A new medical procedure could soon offer a safer way to treat hardened cholesterol build-up in the arteries of heart disease patients.

The procedure, called intravascular lithotripsy (IVL), involves a device that uses sonic pulses to break up hard plaque accumulated in the patient's arteries, said cardiologist Tan Chong Hiok of Mount Elizabeth Hospital.

Plaque, made up of components such as cholesterol, fats and calcium, can cause narrowing of the arteries and limit blood flow.

Known as atherosclerosis, this condition is typically treated using angioplasty, in which a small balloon at the end of a catheter is sent to the site of the blockage through a patient's blood vessels.

The balloon inflates to physically push the plaque aside and expand the artery before a stent is put in place to keep it open and maintain good blood flow.

But this may not be effective if the plaque has hardened, Dr Tan said.

"Some patients may see a doctor late, for reasons like ignoring or not noticing the symptoms, or not going for regular check-ups," he said.

"Over time, say, three years or more, calcium gradually gets deposited onto this cholesterol plaque, making it rock hard. This renders angioplasty ineffective as the ring of calcium deposited inside the artery walls cannot expand."

Most discover the blockage at an earlier stage, so such cases are not common, making up about 5 per cent of patients with the condition, Dr Tan said.

These patients may have discovered the blockage only when they saw a doctor after experiencing chest pain, discomfort or a heart attack, he added.

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Previously, these cases would be treated by sending a tiny drill to the blockage site which breaks up the plaque using friction, Dr Tan said.

But the device can be cumbersome to use and the procedure risks causing the walls of the patient's blood vessels to tear, he added.

"Because of these issues, doctors may be hesitant to recommend the procedure or to perform it."

IVL is simpler and less risky, he said. It is similar to angioplasty in that it also involves a catheter and balloon.

The catheter can deploy a shock wave that cracks and breaks up the plaque before the balloon is inflated. A stent can then be placed.

Sonic waves have been used since the 1980s to break up kidney stones so that they can be passed out in a patient's urine instead of requiring surgery.

But medical professionals have started to apply the concept to plaque in blood vessels only recently, Dr Tan said.

The IVL device was invented by an American start-up called Shockwave Medical and has been used here since late August.

Dr Tan, one of the first doctors to apply the technique here, said he has used the IVL device to treat three patients.

Some public hospitals, such as Tan Tock Seng and Changi General, as well as the National Heart Centre, have also started offering the procedure, he added.

About 50 patients in Singapore have benefited from it.

Regulator Health Sciences Authority (HSA) said an application to register the IVL system from Shockwave Medical has been filed.

The full registration could take up to a year to be approved.

"In the meantime, some local healthcare institutions have applied to use the IVL system for selected patients via HSA's special authorisation route," the HSA said.

Doctors or healthcare institutions are responsible for the proper use of such devices and must report any adverse outcomes to the HSA, it added. "Healthcare institutions are similarly held accountable."