• Surgical procedure in which the diseased mitral valve is replaced by a mechanical or biological tissue valve, commonly due to mitral stenosis, regurgitation, or severe prolapse.
• Mitral valve (MV) repair, when feasible, is usually preferred over replacement for the surgical treatment of mitral regurgitation (1,2) [A]. Retrospective studies of MV repair appear to demonstrate lower operative mortality, greater improvement in LV function, and higher overall survival at 10 years as compared with MV replacement.
• Most often, mitral valve surgery is performed in conjunction with either coronary bypass surgery or another valvular surgery; less frequently, the mitral valve abnormality is an isolated problem requiring cardiac surgery.
• Following sternotomy and opening of the pericardium, venous and arterial cannulations are performed. The patient is then taken onto full cardiopulmonary bypass (CPB). After the heart is arrested, the left atrium is opened to expose the mitral valve. The valve leaflets are excised and the annulus is debrided. If feasible, chordae are preserved. The annulus is then measured to properly match the prosthetic valve. Interrupted sutures are placed through the annulus for its entire circumference and then passed through the sewing ring. The prosthesis is securely tied in place.
• Systemic warming is initiated during the final stages of the valve implantation. After closure of the left atriotomy, the patient is placed in the head-down position and all remaining air is vented from the left heart through the LV vent. The cross-clamp is removed. Chest tubes are placed and the patient is weaned from bypass.
• Minimally invasive mitral valve surgery through smaller incisions with specialized instruments is being explored; for surgery on the valve itself, conventional instruments and techniques are used. Only selected patients are eligible for these approaches. There are, as yet, no randomized comparisons of conventional and minimally invasive approaches with regard to clinical outcome, complications, and cost.

• Supine with the arms positioned next to the body.
• The patient may be temporarily placed in Trendelenburg at the time of de-airing of the ventricles before coming off bypass.

• Median sternotomy is the standard incision.
• Alternative incision sites (e.g., via a right mini-thoracotomy) are used as part of "minimally invasive mitral valve surgery."

Time typically varies between 4–8 hours depending on the experience of the team, the type of approach (standard versus minimally invasive approach), and technical difficulties.

• Cardiopulmonary bypass machine leads to dilution.
• Blood loss typically ranges between 1,000–2,000 cc.

Surgical intensive care unit for 1–3 days; 7–10 days total in the hospital.

• Cardiopulmonary bypass machine (operated by a perfusionist).
• Standard equipment for open heart surgery.
• Minimally invasive approaches require special equipment.
• Transesophageal echocardiography probe (intraoperative examination performed by echo-trained anesthesiologists or cardiologists).

Incidence

N/A

Prevalence

About 65,000 MV repairs and replacements are performed in the US each year.

• Bleeding, reoperation, stroke, renal failure, prolonged ventilation, and infection are known complications.
• The incidence varies depending on preoperative status, length, and type of operation.
• The 2008 ACC/AHA valvular disease guidelines refer to risk stratification models to estimate the risk of in-hospital mortality and morbidity of valve surgery with or without coronary artery bypass surgery (2) [B].
  • US based registry by the Society of Thoracic Surgeons (STS) (3) [B]. Includes data from nearly 90% of cardiac surgery providers in the US and may provide the most accurate risk stratification for valve replacement.
  • European system for cardiac operative risk evaluation ("Euro Score")
  • Scoring system developed from Great Britain's and Ireland's national data base

• Varies significantly with age, co-morbidities, type of valvular lesion, ventricular function, concomitant valvular surgery, and/or bypass surgery.
• Risk stratification models are useful to predict mortality risk for the individual patient (see under morbidity).

History

• See chapters on mitral stenosis, regurgitation, and prolapse.
• Determine if there is a history of esophageal strictures or other abnormality that would prohibit placement of a transesophageal echocardiography probe during the procedure.

Signs/Physical Exam

Detailed description available in chapters on MV regurgitation, MV stenosis, and MV prolapse.

Labs/Studies

• Preoperatively, a transthoracic echocardiography and sometimes a transesophageal echocardiography are obtained.
• Coronary angiography is also routinely performed to determine whether the patient requires concurrent coronary bypass grafting.

Consider gentle anxiolysis with benzodiazepines.

Morbidity and mortality risks vary with the extent of surgery (e.g., coronary bypass surgery in addition to valve replacement) and preexisting comorbidities.

Skin flora is the greatest concern. Cefazolin may be utilized within 60 minutes prior to incision if the patient is not a carrier of multi-resistant bacteria and does not have an allergy; repeat every 3–4 hours until chest closure. Alternatively, vancomycin may be considered.

• General anesthesia in the US.
• There are case reports of open heart surgery performed under epidural with sedation in other parts of the world.

• ASA standard monitoring.
• Arterial line, most often, placed prior to induction; non-pulsatile flow during bypass does not allow for accurate non-invasive blood pressure measurement.
• Central venous access is usually obtained after induction; pulmonary artery catheter placement may be considered.
• Transesophageal echocardiography is frequently used intraoperatively to guide and assess MV repair/replacement.

• The goal is to provide hemodynamic stability throughout the induction period; gentle administration of propofol with pressors or etomidate is most often used in combination with fentanyl.
• Mask ventilation prior to endotracheal tube placement is performed except in cases of increased aspiration risk when a rapid-sequence induction is chosen.

• Patients are usually maintained with oxygen/volatile agents and intermittent doses of opioids and non-depolarizing muscle relaxants.
• During bypass, a volatile agent is added to the blood by the perfusionist through the bypass machine.
• The management of patients during bypass varies substantially by institution and practitioner.
• On bypass, the target mean arterial blood pressure is typically between 50–80 mm Hg.
• On bypass, the patient's body temperature is cooled at the beginning and warmed to normal body temperature before the termination of bypass.

• Patients remain intubated and are transferred to the intensive care unit.
• Postoperative sedation is typically provided with propofol infusion or most recently with dexmedetomidine infusion. The latter appears to have a lower risk for the development of postoperative delirium.