Coronary Angiogram and Percutaneous Coronary Intervention
A coronary angiogram is a procedure that uses X-ray imaging to see your heart’s blood vessels. The test is generally done to see if there’s a restriction in blood flow going to the heart. Coronary angiograms are part of a general group of procedures known as heart (cardiac) catheterizations. Cardiac catheterization procedures can both diagnose and treat heart and blood vessel conditions. A coronary angiogram, which can help diagnose heart conditions, is the most common type of cardiac catheterization procedure. During a coronary angiogram, a type of dye that’s visible by an Xray machine is injected into the blood vessels of your heart. The X-ray machine rapidly takes a series of images (angiograms), offering a look at your blood vessels. If necessary, your doctor can open clogged heart arteries (angioplasty) during your coronary angiogram.
Exercise treadmill test allows us to assess the response of your heart to exercise. This is done by recording your electrocardiogram (ECG) while walking on a treadmill machine. We also monitor your symptoms and blood pressure (BP) during the test. This test is used to detect significant blockages of the heart arteries and is also used to assess for abnormalities of heart rhythm.
Coronary angioplasty, also called percutaneous coronary intervention, is a procedure used to open clogged heart arteries. Angioplasty involves temporarily inserting and inflating a tiny balloon where your artery is clogged to help widen the artery. Angioplasty is often combined with the permanent placement of a small wire mesh tube called a stent to help prop the artery open and decrease its chance of narrowing again. Some stents are coated with medication to help keep your artery open (drug-eluting stents), while others are not (bare-metal stents). Angioplasty can improve symptoms of blocked arteries, such as chest pain and shortness of breath. Angioplasty can also be used during a heart attack to quickly open a blocked artery and reduce the amount of damage to your heart.
Coronary angiography is the process of injecting dye into the arteries of the heart to allow the cardiologist to see what the arteries look like and where there may be narrowing.
Coronary angioplasty (often referred in short as PTCA or PCI) is a procedure to open up arteries of the heart that are significantly narrowed or blocked. The procedure usually consists of several steps.
- Getting entry into an artery that leads to the heart. This commonly involves either the leg artery (groin area) or the hand artery (wrist). A small tube is placed in the artery that allows introduction of different devices that may be needed.
- Angiography is performed. The doctor injects dye from a long tube (catheter) inserted from the leg or hand artery that goes to the opening of the heart arteries. X-rays are taken and the pictures are seen immediately on a display.
- The cardiologist can gauge the size, the branches and course of the arteries of the heart. The severity of the narrowing can then be estimated from these pictures.
- If the narrowing is considered severe enough to compromise the flow of blood and oxygen to the heart muscle, angioplasty is performed. This usually is done by first introducing a very fine wire (similar to the thickness of your hair) across the narrowing. A balloon can then be brought to the narrowing and the artery stretched open. It is common then to place a fine wire mesh (stent) to the stretched area to ensure that the narrowed portion of the artery remains open.
The overall risks of such procedures are uncommon. Angiography has a lower risk usually estimated at less than 1% overall for all serious complications. Angioplasty however has a slightly higher risks and this includes
- Risk of Death < 1%
- Risk of stroke <1%
- Risk of heart attack <2%
- Complication resulting in need for urgent bypass surgery <0.5%
- Abnormal heart rhythms requiring electrical shock to restore normal rhythm <0.1%
- Damage to the arteries in the groin or wrist that requires surgical repair <1%
- Need for blood transfusion <0.5%
- Life threatening allergic reaction to the dye <0.1%
- Radiation exposure resulting in burns or cancer <0.0003%
- Kidney damage due to the dye is rare in persons who have normal kidney function.
The risks mentioned above refer to complications that usually occur during the procedure or shortly thereafter. However, longer term problems include
- Re-narrowing. This usually occurs within 6 months to a year after the procedure. With uncoated stents, this can occur in about 20-30% of cases. With drug-coated stents, this occurs usually in <10% of cases. Re-narrowing can be treated with repeat angioplasty or surgery.
- Clot formation in stents. This is a very serious problem as a clot forming within a stent can block the artery totally and cause a heart attack. This usually occurs within the first month of a stent insertion and occurs in <1% of cases. Clots forming after a month are rare following placement of an uncoated stent. Drug coated stents however appear to have a risk of 0.5% to 0.6% of clots forming up to 4 years after insertion.
The choice of using a drug coated stent or an uncoated stent should be discussed based on individual factors and patient preference.
Coronary artery bypass grafting (CABG) can be considered as an alternative to angioplasty. However, CABG requires a significantly longer time for recovery when compared to angioplasty. CABG may be preferable in certain patients including those with multiple narrowings, left main (the main heart artery) narrowing and diabetics.
Medical treatment or taking only medicines is an alternative. Present clinical studies suggest that angioplasty is superior to medical treatment in patients for relieving symptoms such as chest pain or breathlessness. Angioplasty does not appear to have a benefit in reducing death or heart attacks. The number of long term medications for symptom relief following successful angioplasty however can be dramatically reduced. These studies however apply to patients with stable symptoms and not those who are experiencing heart attacks or have unstable situations.
Additional tools used during angiography or angioplasty
IVUS or intravascular ultrasound is a miniaturized ultrasound probe that can be placed into the heart arteries. This can help the cardiologist determine the inside of the heart artery in terms of the severity of narrowing and the amount of cholesterol deposits within the wall of the artery. The results from an IVUS can give very specific information on the diameter and size of the artery and can also be used to see if a stent is well placed and expanded within the artery. A well placed and appropriately sized stent reduces the longer term problem or re-narrowing and clots.
This is a wire (thickness of a hair) with a miniature pressure probe at the tip of the wire. In certain situations, narrowing within the arteries can seem intermediate on angiography. In these cases, the pressure wire can help determine if the narrowing is compromising blood flow. The wire can be placed before the narrowing in the artery and the pressure at this point can be compared to a point in the artery beyond the narrowing. The pressure drop caused by the narrowing can then be assessed. If the pressure drop across the narrowing is greater than 20%, angioplasty should be considered.
These additional tools help your cardiologist determine with greater accuracy if angioplasty for intermediate narrowings should be performed.
Some narrowings have large deposits of calcium and this produces a narrowing that is not easily dilated with such balloons or stents. In most situations, the balloons used under high pressures can overcome such narrowings. However, with severe deposits of calcium, a device known as a rotablator may be required. This is a miniature “drill” with a metal tip shaped like an olive and coated with small diamond chips. The tip can be rotated at 160000 rpm and this is advanced gently through the narrowing, reducing the calcium deposits into fine powder. Once the calcium is removed, stenting can be successfully carried out. Overall complication rate of the angioplasty is about 2-3% if rotablation is performed.
Additional tools used during angiography or angioplasty.
Acute or emergency angioplasty
Acute angioplasty is performed in the setting of a heart attack. A heart attack most commonly occurs when a clot chokes up a pre-existing narrowing resulting in no blood flow to the heart muscle. To reduce damage to the heart muscle, angioplasty is considered the ideal treatment as it is able to restore blood flow in more than 90% of cases and be done in a timely fashion. The risk of an emergency angioplasty for serious complications is between 5-10%. Factors such as a person’s age, the size of the heart attack can influence the risk during the procedure.
Chronic Total Occlusions
Chronic total occlusions also known as CTOs, are narrowings that are totally occluded that have been present for some time. These are different from the total occlusions that occur in the acute setting of a heart attack. The blockages in the CTOs are sometimes very resistant to penetration and dilation and the success rates can vary between 50-90%. Predictors of success include the age of the CTO, the amount of calcium deposits in the artery, the length of the total blockage and position of the blockage. A CTO can take many hours to successfully unblock. Occasionally, a special X-ray called a CT angiogram done before angioplasty can help in developing a strategy to successfully overcome a CTO.
SAPHENOUS VEIN GRAFT
In bypass surgery, veins often taken from the leg are used as new pipes to supply blood to the heart muscle. These veins can become narrowed or blocked after initial successful surgery. The veins unlike the heart arteries degenerate over time and develop very severe accumulation of soft cheese like material in the walls of the veins. If angioplasty was performed to these vein grafts, there is a high risk that these soft materials would dislodge into smaller particles and flow downstream to the smaller arteries in the heart muscles causing a total blockage. Special techniques are needed to prevent this down stream flow of debris and ensure a successful result. These include uses of filters and balloons to catch the debris during angioplasty and to remove them from the body where they would do no harm.
Left Main Stenting
The left main is the main artery that gives rise to two main branches of the heart artery. If the left main is blocked, about 2/3 of the heart muscle will lose their blood supply. Due to the importance of the left main, conventional treatment for left main narrowings is bypass surgery. Angioplasty is an alternative treatment option. However, with the problem of ensuring good flow to both branches and the concern over stent clots, left main angioplasty should only be performed after considering the bypass option.
This is a procedure that combines both minimally invasive bypass surgery with percutaneous angioplasty (balloon and stenting). This type of procedure is not new and has been done since the mid 1990s.
There are three main arteries of the heart. They are the left anterior descending artery (LAD), right coronary artery (RCA) and left circumflex artery (Lcx). The LAD artery runs down the front of the heart and in the majority of people is the most important of the three arteries as it supplies the bulk of the muscles of the left heart chamber.
Present evidence gained from many years of experience still suggests that certain types of grafts used in bypass surgery can last longer than using stents. In particular, a graft taken from the breast bone called the left internal mammary artery (LIMA) when connected to the left anterior descending artery (LAD) of the heart provides a long lasting result. Such grafts have also proven to increase life span. The expected failure rate of the LIMA to LAD graft is only about 10% after 10 years.
Stents on average may have a re narrowing rate of up to 20% by the first 6 months. Even drug coated stents have rates of re narrowing that are at best about 5-10% by the 1st year. In addition, narrowings in the artery that are not stented have a chance of progressing to become more narrowed with time. Drug coated stents also have a down side which is called thrombosis (sudden formation of blood clots) that can occur after the initial stenting. This is rare, occurring in about 0.5-0.6% of people per year who have have drug coated stents placed. However, a stent in the LAD artery which suddenly clots has a high likelihood of causing death.
While the LAD artery lies on the front surface of the heart, the other two arteries run a course to the back and bottom of the heart. To do a full bypass of all three arteries, the patient is usually placed on a heart-lung bypass machine and the heart is made to stop beating. The increased manipulation of the heart during operation can lead to increased risk of complications. Another problem termed “pump head” can occur when patients are placed on the heart-lung bypass machines. This is due to small showers of debris that can cause tiny “strokes” and may result in memory loss and forgetfulness after the operation.
Grafting of the other two arteries (RCA and Lcx) are also usually performed by using veins taken from the legs. These veins are not as robust as the LIMA artery with blockage rates of up to 20% by the first year after operation.
Essentially beating heart surgery is done and the LIMA artery is grafted to the LAD artery. This avoids the need to stop the heart and therefore the need to place a patient on heart-lung bypass. Excessive manipulation of the heart is also avoided as the LAD artery lies on the front surface of the heart. The scars following such surgery is also much smaller and there is no need to take veins from the legs.
Narrowings that may be present in the other two arteries can then be done by angioplasty following surgery. Presently, drug coated stents can be placed which provide low rates of re narrowing. If clots formed in such stents, they would usually be less dangerous than would have occurred if the stents were in the LAD artery.
The approach of bypass surgery alone or angioplasty alone remain the mainstream ways of improving blood flow in blocked heart arteries. Hybrid revascularisation should only be considered in patients with appropriate types of blockages and/or who may be too high risk for the more traditional approaches. Hybrid revascularisation requires surgeons and cardiologists to work closely together and co-ordination of such approach needs to be carefully arranged. In the majority of patients, there may not be an added advantage for this hybrid approach due to the increased need for procedures and cost involved. There are also specific advantages and disadvantages of this hybrid approach. Patients considering such an approach should have a careful discussion with both their surgeon and cardiologist before a decision is taken to undergo this form of procedure.