WHAT IS CORONARY ANGIOGRAPHY AND ANGIOPLASTY ?
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.
Risks of procedure
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.
Angioplasty is associated with a small but appreciable risk. The decision for angioplasty should be considered carefully to ensure that the benefits outweigh the potential risks. The risks also vary with each individual depending on age, heart function, other diseases and whether the procedure is done as an emergency or in a stable setting.
Longer term complications
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.