Surgical Management of Minimally Invasive Aortic Valve Operations

History of Minimally Invasive Aortic Valve Surgery

Since the 1960s, cardiac valve surgery has traditionally been approached through a median sternotomy, an incision that extends from the sternal notch to the xiphoid process and carried through the entire sternum. The advantages of the incision are complete exposure of the heart and ascending aorta as well as operative speed. Overall mortality with this procedure has remained low between 2% and 5%.^2-4 Disadvantages include pain, risk of mediastinitis, wound dehiscence, sternal instability, and poor cosmesis from a large incision. ⁵ In the midst of tremendous advances in surgery toward minimally invasive techniques, investigation began with decreasing the incision size needed to perform cardiac surgery. In 1996, initial cardiac valve research in a canine model demonstrated successful mitral valve replacement though a 2.5-cm port with percutaneous cardiopulmonary bypass. ⁶ This technique was quickly applied to humans. In 1996, Cosgrove and Sabik ⁷ reported a minimally invasive approach to aortic valve replacement in patients at the Cleveland Clinic. By 1997, minimally invasive approaches to both aortic and mitral valve replacements/repairs were practiced in multiple US institutions. ²

Since 1996, 4 minimally invasive approaches to aortic valve surgery have been described: (a) right parasternal incision, (b) transverse sternotomy, (c) right minithoracotomy, and (d) hemisternotomy. The right minithoracotomy and hemisternotomy are frequently used today. Even though the right parasternal incision and the transverse sternotomy are no longer in practice, they will be briefly reviewed for their historical value and contribution to the modern approaches.

Transverse Sternotomy

In the later 1990s, other groups were attempting aortic valve surgery through a transverse sternotomy and a reverse Z sternotomy incision. For a transverse sternotomy, an 8- to 10-cm horizontal incision was made at the second or third intercostal space with transection of the sternum and both internal mammary arteries. ⁹ A pediatric retractor was placed to expose the aortic root with arterial cannulation in the ascending aorta. Venous cannulation was either placed in the superior vena cava, the right atrium, or through the femoral vein. The reverse Z sternotomy was similar with a 10-cm transverse skin incision; however, the sternum was divided transversely from the left second intercostal interspace to the midline of the sternum, vertically along the midline of the sternum to the fourth intercostal interspace, and then transversely to the fourth intercostal interspace on the right side to form a reverse Z ( Figure 1 ). ¹⁰ The pleural spaces were not entered and the internal mammary arteries were not divided. Both incisions had a relatively high rate of complications with periprosthetic leaks, postoperative bleeding, and difficulty in conversion to median sternotomy. ¹¹ Therefore, neither incision is frequently used today.

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Figure 1.

Initial approaches to minimally invasive aortic valve surgery: (A) right parasternal incision, (B) transverse sternotomy, and (C) reverse Z sternotomy with the dashed line indicating the transverse skin incision

Minithoracotomy

The 2 predominant minimally invasive approaches that are practiced today are the right minithoracotomy and the hemisternotomy ( Figure 2 ). In 1997, amid the several attempts to perform aortic valve replacement through a smaller incision, Benetti et al ¹² described a small right anterolateral thoracotomy that preserved all costal bones and cartilage. A 6- to 7-cm transverse incision was made over the third intercostal space. A special retractor was placed to expose the pericardium without removal of any ribs or cartilage. The pericardium was incised and tacked to the skin to improve exposure of the right atrium, aortic root, and right superior pulmonary vein. The femoral artery and right atrium were cannulated with a venting cannula in the right superior pulmonary vein. The aorta was cross-clamped with antegrade cardioplegia given. A transverse aortotomy was made and 3 commissural sutures were placed to pull the annulus into the field. Following replacement of the aortic valve, the aortotomy was closed and the heart was deaired through the aortic root and the venting cannula. Advantages include avoidance of any sternal incision and therefore the potential for a more rapid recovery. Disadvantages of this incision included difficulty with conversion to median sternotomy and pain from the thoracotomy incision. However, this incision remains popular at some institutions and has been met with great success. ¹³

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Figure 2.

Modern approaches to minimally invasive aortic valve surgery: (A) right minithoracotomy, (B) the inverted T hemisternotomy, (C) the J-shaped hemisternotomy, (D) the reverse L-shaped hemisternotomy, and (E) the reverse C-shaped hemisternotomy

Surgical Considerations Regarding Cardiopulmonary Bypass

There are 3 major areas of concern for cardiothoracic surgeons regarding technique for cardiopulmonary bypass during aortic valve surgery: (a) the placement of cannulae, (b) the method of cardioplegia, and (c) venting the left ventricle (LV). There are a wide variety of locations for placement for venous and arterial cannulae. The goal of venous cannulation is to provide complete venous drainage from the right atrium. Venous cannulae may be placed directly into the right atrium or advanced to the right atrium from the internal jugular vein or the femoral vein. This latter option offers the advantage of an improved operative field of view since the cannula is not in the operative field. If placing the cannula in the femoral vein, this may be accomplished with a femoral cut-down or percutaneously under ultrasound guidance with further advancement to the right atrium under transesophageal echocardiographic (TEE) guidance. Similarly, arterial cannulation can be placed in a variety of locations, including the ascending aorta, femoral artery, or the right subclavian/axillary artery. The goal of the arterial cannula is to provide an adequate return of oxygenated blood to the brain and body. Femoral arterial access may be percutaneous or via a groin incision. Arterial cannulation in the femoral artery is not physiologic in that it will provide retrograde flow to the visceral organs and the arch vessels, including cerebral blood flow. In contrast, a cannula placed in the right axillary or subclavian artery will provide antegrade flow. Reports have suggested that femoral cannulation may have greater neurologic consequences, ¹⁸ as there is a risk of embolism from iliac or abdominal aortic calcifications and the risk of creating a dissection flap with retrograde flow. As such, cannulating the ascending aorta in the operative field may be the safest and preferred method.

Cardioplegia, a solution that arrests mechanical and electrical activity of the heart, is the key for myocardial protection during open cardiac surgery. Cardioplegia can be delivered to the coronary vessels in antegrade or retrograde fashion. Traditionally, cardioplegia was given in an antegrade fashion directly into coronary ostia following cross clamping the aorta. However, antegrade cardioplegic perfusion may have limited delivery distal to coronary artery narrowings ¹⁹ and requires intermittent disruption of the flow of the operative procedure. Retrograde cardioplegia, administered through cannulation of the coronary sinus, was evaluated and popularized in the early 1980s. ²⁰ This technique had equivalent myocardial protection while avoiding damage to the coronary ostia and allowing repeat administration without interruption of the procedure. ²¹ Cardioplegia further evolved to a combination of both antegrade and retrograde delivery. ¹⁹ During minimally invasive procedures, placement of the coronary sinus catheter can be challenging through the small incision without exposure of the inferior portion of the right atrium. In our experience, we use a specially designed catheter (Edwards Lifesciences, Irvine, CA) that is placed through the right internal jugular vein and passed under fluoroscopy into the coronary sinus prior to starting the procedure.

The third area of concern related to cardiopulmonary bypass during aortic valve operations is how to vent the LV. Despite complete heart bypass with decompression of the right atrium, the left heart continues to receive blood from collateral vessels from the lung. Ventricular venting during cardiopulmonary bypass came into popularity during the late 1970s as a key maneuver to prevent overdistention of the LV with subsequent pulmonary edema in addition to maintaining a bloodless field during aortic valve surgery. ²² A venting cannula is frequently placed through the right superior pulmonary vein and passed through the left atrium and mitral valve to rest in the left ventricle. This is commonly placed directly into the right superior pulmonary vein through the sternotomy. During minimally invasive AVR, the right superior pulmonary vein may be difficult to visualize in order to place an LV venting catheter. Other options include vent placement into the apex of the LV and a suction-assisted cannula placed in the main pulmonary artery. ²³ In addition to placing a vent into the pulmonary artery directly, we have also used a pulmonary artery suction catheter (EndoVent, Edwards Lifesciences, Irvine, CA) placed through the internal jugular vein.

Our Approach to Minimally Invasive Aortic Valve Replacement via Hemisternotomy

Patients are evaluated in clinic preoperatively with minimally invasive approaches in mind. Traditional median sternotomy is favored in patients with significant obesity or a chest wall abnormality that would increase the depth of the incision or make the exposure challenging. Median sternotomy is also favored if there is a significant coronary disease or other valvular disease requiring concomitant procedures in addition to AVR. Also, patients with poor right ventricular function are not considered good candidates for minimally invasive AVR to ensure optimal drainage and protection of the right heart. Importantly, redo operations are not a contraindication. ²⁴ At our institution, we have recently shown that the risk of reoperative AVR is similar to primary replacement. ²⁵

Similar to conventional AVR, patients have a Swan–Ganz catheter and a radial arterial line placed preoperatively for monitoring. In some patients, we have our anesthesia colleagues place a retrograde cardioplegia catheter placed from the right internal jugular vein to the coronary sinus using fluoroscopy and/or or a specially designed pulmonary artery catheter with suction assistance for venting of the heart. External defibrillator pads are placed, since conventional adult cardiac defibrillator paddles are too large for the incision. TEE is routinely used prior to the incision to allow preoperative assessment cardiac function and anatomy. A 6- to 9-cm vertical midline incision is made from the sternomanubrial junction to the third or fourth intercostal interspace. Electrocautery is used to mobilize superiorly above the sternal notch and inferiorly to the right fourth intercostal space avoiding the internal mammary artery. The sternum is divided in a “J” fashion. A pediatric Finochietto retractor is used to expose the pericardium and upper mediastinum. The pericardium is incised and pericardial tacking sutures to the dermis are placed to elevate the pericardium and ascending aorta. With the assistance of epiaortic ultrasound looking for calcifications, an appropriate cannulation site is chosen in distal ascending aorta and the aorta is cannulated. For venous cannulation, our preference is to place a multistage venous cannula percutaneously through the right femoral vein under TEE guidance. The multistage cannula allows venous drainage of the superior vena cava, right atrium, and inferior vena cava. Suction assisted drainage allows for smaller cannulae and more complete drainage. A pediatric left ventricular vent is placed into the right superior pulmonary vein and passed through the mitral valve into the left ventricle. Following cross clamping the ascending aorta, antegrade cardioplegia is infused into the aortic root. In cases of significant aortic insufficiency, cardioplegia is administered directly into the coronary ostia for initial arrest. Retrograde cardioplegia is infused to attain electrical and mechanical quiescence, and cold ice slush is placed on the heart. Carbon dioxide is continuously infused at 8 L/min in the operative field to decrease the risk of air embolism. After transverse aortotomy, commissural sutures are placed to bring the aortic valve into view. For AVR, the aortic leaflets are excised with an incision carefully following the plane between the calcifications and the annulus. Once the native aortic valve is excised and the annulus is debrided adequately, the annulus is measured and the largest valve size possible is chosen. We prefer to place nonpledgeted horizontal mattress sutures from the ventricle to the aorta. ²⁶ The sutures are passed through the prosthetic valve and the valve is seated in the annulus. Care must be ensured that the coronary ostia are not obstructed by the valve posts or sewing ring. After the sutures are tied down, the aortotomy is closed in 2 layers of 4-0 polypropylene suture. Two mediastinal drainage tubes are placed from the epigastrium. If the right pleural space is entered, one drainage tube is fed into the pleural cavity. We prefer to place ventricular pacing wires on the inferior surface of the right ventricle prior to removing the aortic cross clamp for aid in visualization. After warm blood or “hot shot” administration, the cross clamp is removed. Any ventricular fibrillation must be treated quickly since the LV cannot be decompressed well manually or though the smaller LV vents in place. If unable to defibrillate the heart with the pediatric paddles, defibrillation should be performed transdermally with the lungs inflated. Once a regular rhythm is achieved, the heart is deaired mechanically with confirmation from TEE. After coming off cardiopulmonary bypass, the mediastinum is inspected, and hemostasis is achieved. TEE is used to evaluate the function of the prosthetic valve, determine the presence of a paravalvular leak, and look for wall motion abnormalities that could result from myocardial ischemia. The sternum is reapproximated with 4 steel wires. The skin is closed in several layers with absorbable suture. Our protocol is to take the patient to the intensive care unit intubated with a timely extubation protocol within 2 to 4 hours.

Minimally Invasive Aortic Valve Replacement Versus Conventional Sternotomy

There are several potential advantages to a minimally invasive approach distinct from potential cosmetic benefits. Specifically, compared with conventional sternotomy, minimally invasive AVR has been associated with less blood transfusions required, decreased length of stay, less postoperative pain, less pain medication usage, and a faster return to normal activity.^2,4 Minimally invasive AVR nearly halves the requirement for blood transfusion (from 2.8 to 1.6 units per patient with many patients requiring no blood transfusion). Additionally, patients are able to return to routine activity in half the time (4.6 days vs 9.4 days with conventional AVR, P = .0002). ² Further benefits include decreased postoperative chest tube drainage (229 mL vs 369 mL, P < .05), shorter postoperative ventilatory support (7.26 hours vs 11.26 hours, P < .05), and a shortened hospital course (6.2 days vs 9.4 days, P < .01). ²⁷ Decreased blood loss during the minimally invasive procedure may be secondary to less bleeding from the sternal edges that continues throughout the case. Additionally, there is less pericardial contact with blood through a smaller incision. Pericardial contact with blood leads to a decrease in fibrinogen and therefore an alteration of the clotting cascade. ²⁸ Other benefits include reports of decreased time to extubation with a minimally invasive approach, improved cosmesis, and a potential 20% reduction in total charges.^4,29,30

The most important question as to whether the same quality of aortic valve surgery can be performed though a significantly smaller incision, and the answer to date is clearly yes. In evaluating more than 1000 minimally invasive AVRs, Tabata et al ³¹ showed long-term results comparable to conventional median sternotomy with an operative mortality of 1.9% and actuarial 5-year survival of 84%.

Potential Disadvantages of Minimally Invasive Technique

Adaptation to a more novel technique with smaller incisions is accompanied by a learning curve for the surgeon. In a single center experience of more than 900 cases of minimally invasive AVR from Brigham and Women’s Hospital, aortic cross-clamp and cardiopulmonary bypass times decreased by more than 12% with increasing experience. ³² The minimally invasive approach also poses new challenges with the frequent need for femoral access and smaller chest incisions. There have been concerns regarding the potential for groin wound infections from femoral incisions for access to the femoral vessels. Grossi et al ³³ reported a 0.4% wound infection rate from the femoral incision in their review of their experience with more than 700 patients. ³³ With a smaller thoracic incision, there is a potential disadvantage of a decreased ability to fully deair the heart and therefore lead to neurologic sequelae. This has been minimized with continuous carbon dioxide flowing into the operative field to minimize cardiac air and confirmation of deairing the heart with TEE. A comparison of minimally invasive approach versus the traditional median sternotomy in more than 500 patients showed no significant differences in stroke with the minimally invasive approach. ³⁴ In addition, no long-term conduction abnormalities have been identified.^4,35

Transcatheter Aortic Valve Replacement

Minimally invasive approaches to aortic surgery through hemisternotomy and minithoracotomy are significant advances in cardiac surgery with tremendous benefit offered to the patient. However, despite these advances, there remains a group of patients with critical aortic stenosis that are poor surgical candidates for conventional AVR. According to the Euro Heart Survey on Valvular Heart Disease in 2003, almost one third of patients with severe valvular disease who could benefit from AVR were deemed inoperable secondary to medical comorbidities. ³⁶ This population may be greatly served by a less invasive, catheter-based technique that does not require sternotomy. In 1986, Cribier et al ³⁷ described early successful treatment of severe acquired aortic valve stenosis using percutaneous balloon dilation of the aortic valve catheter. Although there is an acute improvement in the aortic valve area following balloon aortic valvuloplasty, this technique is limited with frequent restenoses, poor functional improvement, and dismal long-term outcomes even with repeat dilations. ³⁸ In 2002, Cribier et al ³⁹ reported the initial human case description for percutaneous transcatheter aortic valve implantation in an inoperable patient with severe aortic stenosis. The aortic valve was delivered in antegrade fashion from the right femoral vein, via a transseptal catheterization with the patient under mild sedation. ³⁹ This approach was technically complex, as it required access across the atrial septum and mitral valve to reach the aortic valve position.

This procedure has since evolved, and 2 approaches for transcatheter aortic valve replacement (TAVR) have been developed: a retrograde transfemoral aortic valve replacement and an antegrade transapical aortic valve replacement. It is important to note that with TAVR, the native aortic valve is not excised but is compressed into the sinuses with an expandable stent containing the aortic valve prosthesis.

Transfemoral Transcatheter Aortic Valve Replacement

Transfemoral TAVR requires femoral arterial access, passage of a delivery sheath and valve around the aortic arch, and retrograde placement of the stented aortic valve prosthesis across the native valve ( Figure 3 ). In 2005, a Canadian group led by Webb ⁴⁰ evaluated a group of patients deemed inoperable with secondary excessive surgical risk. Using a catheterization laboratory with a sterile set up and high quality fluoroscopy, both femoral arteries and one femoral vein were accessed percutaneously. Balloon aortic valvuloplasty was performed. The femoral arterial access was then dilated to accommodate a large sheath that extended beyond the iliac arteries and terminated in the distal abdominal aorta. An equine pericardial trileaflet valve was attached to a stent and compressed over a specially designed valvuloplasty balloon catheter. The valve apparatus was passed through the arterial introducer sheath, while the other femoral arterial access was used to insert a deflection catheter as a guide. Once in the appropriate position across the aortic valve, rapid right ventricular pacing was used to minimize pulsatile flow from the left ventricle that could dislodge the valve during implantation. The valve was rapidly expanded over the balloon tipped catheter. Positioning, paravalvular leak, and coronary patency were assessed using aortic root angiography and echocardiography. Femoral arterial access was then closed surgically. There was a moderate learning curve to the procedure and outcomes improved over time. The first 2 patients suffered arterial complications that led to procedural modification with longer catheter use. Initially, the procedure was done under conscious sedation. However, later patients were all placed under general anesthesia to facilitate sheath placement, intraoperative TEE, and airway management. Overall outcomes showed that the valves were successfully deployed in the correct position without covering the coronary ostia and immediate improvement of the transaortic pressure gradient and aortic valve area. Paravalvular leak rates were present in more than 50% but few were significant enough to cause symptoms and overall have been well tolerated out to 2 years.

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Figure 3.

Transfemoral approach to transcatheter aortic valve replacement

The major limitation with this approach is the size and tortuosity of the femoral and iliac vessels to allow for safe delivery of these large profile devices (18-24 Fr). To alleviate these obstacles, later revisions of the initial catheter allow for flexion of the distal aspect of the catheter. Additionally, the valve deployment system adopted a more tapered nose to assist in crossing a stenotic aortic valve. Whereas initial catheter-based AVRs were performed valves made of equine pericardium, current transcatheter valves are constructed from bovine pericardium. Major vascular injury occurs in 8% to 11% of patients and is primarily due to iliac artery rupture or dissection.^41,42 With increasing experience, this complication may be decreasing.

Transapical Transcatheter Aaortic Valve Replacement

In 2005, Walther et al ⁴³ devised a strategy to place the TAVR through the left ventricular apex using a porcine model. Adaptation to humans was demonstrated by Webb et al with their initial experience with antegrade transapical TAVR in patients who were deemed unsuitable surgical candidates and who could not tolerate a transfemoral approach secondary to stenosis, calcifications, or vessel tortuosity. ⁴⁴ Following their initial success with transapical access, a multicenter clinical trial was performed in Europe, including high-risk patients older than 75 years. ⁴⁵ For the transapical approach, a bovine pericardial trileaflet valve was constructed and attached to a steel stent that was compressed on a valvuloplasty balloon catheter in a similar fashion to that used in the transfemoral approach. In a hybrid operating room complete with high-definition fluoroscopy, the procedure was performed by teams, including cardiologists, cardiac surgeons, and cardiac anesthesiologists. The patient was placed under general anesthesia. The left ventricular apex was accessed through a 5- to 8-cm anterolateral minithoracotomy in the fifth or sixth interspace over the point of maximum impulse. The pericardium was opened and 2 purse string sutures were placed at the left ventricular apex lateral to the left anterior descending coronary artery. Temporary ventricular pacing wires were placed for rapid ventricular pacing during valve deployment. The femoral vessels were exposed on one side and cardiopulmonary bypass cannulae were available if necessary. The contralateral femoral vein had a venous wire placed for access and a sheath was placed in the femoral artery for contrast aortography. Under fluoroscopy, the apex was punctured with insertion of a soft wire followed by a 14 Fr introducer sheath placed across the aortic valve. The soft wire was replaced with a stiff wire into the descending aorta. Standard balloon aortic valvuloplasty was performed. The 14 Fr sheath was exchanged for a 33 Fr transapical delivery system with the catheter positioned with the stent in the aortic annulus. The stent with the valve was expanded during rapid ventricular pacing to minimize cardiac movement that occurs with typical cardiac conduction. TEE was used to confirm placement. Following adequate placement, the transapical sheath was removed and the ventricular apex was closed with the 2 purse string sutures. The pericardium was reapproximated and a chest tube was inserted. The wound was closed in layers in standard fashion.

Initially, the transapical approach resulted in good positioning of the valve prosthesis more than 93% of the time. Approximately 7% of patients had incorrect positioning of the valve and required perioperative conversion to median sternotomy for repair. Although this early experience has been significantly improved upon, it highlighted the importance for a hybrid operating room that was fully equipped for transcatheter procedures and open techniques with cardiopulmonary bypass. Femoral cannulation for cardiopulmonary bypass was performed in the beginning of the study, but with increasing experience, a femoral wire was placed in the femoral vein for access with no cannulation needed. Overall, patients did well with a short intensive care unit stay and relatively low mortality. Thirty-day all cause mortality was 13.6%, which was half of the predicted risk of mortality from an open aortic valve replacement in these high-risk patients. None of the deaths were found to be valve related, as the valves appeared to be well positioned and functional on autopsy. Additionally, the stroke rate in the study was low (3.4%), which was attributed to an antegrade technique with minimal wire and catheter manipulation in the aorta.

PARTNER Trial

Transcatheter aortic valve replacement has been approved in Europe, and initial trials have completed enrollment in the United States. The PARTNER (Placement of AoRtic TraNscathetER valves) trial is a Food and Drug Administration–approved pivotal trial comparing conventional AVR or medical management to TAVR. The particular valve used in this study is with the SAPIEN valve (Edwards Lifesciences, Irvine, CA), a bovine pericardial trileaflet valve mounted on a balloon expandable steel stent. The PARTNER trial has 2 parallel cohorts that include the highest risk cardiovascular surgery patients: (a) Cohort A randomized 699 high-risk (although not inoperable) surgical patients to either traditional AVR or to TAVR via a transfemoral or transapical approach and (b) cohort B randomized 358 high-risk, inoperable patients (with expected operative mortality of >50%) to transfemoral TAVR or medical management alone.

The results from the cohort A from the PARTNER trial were recently published. In this noninferiority study of high-risk surgical patients, TAVR was found to be no different from conventional AVR in all cause mortality at 1 year (TAVR = 24.2% vs aortic valve replacement = 26.8%, P = .001 for noninferiority). Similarly, there were no significant differences in the rates of death between the transfemoral TAVR cohort and the surgical group and between the transapical TAVR cohort and the surgical comparison group. Overall, TAVR was associated with an increased risk of major stroke (3.8% vs 2.1%, P = .20 at 30 days; 5.1% vs 2.4%, P = .07 at 1 year) and major vascular complications (11.0% vs 3.2%, P < .001). ⁴² The increased rate of vascular complications was expected given that vascular access was necessary for delivery of the transcatheter valve. Although it was not statistically significant, the tendency toward major stroke in the TAVR group is concerning and may be secondary to embolic phenomenon.

Cohort B results were published in late 2010 showing the outcomes of the 358 patients that were randomly assigned to standard medical therapy (including balloon aortic valvuloplasty) or to transfemoral TAVR with balloon expandable bovine pericardial valve. At 1 year, the death rate was significantly lower in the TAVR group (30.7% vs 50.7%, P < .001). ⁴⁶ Despite the marked improvement in patient survival with the TAVR, there were major procedural hazards, including an increased incidence of major strokes (5.0% vs 1.1%, P = .06) and major vascular complications (16.2% vs 1.1%, P < .001). Although there were higher complication rates, transfemoral aortic valve implantation appears to be superior to medical management with further modification needed to decrease complications.

The initial results from the PARTNER trial indicate that transcatheter aortic valve implantation is a feasible treatment option in high-risk patients with calcific aortic stenosis. More investigation is needed to determine the role for TAVR in a healthier subset of the population and in the treatment of other aortic pathology, such as bicuspid valves. Regardless, the results are very encouraging and demonstrate another breakthrough in cardiac surgery. Similar to the minimally invasive approaches discussed earlier in the chapter, transcatheter approaches will continue to evolve and improve demonstrating the rapidly progressive nature of modern cardiac surgery.

Future Directions

The only certainty for the future of aortic valve surgery is that it will be rapidly evolving. It is doubtful that the median sternotomy will continue to serve as the standard of care or that any one approach will be able to have an extended reign as the surgical standard. Presently, the transfemoral approach to aortic valve implantation appears to be the least invasive approach. One of the major limitations to this technique is the size of the arterial sheath needed to introduce the aortic valve. This is especially problematic in patients with femoral and aortoiliac occlusive disease. The Edwards original SAPIEN heart valve system that was evaluated in the PARTNER trial requires a 22 or 24 Fr introducer catheter. The newer SAPIEN XT has an 18 or 19 Fr delivery system depending on the valve size. The CoreValve (Medtronic, Minneapolis, MN) is under evaluation by an FDA approved trial and is delivered through an 18 Fr sheath. If femoral arterial disease is too severe, iliac or aortic conduits can be considered. While these were not allowed in the first PARTNER trial, they seem a likely solution to severely calcified or tortuous femoral vessels.

With the imminent rise in transcatheter techniques, the setup for the cardiac surgery operating room must change. Hybrid operating rooms are likely to become a necessity with the combination of sterile operating equipment and imaging techniques, such as catheterization grade fluoroscopy, TEE, and 3-dimensional intravascular ultrasound. The hybrid rooms will have sufficient equipment for transcatheter interventions with alternative plans in place for major vascular catastrophe, hemodynamic instability, cardiac injury, or valve misplacement. During these procedures, cardiopulmonary bypass equipment and instrumentation needed to perform median sternotomy should be readily available as a safe alternative.

The hybrid operating room provides an integrated stage for cardiac surgeons, cardiologists, echocardiographers, and anesthesiologists and sets the stage for the development of a “heart team” approach to patient care. The Society of Thoracic Surgeons recently issued a statement that an integrated multidisciplinary “heart team” would be the expected collaborative approach to the diagnosis, management, and treatment of heart disease. ⁴⁷ The collaboration across multiple fields of medicine will hopefully lead to improved patient care and continued innovation.