WHAT IS CARDIAC CATHETERISATION?
Cardiac catheterisation is performed prior to heart surgery to determine if surgery is necessary and if so, what surgery to be performed. An interventional cardiologist will carry out this procedure and he may also carry out additional interventions such as balloon angioplasty and stenting.

The Procedure
Usually performed as an outpatient procedure and the patient is able return home the same day. Prior to catheterisation, medication is given for relaxation. A needle is inserted into a vein in the hand for the necessary intravenous medication. In the cardiac catheterisation laboratory (cath lab) sticky electrodes are applied for an ECG. The insertion site, usually in the groin, is antiseptically cleansed and local anesthetic injected at the site.

Left heart catheterisation is used to investigate the coronary arteries. A special needle is inserted into an artery at the groin injection site through which a flexible wire is inserted. The needle is removed and a catheter sheath is slipped over the wire and into the artery. The wire is removed, a catheter (a fine hollow tube) inserted through the sheath into the artery and manipulated into a coronary artery. An iodine containing fluid (contrast dye) is then injected into the coronary artery under pressure to obtain the coronary angiogram.

Right heart catheterisation is used to study the valves and chambers of the heart. The special needle is inserted into a groin vein. In a manner similar to that described above, a catheter is inserted into the vein and manipulated toward the heart and into the right atrium. The contrast dye is injected and shows up on X-ray and helps to outline the interior of the heart, the atria and ventricles. The pressures in the chambers of the heart are measured and blood samples may be taken from the catheter to measure the level of oxygen in the various heart chambers.

Possible Complications
Most complications of cardiac catheterisation are minor such as hematoma (blood collection) in the groin area, transient cardiac arrhythmia or transient low or high blood pressure. More serious complications include heart attack, large groin hematoma, loss of pulse to the limb, stroke, perforation of the wall of the heart or an allergic reaction to the contrast dye. The chance of a serious complication necessitating immediate cardiac surgery is nevertheless to be taken seriously, and hence, these procedures are carried out only in hospitals with heart surgery capability.

POST OPERATION
The patient will be observed to have not developed a hematoma at the needle insertion site. Bruising at the needle site is not unusual and is of little significance. The pulse, temperature and feeling in the arm or leg may also be checked. If you notice swelling at the needle site or feel pain, cold or numbness in the arm or leg, it is important that you inform the nurse immediately.

Though during catheterisation, your doctor may get a preliminary idea of your problem, a final determination is made after your doctor reviews the X-ray films, movies and other data taken during the catheterisation. Later your doctor will review with you the findings of the catheterisation and make a recommendation for further care such as a change in medication or heart surgery.

WHAT IS CORONARY ANGIOPLASTY?
Coronary angioplasty is used to 'squash' the atheroma (fatty tissue) in narrowed arteries, allowing the blood to flow more easily.

The Procedure
Although the operation is carried out under local anaesthetic, it involves inpatient stay in the coronary care unit.

A catheter is inserted into an artery in either the groin or the arm. The operator then uses X-ray screening to help direct the catheter to a coronary artery until its tip reaches the narrowed or blocked section.

A sausage-shaped 'balloon', mounted on the end of the catheter, is then gently inflated. This flattens the atheroma that is narrowing or blocking the artery. After one or two minutes the balloon is deflated and removed and an enlarged channel remains, allowing the blood to flow more easily to the heart muscle. Hence, this procedure is otherwise referred to as 'balloon angioplasty'.

Although similar to a cardiac catheterisation test, this procedure can take much longer to manipulate the balloon catheter into the exact right position. While the balloon is being inflated, the patient may experience symptoms similar to that of angina (heart attack pain), but the pain eases very quickly when the balloon is deflated.

Coronary angioplasty cannot be used for all people with coronary artery disease. Before a patient is accepted for coronary angioplasty, they will need to have a cardiac catheterisation test (or angiogram).

Angioplasty can also be used for patients who have had coronary bypass surgeries and in whom the grafts have become narrowed.

COMPLICATIONS
Nine out of ten angioplasty operations are successful. Occasionally the treatment completely blocks off the artery which was previously narrowed and the patient has to undergo immediate bypass graft operation.

ANGIOPLASTY WITH STENT IMPLANT
After angioplasty, the affected arteries may narrow again, usually within four to six months, a condition known as 'restenosis'. This can be prevented by using 'stents' (a short tube of stainless steel mesh) inserted at the part of the artery to be widened by angioplasty.

Once the balloon tip of the catheter has been inflated, the stent is slightly expanded to hold open the narrowed blood vessel and is then left in place after the balloon catheter has been removed.

The stent helps to hold the vessel open. Stents can also help to reduce the risk of complete blockage of the coronary artery which occasionally happens when an angioplasty is being carried out. The patient is given anti-platelet drugs at around the time of the angioplasty and these reduce the risk of clots forming around the new stent.

Post Operation
After the angioplasty, the patient's blood pressure and heart rate will be monitored for four to eight hours along with the pulses in the feet or arm in a special coronary care unit. The site where the catheter was inserted (the 'puncture site') will also be checked. If the puncture site was in the groin, the patient will stay in bed lying on his back for a few hours after the operation.

WHAT IS CORONARY BYPASS SURGERY?
Coronary artery bypass graft (CABG) surgery is an operation designed to detour blood around a narrowed segment of a coronary artery in an effort to restore blood flow to the heart muscle. Usually a vein graft from the leg is used for the bypass, however other vessels may also be used for the graft.

The Procedure
The blood vessel to be used for the graft comes from another vessel from the body and a section of a vein from the leg or the internal mammary artery (an artery that runs down the inside of the chest wall) is used.

In the course of the operation, the surgeon has to make an incision in the middle of the chest and split the breastbone lengthwise. While the heart is being operated on, the flow of blood through the heart and lungs is temporarily stopped by applying a special solution of potassium to the heart. During which time, a heart lung bypass machine takes over the heart's job of pumping and the lungs' job of breathing.

Post Operation
After the operation, there will be a scar down the length of your breastbone and discomfort in the chest which usually lessens over the next few weeks. If a vein has been removed from the leg, there will also be some discomfort and swelling in that area. However it is common for patients to sit up in bed a day or two after the operation and return home after a week.

Complications
Complications that can occur include postoperative bleeding, stroke, irregular heart rhythm (arrhythmias), areas of collapsed lung (atelectasis), wound infection and death in some cases.

SURGERY TO IMPLANT A PACEMAKER
A normal healthy heart has a regular beat within a range of 50 and 100 beats a minute. The heart has four 'chambers', the two upper chambers are called the 'right atrium' and the 'left atrium' (the atria) respectively, and the two lower chambers are the 'right ventricle' and 'left ventricle'.

The heart has a 'natural pacemaker' which is made up of cells on the right side of the heart, which transmits regular electrical impulses across the two atria. Where the atria meets the ventricles (the chambers which serve as a 'pump') there are further cells called the atrio-ventricular node (‘AV node'). As the electrical impulses pass from the AV node to the ventricles, they stimulate a contraction of the heart, which is also a heartbeat.

A patient will require a pacemaker to be implanted in cases of 'heart block', or where there are certain types of irregular heart rate or heart rhythm. In ‘heart block’, the electrical impulses of the heart are slowed down or delayed by an interruption in the heart's normal electrical activity.

At its most advanced, the patient can experience a 'complete heart block', where no electrical impulses cross to the ventricles at all, thereby causing reduced blood flow which may cause breathlessness, fainting, blackouts or even confusion. Heart block is usually caused by heart disease or ageing of the heart.

The Procedure
To treat heart blocks, a pacemaker mechanism is inserted into the chest to help stimulate the heart electrical impulses. There are two possible procedures for this:

Complications
There is a small risk of infection at the site of the pacemaker. If that happens, the pacemaker will need to be removed. There is also a small risk of air leaking from the lungs to the chest during the operation to implant the pacemaker. Chest x-rays taken before a patient leaves the hospital will reveal whether this has happened.

Pacemaker Registration Card
After a pacemaker has been implanted, the patient is given a pacemaker registration card. This has details of the make and model of the pacemaker and it must be made known to any medical professional who is treating the patient, including doctors and dentists.

Patients who have had a pacemaker implanted are advised of the following precautions:
1) They are not to undergo MRI (magnetic resonance imaging) tests.
2) That their pacemakers may trigger alarms with metal detectors, such as in the case of going through airport security checks.

HOW DO PACEMAKERS WORK?
A pacemaking system is made up of a pulse generator (the actual pacemaker) and either one or two electrode leads. Pacemakers with one lead are called “single chamber pacemakers”. Pacemakers with two leads are “dual chamber pacemakers”.

The pacemaker has two parts: the power supply, or batteries, and the electronic circuitry. It is completely covered in metal and sealed to prevent body fluids leaking into the unit. The whole pacemaker weighs only 20 to 50 grams (1 to 2 ounces) and is smaller than a matchbox. Most pacemakers are powered by lithium batteries and last between six to ten years before they need to be replaced.

The electronic circuit in the pacemaker draws energy from the batteries and transforms this into a series of electrical impulses. These are conducted down the electrode lead to the heart. Each electrical impulse discharged by the pacemaker stimulates the heart to contract and produce a heartbeat. The rate at which these electrical impulses are sent out is called the “discharge rate”.

Some pacemakers discharge electrical impulses at a fixed rate but almost all work “on demand” – meaning that it will discharge electrical impulses at the fixed rate only when it senses that the heart has missed a beat, is beating too slowly, or if there is no natural heartbeat.

Some types of pacemakers can speed up the exchange rate when necessary, for example, when you are exercising.

Most pacemakers can be programmed to deliver electrical impulses to the heart at a rate that suits your particular needs. Even after the pacemaker has been implanted, it can be re-programmed if necessary by electromagnetic signals from an external programmer. Some pacemakers have a sensing device which can recognise the rhythm of the heart and respond by automatically changing the discharge rate, without any external programming. Some pacemakers can also analyse and store information about your natural heart rhythms. This information can be retrieved when you attend your follow-up appointments at the pacemaker clinic.

(This article first appeared in Parkway Medicine, April 2002)