transvalvular insufficiency. Another benefit of TEE is its ability to distinguish between thrombus, pannus, and vegetation, which can be critical in treatment planning. In cases of endocarditis, TEE is absolutely essential, as it not only enhances valve and vegetation visualization but also detects abscesses and fistulas with high precision. Furthermore, positron emission tomography (PET/CT) can be valuable in cases of prosthetic endocarditis, adding substantial diagnostic value.

Synchronized CT is another highly recommended test for this patient group, providing essential information to enhance safety in any reoperation procedure. The risks of damage to various structures during a re-sternotomy are considerable. CT provides reference points for the location and proximity of critical structures such as the aorta, innominate vein, right heart chambers, and previously placed grafts. Additionally, it provides details on the degree of aortic calcification, the type and location of paravalvular tissue, and heart rotation. It is estimated that in nearly 20% of cases, CT information prompts a modification in the surgical approach and strategy. For instance, when mediastinal structures are too close to the sternum, peripheral cannulation and initiation of cardiopulmonary bypass (CPB) before sternotomy may be preferred. In mitral or tricuspid surgery cases, even a right minithoracotomy may be considered. Meticulous planning of the surgical strategy and preventive maneuvers have been shown to reduce intraoperative complications, clamping and CPB times, myocardial infarction episodes, and ICU stays.

In patients with a history of coronary surgery, coronary angiography becomes necessary. However, if the risk of coronary disease is low, synchronized coronary CT may suffice for a complete assessment.

Perioperative management and technical considerations
Primarily based on CT findings, different cannulation alternatives for initiating CPB can be considered. If femoral cannulation is chosen, percutaneous ultrasound-guided cannulation can be performed if familiar. External defibrillator pads should be placed in all patients before starting the intervention, as dense pericardial adhesions will likely prevent the use of internal defibrillation paddles. In high-risk anatomical scenarios, it may be prudent to initiate CPB before opening the chest to prevent potential ruptures, although this measure may increase bleeding. Throughout the procedure, meticulous hemostasis must be practiced, with the use of antifibrinolytic agents and coagulation factor replacement as needed to control excessive bleeding.

Planning the myocardial protection strategy is crucial. Cold cardioplegia should be administered following recommended doses and timings. In cases of aortic insufficiency or patent coronary grafts, retrograde cardioplegia may be suitable.

A fundamental practice is to carefully review prior surgical reports. When feasible, the option to modify valve implantation techniques should be considered to simplify surgery. This may involve implanting prostheses in previously placed Dacron conduits, using percutaneous valves in open-heart surgery, or opting for sutureless prostheses. Automated knot-tying devices can also be highly beneficial for reducing surgical times in these cases.

Reoperations on the aortic valve
Reoperations on the aortic valve account for approximately 10% of all procedures related to this valve structure. Published series indicate that this type of reoperation can achieve results comparable to those of primary surgeries. However, due to the particular technical complexity associated with aortic valve reoperations in patients with prior TAVI implants, the mortality rate is higher compared to removing surgically implanted bioprostheses, as detailed in previous blog articles.

Reasonable alternatives to sternotomy may include minimally invasive access routes, such as superior partial sternotomy or anterolateral thoracotomy. These approaches reduce the need for pericardial dissection, decrease the risk of damaging coronary grafts, and preserve sternal integrity. Ultimately, these factors contribute to a higher likelihood of early extubation and lower risk of mediastinitis.

For over a decade, the TAVI valve-in-valve procedure has been used to treat dysfunctions in aortic bioprostheses across various patients, demonstrating safety and rapid post-intervention recovery. However, certain considerations should be noted. Potential drawbacks include higher rates of aortic insufficiency and patient-prosthesis mismatch. These complications have shown an association with higher short-term mortality in high-risk patients compared to conventional reoperations. Nonetheless, understanding long-term outcomes remains limited due to the retrospective nature of studies and limitations in clinical follow-up.

Reoperations on the mitral valve
Achieving proper exposure of the mitral valve during this type of reoperation is crucial. The most commonly used approach is the left atriotomy through the Sondergaard groove. However, due to the firm adhesions that typically develop, the dissection necessary for adequate exposure is not straightforward. Alternatively, the right atrial transseptal approach provides excellent mitral valve exposure and requires less dissection to expose the left atrium. This approach has gained prominence as the predominant choice in mitral reoperations.

When close proximity of vital structures to the sternum prevents standard access, right thoracotomy may be a valid alternative. However, this option is limited in cases of aortic insufficiency exceeding a moderate degree due to ventricular dilation resulting from cardioplegia. Additionally, for concomitant surgeries other than tricuspid surgery, careful evaluation should be performed before selecting this approach.

In cases of severe mitral annular calcification (MAC), the risk of complications is greatly amplified. In scenarios requiring partial or total decalcification of the annulus, the risk of atrioventricular sulcus rupture can be minimized by using a patch of autologous pericardium sutured to the left ventricle, annulus, and left atrium. This patch provides support to the prosthesis. In certain cases, and increasingly when specific anatomical criteria are met, percutaneous prosthesis implantation during open-heart surgery or even percutaneous mitral valve implantation via a transcatheter procedure may be considered. Both techniques have been discussed recently in other blog entries.

If paravalvular leakage is the reason for surgery, various solutions are available. These include using percutaneous closure devices, direct surgical closure, applying a pericardial patch to close the defect, or even implanting a new valve, depending on the size and location of the dehiscence.

In experienced hands, as we have previously detailed, the so-called “Commando” technique can be applied. This involves artificially creating a new mitroaortic curtain using a pericardial patch. In cases of patent grafts, mitral surgery can be effectively performed with the heart in ventricular fibrillation, avoiding graft manipulation and damage.

The most common reasons for mitral reoperation are structural dysfunction and endocarditis. In cases of dysfunction arising after previous mitral repair, usually due to mitral ring dehiscence or neochord rupture, re-repair may be attempted. However, the likelihood of success is lower in a re-repair, although success rates are higher in cases of early dysfunction.

Reoperations on the tricuspid valve
In the absence of the need for concomitant surgery, a right thoracotomy approach may emerge as a valuable alternative. This approach can be performed without requiring aortic clamping, allowing the heart to beat throughout the procedure.

In terms of primary etiology, the two main reasons for this reoperation are bioprosthetic dysfunction and endocarditis. In particular, endocarditis recurrence is more frequent among individuals with endocardial electrodes and those who abuse intravenous drugs (ADVP).

A significant proportion of patients requiring tricuspid reoperation have high surgical risk and limited life expectancy. Therefore, we emphasize the importance of multidisciplinary evaluation and appropriate risk scale application, such as the TRI-SCORE, to support clinical decisions. As highlighted in previous review articles on this blog, timely referral of these patients is essential, before complications associated with right heart failure fully manifest. Severe pulmonary hypertension (PH) is widely recognized as an independent predictor of poor prognosis. Currently, the consideration of the aortopulmonary pressure ratio is emphasized, as it has shown superior predictive value even compared to isolated PH.

COMMENTARY:

This article underscores a fundamental message: assessing the risk associated with cardiac valve reoperations is a complex challenge that must be addressed with an individualized and detailed approach. This is because the risk depends not only on patient parameters but also on the nature of the procedure required. In particularly complex cases, collaboration with a multidisciplinary team can be highly beneficial in ensuring informed and accurate decision-making.

The second core message of the text is that, through rigorous preoperative evaluation, careful perioperative approach, and continuous advancements in surgical techniques, in certain cases, valve reoperation should no longer be considered an automatic predictor of mortality. Surgery remains a highly effective option, especially for patients at low or moderate risk, who need to undergo a valve reoperation.

REFERENCE:

Marin-Cuartas M, de Waha S, Saeed D, Misfeld M, Kiefer P, Borger MA. Considerations for Reoperative Heart Valve Surgery. Struct Heart. 2022 Nov 3;7(1):100098. doi: 10.1016/j.shj.2022.100098.