According to the scan results, Yau's right coronary artery, which supplies oxygen-rich blood to the heart, was severely narrowed in two places. A hard substance called plaque, caused by the cholesterol, had adhered to the internal artery surface and caused his artery to narrow by 80 per cent in one place and 50 per cent in another. He had atherosclerosis, and the narrowed artery walls were reducing blood flow to his heart.

Yau was also in grave danger of a fatal heart attack. Lack of sleep, an angry outburst or even a mild illness - anything that stressed his body - could cause the plaque in the artery to rupture. If it did so and entered the blood stream, his body would form a blood clot in an effort to repair the damage caused by the ruptures. But the clot could completely block the artery instead. Given that the plaque-narrowed sites were so close to the root of the artery, any blockage would most certainly cut off blood supply to Yau's heart, starving it of oxygen and causing the heart muscle to stop working, Leung says.

Next Leung needed to look inside the lesions to confirm the severity of Yau's condition using a conventional coronary angiogram. Leung inserted a catheter into Yau's radial artery on his right wrist and worked it up to the affected coronary artery. Using a tiny probe in the catheter, Leung took cross-sectional images of the narrowed areas in the artery. The angiogram results confirmed the findings.

Since Leung had already inserted a catheter into Yau's body, he swept into action to conduct an intervention in which he could repair the artery without the need for open heart surgery. Leung intended to use a balloon to open up the constricted artery and put a stent in place to keep it open.

A stent is an expandable mesh tube, usually made of metal. It can be collapsed into a smaller diameter so it can travel easily up a blood vessel via a catheter. When the stent is in place at a narrowed site, a balloon under the stent is inflated so that the mesh tube opens up into the required diameter and expands the blood vessel. Leung likens the stent to scaffolding that supports the surrounding structure.

Doctors now get to choose from three types of stent - a bare metal stent, a drug-eluting stent that minimises the thickening of the blood vessel wall, and a bio-engineered stent that is coated with antibodies that help the body build cells around the stent and incorporate it into the blood vessel wall.

Leung says each type of stent has its own trade-offs in terms of the risk of a re-narrowing of the blood vessel, and the amount of anti-platelet medication the patient needs to prevent clotting around the stent. The selection of treatment options depends on the patient's situation. For instance, doctors often recommend elderly patients and those who need to undergo other surgery within a short period of time to implant the traditional bare metal stent or the bio-engineered stent, which requires only four weeks of double anti-platelet medication. Those without such considerations could use the drug-eluting stent that requires a year or more of medication.

As Yau belonged to the latter group, the drug-eluting stent was successfully implanted, and he will need to be on a single anti-platelet medication for the rest of his life. Although he narrowly escaped a potentially fatal health crisis, he still has work to do to protect his health. Leung urged Yau to stop smoking and to carefully manage his high cholesterol levels and hypertension.