PORT ACCESS CARDIAC SURGERY
The Next Generation of Minimally Invasive InterventionDepartment of Cardiothoracic Surgery, Winthrop-University Hospital
What does "port access" mean?
Port access heart surgery represents a new format for the surgical treatment of patients with valvular abnormalities, coronary artery disease, and certain congenital cardiac anomalies. This new approach is based on advanced technology now available through HEARTPORT, a northern California company founded in 1991. HEARTPORT provides a platform for the performance of a variety of cardiac surgical procedures through small incisions ("ports"), without a median sternotomy - while allowing complete access to a non-beating, protected and well visualized heart.
How does port access differ from the other forms of minimally invasive surgery, such as MIDCAB?
MIDCAB involves a small left anterior thoracotomy incision to provide access to the anterior surface of the heart. This incision also allows for the harvesting of the internal mammary artery from the chest wall and subsequent coronary bypass grafting, primarily to the LAD. This approach, known as MIDCAB, requires sewing a donor blood vessel (the IMA) to a surface coronary vessel (the LAD) on the beating heart. This procedure is facilitated by special retraction and stabilization devices, along with pharmacologic agents to slow the heart rate and vigor of contractility. These maneuvers come close to stabilizing and significantly reducing motion to the area where an anastomosis with fine suture is accomplished. Nonetheless, the critical work is performed on a beating, functioning heart.
HEARTPORT provides a platform for the performance of a variety of cardiac surgical procedures through small incisions ("ports"), without a median sternotomy - while allowing complete access to a non-beating, protected, and well visualized heart.
HEARTPORT technology provides for two major additions to the MIDCAB approach. With the use of specially designed cannulae inserted through the femoral artery and vein (with fluoroscopic guidance), the patient can be placed on full cardiopulmonary bypass, without the need for a sternotomy. This capacity is not new, as many of the original open heart procedures were undertaken with this approach 30 years ago.
HEARTPORTS's truly original contribution is its design of a special balloon catheter, inserted through the femoral artery cannula, which can be manipulated into position just above the aortic valve, again using X-ray or echocardiographic guidance. When inflated, this balloon interrupts blood flow to the heart and essentially cross clamps the aorta from within. This "endoclamp" also has the advantage of a central lumen distally, which can deliver a cold blood-potassium solution - known as "cardioplegia" - into the aortic root, to elicit cardiac arrest.
Additional innovative features of the HEARTPORT approach include special catheters designed to widen the margin of safety, thereby extending the utility of this approach to a broader scope of cardiac surgery. Specifically, two catheters are inserted percutaneously by the cardiac anesthetist: one is placed into the pulmonary artery to provide venting and decompression of the heart during "endo-clamping," and the other is directed into the coronary sinus to allow sequential instillation of cold cardioplegic solution in retrograde fashion to optimally protect the heart during cardiac arrest. Through these devices, HEARTPORT provides the capacity to perform a wide variety of "open" cardiac procedures, ranging from the simple to the complex, with many of the specific safety features formerly available only through a standard sternotomy approach.
Which procedures can be performed with HEARTPORT?
HEARTPORT technology can theoretically be applied to the entire spectrum of cardiac surgery, with the most promising application in the approach to the mitral valve. Through a very small right anterior thoracotomy, the left atrium can be exposed and opened, providing a "bird's eye" view of the diseased mitral valve. Thus, valve replacement or mitral repair with valvular preservation can be readily performed through port access, with the heart still and completely protected. Through minor adjustments in cannulation, this approach can be modified to address abnormalities in the right heart, such as tricuspid valve problems and atrial septal defects. HEARTPORT also promises to play a role in single or multi-vessel coronary artery bypass grafting. Currently, the left anterior thoracotomy approach has been utilized with success in providing access to perform mammary artery grafts to the vessels on the anterior surface of the heart (LAD and diagonal branches). Rapidly evolving techniques using sequential grafting and retraction devices now suggest the capability of performing multiple bypasses to lateral and posterior branch vessels - thereby making complete revascularization, using port access technology, a real possibility in the near future.
What advantages does the port access approach offer over standard operation?
Some of the advantages of this new form of minimally invasive heart surgery are obvious, while others remain theoretical and await the test of time.
Clearly, the port access method allows for smaller, less painful, more cosmetically pleasing incisions, while providing most of the advantages of standard sternotomy. There is a strong likelihood of fewer wound complications, including infection and dehiscence. As smaller wounds are likely to be better tolerated, fewer analgesics may be required, allowing for earlier mobilization, potentially earlier patient discharge, and return to an active lifestyle - including resumption of employment. It is conceivable, although not proven, that progress throughout the entire post-operative recovery period may be accelerated, with patients released from the ICU within hours of arrival; ambulating on the first postoperative day as a routine; and ready for discharge within 48-72 hours of operation. Should such a protocol prove workable, a substantial cost reduction could be anticipated.
HEARTPORT provides the capacity to perform a wide variety of "open" cardiac procedures, ranging from the simple to the complex, with many of the specific safety features formerly available only through a standard sternotomy approach.
Another potential great advantage can be found in redo surgery. Patients with a history of prior cardiac surgery are typically at increased operative risk with reoperation, mainly because of the threat of damage to cardiac structures during resternotomy and dissection of surrounding scar tissue. With the use of HEARTPORT and a minimally invasive approach, only small areas of the cardiac surface require exposure and access to these sites - which is usually through virgin tissues (small right or left thoracotomy) without prior scarring.
Some final thoughts...
As with any new medical technology, especially those as heavily market-driven (and "marketeer-driven") as HEARTPORT port access cardiac surgery, there has been an enormous amount of pressure on practitioners to quickly gain the expertise necessary to provide HEARTPORT capability to their patients.
Surgeons at more than 100 centers nationwide are already fully trained in these techniques. This is remarkable, considering the relative infancy of this technology. It is likely that large numbers of these procedures will be performed in the next few years. Ultimately, however, the limitations of this methodology will surface, and the specific role for its application will become more clearly defined. We have considerable doubt that port access cardiac surgery will dominate the landscape; however, we do have confidence that these techniques will represent an important component within the spectrum of approaches to cardiac surgical problems that we can offer at Winthrop.
For further questions regarding port access cardiac surgery, please call the Department of Thoracic and Cardiovascular Surgery at 516/663-2384.
