Port-Access Heart Valve Surgery: Technique and Selection

Port-access heart valve surgery repairs or replaces the mitral or tricuspid valve through a cut of about 3 cm between the ribs, and the aortic valve through a short thoracotomy or upper partial sternotomy, with the heart-lung machine connected through the groin. Dr. Yugal Kishore Mishra also uses it to close atrial septal defects and remove myxomas, once CT and Doppler studies confirm suitable vessels.

Dr. Yugal Kishore Mishra, Chairman, Manipal Institute of Cardiac Sciences | Chief of Cardiovascular Surgery | Chief of Clinical Services, Manipal Hospital, Dwarka, New Delhi, India, walked an audience that included doctors in the Jivo Doctor Network across Africa through the technique with operative video. His point was that the operation inside the heart does not change: the valve repair or replacement follows the same standard practice whether it is done through a sternotomy or a thoracotomy. What changes is how the surgeon gets in, sees and stops the heart. The robotic side of his programme is covered in the complete guide to robotic-assisted cardiac surgery.

What port-access heart valve surgery means

In port-access heart valve surgery the breastbone is not cut. A small incision is made in the fourth intercostal space on the right side of the chest, and the heart-lung machine (cardiopulmonary bypass, or CPB) is connected through cannulas placed in the femoral artery and vein in the groin.

Dr. Mishra listed the operations that can be performed through a minimally invasive approach:

• mitral valve repair and replacement
• tricuspid valve repair and replacement (see the tricuspid valve surgery cost page)
• aortic valve repair and replacement
• atrial septal defect (ASD) closure
• removal of atrial myxoma, a benign tumour inside the heart

The incision has shrunk over his career from around 20 cm for a midline sternotomy, to a small thoracotomy, to about 3 cm today for mitral valve surgery, ASD closure, tricuspid valve surgery and removal of an atrial myxoma.

The three problems every port-access operation must solve

Dr. Mishra framed the technique around three issues. If the surgeon addresses all three, he said, the procedure becomes very simple.

1. Access to the surgical site. This needs two kinds of specialised equipment: long cannulas with side and end holes, and long-shafted instruments designed to work through a small opening.
2. Visualisation. The surgeon can use an endoscope with video assistance, other camera-based views, or robotic assistance.
3. Cardiac standstill and myocardial preservation. The heart has to be stopped and protected while the valve is repaired, without the direct access a sternotomy gives.

Cannulation through the groin and neck

The classic set-up connects the heart-lung machine through the femoral artery and femoral vein. His team uses an open technique, exposing the vessels through a small groin incision, and sometimes now a percutaneous technique, passing the cannulas through the skin and using percutaneous vessel closure devices to seal the artery afterwards. A percutaneous cannula can also be placed in the jugular vein in the neck.

The venous cannula is guided up from the femoral vein through the iliac vein and the inferior vena cava into the right atrium, and on towards the superior vena cava. Because the cannulas are small, blood cannot drain back to the machine by gravity alone, so some form of assisted venous drainage, in which suction helps pull blood into the circuit, is required.

The role of transoesophageal echocardiography

Transoesophageal echocardiography (TEE), an ultrasound probe passed into the oesophagus behind the heart, gives the surgeon the view that a small incision takes away. Dr. Mishra described its uses during the operation:

• guiding cannulation of the femoral artery and vein, and confirming that the venous cannula lies in the right position
• showing the condition of the ascending aorta when the patient goes on bypass
• confirming that cardioplegia, the solution used to stop the heart, has worked and the heart is arrested, since this cannot be seen directly
• helping with de-airing, the removal of air from the heart before it restarts

De-airing is one of the recognised difficulties of the approach, because the surgeon cannot put a hand in. Carbon dioxide blown into the chest through a dedicated cannula helps, alongside the TEE.

Clamping and stopping the heart

A different aortic clamp is used. In Dr. Mishra's technique a transthoracic clamp is introduced through a separate small incision in the right side of the chest, the aorta is clamped and cardioplegia is given. The type of cardioplegia, whether delivered into the aortic root or directly into the coronary arteries, is the surgeon's choice.

Port-access mitral valve repair and replacement

In port-access mitral surgery the valve is reached through a right fourth intercostal space thoracotomy and repaired where possible, or replaced where not, using the same standard techniques as open surgery. The patient is positioned with the right side up. The surgeon makes a fourth intercostal space thoracotomy, places a soft tissue retractor and then a rib retractor, inserts a cannula for carbon dioxide insufflation to help de-airing, and opens the left atrium using a specially designed atrial retractor.

In the repair he demonstrated, the middle scallop of the posterior mitral leaflet (P2) was prolapsing and large. He excised the P2 segment, brought the neighbouring segments of the posterior leaflet together, and tested the valve, which was now competent. An annuloplasty ring, a supporting ring sewn around the valve opening, was then implanted, and the valve tested again. He described the result as very competent.

Where a valve cannot be repaired, it is replaced. One case he showed was a rheumatic mitral valve with dense adhesions, calcification and scarring, which was replaced. The choice of prosthesis follows standard practice: a bioprosthesis (tissue valve) for older patients and a metallic (mechanical) valve for younger ones. In another case a tissue valve designed for the mitral position was lowered into place; Dr. Mishra said this valve has a 15 to 20 year life. For a detailed comparison of the two valve types, see Dr. Z. S. Meharwal's guide to mechanical vs tissue heart valves.

Automated knot fastening

Knot tying is a particular challenge through a small cut, because the surgeon cannot get a hand inside: tying by hand is difficult, and a knot pusher takes time. Dr. Mishra's team now uses an automated knot-fastening device: the device is run down each suture and clicked, and the knot is secured within a fraction of a minute. He called it one of the revolutions in cardiac surgery, because it makes valve implantation through a small incision much faster and the knots very secure.

Aortic valve replacement: right thoracotomy or upper partial sternotomy?

Dr. Mishra replaces the aortic valve through either a right thoracotomy in the second intercostal space or an upper partial sternotomy, and the pre-operative CT scan decides which. The aortic valve sits in the aorta, apart from the rest of the heart, and that observation drives Dr. Mishra's approach. If the surgeon is going to work only on the aorta, there is no reason to make a big incision.

He uses two routes for aortic valve replacement:

• Right thoracotomy in the second intercostal space. After femoral cannulation, a short incision is made between the ribs, the pericardium is opened and the aorta lies directly in front of the surgeon. The aorta is clamped with a specially designed clamp and opened, the calcified valve is removed, the valve sutures are placed and a tissue valve is lowered into the aortic position. Because no bone is cut, he said, the patient can return to work in about three weeks.
• Upper partial sternotomy. Only the upper part of the breastbone is divided. The aorta is clamped and opened, the calcified valve is removed and a tissue valve is implanted. At this depth the knots can still be tied by hand. The wound heals well.

The choice between them comes from the pre-operative CT scan. In one patient he showed, the aorta lay close to the sternum and to the right of it, which made a perfect case for the right thoracotomy approach. In another, the aorta did not run towards the right and lay far from the sternum, which made the patient a candidate for upper partial sternotomy instead. Indicative costs for the operation are on the aortic valve replacement cost page.

Who is a candidate for port-access valve surgery

A patient is a candidate for port-access valve surgery when imaging shows groin vessels large and healthy enough to take the cannulas, an ascending aorta free of significant disease, and lungs that can tolerate single-lung ventilation. Dr. Mishra described this evaluation as really important.

Pre-operative tests

The routine work-up includes a CT scan, chest X-rays, a physical examination and pulmonary function tests. Patients going for coronary bypass or aortic surgery also undergo CT aortography and a detailed evaluation of the peripheral vessels. A Doppler ultrasound study of the femoral artery and vein checks their size and looks for disease, and the CT scan assesses the ascending aorta and the tortuosity (twisting) of the iliac vessels. Pulmonary function testing matters because the operation needs single-lung ventilation: for valve surgery the right lung is deflated.

Relative contraindications

Dr. Mishra listed these as relative contraindications to minimally invasive cardiac surgery:

• peripheral vascular disease
• atheroma of the aorta, and calcification of the ascending aorta
• aortic aneurysm, and conditions that predispose to it, such as Marfan syndrome
• any condition that rules out TEE, such as a narrowed oesophagus
• obesity, particularly morbid obesity
• pleural scarring
• very tortuous femoral and iliac vessels

Tortuous or diseased groin vessels are a contraindication specifically to femoral cannulation. The heart-lung machine can instead be connected through the axillary artery, below the collarbone, or by direct cannulation of the aorta.

Age limits

At the young end, the limit is the size of the femoral artery. Dr. Mishra avoids the minimal access approach in very young children, under about six years old, because their femoral arteries are too small. Above that age it is possible: he has closed an ASD in a seven-year-old using a size 14 femoral cannula. The femoral artery must be large enough to take the cannula. In older patients, the limits are the ones already listed: atheromatous change in the femoral artery, or calcification of the ascending aorta.

How long do valve repairs and replacements last?

Neither a repair nor a replacement valve lasts indefinitely. A repair can fail, and the patient may then need a second repair or a replacement. Dr. Mishra cited the Cleveland Clinic data showing significant repair failure after 10 years even in degenerative mitral disease; in rheumatic disease, repair failure is considerably higher.

Tissue valves, in his words, can be expected to fail after 10 to 15 years. When they do, a transcatheter valve of the kind used for transcatheter aortic valve implantation (TAVI) can now be placed inside the old tissue valve without open surgery, in either the aortic or the mitral position, a technique known as valve-in-valve. With a mechanical valve, failure takes the form of a paravalvular leak (a leak around the valve) or thrombus (clot) formation. A clot may be treated with thrombolysis, clot-dissolving medication; otherwise the mechanical valve has to be replaced again. The catheter-based option is explained further in TAVI and minimally invasive cardiac interventions.

Related reading

The coronary side of Dr. Mishra's programme is in robotic coronary artery bypass surgery. A different surgeon's account of the same operations, including transaxillary and periareolar incisions, is in Dr. Udgeath Dhir's minimally invasive valve surgery: incisions and techniques. Questions doctors asked in the session, including on repair durability and age limits, are on the Live Discussion page. More on the specialty is on the cardiac surgery hub.