Angioplasty advances

Published : Aug 04, 2001 00:00 IST

Angioplasty, a less invasive procedure than bypass surgery to treat coronary artery disease, is being increasingly preferred.

THE combined use of balloons, the devices used in angioplasty procedures to remove blocks in arteries, and stents, the permanent scaffolding for the newly widened artery, has revolutionised the treatment of heart disease by increasing the patients' survival rate by a significant extent and reducing the recurrence of the problem. What started as a procedure to unclog a simple discreet block in the artery, angioplasty is now employed to treat, with the aid of improved technology, complex, long, ulcerated and multiple lesions. Over one million angioplasty procedures are done every year the world over and for 92 per cent of the patients it offers a permanent cure.

Coronary arteries supply a constant flow of oxygen-rich blood to the heart, which pumps a total volume of almost 2,000 gallons of blood through the body each day. When plaque builds up in these arteries, blockages develop. These reduce the blood flow to the heart, causing symptoms ranging from a mild chest pain to a fatal heart attack. The treatment for this problem includes medication to control the disease and surgical intervention such as angioplasty (removal or compression of the plaque) or bypass grafting (detouring the blockages) to restore blood flow.

The major advantage of angioplasty, also called "balloon dilatation" or "percutaneous transluminal coronary angioplasty" (PTCA), is that it is less invasive and can be repeated should there be more blockages. Although not a substitute for bypass surgery, angioplasty, which involves increasing the diameter of clogged vessels and implanting stents (small mesh tubes made of non-reactive metal) to keep the vessels open, is a less risky and less debilitating procedure.

Since its development in the 1960s, coronary bypass surgery has brought relief from severe chest pain and considerably extended life for millions of people. Yet, despite the development of technology, careful selection of patients and the presence of highly experienced cardiac surgeons, bypass surgery has over 5 per cent mortality and morbidity rates. Some patients suffer surgery-related strokes; and in less than 10 years, many require another bypass surgery. Not uncommon are such problems as partial loss of memory and post-operative depression.

Yet bypass surgery is a life-saving treatment for those with conditions such as blockage in the left main coronary artery, severely impaired function of the heart's main pumping chamber, and those with aneurysms, or damaged heart valves. Developments in bypass surgery have no doubt made it safer and longer-lasting but it has been found that many patients who underwent bypass surgery could have benefited just as much from the less demanding angioplasty and stent implantation.

Angioplasty is done under local anaesthesia in a cardiac-catheterisation laboratory with the patient watching the procedure on a television monitor. The procedure involves puncturing the femoral artery in the leg and inserting a tube (sheath) and advancing a guiding catheter (hollow tube) through it to the origin of the blocked blood vessel in the aorta. The catheter acts as a tunnel through which runs a 0.014 inch guide wire, which, after negotiating the block, positions itself at the end of the blood vessel. This wire acts as a rail road over which is advanced a balloon catheter, 2 to 4 millimetres in size. The balloon has a radio-opaque marker. Under fluoroscopy (X-ray) the balloon is positioned across the lesion. Using dilute contrast, the balloon is inflated from one to 20 atmospheric pressures depending on the hardness of the lesion. This cracks open the block and improves the blood flow.

The balloon catheter is then removed. The stent mounted on the delivery catheter is then deployed at the site of the lesion by inflating the balloon. The stent helps optimise the results and reduce the risk of immediate complications. All these operations take 30 to 60 minutes.

The advantages of angioplasty are that as it does not involve surgery, there are no complications involving anaesthesia, blood transfusion and infection. Also, the patient does not suffer physical, psychological or mental trauma. The stay in the hospital is minimal, usually for 24 to 48 hours.

The use of stents has increased dramatically since 1995. With improved design, it is now possible to use stents instead of going in for bypass surgery. Cardio-logists consider stents a revolutionary development as they help reduce the cost of healthcare, and for the patients, the risk in surgery or of morbidity. Medical teams around the world are working on techniques such as intra-coronary radiation (at the time of stent insertion) and coating stents with immuno-suppressive drugs to make them more effective and long-lasting.

Angioplasty has proved to be as good as or even better than by-pass surgery in such situations as stable and unstable angina and acute infarction, that is, in the case of extensive anterial wall infarction or massive heart attack, inferior infarction with right ventricular infarction, haemodynamic instability (heart attack with heart failure and lung congestion) or patients for whom thrombolysis cannot be administered. Angioplasty is preferred even in patients with a stable angina, who continue to have discomfort despite adequate medication or when a large area of the heart muscle is affected.

A problem with angioplasty earlier was that 5 per cent of the patients needed emergency bypass surgery. This problem arose during balloon dilatation with excess dissection. Moreover, in 30 to 40 per cent of those who underwent angioplasty, heart problems recurred within three months.

But the improved stent design and its optimum deployment has changed all that and made angioplasty popular. To 92 per cent of the patients undergoing this procedure, angioplasty offers a permanent cure, is predictable, and offers good results. It has become so safe that the procedure is now done without a stand-by emergency surgical team. Further, the risk of a second procedure, or what is called the "target lesion revascularisation (TLR) rate", has come down significantly, to 6 to 8 per cent from 40 per cent.

Scientific trials around the world have proved the effectiveness of angioplasty with stents. For instance, in a major trial in Argentina 2,759 patients were screened for the effectiveness of the procedure against bypass surgery in multi-vessel blocks. It was found that within the first two years after the procedure, "the survival rate and freedom from myocardial infarction" in the case of patients who had undergone angioplasty with stent implantation were better than those who had undergone bypass surgery (Interventional Cardiology, Volume 37, Number 1, January 2001).

The more recent developments in coated stents, to be available in the market soon, would further enhance the effectiveness of the procedure. For instance, the stainless steel tubes coated with substances such as rapamicin (sirolumus) on BX velocity stent have been proved to eliminate the recurrence of the heart problem (Clinical Investigation and Report, Volume 103, Number 2, January 2001).

Several medical trials have shown that patients with unstable angina, who do not respond to medicines and are certain to end up with a full-blown heart attack or are likely to die prematurely, can be safely treated using stents. For instance, the recently conducted Frisc-2 trial shows that there is a substantial survival advantage for patients with unstable angina using this procedure. Another multi-centred trial, PAMI, shows that patients with acute myocardial infarction (heart attack) can be safely treated with angioplasty. The mortality rate came down from 7.3 per cent (using the conventional treatment, thrombolysis) to 2.3 per cent in the case of angioplasty. The risk of recurrence of heart attack and pain fell dramatically from 28 per cent to 10.4 per cent.

There is, however, the risk of narrowing of the stented segment because of tissue growth in 10 to 20 per cent of the patients depending on the complexity of the disease and the length of the stent used. A number of measures are being tried to prevent this problem.

The cost of stent and angioplasty, which is between Rs.1.25 lakhs and Rs.2.5 lakhs, has made angioplasty less popular. The Chennai-based Sanjiv Agrawal Research and Education Foundation, set up last year by the interventional cardiologist Dr. Sanjiv Agrawal, Chief of Cardiology and ICCU at St. Isabel's Hospital, and Senior Consultant, Interventional Cardiology at Apollo Hospitals, is striving to popularise and make angioplasty more affordable.

The main objectives of the Trust, according to Dr. Agrawal, are to detect coronary artery diseases early by conducting camps, to disseminate information about heart problems and the ways to avoid them, and to provide treatment at affordable costs. The Trust offers a package with stents for Rs.55,000 to Rs.75,000 - half the normal cost. Says Dr. Agrawal: "There is no compromise on quality. The Trust uses the best stents in the world."

Of course the best protection against arterial blockages is prevention by not smoking, by doing regular physical exercise, by controlling blood pressure and blood sugar levels, by following a diet regime, and by maintaining a normal cholesterol level, if necessary by taking medicines. The Trust is keen to create this awareness among the people.

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