Angioplasty

What is Angioplasty?

Angioplasty (informally called balloon dilation) is the mechanical alteration of a narrowed or totally obstructed vascular lumen, generally caused by atheroma (the lesion of atherosclerosis). The term derives from the roots "Angio" or vessel and "plasticos" fit for molding. The term has come to include all manner of vascular interventions typically performed in a minimally invasive or percutaneous method.

Angioplasty: Common Techniques

Most commonly, the Seldinger technique is used to cannulate a blood vessel for access. A guiding catheter is introduced into the arterial (or venous) system and advanced through the system to the location of an obstruction. This in turn is followed by introduction of a guide wire which is advanced though the guide catheter, through the obstruction and extended into the blood vessel lumen beyond the obstruction. Over the guide wire, a balloon catheter is advanced through both the guide catheter and the obstruction. Once in position, the balloon is inflated using high hydraulic pressure so as to force the narrowed vessel lumen to expand, pushing the lesion producing the narrowing outwards. The balloon may also include a stent (compressed over the balloon before expansion) or be followed by a stent/balloon combination so that the expanded stent is left within the previously narrowed lumen to mechanically support patency of the vessel lumen.

One way to unblock (open up the lumen) a coronary artery (or other blood vessel) is percutaneous transluminal coronary angioplasty (PTCA), which was first performed in 1977. A wire is passed from the femoral artery in the leg (most commonly) or the radial artery in the arm up to the diseased coronary artery, to beyond the area of the coronary artery that is being worked upon. Over this wire, a balloon catheter is passed into the segment that is to be opened up. The end of the catheter contains a small folded balloon. When the balloon is hydraulically inflated, it compresses the atheromatous plaque and stretches the artery wall to expand. At the same time, if an expandable wire mesh tube stent) was on the balloon, then the stent will be implanted (left behind) to support the new stretched open position of the artery from the inside.

Angioplasty and stenting is performed through a thin flexible catheter during Cardiac Catheterization with just a local anesthetic to the groin (or wrist) where the catheter was inserted, often making heart surgery unnecessary. While coronary angioplasty has consistently been shown to reduce symptoms due to coronary artery disease and to reduce cardiac ischemia, it has not been shown in large trials to reduce mortality due to coronary artery disease, except in patients being treated for a heart attack acutely (also called primary angioplasty). There is a small but definite mortality benefit (ie., reduction) with this form of treatment compared with medical therapy, usually consisting of thrombolytic ("clot busting") medication.

Angioplasty and Stents

Traditional ("bare metal") coronary stents provide a mechanical framework that holds the artery wall open, preventing stenosis, or narrowing, of arteries feeding critical structures like the myocardium. Traditional stenting is superior to angioplasty alone in keeping arteries open.

Newer drug-eluting stents (DES) are coated with drugs that prevent re-stenosis of the artery. Three drugs, sirolimus, everolimus and praclitaxel, have been demonstrated effective and safe in this application by stent device manufacturers and are being used.

Angioplasty Risks

Risks of angioplasty are fortunately uncommon, and the procedure is widely practiced. Coronary angioplasty is usually performed by an interventional cardiologist, a medical doctor with special training in the treatment of the heart using invasive catheter-based procedures.

Angioplasty is sometimes referred to as Dottering, after Dr C.T. Dotter, who, together with Dr M.P. Judkins, first described angioplasty (without the balloon) in 1964 (Circulation 1964;30:654-70). As the range of procedures performed upon lumens of coronary arteries has widened, the name of the procedure has changed to percutaneous coronary intervention (PCI).

Risks of Angioplasty

Angioplasty has become considerably safer over the years and is now commonly performed. Although it is associated with some risks these are considerably less than for open-heart bypass surgery with its resulting post-operative pain. However the likelihood of recurrence of angina, and requirement for repeated procedures has been higher with angioplasty. The latest trial (ARTS II) has suggested that PCI with DES may be superior, at least in the short term.

Some chest discomfort occasionally may be experienced and it is for this reason that the patient is awake during minimally invasive angioplasty; the reporting of any symptom allows the cardiologist to take necessary immediate action. Bleeding from the insertion point in the groin is common, in part due to the use of anti-platelet clotting drugs. Some bruising is therefore to be expected, but occasionally a haematoma/hematoma may form. This may delay hospital discharge as flow from the artery into the haematoma may continue (pseudoaneurysm) which requires repair. Infection at the skin puncture site is rare and dissection (tearing) of the access blood vessel is uncommon. Allergic reaction to the contrast dye used is possible, but has been reduced with the newer agents. Deterioration of kidney function can occur in patients with pre-existing kidney disease, but kidney failure requiring dialysis is rare. Vascular access complications are less common and less serious when the procedure is performed via the radial artery.

In the long term, the most common risk is of the stent restenosis, as discussed above. This has been reduced considerably with the use of newer stents coated with certain medicines (drug-eluting stents). The most serious risk is the rare provocation (3%) of a heart attack during or shortly after the procedure; this may require emergency open cardiac surgery. Angioplasty carried out shortly after a myocardial infarction has a risk of causing a stroke of 1 in 1000, which is less than the 1 in 100 risk encountered by those receiving thrombolytic drug therapy.

The overall risks of death with angioplasty is approximately 1%, but the underlying severity of the heart disease, fitness of the patient and presence of other illness affect each individual’s risk. Hence for those with relatively minor heart disease, preserved good cardiac function, reasonable level of fitness and absence of other illnesses, the risk will be considerably less than this.

When failures of PTCA occur, they are often treated using coronary artery bypass grafting (CABG).

Peripheral Angioplasty

Peripheral angioplasty refers to the use of similar techniques in opening blood vessels other than the coronary arteries. It is often called percutaneous transluminal angioplasty or PTA for short. PTA is most commonly done to treat narrowings in the leg arteries, especially the common iliac, external iliac, superficial femoral and popliteal arteries. PTA can also be done to treat narrowings in veins.

Renal Artery Angioplasty

Atherosclerotic obstruction of the renal artery can be treated with angioplasty of the renal artery (percutaneous transluminal renal angioplasty, PTRA). Renal artery stenosis can lead to hypertension and loss of renal function.

Carotid Angioplasty

Generally, carotid artery stenosis is still not treated with angioplasty and stenting in most hospitals, due to the increased risk of embolic stroke with the procedure. But this is changing since the FDA has approved the first cartoid stent system (Guidant) in August 2004 and the second (Abbott) in September 2005. The system usually comprises a stent along with an anti-embolic device designed to reduce or trap atheroma and clot debris. Angioplasty and stenting is increasingly being used to also treat carotid stenosis, with success rates similar to carotid endarterectomy surgery. Simple angioplasty without stenting is falling out of favor in this vascular bed. A large trial comparing endarterectomy and stenting found stenting equally efficacious.