Recently a good friend underwent multiple ‘stenting’ for heart artery blockages that prevented what could have been a major heart attack. Having been involved in the ‘business’ of cardiac medicine and surgery for almost 40 years, I think that perhaps it is time to try and explain some, and I emphasise the ‘some’ part of what we do to my readers. I have over the years taught this subject to nurses, medical students, medical trainees and to physicians that are preparing to become experts in this field.

More importantly, I have tried to explain most of the procedures performed in cardiac medicine and surgery to patients who were going to undergo such procedures. However, much I might try to simplify what we do, it is still difficult for most people to really understand what exactly is being done. I hope that with some very basic information that I will provide, interested readers can then read up further on these issues on the Internet.

First the basics. The heart is a simple pump that pushes the blood around to provide energy to different parts of the body. Like all other parts of the body, the heart also supplies itself with energy through blood vessels known as ‘coronary’ arteries. These are essentially tubes that start big and branch out becoming smaller like the branches of a tree. In humans there are two major arteries -- the right coronary artery and the left main coronary artery that supply the heart. These then branch off into smaller arteries. The left main artery gives off two major branches, the left anterior descending (LAD) and the left circumflex. These two major branches on the left and the right coronary artery are the three major arteries and when all have blockages, that then is called triple vessel disease.

Unlike many other organs in the human body, the heart has one major disadvantage. Even if only a branch of a major blood vessel (artery) gets blocked, almost always by a blood clot sitting on top of a pre-existing blockage, some part of the heart muscle being supplied by that branch will eventually suffer irreversible damage. This damage is called a ‘heart attack’ or in medical lingo a ‘myocardial infarction’. Here the similarity to the tree mentioned above becomes important. Bigger the branch that is blocked, greater the damage and if a primary artery gets blocked, the damage could lead the heart to fail causing death.

In essence, the entire emphasis of medicine concerning diseases of the arteries of the heart (coronary artery disease) is to prevent or ‘abort’ a heart attack and if it occurs, to limit the damage it produces.

A heart attack is the end point of coronary artery blockages but before that happens, there can be warning signs. The most important warning sign is ‘angina pectoris’ or simply put it is a feeling of pressure, squeezing or pain in the chest that usually occurs during physical activity and subsides during rest. What happens is that some part of the heart muscle that was doing fine when the person was resting is not getting enough blood to fulfil its energy needs during exercise or exertion. This lack of blood/energy/oxygen produces the uncomfortable feeling identified as angina. Angina that occurs predictably and then subsides predictably is known as ‘stable angina’. Treatment of this type of angina is primarily by medicines that try and make the heart work less hard and do with whatever energy is available to it.

If angina persists in spite of medicines, or gets worse then some sort of ‘intervention’ is required. Treatment with medicines as mentioned above is aimed at decreasing the amount of work the heart does. Interventions on the other hand aim to bring more blood to those parts of the heart that are not getting enough blood for it to work adequately.

Interventions are of two types. Surgical interventions are performed by cardiac surgeons and are based on using alternate blood vessels from other parts of the body to re-route the blood past the blockages in the heart arteries. This operation or procedure is known as ‘coronary artery bypass grafting’ (CABG) -- due to this acronym, the procedure is often called a ‘cabbage’. A CABG requires the alternate grafts to be sown into place directly on the heart.

The other type of interventions are performed by ‘interventional cardiologists’ using techniques based on passing needles through the intact skin into arteries and then threading wires and catheters into arteries through these needles. All such procedures are lumped under the term ‘percutaneous catheter interventions’ (PCI). To bring more blood, PCI can open up the artery from the inside by inflating a balloon at the place where the artery is blocked. This procedure is called a ‘balloon angioplasty’. Angioplasty is now usually combined with placement of a thin wire mesh tube (stent) that is opened up along with the angioplasty catheter to keep the open artery open.

What used to be called ‘unstable’ or unpredictable or excessive angina in the past has now become a part of what is called an ‘acute coronary syndrome’ (ACS). ACS, the sort of angina just mentioned, also includes heart attacks where the Electrocardiogram (ECG) does not show major changes (non-ST segment elevation MI: non-STEMI), or heart attacks with obvious ECG changes (STEMI). All patients with ACS should undergo ‘coronary catheterisation’ to determine the extent and nature of the coronary blockages. Severity of blockages is expressed as a percentage of the artery lumen that is blocked. Anything above 50 per cent is significant and above 75 per cent is deemed critical.

Patients that have not yet gone on to develop a heart attack can be treated by CABG or by PCI depending on the extent and type of coronary blockages that are present. However, once there is evidence of an evolving heart attack then PCI if possible is the preferred method of treatment.

Treatment of what within the spectrum of ACS is called STEMI depends on time between the start of chest pain and arrival in the hospital. Once the blood supply to heart muscle is interrupted, irreversible damage occurs in about six hours. In patients that arrive ‘early enough’, PCI is again the best treatment available. In patients with STEMI, PCI is usually preceded by use of special medicines to break up the clot before stent placement.

For coronary disease patients that have symptoms not controlled by medicine but who are not in the process of having a heart attack, the treatment depends on the extent of blockages, the arteries involved and the overall condition of the patient. Generally, patients with blockages of the left main artery, severe blockages of all major arteries with previous heart attacks that has diminished heart function and diabetic patients with more than two blocked arteries are better off with a CABG rather than a PCI. However, many patients that will do better with a CABG will opt for a PCI to avoid the pain and discomfort associated with major surgery.

Finally, one important clarification. PCI/stent placement is not heart surgery and physicians performing these procedures are ‘cardiologists’ and not heart surgeons.