Gardner L. Yost and Steven F. Bolling
Indications and Patient Selection
Return of Valvular Dysfunction: Presenting as MR after attempted repair of dysfunctional valve. This is frequently a result of incorrect ring sizing or failure to use a ring and results in progressive annular dilation. MV reoperation after primary repair has been reported to occur at a rate of 0.5–1.5%.
Structural Valve Degeneration: Presenting as MR from leaflet tear or calcification, this complication of bioprosthetic valves occurs in 60% of patients at 15 years. Indications for replacement are presence of new murmur with congestion symptoms and documentation of valve dysfunction.
Prosthetic Valve Thrombosis: Occurring at a rate of 0.3–1.3% per patient year, these patients often present with symptoms of heart failure. Smaller thrombi (less than 3mm) can be treated with anticoagulation with or without thrombolysis. Larger thrombi often require surgical intervention – either thrombectomy or valve replacement.
Periprosthetic Leak: A relatively rare indication for reoperative mitral surgery is periprosthetic leak which comprises approximately 1% of operations. When the valve itself is competent, periprosthetic leak is best managed with direct repair, but when significant dehiscence or valvular dysfunction is present, the valve may require excision and reconstruction.
Endocarditis: Indications for reoperation on either prosthetic or native valve endocarditis include severe MR with or without CHF, refractory sepsis, culture of antibiotic resistant organism, endocarditis which is caused by Staphylococcus aureus, a gram negative, or is fungal, mitral annular abscess, new conduction abnormality, vegetations >1cm, or embolic disease.
Reoperation: The increased risk of reoperation must be considered for all second time mitral valve surgeries. It is important to note that while injury during sternotomy is more frequent in patients who have undergone previous CABG and who have had previous radiotherapy, history of mitral surgery does not specifically place patients at higher risk for this complication. Axial imaging is a helpful strategy to identify cardiovascular structures at risk of damage, and peripheral cannulation for bypass, as well as initiation of bypass before sternotomy, aid the surgeon in dealing with and avoiding these injuries.
Outcomes after Reoperation
When technically feasible, mitral valve re-repair can be safely performed with outcomes similar to mitral valve replacement. The most common scenario is technical failure of the initial repair; for instance, insufficient valve tissue resection or ring annuloplasty in which the annular sutures are not placed in the true annulus.
Diagnosis and Imaging
Patients with mitral valve dysfunction most often present with symptoms of heart failure including dyspnea, volume overload, pulmonary hypertension, and atrial fibrillation. Echocardiographic examination of the valve is required to determine the etiology of the mitral dysfunction and for operative planning. A CT scan can be obtained to determine whether any cardiovascular structures are adjacent to the posterior sternum and at risk of injury during re-entry.
Operative Approaches
The mitral valve has been historically accessed via multiple surgical approaches. Fundamental to any approach is achieving excellent and practical exposure of the valve. The most common approaches for reoperative surgery are via median sternotomy and right thoracotomy, though the left thoracotomy has been used when access to the right chest is not advisable (perhaps due to history of radiation or pleurodesis). Re-sternotomy provides adequate access to the mitral valve and is the exposure of choice when concomitant operations are required. This technique incurs risk of injury to prior grafts, sternal dehiscence, or inadvertent cardiac injury, a problem which may be of particular concern in patients whose valve disease has led to cardiomegaly and atrial thinning. Injury to a patent LIMA graft has an associated mortality rate near 50%. The right thoracotomy is a safe alternative to the re-sternotomy which provides excellent exposure to the mitral and tricuspid valves. Bicaval venous cannulation and central or peripheral arterial cannulation may be used, though femoral cannulation may be preferred when re-entry is deemed to be high risk. The mitral valve may be accessed directly through the left atrium via Sundergaard’s groove, or through the right atrium by means of an atrial septostomy. Compared to re-sternotomy, the right thoracotomy results in shorter CPB times, less blood product use, and lower rates of LIMA injury. Additionally, a mini-thorocotomy approach has gained attention as this strategy results in reduced mortality and lower transfusion rates compared to re-sternotomy or thoracotomy.
Transcatheter mitral valve replacement is an emerging frontier which provides a minimally invasive means for valve replacement in native mitral valve regurgitation, valve-in-valve degenerated bioprostethic valves, and valve-in-annular ring. In the case of a previous valve replacement, sizing of the transcatheter ring is simplified, but when an annuloplasty ring or calcification are present, this planning may be more challenging and intra-operative 3D echo is utilized during deployment. Delivery strategies include transapical and transvenous-transseptal. There are currently several types of valves available which differ in their delivery and anchoring mechanisms. At this time important data regarding valve design, patient selection, and anti-coagulation are missing.
Complications
The complications of reoperative mitral surgery include all those of primary valve operations, namely circumflex artery or conduction system injury secondary to excessively deep annular sutures, systolic anterior motion, and damage to the aortic valve apparatus. The reoperative surgeon should additionally focus effort on the preservation of both the mitral annulus, as excessive debridement can cause atrioventricular disruption, and the sub-valvular apparatus as damage to this structure decreases contractility and valve competence.
Postoperative care
Postoperative management of reoperative mitral patients is similar to that of primary mitral repair. Aggressive diuresis is required depending on the extent and chronicity of MR and preoperative fluid overload. When mitral valve competence has been restored there may be unmasking of LV dysfunction necessitating inotropic support and volume reduction. Likewise, RV dysfunction can occur, particularly in patients with pulmonary hypertension and with poor myocardial protection. Volume optimization, inotropic support, and pulmonary vasodilation may be required to treat RV dysfunction.
Suggested Readings
- Mehaffey HJ, Hawkins RB, Schubert S, et al. Contemporary outcomes in reoperative mitral valve surgery. Heart. 2018;104:652-656.
- Alkhouli M, Alqahtani F, Berzingi C, Cook CC. Contemporary trends and outcomes of mitral valve surgery for infective endocarditis. J Card Surg. 2019;34:583-590.
- Atluri et al. Redo mitral valve surgery following prior valve repair. J Card Surg 2018. 33(12):772-777.
