Minimally Invasive, Mini-Thoracotomy Aortic Valve Replacement
Keywords: minimally invasive, minithoracotomy, aortic valve replacement, Operations for Valvular Heart Disease
Step 1. Introductory Considerations
· Minimally invasive valve surgery has numerous benefits compared with a standard median sternotomy. These benefits include reduced surgical trauma, blood loss, transfusion require- ments, and reoperations for bleeding. Ventilation times and intensive care unit and hospital lengths of stay are also reduced. Patients undergoing minimally invasive surgery also experience a more rapid return to functional capacity and less use of rehabilitative resources, which has resulted in additional costs savings as well.1-5
· The incisions and approaches used in minimally invasive aortic valve surgery have evolved over time. The concept was first introduced in 1996 by Cosgrove et al.,6 who described a right parasternal incision approach. This later proved to cause significant chest wall instability and has since been abandoned. Currently, minimally invasive aortic valve surgery is usually performed via an upper hemisternotomy approach, either with a T or L transection of the sternum at the level of the third or fourth intercostal space.7,8 A lower hemisternotomy and manubrial approach have also been described.9,10 The only true sternal-sparing procedures are an axillary approach or right minithoracotomy, entering the thoracic cavity via the second or third intercostal space.11 The focus of this chapter will be on the latter method.
· The right minithoracotomy can be used in most subsets of patients requiring an aortic valve replacement (AVR). Definitive contraindications to a right anterior thoracotomy approach include patients with a severely calcified aorta (porcelain aorta), evident preoperatively by cardiac catheterization or computed tomography (CT) scan or intraoperatively by palpation, patients who cannot be safely cannulated peripherally due to peripheral vascular disease or centrally due to calcium in the aorta, and patients who require a valve-sparing operation. The aforementioned groups require greater exposure of the operative field. Patients who present with previous right thoracic surgery or dense adhesions from an inflammatory reaction may undergo a minithoracotomy approach. In this particular group, minimal dissection is performed in the pleural cavity, and the pericardial space is immediately entered and exposed.
· The benefits of the minithoracotomy over a standard sternotomy AVR have also been seen in higher-risk patients, including older patients (> 75 years old),1 obese patients (body mass index [BMI] > 30 kg/m2),2 patients with chronic obstructive pulmonary disease (COPD),4 and patients with a low ejection fraction (< 35%). Several studies have demonstrated a lower morbidity and mortality in these higher-risk patients.12 An extended application of this procedure can be offered to patients who require replacement of the ascending aorta and hemiarch along with an AVR.13 Most of these procedures are performed under deep hypothermic circulatory arrest and retrograde cerebral perfusion. In patients requiring a full root replacement due to aneurysmal disease or a small aortic annulus, an aortic root replacement with reimplantation of the coronaries can also be performed. In addition, reoperative aortic valve surgery in patients with prior valve surgery or coronary revascularization via a right minithoracotomy approach is feasible.14,15 All these procedures are more technically challenging and require additional experience. Other applications include AVR with aortic root enlargement, AVR with a septal myectomy, and AVR with a single bypass to the proximal or distal right coronary artery (RCA). The posterior descending artery is difficult to visualize with this approach. In patients with coronary artery disease amenable to percutaneous intervention, a hybrid approach is preferable. A percutaneous intervention can be performed at any time prior to the minimally invasive valve surgery. A minithoracotomy approach can be offered to patients receiving dual antiplatelet therapy.16,17
· The preoperative workup includes routine blood work, chest radiography, cardiac catheterization, and echocardiography. A routine CT angiogram is not necessary unless severe peripheral vascular disease is suspected by history or physical examination, although a CT angiogram is highly recommended when initiating a minimally invasive program. Stroke rates are low in patients undergoing femoral cannulation, despite the use of retrograde arterial perfusion,18,19 and are comparable to rates in patients undergoing a sternotomy valve procedure.
· Routine CT scans of the chest are not necessary either, although others have defined inclusion criteria based on CT scan findings, which may be beneficial initially.5 Chest CT scans may also potentially diminish the incidence of conversions.
· The anatomy of certain patients can pose additional challenges when performing the procedure via a right minithoracotomy approach. A chest x-ray demonstrating the right border of the heart adjacent to the right border of the vertebral column may be associated with the heart being displaced toward the left side of the chest. This is also true for patients with a pectus excavatum. If the angle of the aorta and ventricle lie at 90 degrees on the ventriculogram (cardiac catheterization), visualization of the aortic valve may be more challenging. Visualization of the aortic valve is usually more challenging in patients with a bicuspid aortic valve. Although challenging, these anatomic variants are not definitive contraindications for the surgery.
· A single-lumen endotracheal tube is inserted, and double-lung ventilation is used throughout the operation. If visualization of the heart is impaired by the lungs, the lungs are temporarily deflated, or cardiopulmonary bypass can be initiated early in the procedure.
· Single-lung ventilation with a double-lumen endotracheal tube or bronchial blocker is not performed unless significant pleural adhesions limit visualization and dissection. Cases of unilateral reexpansion pulmonary edema secondary to single-lung ventilation have been reported.20
Figure 10.1 Femoral arterial and venous cannulation.
Figure 10.2 External landmarks for right mini thoracotomy incision.
· The preoperative preparation includes insertion of a left radial arterial line and right internal jugular or left subclavian vein Swan-Ganz catheter. A left radial arterial line is always preferred in case right axillary artery cannulation is required. Patients undergoing reoperative aortic valve surgery will have a temporary transvenous pacemaker inserted after the induction of anesthesia.
· The patient is induced with a muscle relaxant (fentanyl and midazolam). A volatile agent is administered throughout the surgery. Remifentanil is started immediately prior to exposing the artery and vein for cannulation. Heparin (300-400 units/kg) is also given at this time in preparation for cannulation. The dosage of remifentanil is increased prior to the chest incision. While on cardiopulmonary bypass, the remifentanil dose is lowered, and midazolam is administered. After weaning from cardiopulmonary bypass, remifentanil is continued at a low dose. At completion of the operation, the patient is transported to the intensive care unit and continued on remifentanil.
· Every patient should have a thorough intraoperative two-dimensional (2D) and three-dimensional (3D) transesophageal echocardiographic assessment. The sizes of the aortic annulus and ascending aorta are measured. Left ventricular function is assessed. The mitral valve is visualized and analyzed. If mitral valve pathology requiring repair or replacement is identified, patient positioning may need to be changed. Assessment of atherosclerotic disease in the ascending and descending aorta is performed. Evidence of a grade 4 or 5 free-floating atheroma in the descending aorta would preclude femoral cannulation and retrograde arterial perfusion. Positioning of the venous cannula in the superior vena cava (SVC) is performed with trans-esophageal echocardiography (TEE). A bicaval midesophageal view done at 80 to 100 degrees is used for placement of the venous cannula into the SVC. TEE is also used in reoperative aortic valve surgery for insertion of a retrograde cardioplegia cannula. A midesophageal, four-chamber view at 0 degrees is used for guiding placement of a retrograde cannula into the coronary sinus if necessary.21
· Intraoperative fluoroscopy can also be used to aid placement of the venous guidewire and cannula when the wire cannot be visualized by TEE. Intraoperative iliac and abdominal aortic angiograms with fluoroscopy are obtained when there is uncertainty after insertion of the femoral arterial cannula or when calcified plaques are encountered during cannulation.
Figure 10.3 Right mini thoracotomy exposure with soft tissue retractor and rib spreader.
Figure 10.4 Left ventricular vent in right superior pulmonary vein.
· Patients receive 2 g of a cephalosporin within 1 hour of skin incision and every 8 hours thereafter for 48 hours. Patients allergic to penicillin receive 1 g of vancomycin within 1 hour of skin incision and every 12 hours for 48 hours thereafter. Dosing will be altered depending on renal function. Patients who have been admitted to the hospital for an extended period of time before their scheduled surgery will receive vancomycin.
· Patients are positioned supine, with the arms at the side. A roll is not placed between or below the scapula to elevate the chest. Defibrillator pads are placed on the patient’s back. One pad is placed on the right posterior shoulder and the other on the left lower posterior thorax. The chest is prepped with chlorhexidine. In addition, the inguinal region and lower extremities are prepped for peripheral cannulation and for vein harvesting, if required.
· A femoral platform is the access site of choice. Left femoral artery and vein cannulation are preferred because most patients undergo a cardiac catheterization via the right femoral artery. A CT angiogram is not routinely obtained unless severe peripheral vascular disease is suspected. Prior to cannulation, the patient is fully heparinized (300-400 units/kg). A 2- to 3-cm longitudinal skin incision is made above the inguinal crease. This approach, along with limited dissection of the anterior aspect of the vessels, decreases the incidence of seroma formation. Careful attention is paid to assessing the quality of the artery. Presence of a posterior horseshoe calcified plaque is not a contraindication for cannulation. Circumferential calcification would negate cannulation. A 5-0 Prolene purse-string suture is placed on the anterior aspect of each vessel. A modified Seldinger technique is used for cannulation. A guidewire is advanced into the proximal descending aorta and verified by TEE. Passage of the wire should be performed without resistance. Thereafter, an arterial cannula is inserted into the artery. The size of the cannula chosen will depend on the patient’s body surface area. Occasionally, when passing the cannula over the guidewire, plaque may be felt as the cannula is being advanced. The cannula is advanced as long as there is no resistance. If any resistance is encountered while advancing the cannula, an alternative access site should be chosen. If any concerns exist, intraoperative angiography is performed, with contrast injected through the cannula side port.
· When the femoral artery is small, circumferential dissection of the vessel is performed, proximal and distal control of the artery is obtained, and a direct arteriotomy is performed. The guidewire is back-loaded in the arterial cannula, and the cannula is introduced into the artery. The guidewire is advanced, and then the cannula is passed over the guidewire (Fig. 10.1). If an alternative cannulation site is required, the right axillary artery is the next access point of choice. In this case, a 2-cm skin incision is performed 1 to 2 cm beneath the clavicle, medial to the deltopectoral groove. Care is taken not to injure the surrounding nerves. The vein is usually encountered first and is inferior to the artery. The artery is commonly deep, and the pulse is palpated to guide the dissection. Once exposed, the artery is encircled proximally and distally with vessel loops. A direct arteriotomy is preferred for passage of the cannula. Intraoperative fluoroscopy and angiography is always performed. Of note, a Seldinger technique can be used, although the risk of damaging the vessel is greater. Central cannulation can also be performed. In these cases, the pericardium is opened, and all the pericardial retraction sutures are placed. Purse-string sutures are then placed as distally as possible in the ascending aorta, and a Seldinger technique is also used for cannulation.
· Once arterial cannulation is completed, femoral venous cannulation is performed using a Seldinger technique. A 180-cm wire is passed through the femoral vein and into the SVC under TEE guidance. A 0-degree bicaval view is obtained for placement. Thereafter, a 25 F venous cannula is advanced deep into the SVC. To obtain adequate venous drainage, the cannula should be in the SVC and vacuum drainage applied. Vacuum assistance with 35 mm Hg of negative suction is applied and increased to 65 mm Hg, if necessary. The application of negative pressure causes an increase in the formation of gaseous microemboli, although this has not been proven to be harmful. Studies have demonstrated that surpassing 60 mm Hg of negative pressure does not increase the incidence of neurologic events.22 Additional venous drainage is required in case of right-sided distention or dislodgment of the venous cannula into the right atrium. In these cases, a 4-0 purse-string suture is placed on the SVC, and additional sump suction is inserted into the SVC.
· A 5- to 6-cm right minithoracotomy skin incision is performed 1 cm lateral to the sternum at the level of the second or third intercostal space (Fig. 10.2). Once the skin and subcutaneous tissues are entered, limited dissection of the pectoralis muscle is performed. Exposure can be challenging in young muscular patients. The intercostal muscle is then entered. The right internal mammary artery and vein are identified and transected between two clips. Care is taken to visualize each vessel clearly. The lower costal cartilage is transected immediately lateral to the sternum. Alternatively, the cartilage can be left intact and a rib spreader inserted to gain additional exposure. This option can cause a residual chest wall defect, which could lead to paradoxic chest wall motion.
· A soft tissue retractor is inserted into the pleural cavity and provides improved visualization. An intercostal rib spreader is placed to provide additional exposure. A chest tube incision (utility port) is then made several interspaces below the chest incision. Intravenous tubing is placed through the utility port and passed out from the chest incision. This tubing functions as a guide to pass cannulae and tubes and avoids creating multiple false tracks through the chest wall. In addition, this will decrease the potential of injuring the intercostal vessels (Fig. 10.3). At this point, cardiopulmonary bypass is instituted, and the lungs are deflated. The pericardium is opened over the aorta, and the incision extended down toward the inferior vena cava. Care is taken not to open the pericardium superiorly past the aortopericardial reflection. A pericardial stay suture is placed at the level of the right superior pulmonary vein and tacked to the skin to aid exposure. An additional pericardial retraction suture is placed at the level of the SVC.
· The right atrium is retracted to the left, and the pericardium adjacent to the right superior pulmonary vein is retracted to the right. A purse-string suture is placed on the right superior pulmonary vein (Fig. 10.4). A blunt-tipped left ventricular vent is inserted into the left atrium or left ventricle. This is then exteriorized through the chest tube incision (utility port).
· A purse-string suture is placed around the lateral aspect of the right atrial appendage, and a retrograde cardioplegia cannula is inserted into the coronary sinus. The end of the cardioplegia cannula is bent at a 45-degree angle approximately 1 to 2 cm from its tip. This will usually facilitate placement into the coronary sinus. If this maneuver is not successful, the cannula is removed, and the tip is straightened and reinserted. TEE guidance is used to assess entry into the coronary sinus. On the midesophageal four-chamber view, at a probe depth of 30 to 35 cm with the transducer angle between 0 and 20 degrees, the mitral and tricuspid valves are visualized. After advancing the probe slightly, the coronary sinus in the long-axis view can be appreciated just above the attachment of the tricuspid valve septal leaflet to the interventricular septum.21 Once the cannula is visualized in the coronary sinus, the stylet is removed, and the cannula is advanced an additional 1 to 2 cm into the coronary sinus. It is important to advance the cannula further once visualized in the coronary sinus to avoid dislodgment.
· There are four points to confirm proper placement of the retrograde cannula. The first is TEE visualization of the cannula. The second is dark venous blood return from the cannula immediately after proper placement. The third is ventricularization of the pressure transduced from the cannula. The fourth is visualizing active blood return from the coronary ostia after delivering cardioplegia. The cardioplegia catheter is also exteriorized through the utility port.
· Alternatively, and preferentially, retrograde cardioplegia cannulation is omitted, and the right atrial appendage is retracted with a no. 2 silk loop. This loop is tunneled through the utility port and pulls the right atrial appendage inferiorly to improve visualization of the aortic root (Figs. 10.5 and 10.6).
· Additional pericardial sutures are placed. It is important not to open the pericardium superiorly up to its insertion on the aorta (Fig. 10.7). This will limit the ability of the pericardium to provide the necessary retraction. Each maneuver will help lead to the next step in facilitating additional exposure. In general, one should not make judgment on the exposure or one’s ability to perform minimally invasive AVR until the patient has been placed on bypass, and the heart and lungs are decompressed.
· A plane is then established beneath the aorta and above the superior aspect of the right branch of the pulmonary artery for placement of the aortic cross-clamp. The aorta is not dissected free from the main pulmonary artery. A retractable, shafted, cygnet cross-clamp is then used to cross-clamp the ascending aorta. A 6-inch, 14-G angiocatheter is inserted into the aorta to deliver an induction dose of cardioplegia (Fig. 10.8). Thereafter, retrograde cardioplegia is delivered at 20-minute intervals or sooner, if required. Additional doses of cardioplegia are given directly into the coronary ostia if blood return is not visualized from both ostia during delivery of retrograde cardioplegia or if there is a suspicion that the coronary sinus cannula was not properly placed. However, note that this aforementioned cardioplegia strategy is no longer used since the implementation of extended-effect cardioplegia solutions.23 A modified del Nido solution (four parts blood to one part crystalloid) containing 40 mEq potassium is delivered either into the aortic root or directly into the coronary ostia. A 2-L induction dose will allow at least 90 to 100 minutes of safe protection. Of note, no studies to date have confirmed the degree of protection that this particular cardioplegia method provides in the adult cardiac surgical patient.
· The patient’s temperature is allowed to fall to 34°C (93.2°F). Active cooling is not performed unless the ascending aorta and hemiarch are being replaced.13 In these cases, the SVC is encircled with a vessel loop, a 4-0 Prolene purse-string suture is placed on the SVC, and a 24 F wire-reinforced venous cannula is tunneled through the utility port and into the SVC. This is used for retrograde cerebral perfusion during the period of deep hypothermic circulatory arrest. In this case, the patient is cooled to 20°C (68°F).
Figure 10.5 Silk loop placed on tip of right atrial appendage.
Figure 10.6 Right atrial appendage retracted with silk loop.
Figure 10.7 Pericardial incision.
Figure 10.8 Delivery of antegrade cardioplegia.
· An aortotomy is made at the level of the linear fat pad located on the anterior aspect of the aorta with long-shafted Metzenbaum scissors (Geister Medizintechnik, Tuttlingen, Germany). Care is taken to stay at least 2 cm from the cross-clamp. A silk suture is then placed on the upper aspect of the aortotomy to allow retraction of the aorta and exposure of the aortic valve (Fig. 10.9). When the ventricular fat overlying the RCA impedes visualization, another retraction suture can be placed on this fat pad and tacked to the pericardium. CO2 is infused into the operative field at a rate of 2 L/min throughout the entire procedure. Infusing higher amounts of CO2 will raise the patient’s CO2 levels while on cardiopulmonary bypass and will pose an arduous task for the perfusionist to sweep off. Long-handled conventional Metzenbaum scissors or long-shafted Mayo scissors are used to resect the aortic valve. If needed, a rongeur is used to débride additional calcium. Because the assistant has limited visibility to help suction the calcium, the rongeur is held in one hand and the suction in the other simultaneously. After excision of the valve, the root and left ventricle are irrigated to remove any residual debris. Thereafter, 3-0 Prolene sutures are placed at the level of the commissures to provide a so-called no-touch technique for exposure of the aortic valve. An aortic valve exposure device (Aortic Cuff [small, medium, or large], Miami Instruments, Miami, FL) is used to provide further exposure, if necessary (Fig. 10.10). The valve sutures are then placed on the aortic annulus in the conventional manner (Fig. 10.11). The valve is sized, and the valve of choice is selected. After the sutures are placed through the sewing cuff, the valve is delivered onto the annulus. The valve usually requires manipulation to cross the sinotubular junction. Once seated on the aortic annulus, each suture is tied down carefully (Fig. 10.12). In certain cases, some of the sutures can be tied manually, but one must avoid excessive traction on the suture to avoid tearing the annulus, which will lead to a paravalvular leak. Each knot is inspected prior to cutting the suture to ensure that an air knot does not exist. If an air knot has occurred, the knot is teased and unraveled. This same suture is then tied again. Once the valve is properly seated, the aortotomy is closed in the desired fashion (Fig. 10.13).
· Prior to removal of the cross-clamp, the acute margin of the right ventricle is retracted with a sponge stick, and the muscular wall of the inferior aspect of the right ventricle is visualized. A ventricular pacing wire is placed very superficially on the epicardium. It is important to perform this maneuver with the heart empty prior to removing the cross-clamp (Fig. 10.14). After the clamp is removed, it is virtually impossible to place a ventricular lead on the inferior wall of the right ventricle. An atrial pacing wire can be placed, although this is rarely necessary. The patient is then placed in a Trendelenburg position, the heart is filled, and air is removed from the aortic root. The cross-clamp is removed and the angiocatheter, which was initially used to deliver antegrade cardioplegia, is placed back into the aortic root for further removal of air. The heart is filled and allowed to eject during this time. The left ventricular vent, which was placed in the right superior pulmonary vein, also aids air removal.
· Instruments are not placed directly through the chest incision to manipulate the heart. Once there is TEE confirmation of adequate air removal, two purse-string sutures are placed to seal the antegrade cardioplegia delivery site. The patient is subsequently weaned from cardiopulmonary bypass. After half of the protamine is administered, the femoral venous cannula is removed, and the purse-string suture is tied. After complete administration of the protamine, the arterial cannula is removed, and the purse-sting suture is tied as well.
· A Blake chest drain is placed over the main pulmonary artery and advanced into the posterior pericardial well (Fig. 10.15). An additional Blake drain is placed posteriorly and laterally in the pleural space. The Blake drains, pacing wire, and pain management catheters are all exteriorized through the utility port.
· Closure of the chest wall needs to be meticulously performed to avoid paradoxic chest wall motion and maintain chest wall stability. Once hemostasis is obtained, one additional clip is placed on either side of the transected right internal mammary artery and vein. Care is taken not to place an excessive number of clips because of the potential of tearing the vessels. The ON-Q Pain Relief System (Halyard Health, Alpharetta, GA) has two catheters, which are placed freely in the pleural space and connected to a dispenser that delivers 0.25% bupivacaine (Marcaine) at 4 mL/hr for 3 days. Alternatively, one catheter can be placed freely in the pleural space and the other extrapleurally, adjacent to the entered intercostal space. A 1-0 Vicryl suture is placed through the sternum and then through the transected cartilage. This suture is tied, and then the same suture is placed in a figure-of-eight fashion from the transected rib to the upper rib. Thereafter, 0 Vicryl sutures are used to approximate the intercostal muscle to the periosteum of the rib. The sutures are continued laterally, incorporating as much of the intercostal muscle as possible. The last suture is locked, and the second layer of the closure approximates the fat pad that lies underneath the pectoralis muscle. This suture is continued medially and locked again. The pectoralis muscle is then approximated in a two-layer fashion. The skin is cosmetically closed in routine fashion11 (Fig. 10.16).
Figure 10.15 Blake chest tubes placed in pericardial space and pleural space.
Figure 10.16 Skin closure.
· On arrival to the intensive care unit, a rapid ventilator weaning protocol is instituted, depending on the patient’s condition. The amount of bleeding from the chest tubes is usually insignificant. Chest tube drainage of more than 75 to 100 mL/hr is not common. If this occurs, reexploration should be considered unless a coagulopathy is suspected or the patient is on clopidogrel (Plavix). It is common for patients to have an air leak, which is caused by having two Blake drains adjacent to each other and exteriorized through one chest tube incision. The drains, pacing wire, and pain management catheters (ON-Q) are usually removed on the third day. The drains are usually not removed earlier due to persistent serous drainage. Patients who do not have coronary artery disease will be placed on nonsteroidal antiinflammatory drugs for 3 weeks.
· A minithoracotomy, minimally invasive aortic valve surgery, is a true sternal-sparing minimally invasive procedure. Benefits include diminished ventilator time, reduced intensive care unit and hospital lengths of stay.1-5,19,24 In addition, patients can return to their normal lifestyles sooner because of less surgical trauma and improved chest wall stability, which allows them to be more functional sooner compared to standard sternotomy patients. Other benefits include less transfusions and analgesics and improved cosmesis.19,25 A decrease in the composite complication rate in higher-risk patients (e.g., obese patients, patients > 75 years, patients with COPD or low ejection fraction),1,2,4 as well as a decrease in surgical mortality, have been documented.12,24 A minimally invasive valve program is an essential addition to any cardiac surgical service and offers patients additional options for the treatment of aortic valve disorders. In addition, it provides cardiac surgeons with alternative techniques to address concomitant valvular and aortic pathologies. Considering the rapid development of transcatheter aortic valve technology with direct access implants as a treatment option, as well as the future availability of surgical sutureless aortic valves, the minithoracotomy approach is a useful technique in our armamentarium. Finally, the ability to perform less invasive surgical techniques such as this one is essential for surgeons who wish to remain relevant.
1. Lamelas J, Sarria A, Santana O, Pineda AM, et al. Outcomes of minimally invasive valve surgery versus median sternotomy in patients 75 years or greater. Ann Thorac Surg. 2011;91:79–84.
2. Santana O, Reyna J, Grana R, et al. Outcomes of minimally invasive valve surgery versus standard sternotomy in obese patients undergoing isolated valve surgery. Ann Thorac Surg. 2011;91:406–410.
3. Schmitto JD, Mokashi SA, Cohn LH. Minimally-invasive valve surgery. J Am Coll Cardiol. 2010;56:455–462.
4. Santana O, Reyna J, Benjo AM, et al. Outcomes of minimally invasive valve surgery in patients with chronic obstructive pulmonary disease. Eur J Cardiothorac Surg. 2012;42:648–652.
5. Glauber M, Miceli A, Bevilacqua S, Farneti PA. Minimally invasive aortic valve replacement via right anterior minithoracotomy: early outcomes and midterm follow-up. J Thorac Cardiovasc Surg. 2011;142:1577–1579.
6. Cosgrove DM 3rd, Sabik JF. Minimally invasive approach for aortic valve operations. Ann Thorac Surg. 1996;62:596–597.
7. Johnston DR, Atik FA, Rajeswaran J, et al. Outcomes of less invasive J-incision approach to aortic valve surgery. J Thorac Cardiovasc Surg. 2012;144:852–858.
8. Tabata M, Umakanthan R, Cohn LH, et al. Early and late outcomes of 1000 minimally invasive aortic valve operations. Eur J Cardiothorac Surg. 2008;33:537–541.
9. Fenton JR, Doty JR. Minimally invasive aortic valve replacement surgery through lower half sternotomy. J Thorac Dis. 2013;5:S658–S661.
10. Burdett CL, Lage IB, Goodwin AT, et al. Manubrium-limited sternotomy decreases blood loss after aortic valve replacement surgery. Interact Cardiovasc Thorac Surg. 2014;19:605–610.
11. Santana O, Reyna J, Benjo AM, Lamas GA, Lamelas J. Outcomes of minimally invasive valve surgery in patients with chronic obstructive pulmonary disease. Eur J Cardiothoracic Surg. 2012;42:648–652.
12. Merk DR, Lehmann S, Holzhey DM, et al. Minimal invasive aortic valve replacement surgery is associated with improved survival: a propensity-matched comparison. Eur J Cardiothorac Surg. 2015;47:11–17.
13. LaPietra A, Santana O, Pineda AM, et al. Outcomes of aortic valve and concomitant ascending aorta replacement performed via a minimally invasive right thoracotomy approach. Innovations (Phila). 2014;9:339–342.
14. Pineda AM, Santana O, Lamas GA, Lamelas J. Is a minimally invasive approach for re-operative aortic valve replacement superior to a standard full sternotomy? Interact Cardiovasc Thorac Surg. 2012;15248–15252.
15. Pineda AM, Santana O, Reyna J, et al. Outcomes of reoperative aortic valve replacement via a right mini-thoracotomy versus a median sterntomy. J Heart Valve Dis. 2013;22:50–55.
16. Santana O, Pineda AM, Cortes-Bergoderi M, et al. Hybrid approach of percutaneous coronary intervention followed by minimally invasive valve operations. Ann Thorac Surg. 2014;97:2049–2055.
17. Santana O, Funk M, Zamora C, et al. Staged percutaneous coronary intervention and minimally invasive valve surgery: results of a hybrid approach to concomitant coronary and valvular disease. J Thorac Cardiovasc Surg. 2012;144:634–639.
18. LaPietra A, Santana O, Mihos CG, et al. Incidence of cerebrovascular accidents in patients undergoing minimally invasive valve surgery. J Thorac Cardiovasc Surg. 2014;148:156–160.
19. Glauber M, Gilmanov D, Farneti PA, et al. Right anterior minithoracotomy for aortic valve replacement: 10-year experience of a single center. J Thorac Cardiovasc Surg. 2015;150:548–556.
20. Madershahian N, Wippermann J, Sindhu D, Wahlers T. Unilateral re-expansion pulmonary edema: a rare complication following one-lung ventilation for minimal invasive mitral valve reconstruction. J Card Surg. 2009;24:693–694.
21. Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr. 2013;26:921–964.
22. Lou S, Ji B, Liu J, et al. Generation, detection and prevention of gaseous microemboli during cardiopulmonary bypass procedure. Int J Artif Organs. 2011;34:1039–1051.
23. Matte GS, del Nido PJ. History and use of del Nido cardioplegia solution at Boston Children’s Hospital. J Extra Corpor Technol. 2012;44:98–103.
24. Glower DD, Desai BS, Hughes GC, et al. Aortic valve replacement via right minithoracotomy versus median sternotomy: a propensity score analysis. Innovations (Phila). 2014;9:75–81.
25. Brown ML, McKellar SH, Sundt TM, Schaff HV. Ministernotomy versus conventional sternotomy for aortic valve replacement: a systematic review and meta-analysis. J Thorac Cardiovasc Surg. 2009;137:670–679.