In developed countries such as Singapore, heart attack is major killer. This is because our food is rich in fat and our life style is sedentary.
This leads to deposits of cholesterol in the arteries of our hearts. When this happens, we become at risk of getting heart attack.
Ordinarily, when a segment of an artery is partially blocked, it can be treated with a stenting procedure. In essence, a wire is passed down the narrowed segment, a 'balloon' follows and is inflated to open the blocked segment.
Then a 'stent', which is a tube made of wire mesh, is then placed in the segment to keep the vessel opened. This procedure is now commonly performed safely by cardiologists who are trained appropriately.
When the narrowed segment is not treated, it may lengthen or become completely blocked. The longer the blockage stays, the harder it becomes. This is because calcium, which is like rock, will be deposited in this cholesterol plague over time. The longer the plaque stays, the harder the blocked segment becomes.
When the artery becomes completely blocked and hardened, it is like pouring concrete down the pipe. The hardened concrete-like cholesterol does not allow the ready passage of wire, balloon or stent. Therefore, chances of successfully opening this artery with stents are only 50 per cent.
Patients are then left with the option for coronary artery bypass operation or medical treatment only.
New techniques have been developed to open up completely occluded arteries. It is known that when a segment becomes completely blocked (for example the Right Artery in figure 1), very fine hair-liked capillaries called 'collaterals' may open up beyond the blocked segment. These capillaries connect the blocked artery some distance below the blockage point to the normal Left Artery.
In figure 2, the Left Anterior Descending Artery can be seen to give rise to a small capillary connecting to the right artery beyond its blockage point.
This is like when a main expressway is congested, cars will use the secondary roads to go pass the congestion.
It was further found that these fine channels allow the passage of wire for stenting. Therefore, instead of passing the stenting wire from above the blockage, the stent wire is now passed from the Left Artery into the capillary.
It will traverse the capillary and join the Right Artery. Finally it will approach the Right Artery blockage from below. This is seen in figure 3 where the stent wire makes a full loop.
The rest of the stenting can then be completed and the artery opened (Fig. 4). This highly skilled and complex procedure is called the 'Retrograde' approach.
This means that the completely blocked artery can be opened without surgery.
Using retrograde and other techniques, Dr Tan has managed to achieve a success rate of 85 per cent for opening up completely blocked arteries, thereby saving many patients from the stress and risks of bypass operation.
This article was contributed by Dr Tan Chong Hiok, Senior Consultant of Cardiology at the Parkway Heart and Vascular Centre
He is also the Senior Consultant and Director of Catheterisation in Changi General Hospital, Senior Visiting Consultant for National Heart Centre Singapore and Visiting Consultant for Tan Tock Seng Hospital.
Dr Tan is currently the only cardiologist who is duo-accredited in interventional cardiology and echocardiology.