Clinical Procedures

Below are some common clinical procedures in myocardial revascularization and valvular disease treatment.

While there are many variations within each specific technique, the general procedures are described below so that they can be used as a point of reference when comparing to the methods presented in our robotics and laser technology sections.

Clinical Procedures for CHD:
Clinical Procedures for Valvular Disease:
CABG
Valve Replacement
OPCAB
Valve Repair
Angioplasty and Stents
Minimally Invasive Valve Repair
Minimally Invasive Coronary Artery Surgery
 

 

Coronary Artery Bypass Grafting (CABG)
• Coronary Artery Bypass Grafting (CABG) is widely considered the "gold standard" in this type of heart surgery. It involves making a large incision in the chest and placing the patient on the heart-lung machine (blood membrane oxygenator).

• CABG involves creating a 6 to 8 inch incision in the chest (a thoractomy), stopping the heart, placing the patient on a heart-lung machine, harvesting an artery from another area of the body to make a graft, and performing a bypass procedure.

• The bypass, like a bypass on a highway, is an occluded region of one or more coronary arteries with a vascular graph downstream and upstream of the occlusion.

 

• CABG requires a median sternotomy, or incision down the front of the chest through the breastbone so that the surgeon may see the heart.

• The surgery involves two surgeons for a total of five to seven specialists. One surgeon harvests the graft from the patient's saphenous vein, mammary artery, or radial artery. The saphenous vein from the leg is usually used to create the detour around the obstruction in the coronary artery.The other surgeon works on the heart and can bypass up to four arteries at a time.

• Traditionally, the heart is stopped during the CABG process and the patient is kept alive by a heart-lung machine during the operation.

• Blood flow is redirected through the heart-lung machine, which acts as the heart's pump, and provides oxygen to the blood to keep the rest of the body perfused.Patients are on the pump for thirty minutes to a few hours. The "pump team," responsible for the heart lung machine operation, sets up the machine to withdraw blood from the vena cava of the patient and return it to the aorta through tubing.

 

(51)

• After the procedure, the patient spends one to three days in the Intensive Care Unit and usually an average of seven to ten days in the hospital. After discharge patients can resume normal activities and full recovery occurs in three to nine months. Some patients exhibit "pump head," cognitive impairment thought to be caused from the heart-lung machine. (5.8,5.9)

 

Mortality

CABG surgery carries a high mortality rate. About 1% die intraoperatively and another 2-3% die within ninety days. (5.10)

 

Incidence

• CABG is the eighth most common surgical procedure in the United States.

• An estimated 750,000 bypass surgeries were done worldwide in the year 2000, using extra-corporeal oxygenation (heart-lung machine) (5.10)

(5.2)

 

Prevalence

• It can be estimated that the prevalent population is about eight times the incident population, meaning that about 6 million people in the world are living with CABG procedures. (5.10)

 

Cost

• First year costs for the patient (which include the procedure, hospitalization, and followup) are estimated at $32,000, and follow-up costs each year afterwards are about $7,000. (5.10)

• Revenues from bypass surgery exceed cost and can even make up for loss in other areas of the hospital. (5.9)

 

Off-Pump Coronary Artery Bypass (OPCAB)

• During this procedure, the surgeon opens the patient's chest with a 12- to 14-inch incision over the breastbone and divides it to expose the heart.

• Simultaneously, the mammary artery and/or the greater saphenous vein from one of the patient's legs or other blood vessels are "harvested" for use in the bypass procedure.

• Since the heart is still beating, a mechanical heart stabilizer is employed to restrict the heart movement while the bypass procedure is being performed. The surgeon also uses suction-based devices to rotate the heart to provide access to the coronary arteries. (5.12)

 

(5.6)

(5.7)

 

Angioplasty and Stents

• Percutaneous transluminal coronary angioplasty is also known as PTCA, coronary artery balloon dilation or balloon angioplasty.

• It is the least invasive approach to myocardial revascularization.


• Carried out under a local anaesthetic and mild sedation, the procedure is done by first passing a fine tube (catheter) into a large artery in the groin or arm and then a guidewire, with the deflated balloon at the end, is passed down the tube. Using X-rays, the doctor can follow the balloon as it goes up towards the heart and correctly position it in the artery that is narrowed.

• Once in place, the balloon is inflated in the narrowed segment and then deflated after a few minutes. After the balloon has been used, it is removed.

• The doctor injects an iodine contrast agent and X-ray pictures to check that the coronary arteries have been re-opened. The procedure lasts between 15 and 45 minutes.

 

 

 

(5.3)

(5.4)

• Once the balloon has been used, a stent may be placed inside the re-opened artery to hold it open.

• Stents are made out of a meshwork which is collapsed while it is passed along to the tip of the catheter and then opened up once in position in the narrowed artery. (5.9)

 

Incidence

• About 3-4 million angioplasties are performed every year, and 70-09% of these utilize stents.


• 10-20% of these procedures involve the use of drug-eluting stents. (5.10)

(5.5)

 

Cost

• First year costs for the patient (which include the procedure, stent, hospitalization, and followup) are estimated at $21,000, and follow-up costs each year afterwards are about $4,300. (5.9)


•Bare-metal stents cost about $1,000, and the drug-eluting stent currently costs $3,195. (5.11)
Johnson & Johnson is currently the only FDA approved drug-eluting stent, while several other manufacturers provide stents worldwide.

 

Minimally Invasive Coronary Surgery

• Minimally invasive coronary artery surgery is also called limited access coronary artery surgery. It is the general term for procedures that reduce trauma by using small ports instead of large incisions.

• It is usually performed using one of two approaches.

(1) MIDCAB (minimally invasive coronary artery bypass) (6.4)
(2) PACAB (PortCAB, or port-access coronary artery bypass)

 

Minimally Invasive Direct Coronary Bypass (MIDCAB)

This procedure is limited to a small subset of patients requiring bypass surgery who need only 1-2 bypasses.
(6.2)

• During the operation, the surgeon makes an incision approximately 6-10 cm long on the front of the chest toward the left side.

•The pectoral muscles are divided and a small portion of the front of the rib, the costal cartilage, is removed.

•The surgeon clamps off the internal mammary artery (IMA), which lies just beneath this cartilage, and frees its lower end. An opening is made in the pericardium, the sheath covering the heart.

•A mechanical stabilizer is attached to the heart to reduce its movement, and the surgeon connects the mammary artery below the blockage to the left anterior descending (LAD) artery and/or one of its branches.

• Once the clamp on the mammary artery is released, blood can flow from the IMA through the LAD artery, bypassing the blockage and providing oxygen-rich blood to the heart muscle. (6.4)

(6.3)

 

Port-Access Coronary Artery Bypass (PACAB)

• In PACAB, a series of small holes or "ports" in the chest are made instead of large incisions. Surgical equipment assists in viewing and performing the bypass.
(6.1)

 

Valve Replacement

• If a surgeon cannot repair a heart valve, the valve is removed and replaced with an artificial (prosthetic) valve by sewing it into the remaining tissue from the natural valve.

• Throughout the world, 95% of all valve replacements are performed for mitral or aortic valves. The mitral valve is positioned in the heart´s left side, between the left upper chamber (left atrium) and the left lower chamber (left ventricle). The aortic valve separates the left ventricle from the aorta (which carries blood to the body).



 

There are are two types of prosthetic valves used for replacement:

(1) Mechanical Valves

• Mechanical valves is carefully designed to mimic the native heart valve. It has a ring, like your own natural heart valve, to support the leaflets. The mechanical valve opens and closes with each heartbeat, permitting proper blood flow through the heart. To prevent any blood clots from developing on the valve, which can cause complications, a patient with a mechanical valve replacement is required to take anticoagulation medicine (blood thinners) daily.



(2) Bioprosthetic Valves

• A tissue valve is a native valve taken from an animal. Once the tissue is explanted (removed), it is chemically treated and prepared for human use. Some tissue valves have a frame, or stent, that supports the valve, and some valves are stentless (no framework). A very thin polyester mesh cuff is sewn around the outside of the valve for easier implantation.

• A homograft or allograft is a human valve obtained from a donor. TBecause the availability of these valves depends on donors, supply is limited.  
     
Incidence

• There were an estimated 244,000 heart valve replacements performed globally in 2000 (4.4)

 

Cost
• The cost per procedure is estimated at $60,000 to the patient, and follow-up costs are about $5,000 per year afterwards (4.4)

 

Valve Repair
There are several different techniques in repairing heart valves:
Valvuloplasty
Annuloplasty
 

• Valvuloplasty is a technique aimed at making sure the flaps of the valves (or leaflets) close properly, preventing blood from backing up into the atrium. In the healthy heart, blood flows from the upper chamber (atrium) to the lower chamber (ventricle), and from the ventricle to the body.

• Sometimes a scalpel is used to cut the fused leaflets (commissures) near the ring, which may help them open and close better. In other cases, a balloon catheter, similar to a catheter used during angioplasty, is inserted into the valve. The balloon is inflated, splitting the commissures and freeing the leaflets to open and shut fully.

• Annuloplasty is a technique aimed at repairing the fibrous tissue at the base of the heart valve (the annulus). Sometimes, the annulus becomes enlarged, which enables blood to back up into the atrium. To repair this, sutures are sewn around the ring to make the opening smaller. This creates a purse string effect around the base of the valve and helps the leaflets meet again when the valve closes.

• Sometimes when repairing the annulus, it is necessary for the surgeon to implant an annuloplasty ring. A ring is used to correct a problem, provide support for the valve, and reinforce other repair techniques or any combination of these. (6.5)

 

Minimally Invasive Valve Surgery

Several types of minimally invasive valve surgery are currently being performed: (6.6)

 

Aortic Valve Replacement (AVR)

Through an incision approximately 4-6 cm, the aortic valve can be surgically replaced

 

Mitral Valve Repair or Replacement (MVR)

Through a minimally invasive incision approximately 4-6 cm, the mitral valve can be surgically repaired or replaced. This is becoming the standard of care for most patients requiring isolated valve repair or replacement.

 

Tricuspid Valve Repair or Replacement (TVR)
Through the same size incision as above, the tricuspid valve can be surgically repaired or replaced.