THE PORT ACCESS TECHNIQUE
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What is the Port Access technique? ¨ Instrumentation ¨ Procedure ¨ Benefits ¨ Company Specific Instrumentation ¨ Prevalence and Scope ¨ PACAB v. MIDCAB ¨ PACAB References
What is the Port Access Technique?
Traditional open-heart surgery is just that, "open heart." The port access technique allows surgeons to forgo the traditional sternotomy (a cut through the breastbone) and operate on the heart through a number of smaller incisions. The patient is hooked up to a heart lung machine without opening the chest. The anastomosis or other procedure can thus be performed on an arrested heart allowing for greater surgical precision. The comparatively small incisions greatly reduce the amount of post-operative pain experienced by the patient, speed recovery and scar less noticeably.
Instrumentation
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A. Three small incisions are made in the chest wall near the armpit. Three ports are then inserted into the chest. Each port is a hollow metal tube with a diameter no bigger than a pencil, and has a valve at one end. Specially designed surgical tools are passed through the ports during the operation. [2]
B. A telescope is inserted into the chest via a slightly larger cut in the chest wall. To the scope is attached a fully maneuverable video camera that is used to view the entire surgical field. Aside from echocardiography this scope is the surgeons sole means of viewing the heart during the closed chest procedure.
C. Cannulae, small plastic tubes, are connected to the arterial and venous patient blood circulation. A small incision is made in the upper thigh and the cannulae are inserted with the aid of fluoroscopic guidance into the femoral artery and vein. Through these conduits the patient is placed on cardiopulmonary bypass.
D. Higher upstream on the femoral artery a catheter is inserted and guided towards the aorta. This guide wire is equipped with an inflatable tip. When the catheter is properly positioned just outside the aortic valve that tip is inflated, occluding the vessel. This technique eliminates the need for an external clamp on the aorta. Once the tip is inflated, cardioplegic solution is administered through the catheter. The solution arrests the heart and protects it during surgery. |
Diagram of port access [1] |
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direct video viewing [5] |
echocardiography [5] |
cardiac fluoroscopy [4] |
Procedure
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The patient is first connected to the heart lung machine. Blood is drawn from the patient's arterial system in one of two locations. The most popular method is to cannulate the femoral artery as mentioned above. A second, less-proven technique is to directly cannulate the artery through one of the four ports in the chest wall. Blood is returned to the patients venous system either through the femoral or jugular vein In the former case the cannula is threaded downstream and set in the inferior vena cava while in the latter case it is threaded towards the superior vena cava. In some procedures both insertion sites are used. |
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The ports are then inserted into the chest. Near the armpit, three pencil size incisions are cut and the ports are inserted through the chest wall. The scope is threaded through the first hole and all areas of the surgical field (inside the thoracic cavity) are viewed directly. At this stage the echocardiogram and fluoroscopic monitors are positioned to view the insertion of the endoarotic clamp. |
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The catheter is inserted into the femoral artery and threaded up the bloodstream to the root of the aorta, next to the aortic valve. At the tip of the catheter, the balloon is inflated, effectively occluding the lumen of the aorta. Cardioplegic solution is released form the tip, arresting the heart. The figure at left also diagrams an alternative method to administering cardioplegia. A catheter is inserted into the jugular vein rather than the femoral artery, and then directed into the coronary sinus. |
Once the cardioplegic solution has taken effect the surgical team may proceed with the operation. All techniques are performed through the ports in the chest wall with specially designed tools. It goes without saying that operating through the chest with indirect viewing techniques requires great precision and a great deal of training.
Benefits
- Dramatic reduction in pain. The main source of postoperative patient discomfort in conventional surgery results from the full sternotomy. Because this technique only requires a few small cuts in the chest wall, the pain us considerably reduced.
- Reduced ICU and hospital stay.
Again this results from the smaller incision points. Less tissue needs to heal so the risk of postoperative bleeding is lower. This means a shorter stay in the intensive care unit and the hospital. The patient usually leaves the hospital within 2 or 3 days compared 7-10 in conventional heart surgery.
- Accelerated recovery time.
Port access patients are able to return to work within 3 weeks of the operation, and sometimes sooner. Conventional surgery extends this leave to 7 or 8 weeks.
- Improved postoperative pulmonary function.
- Improved quality of life
- Reduced need for inpatient cardiac rehabilitation
- Improved Cosmetics
. [6]
For further analysis on the benefits and drawbacks of port access see our
comparison page.
Company Specific Instrumentation
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The leaders in port access devices and technology. Their EndoDirectTM and EndoCPBÒ Systems are the most widely used instrumentation systems used by contemporary heart surgeons for PACAB. Both systems can be used for mitral valve repair, multivessel CABG and atrial septal defect. The systems both use an EndoClamp-STTM Aortic Catheter and include arterial and venous cannulae, sinus and pulmonary catheters. Heartport also has a popular incising introducer for cannula insertion. |
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Left: EndoDirectTM |
Right: EndoCPB Ò |
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Genzyme's Endoscopic coronary artery bypass grafting (EndoCABGTM) system is another popular instrument system. Their EndoCABG ports are nonreflective on the surface so they are frequently used in videotaped operations. They feature the widest range of instrument mobility of any port and feature a one way valve that maintains a positive pressure inside the operative site. Genzyme also features a well-liked endoscope. |
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Medtronic features an extra long body cannula for peri-sternotomy and port incisions (left). The cannula is kink resistant and is introduced bloodlessly. The Carpentier® Bi-Caval Femoral Venous Cannula (right) is an alternative, it efficiently drains the heart by simultaneously accessing the superior and inferior vena cavae. |
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St. Jude Medical makes its mark with an extensive array of introducers including the
Fast-CathTM, MaximumTM, Maximum XtraTM, and Maximum ACTTM (left). The company's line is the largest in the world St. Jude is also the parent company of Daig
, makers of the Angio-SealÒ hemostatic puncture closure device (right). This locates the puncture wound from the femoral vein or artery puncture site, and closes it in a matter of days. This eliminates the need for pressure dressings or other more painful methods of hemostatic punctures.
Prevalence and Scope
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Port Access is slowly progressing from the level of "investigative technique" into "proven surgery." It is used today for a variety of procedures. (see table at right). The exact number of surgeries performed yearly is hard to pin down but an accurate estimate can be pinned down with the following data.
The Port-Access International Registry, an exhaustive study, encompassed all procedures that took place at 65 surgical centers worldwide. In their update (.pdf  ) the study cites 3,210 patients in 2 years and 2 months. A conservative is that the 65 centers were about 1/3 of all of those performing the surgery. This places the number of procedures per year between 5,000 and 7,000 [7], [8]
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Surgical Procedures W/ Port Access [6]
 Multi-Vessel Coronary Artery Bypass Grafting (CABG)
Mitral Valve Repair or Replacement (MVR)
MVR/Tricuspid Repair
MVR Redo
MVR/CABG
Aortic Valve Replacement (AVR)
Congenital Heart Defect Surgery, including Atrial Septal Defect (ASD) & Ventricular Septal Defect (VSD)
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Dr. Stephen Colvin, Chief of Cardiothoracic Surgery at the NYU Medical Center estimates that "port-access will be the preferred method in about 30-50% of coronary bypass and virtually all valve procedures at NYU Medical Center." Currently surgeons there are performing 7-10 cases per week. [9], [10]
The Safety of the procedure has been proven in numerous clinical trials.
Click here to view the overall safety of PACAB (word file) [7]
Click here to view the safety of PACAB v. Conventional CABG (word file) [10]
These data show lower rates of operative mortality and post-operative atrial fibrillation for PACAB. Incidence of stroke, myocardial infarction, reoperation, multiorgan and renal failure all are lower for port access as well. For further analysis see The Port Access International Registry
Still some concerns remain about the surgery procedure. Rates of aortic dissection during aortic catheterization were high during the first half of the International Registry Study. During the second half they fell to a normal rate (0.18%) demonstrating the safety if strict guidelines are followed. In addition, the removal of air during surgery is a concern. Because the surgeon does not have direct access to the surgical field he or she can not directly suction air from the heart. Tiny air bubbles might get caught in the blood stream leading to stroke or embolism.
The future of port access research lies in the ability to properly identify surgical candidates. Those with significant amounts of atherosclerotic plaque, protruding or ulcerated atheromas or obesity are generally not considered candidates for keyhole surgery. More precise definition of patient criteria will reduce the number of complications during surgery.
PACAB v. 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 (IMA) from the chest wall and subsequent coronary bypass grafting. The donor vessel, (IMA) is sewn to a surface coronary vessel on the beating heart. This procedure is facilitated by special retraction and stabilization devices, along with pharmacological 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 fine suture is accomplished. Nonetheless, the critical work is performed on a beating, functioning heart.
[3] IN contrast, PACAB involves a heart that is arrested and protected with cardioplegic solution. The incision sites are no bigger than 5 cm, much smaller than the 12 cm cut in MIDCAB. The surgical field can not be viewed directly as in MIDCAB. It is viewed through echocardiography and video.
