Evaluation, Common Pitfalls, and Complications

Mitral Valve Surgery Guidelines

In patients of suitable surgical risk, MV surgery should be contemplated when a guideline-based indication for surgery is present. Complete guidelines can be obtained elsewhere. However, it is worth noting specific subtleties relevant to MR where errors in decision-making are more common. Differentiating between primary and functional MR is critical, as not only do the indications for surgery differ based on the presence or absence of symptoms and the degree of heart failure, but the repair techniques also differ, including the decision to place a ring versus a band, band sizing, and leaflet interventions.

• MV surgery is a Class I recommendation for symptomatic patients with chronic, severe primary MR and left ventricular ejection fraction (LVEF) greater than 30%.

• MV surgery is a Class I recommendation for asymptomatic patients with chronic, severe primary MR and LVEF 30% to 60% and/or left ventricular end-systolic diameter (LVESD) at least 40 mm (45 mm, European guidelines).

• MV surgery is reasonable (Class IIa recommendation) for asymptomatic patients with chronic, severe primary MR and LVEF at least 60% and LVESD less than 40 mm if the likelihood of repair is at least 95%, mortality risk is less than 1%, and operation is performed at a center of excellence.

  • European guidelines more specifically modify this subset to asymptomatic patients with preserved LV function who also have new-onset atrial fibrillation (AF) and pulmonary hypertension at rest, without the stipulation for the likelihood of durable repair or mortality/risk. Also, a specific category is included for asymptomatic, severe MR with preserved LV function in those with flail leaflet, with the stipulation for the likelihood of repair with low mortality/risk.

• MV surgery may be considered (Class IIb recommendation) for severely symptomatic patients (New York Heart Association [NYHA] Class III or IV) with chronic, severe secondary MR with persistent symptoms despite guideline-directed medical therapy for heart failure.

The fastest-growing segment of the United States population is the elderly, and the prevalence of valvular disease increases with age. The diagnostic and therapeutic complexity of valvular heart disease increases in conjunction with the costs to provide this care as the number of medical and procedural therapies grow. However, these advances expand the cohort of patients with valvular disease who may benefit from evaluation by a valve-specific team at a center of excellence. For these reasons, those of prohibitive surgical risk or patients who may currently lack a clear indication for surgery still benefit from evaluation by a heart team who will ensure guideline-directed diagnostic studies, medical treatment, follow-up, and pursue alternative therapies. A recently published expert consensus statement outlines minimum requirements for centers offering valvular interventions, with a focus on the capabilities of centers offering MV surgery and transcatheter MV interventions in the setting of a valvular heart disease system of care.

A gap analysis related to the care of MV regurgitation was published in 2016 and highlights several of the pitfalls associated with MV surgery guidelines.

Concomitant Procedures

In patients referred for MV surgery, a transthoracic echocardiogram (TTE) has almost certainly been performed. This TTE, and any prior available echocardiograms, should be reviewed in detail by the surgeon. If the quality of the TTE is insufficient to evaluate the function of all cardiac valves, other structural anatomy, and biventricular function, a repeat TTE or transesophageal echocardiogram (TEE) should be obtained. We have a low threshold for obtaining a TEE whenever any additional valvular abnormality is identified on TTE. We also obtain TEE when the process responsible for MV pathology is not obvious. For example, a TEE is warranted in cases of restrictive valve disease that appears functional but is without any underlying ventricular dysfunction, with consideration of valvulitis or amyloid disease if ventricular walls are thickened in an elderly patient.

The aortic valve should be evaluated for aortic stenosis (AS) or aortic insufficiency (AI), and if present at more than a mild degree, TEE is warranted. It is more common to diagnose significant MR while working up AS (present in 15% to 20% and primary in about 50%) than to find AS while working up primary MR. However, in the setting of classical low-flow, low-gradient AS, where the severity of AS may not be appreciated, the patient may be sent initially for evaluation due to MR. It is important to consider the effect of MR when evaluating AS, as the severity of MR is a major determinant of a low-flow state, which may underestimate the degree of AS and result in one or both valve lesions being observed rather than intervened upon. Aortic valve surgery, concomitant with MV surgery, is recommended for severe AS or AI (Class I) and considered reasonable for moderate AS or AI (Class IIa). However, simultaneous aortic and MV surgery is associated with increased mortality. Therefore, after assessment of individual patient risk, consideration may be given to staged procedures, that is, MV repair followed by transcatheter aortic valve replacement (TAVR) or, alternatively, surgical aortic valve replacement (SAVR) or TAVR with a period of observation for improvement in functional MR, followed by percutaneous MV intervention if necessary. ^{, ,}

Another scenario that warrants thoughtful consideration is the presence of simultaneous AS and MS, which may be due to degenerative disease or, less commonly, rheumatic disease. In fact, this scenario is not uncommon, as up to 17% of concomitant aortic valve-MV operations are for AS/MS, suggesting the need for particular mention. The physiology of the combined lesions can complicate echocardiographic diagnosis, and suspicion of combined AS/MS based on the appearance of significant calcification or thickening may indicate invasive hemodynamic pressure measurements for sound diagnosis. Although both the American and European valvular heart disease guidelines address concomitant aortic and MV surgery for respective stenoses, in conjunction with other cardiac surgeries, they do not specifically address this challenging combined lesion set. Double valve surgery for combined degenerative stenotic disease has nearly twice the mortality rate of isolated surgery based on Society of Thoracic Surgeons (STS) data. The presence of both AS and MS is historically associated with 40% to 50% mortality over a 10 to 20 year period, and patients with AS are more likely to have NYHA class IV heart failure, dialysis dependence, and associated valve insufficiency when MS is present compared to when it is not. TAVR has been increasingly used in this high-risk scenario; in fact, about 10% of TAVR valves are placed in patients with MS, with a resultant increased incidence of 1-year adverse outcomes. The emergence of more transcatheter MV options has expanded the possibilities of managing this problem through a totally percutaneous route, although data is lacking. Though currently under formal clinical trial investigation, we have implemented surgical implantation of a transcatheter valve in native mitral annular calcification (SITRAL) concomitantly with TAVR for aortic stenosis with some early success.

Functional tricuspid regurgitation is common in the setting of MR, with at least moderate tricuspid regurgitation (TR) occurring in up to 20% of patients. Although multiple studies show improvement in the grade of TR after the reduction in volume overload that occurs with MV surgery, the long-term effect is not optimal. TR is found in up to 74% of patients followed long term after left side valve surgery. Additionally, reoperation for tricuspid valve disease confers operative mortality up to 37%. The challenge in cases of functional tricuspid regurgitation is determining which patients will have a long-term favorable improvement in TR due to right ventricle (RV) remodeling and volume overload reduction by MV surgery alone and which patients require concomitant TV surgery.

Fortunately, there are prospective, randomized trials in progress to address this question, but these are not completed as of yet. There are, however, multiple retrospective studies that evaluate small cohorts of patients at single centers, comparing outcomes in MV surgery patients who have or have not undergone concomitant tricuspid valve repair. ^, Clearly, selection bias is inevitable with this design. Additionally, the criteria to opt for tricuspid valve surgery vary by study, some basing the decision on the grade of TR, annulus size, RV dysfunction, or a combination, making a meta-analysis or systematic review difficult. All current guidelines related to tricuspid valve surgery have a “C” level of evidence. Concomitant tricuspid surgery is recommended for patients with severe tricuspid regurgitation at the time of left-side valve surgery (Class I). Concomitant tricuspid valve repair can be beneficial (Class IIa) for any grade TR when there is tricuspid annular dilation (annulus greater than 40 mm on TTE, greater than 21 mm/m ² indexed to body surface area, or greater than 70 mm on direct intraoperative measurement) or prior evidence of right-sided heart failure. Concomitant tricuspid repair may be considered (Class IIb) in patients with pulmonary artery hypertension. A best-evidence review found that the downside to concomitant tricuspid valve surgery was prolonged clamp, cardiopulmonary bypass, and total operative times, but this effect on surgical times did not result in an increase in perioperative complications or mortality. A study following postoperative patients by echocardiographic imaging found improved right ventricular function and geometry if TV annuloplasty was performed. With median 7-year follow-ups, two studies have shown that if mild-moderate TR in the setting of tricuspid annular dilation or RV dysfunction was left untreated during MV surgery, patients had persistent or worsened TR long-term and freedom from moderate-severe TR, or TR progression declined over long-term follow-up. ^, A recent study from 2020 showed that aggressive adherence to guideline recommendations in 171 consecutive patients was safe, with a low mortality rate, pacemaker rate equivalent to isolated MV surgery, and high freedom from moderate or worse TR at 14 months. The conclusions of most of these studies are a recommendation for more aggressive adherence to guidelines regarding concomitant TR at the time of MV surgery.

Hypertrophic cardiomyopathy (HCM) is the most common inherited myocardial disease, with wide phenotypic expression, frequently occurring in conjunction with MR. The mechanism for MR can be multifactorial, complicating operative planning. Septal hypertrophy narrows the left ventricular outflow tract (LVOT), which can create a dynamic outflow tract obstruction during systole, especially with any abnormality in the MV. In most cases, septal myectomy alone will eliminate the pressure gradient, resolving both the systolic anterior motion (SAM) of the anterior mitral leaflet and the associated SAM-related MR. However, there are phenotypic variations of HCM with anatomic abnormalities of the MV/subvalvular apparatus favoring SAM by anteriorly shifting coaptation. These abnormalities include elongation of the anterior leaflet, anterior displacement and abnormal insertion of papillary muscles, and abnormal attachment of chordae. Typical primary etiologies for MR may coexist as well, such as flail or prolapsing leaflets. In these situations, concomitant MV repair is required to relieve LVOT obstruction and address valvular abnormalities causing MR, in addition to myectomy. There also exist phenotypes where MV abnormalities are present in association with little to no septal hypertrophy. It is important to recognize the possibility of HCM when SAM is present on preoperative TTE, even if there is minimal septal hypertrophy, because a limited myectomy may ultimately be required to alleviate LVOT.

Diagnosing concomitant coronary artery disease (CAD) with degenerative MV disease has implications on the approach to the operation, eliminating the option for typical minimally invasive techniques if present and warranting bypass. In a single-institution review of a 20-year experience with degenerative MV disease, 26% of MV operations for degenerative disease included coronary artery bypass grafting (CABG). In contrast to ischemic functional MR, where a diagnosis of CAD is mandated and thus workup is aimed at defining its severity, in patients with degenerative MR, the incidence of concomitant CAD should mimic the general population. Therefore, a standardized system for coronary clearance should be routinely followed in these patients based on risk factor analysis. Importantly, there is better long-term survival when MV repair is performed over replacement in patients with degenerative MR undergoing MV surgery with concomitant coronary artery bypass. In individualized cases, minimally invasive MV surgery may be staged with percutaneous coronary intervention (PCI) though this requires careful planning and thoughtful consideration by the heart team.

At the patient encounter, any arrhythmias should be specifically elucidated on history, physical exam, and electrocardiogram. As previously discussed, the presence of any arrhythmias, particularly AF, has implications on timing and indications for MV surgery. Guidelines for the surgical management of AF divide indications into concomitant and stand-alone ablation. Guidelines for concomitant surgical ablation are further separated into two scenarios—symptomatic patients who are intolerant to at least one Class 1 or 3 antiarrhythmic and symptomatic patients who have yet to start a Class 1 or 3 antiarrhythmic. In both cases, concomitant ablation is a Class IIa recommendation for all categories of AF (paroxysmal, persistent, long-standing persistent) except in long-standing persistent AF where an antiarrhythmic has not been started, in which case the recommendation is Class IIb. The guidelines conclude that a more extensive ablation is superior to pulmonary vein isolation (PVI) and that a biatrial procedure should be considered in symptomatic patients and those with long-standing persistent AF. Intervention has also been recommended in the literature for asymptomatic patients to improve quality of life and survival while decreasing the risk of stroke or heart failure; however, these indications were not included in the most recent guidelines.

Prior to MV surgery, computed tomography (CT) of the chest is routinely obtained, with the mandatory addition of abdomen and pelvis imaging with contrast if a minimally invasive approach is under consideration. The most common findings that alter our planned operative approach are proximal aortic or peripheral arterial disease, as these affect clamping and cannulation strategies. Details are discussed later in this chapter. Additional findings on CT that may impact the operation are concomitant aneurysms of the aortic root, ascending aorta, or aortic arch. Even when cardiac surgery is planned, the recommendation for replacement of the thoracic aorta remains dilation of at least 5.5 cm in the absence of connective tissue disorders, including bicuspid aortic valve, which may otherwise mandate a lower threshold for repair.

Operative Approach

The surgical approach to the MV can be broadly divided into sternotomy or sternum-sparing techniques. A sternum-sparing approach involves access to the MV through the right chest, whether by mini-anterolateral thoracotomy or robotic-assisted surgery. The decision regarding which approach to pursue depends on multiple factors, some of which are objective, based on preoperative imaging studies and patient characteristics, while others depend on surgeon experience and judgment as well as patient preference.

Sternotomy is clearly the approach of choice when certain concomitant procedures are indicated, including aortic valve replacement, aortic aneurysm repair, or Coronary artery bypass grafting (CABG). However, alternative treatment modalities to address concomitant pathologies, such as TAVR or PCI, may be more appropriate options in individualized patient scenarios. This determination is based on patient and pathology factors, such as age, frailty, and expected benefit to the patient’s recovery by accessing the MV in a minimally invasive manner rather than sternotomy. In particular, the surgeon must consider the presence of a hostile mediastinum due to prior surgery or radiation and patent bypass grafts under the sternum or around the right atrium in patients with a prior history of CABG. In these situations, entry to the pericardium and left atrium may be simplified by approaching the mediastinum from the right chest, and alternative treatments for concomitant pathology may be advantageous.

Any patient being considered for a minimally invasive approach to MV surgery requires a CT-angiogram of the chest, abdomen, and pelvis. Our preferred site for peripheral cardiopulmonary bypass cannulation is the right common femoral artery and right femoral vein. CT-angiography allows evaluation of the extent of calcification at the cannulation site and vessel size, either of which may preclude utilization of the femoral artery for cannulation ( Fig. 21.1 ). Likewise, the presence of extensive calcification or plaque within the aorta is a contraindication to the use of retrograde flow due to the risk of embolic stroke, which is two to three times more likely with peripheral cannulation than central. ^, When any of these findings are present, we must decide whether to persist in the minimally invasive route by finding an alternative cannulation site, such as the right axillary artery, or to adjust plans and proceed with sternotomy. This decision is often made by determining the relative benefit we expect a patient to derive from a minimally invasive approach, which includes less blood utilization, shorter ICU length of stay, and a faster return to work and driving.

Additional information that should be gleaned from the preoperative CT scan includes the presence of ascending aorta calcification that would preclude the placement of an aortic cross-clamp. In such cases, when a minimally invasive approach is planned, either an aortic balloon occlusion device is required, or the operation must be performed with cold fibrillatory arrest. A dilated ascending aorta and/or aortic root is a relative contraindication to balloon occlusion due to the tendency for balloon migration. Balloon migration can hinder exposure of the MV and may cause AI by distorting the root, altering the delivery of cardioplegia and causing left ventricular distention, both of which impair adequate cardioprotection.

Lung windows must also be evaluated on the preoperative CT. Severe chronic obstructive pulmonary disease (COPD) is a relative contraindication to accessing the MV valve from the thorax due to the risk of prolonged ventilator dependence as a result of longer clamp and cardiopulmonary bypass times. In patients with severe COPD, it may be safer to perform MV surgery through sternotomy to limit these times.

In our experience, robotic-assisted surgery is the preferred approach in cases where MV repair is likely and anatomy favors peripheral cannulation. Robotic-assisted surgery provides the advantages of a clear, magnified, 3D view of the MV and subvalvular structures. The degrees of freedom allowed by wristed robotic instruments facilitate annulus suture placement. An assistant who is facile with suture organization and tying knots extracorporeally is essential to expedite these portions of the procedure. In patients where the likelihood of MV replacement is high, we prefer a port-access mini-anterolateral thoracotomy approach simply because prosthetic valves are too large to fit through the incision used for the assistant port in robotic cases.

Other considerations in planning the MV approach include patient size factors, such as the height of the thorax, amount of the chest occupied by the heart, and severe elevation of the right hemidiaphragm. Despite the use of diaphragm and pericardial retraction sutures and proper patient positioning, space restrictions may limit the ability to adequately expose the MV to safely and efficiently complete the operation minimally invasively ( Fig. 21.2 ).

Once the minimally invasive approach has been chosen, avoidance of conversion to sternotomy is critical, though this still occurs in about 1% of cases in the hands of experts. In one study, conversion to sternotomy is associated with a host of poor outcomes, including increased cardiopulmonary bypass time, increased likelihood of postoperative low cardiac output syndrome with the need for aortic balloon pump or extracorporeal membrane oxygenation, increased postoperative renal failure, respiratory failure, stroke, multisystem organ failure, and increased 30-day mortality.

Repair or Replacement?

With few exceptions, the determination of whether to repair or replace the MV should be made preoperatively based on a review of the TTE. In nearly all cases of primary MR, the valve can be repaired, and repair is the default intervention of expert surgeons. When the etiology is due to a prolapsed or flail leaflet segment(s), the affected segment(s) can usually be determined on TTE based on the trajectory of the regurgitant jet and the medial/lateral location on the annulus where the raised leaflet is seen. This information informs planning regarding the extensiveness of MV repair maneuvers that will be required. When repair is undertaken in secondary MR, placement of a reducing annuloplasty ring may be all that is required. Preoperative TTE does not provide an accurate estimate of annulus sizing and should be based on intraoperative measurement. However, the TTE is useful to note whether any predictors of postrepair LVOT obstruction are present that will need to be addressed during the procedure and which may alter the decision whether to downsize versus true-size the annuloplasty ring. MV replacement is acceptable when the following findings are present on TTE:

• Mitral stenosis or regurgitation caused by rheumatic disease where leaflets and/or chordae are thickened, fused, and motion restricted. Although in some cases of rheumatic disease, repair may be technically possible, progression of the disease is likely, so replacement is typically chosen. In many cases, chordae are thickened and shortened to the point where even a chordal-sparing technique is not possible.

• Significant mitral annular calcification (MAC) is present. In these cases, 4-dimensional cardiac CT is helpful to evaluate the extent of calcification and annular involvement. There are multiple techniques for replacement, including debridement of calcification, but when MAC is so extensive that it limits traditional MV replacement, we favor placement of a balloon-expandable valve into native MAC under direct and thoracoscopic vision. , This technique negates the need for annulus debridement, limiting the risk of groove disruption. These complicated techniques need to be performed at centers of excellence by surgeons with extensive experience. In cases with limited MAC, repair may still be feasible with calcium debridement, resection of the affected portion of the valve leaflet, and leaflet repair with annuloplasty.

• Mitral regurgitation caused by a short anterior leaflet. In this case, although a repair may be technically possible by pulling in the free edge of the posterior leaflet, the coaptation height is likely to be too short for durable long-term repair. Also, by shifting the coaptation point anteriorly, the risk of LVOT obstruction by SAM of the anterior leaflet is created. When this scenario is present, a standard chordal sparing replacement is our preferred choice.

• Significant leaflet or annulus destruction by infectious endocarditis. TEE, and in some cases cardiac CT, is required to determine the extent of annulus destruction. When endocarditis is secondary to intravenous drug use, every attempt to repair the MV should be made to avoid implantation of prosthetic material that will be at increased risk of reinfection with continued drug use and at increased risk of thrombosis due to noncompliance with anticoagulation. When the infection involves either the left noncommissural aortic annulus or the anterior mitral annulus, involvement of the aortomitral curtain must be carefully ruled out, as this finding may require replacement of both the aortic valve and MV with a reconstruction of the aortomitral curtain.

• Ischemic mitral regurgitation (IMR) is present. This diagnosis portends a poor prognosis, and patients are often high-risk surgical candidates. When we encounter this problem, we obtain cardiac MRI to evaluate left ventricular dysfunction and viability before proceeding with surgical decision-making. Guidelines favor optimal medical therapy for heart failure along with cardiac resynchronization therapy (CRT) for severe MR with reduced ejection fraction (EF) and left ventricular (LV) dyssynchrony, with randomized controlled trials (RCTs) showing improvement in rehospitalization and survival. However, this improvement may only manifest in about half of patients. In those who do not have improved symptoms or quality of life with progressive LV remodeling and increased LV dysfunction (end-stage heart failure), transplantation or left ventricular assist device (LVAD) is a more effective treatment. In those with continued symptoms despite optimal medical and device therapy, without end-stage heart failure, with viable areas of the myocardium and high-grade proximal coronary lesions, surgery may be indicated. Due to a lack of evidence showing a survival benefit to concomitant MV surgery, indications are limited. There is a Class IIa recommendation for MV repair by reduction annuloplasty or replacement for chronic severe IMR when CABG or aortic valve surgery is being performed. Despite several studies, including three RCTs (Randomised Ischaemic Mitral Evaluation (RIME) Trial, POINT, and Cardiothoracic Surgical Trials Network [CTSN] ) showing no survival benefit to MV repair in chronic moderate IMR, concomitant MV surgery in chronic moderate IMR with CABG is a Class IIb recommendation due to the proven improvement in reverse LV remodeling, LVEF, NYHA class, and MR grade. Another CTSN RCT showed similar survival comparing isolated reduction annuloplasty repair and replacement groups at 2 years for severe IMR with reduced MR recurrence and heart failure readmissions in the replacement group. Therefore, surgical decision-making remains controversial in IMR and should be made in collaboration with an experienced heart team. When indications for surgery are met, proceeding with MV replacement is an acceptable option.

Preoperative Medical Optimization

Evaluation of any patient with MV pathology must begin with a thorough history and physical exam. History should focus on the severity and progression of symptoms. While chest pain solely as a result of MV disease is possible, a chief complaint of angina should elicit a more complete workup for an alternate cause. Heart failure symptoms are more common and are sometimes subtle or progress so slowly that patients adjust their lifestyle without recognizing any change. Careful questioning can elicit these subtle points, specifically with regard to any limitations in physical activity that may be attributable to heart disease that has been compensated for by exertion modifications. In particular, the surgeon should probe for small changes since any prior visits. Specific questions about tiredness or daytime napping may clue the surgeon to symptoms unrecognized by the patient. Having a family member or close friend present during the patient visit is often helpful in eliciting the presence or progression of symptoms.

A thorough medical history should identify any problems that require optimization preoperatively. Taking into consideration medical comorbidities in conjunction with heart failure severity will render a prohibitive patient risk for MV surgery in some cases. These patients will be best managed with optimal guideline-directed medical therapy directed by the heart team. In some cases, the patient may be eligible for consideration for transcatheter MV interventions. This decision-making process can be guided by the use of the surgical risk calculator provided by the Society of Thoracic Surgeons.

An accurate medication history is also crucial. Many patients whose heart failure regimen is optimized will experience improvement in symptoms, ventricular function, and in turn, the severity of MR. Similarly, patients with pacemakers may experience improvement in symptoms and function by optimizing pacer timing.

Antiplatelet and anticoagulant medications must be noted, and an appropriate preoperative plan regarding when and whether to hold these medications should be made.

Physical exam should focus on signs of volume overload. The lungs should be auscultated for signs of edema. The abdomen should be assessed for ascites or hepatomegaly. Extremities, including feet and ankles, should be examined to determine the extent of peripheral edema. Careful examination of the extremities will also alert to the presence of wounds as a result of arterial occlusive disease, venous stasis, or diabetes.

Basic laboratory studies, including nutritional markers and serum chemistry, should be ordered. All patients should have two-view plain films of the chest to evaluate for cardiomegaly and pulmonary edema or signs of pulmonary disease.

Based on the above evaluations, additional functional assessments and/or frailty evaluations may be warranted. Such evaluations include a 6-minute walk test, sit-to-stand test, and a mini-mental status exam. Each of these studies may further elucidate whether a patient has sufficient baseline resilience to withstand the surgical insult and recover well following MV intervention.

After taking into consideration all of these factors, certain high-risk surgical candidates benefit from preadmission prior to MV surgery. They should be evaluated by a heart failure cardiology team to establish a plan for medical optimization, including intravenous diuretic therapy with or without the aid of inotropes and monitoring for organ dysfunction if at risk during this process. Preadmission also allows for bridging of anticoagulation, if necessary. Finally, preadmission also facilitates continuity of care with the appropriate specialist consultants if a complicated postoperative course is anticipated, particularly the nephrologists.