RISKS AND BENEFITS
The whole point of having a heart operation is to get rid of your symptoms and to increase your life expectancy. It is a major undertaking, but is becoming increasingly safe nowadays as research and technology move forward. Most cardiothoracic centres in this country perform between four and ten heart operations every day. This means that over 30,000 people have heart surgery in this country every year.
For most of these people, it puts an end to their symptoms, whether angina or breathlessness, and brings a vast improvement in their quality of life, and in many cases a complete return to normal. Ask anybody who used to get angina what it feels like to be free from it again, and you will have an idea of the kind of relief surgery can offer. It appears to be really easy these days, because most people whose cases are straightforward go home about five or six days after their operation. Nevertheless, heart surgery is still a major operation, however skilled or advanced we become at it, and it is important that, for all its benefits, the potential risks are taken seriously.
When you are going to have a heart operation, your surgeon will discuss the risks with you, usually at the clinic when you first see him or her, and again the day before the operation. You will be asked to sign a consent form during one of these visits. This is a declaration by you that you understand the nature of the operation, and the risks of death and other complications associated with it.
It is very important that you and your family understand the risks involved when you sign the consent form. Doctors talk about risk in terms of the chances of death during the operation, and the chances of developing a serious complication such as a stroke. There are, of course, a great number of potential complications but most of these are minor, such as wound infections, chest infections and constipation. The major complications such as stroke and temporary kidney failure are always discussed in detail with the patient.
The two main factors that contribute to the risk of your operation are the type of operation itself, and your health before the operation. Obviously some operations take longer than others, and some are more complicated than others. In general, the longer and more complex your operation, the greater the risk.
More importantly, the health of the patient before the operation must be carefully considered. Someone who has no other medical problems, apart from that for which they are having the operation, would be considered ‘low risk’. On the other hand, if you have other serious medical problems, such as lung disease or kidney disease, your risks are going to be higher. The condition of your heart also needs to be taken into consideration. If you have never had a heart attack, and it is working well as a pump, you are at lower risk than somebody who may have some scarred areas of muscle from heart attacks and whose heart is less efficient.
The surgeon will take these things and many other factors, such as your age and whether you still smoke, into consideration, and calculate a percentage risk for you personally, for both death and serious complications. The figure quoted is carefully calculated for each individual patient according to a large number of different features. He or she will tell you this figure and explain why before you sign the consent form. For most patients undergoing heart surgery the risk of both of these tragic eventualities is between two and three per cent.
Heart surgery is offered to patients for one (or both) of two main reasons: these are for symptomatic benefit or prognostic benefit. Symptomatic benefit is very easy to understand, and applies to people who get severe angina or breathlessness despite maximal drug therapy. It is all related to quality of life and, if you find that the kind of life that you would like to lead is severely restricted, the chances are that you should undertake the risks of surgery. If you are offered prognostic benefit, it means that your chances of living longer are better with surgery than without it, and are usually related to the severity of the disease as shown on the angiogram.
It is difficult to offer prognostic benefit to patients over the age of 70, because this group are more likely to have unrelated illnesses and disease, which may reduce life expectancy in themselves. Obviously, some patients fall into both categories.
WAITING TIMES AND CANCELLATION
The very nature of cardiac surgery makes it very unpredictable. There are very many ‘emergencies’, each of which takes up an operating theatre slot, and a bed in the intensive care unit (ICU) or ward. This has two effects on you as the routine waiting-list patient:
• The waiting time that you are given may not be accurate and, even when you get given a date for admission, you may find that when you ring the ward in the morning as instructed there is no bed for you and you can’t come in. This can be very frustrating for you, because you may well be frightened or apprehensive about the operation, and have worked yourself up for it. The staff are all aware of this and do not cancel admissions unless it is absolutely necessary, but if emergency cases have taken the beds it cannot be avoided.
• When you have been admitted for your operation, there is still a chance that your operation may be cancelled until another day. Again, this is usually caused by an emergency case taking your operation slot, or sometimes if there are no beds on the ICU. When you have had your operation, you need to go to the ICU, usually for one night. You are usually expected to move back to the ward the following day. This makes a space for the next patient to have his or her operation and go to the ICU. Sometimes, a patient might be a bit slow to wake up, or may need an extra day or so on the ICU. This effectively prevents another person’s operation from being performed. Unfortunately, it is impossible to predict who will stay more than one night, but we still need to allocate patients to specific operating lists. This is why there are so many cancellations. If you are cancelled, however, you will not usually be sent home, but be put first on your consultant’s next operating list. This may be the next day, but sometimes you might have to wait a little longer. Sadly, there is nothing any of the staff can do to prevent this.
PREPARING FOR SURGERY
Unless you have a particularly complicated problem, which means that you need some specialised investigations as an in-patient, you will normally be admitted to hospital the day before your operation. Some hospitals ask you to attend a pre-admission clinic the week before. Either at this clinic or in hospital the day before your operation, there are a number of routine tests and checks that you will have to go through (see the box). The medications that you are taking will also be checked by the doctor, because there are some that need to be stopped before surgery.
There are not many essentials that you need to bring to hospital with you, but bear in mind that you will be there for about six days, and wardrobe and locker space can be quite limited. Make sure that any pyjamas or other clothes you bring are not too tight fitting, particularly around the neck, because you will have a number of scars and drips.
For women, a supportive, well-fitting cotton bra will help you to be comfortable, even more so if it is one size too big. Apart from your washing kit and something to read, there is nothing else essential. After a couple of days you will be walking around freely, so some casual clothes are useful. These can always be brought in by a friend or relative at that stage.
The ward nurse will familiarise you with the ward environment, and explain to you about shaving your chest for the operation (for a man), and your legs if you are having coronary artery bypass surgery. In some hospitals a member of the nursing staff will actually shave you. Whether it is you or one of the staff, it is important to avoid cuts and abrasions as they are a potential source of infection. He or she will also explain to you about the premedication (pre-med), which is a drug that you are given to relax you about an hour before your operation. Sometimes it takes the form of a tablet, and sometimes a small injection.
You will be seen by a doctor fairly soon after your admission, whose job is to ‘clerk you in’, and check that everything is as it was when you were seen in clinic. They will also examine you physically to confirm that you are fit for an operation. A word of warning: if you have a cold or flu it is very important that you tell somebody on the ward, either a nurse or a doctor. If you do have either of these conditions, you will have a much higher chance of developing a chest infection while on the ventilator, and so your operation should be cancelled or postponed until your are better.
Routine blood tests, ECG and chest X-ray are performed and checked by one of your doctors to make sure nothing has changed, and you will be asked to sign a consent form after all the details and risks of the operation have been thoroughly explained to you.
You will then be visited by three people who have a key role in your care:
1. The surgeon: he or she will usually come to see you on the evening before your operation to answer any final questions, and to make sure everything is in order.
2. The anaesthetist: he or she is one of the first people you will meet when you arrive in the operating theatre the next day. It is his or her responsibility to see that you are fit for a general anaesthetic.
3. The ICU nurse: when you wake up after your operation, you will be in the ICU. This is a very intimidating environment with lots of people and noises. You will have a tube in your throat helping you breathe, and you will be connected to several drips and machines. The ICU nurse will explain all this, help to reassure you and answer any questions that you may have.
You need to be starved for at least six hours before your operation. If you are going to theatre in the morning, you are simply told not to eat or drink anything from midnight. If your operation is in the afternoon, you are usually allowed a light breakfast. It is vital that you do not break this rule and do not eat or drink anything, because it is dangerous for you, and your operation will have to be cancelled. You are allowed to brush your teeth and have mouth washes, however. People with diabetes will often have a drip put up before the operation, and blood sugar will be carefully monitored by the ward staff during the period of starvation.
If you have had an operation before you will know what a general anaesthetic (GA) is. If not, it simply means that you get put to sleep for your operation so you do not feel anything, and then woken up at the end of it. This is performed by a mixture of gases and intravenous drugs, and while you are asleep a machine called a ventilator breathes for you. This is necessary because one of the anaesthetic drugs paralyses all your muscles including the ones that you use to breathe.
When you arrive in the operating department, you will be greeted by a member of the operating team, usually a theatre nurse or operating department practitioner (ODP). This person will welcome you and make you feel comfortable before transferring you to a room adjoining the theatre, called the anaesthetic room. This is where you will meet your anaesthetist again, and where you will be put to sleep for your operation. The theatre nurse or ODP will ask you a number of questions and go through a series of checks to make sure that everything is in order (including checking that you are the right patient!). In this room, you will have two drips put into your arm, one in a vein for the anaesthetic drugs, and one in an artery in your wrist which measures your blood pressure continuously. You will also be attached to an ECG monitor. At this point you are ready to be put to sleep, and the anaesthetist will give you oxygen through a mask for a minute or two. A drug is then injected down through your drip which will make you go to sleep very quickly. It is important to realise that this is the last thing you will remember before you wake up in ICU.
When you are asleep, your muscles are paralysed, so you will be connected to the ventilator which will breathe for you. Before you go into theatre, several other tubes and drips will be put into you, but of course, you will not feel any of this. Among these are a urinary catheter, which is a tube put into your bladder, and a ‘central line’, which is a drip put into one of the veins in your neck. This is similar to the drip in the vein in your arm, but usually has three or four channels to allow the infusion of several different drugs that you may need during and after surgery. You are now ready for your operation!
Before it is possible to perform an operation on the heart, several special factors must be taken into account. One is that the heart is a beating organ, and does not stay still, which obviously creates problems in performing delicate surgery. In the 1950s a machine was developed which enabled surgeons to stop the heart and lungs while the operation was being done. It is called the cardio
pulmonary bypass machine, and is the main reason why heart surgery has only been possible for such a short period of time compared with other branches of surgery. Although the technology continues to be improved all the time, the principles involved are the same now as they were then.
Although it has been an incredible breakthrough for heart surgery, the basic principles behind it are quite simple. The heart pumps blood to the body and the lungs, so if you are going to stop the heart and lungs, what do you need to do? The answer is, of course, artificially to do the job of the heart, so you need to have a pump. You also need to make sure that oxygen is put into the blood, because the lungs are stopped, so you need an oxygenator. If you can make a machine to fulfil those requirements, you are well on your way to developing the heart–lung machine.
The machine basically works as follows: the surgeon puts a big pipe (venous line) in the right atrium, which collects all the blood returning to the heart through the vena cava. He or she puts another pipe into the aorta near the heart (aortic line). These two pipes are connected by lengths of tubing which pass through the machine.
When the machine is switched on, blood is siphoned down the venous line into the machine where it is oxygenated, and then pumped back into the aortic line. A completely closed circuit then exists, and the heart and lungs can be stopped, because their jobs are being performed artificially. The heart is stopped either electrically or chemically, as we shall explain later, and the lungs are stopped by getting the anaesthetist to switch off the ventilator. Oxygen-rich blood is being circulated around the body to all the organs as required for normal function.
The cardiopulmonary bypass machine is operated by a highly trained specialist called a perfusionist. It is the perfusionist’s job carefully to control the machine during the period of cardiopulmonary bypass, when the heart and lungs are switched off. The perfusionist can control several things, such as the rate of flow of the pump, and the temperature of blood passing through. Temperature is important, because the metabolic rate of the body is much lower when cold, and this helps to protect the heart during the time it is not beating, because it requires fewer nutrients and expends less energy.
Traditionally, most heart surgery has been performed at lower temperatures than normal body temperature, commonly between 28°C and 34°C, depending on the preference of the individual surgeon. Much research has been directed at ‘warm heart surgery’ over the last few years, because it was thought to confer advantages of its own compared with the advantages of cooling as outlined above. It has been scientifically shown that certain forms of warm heart surgery are safe, and for this reason it is becoming more and more widely used. Whichever temperature method is used is safe, however, and makes little difference to the rest of the operation.
PROTECTING THE HEART
Unfortunately, when a heart is stopped, its cells will start to get damaged unless there is some way of protecting them. Low temperatures are one way, but this alone is not enough.
The concept of ‘myocardial protection’ has therefore been developed to deal with this problem, and nearly all heart operations use this. By stopping the heart in a certain way, its energy expenditure and requirements are reduced, and the minimum amount of harm is caused, effectively protecting the heart muscle. There are two broad ways of stopping the heart during cardiopulmonary bypass – one is chemical and one electrical:
• The chemical method involves infusing a solution called cardioplegia directly into the heart. This solution can be either blood or a clear fluid, can be warm or cold, and contains large amounts of potassium. The cardioplegia is forced down the coronary arteries so that it gets to bathe every cell in the heart. The potassium causes the heart to stop beating for a short period of time (up to about half an hour), during which the surgery can take place. The heart starts beating spontaneously once this has worn off, and if the operation has not quite finished, some more cardioplegia can be given to keep the heart still. The advantage of cardioplegia is that it can be topped up as many times as required, which is very useful in particularly long or tricky operations. It is usual to give a repeat or top-up dose every 20 to 30 minutes to keep the heart fully still and protected.
• The electrical method is called intermittent fibrillation, and involves connecting two leads from a machine (called a fibrillator) directly to the heart. When the fibrillator is switched on, the heart stops beating and develops a very fine tremor. The heart can be defibrillated back to beating again with a different machine called a defibrillator. This is done between each bypass graft, to give the heart a rest from the tremor, explaining why the technique is called intermittent.
It does not matter which method is used because they both work very well. Although individual surgeons have their own preferred method, research has not yet clearly demonstrated a great advantage of any one method over another. Most surgeons use the method with which they are most comfortable, but retain the ability to use an alternative technique should the need arise.
An increasing number of operations are now being performed on the beating heart without the need for cardiopulmonary bypass. This is known as off-pump coronary artery bypass or OPCAB and is dealt with later.
There are a number of potential complications that may occur during cardiac surgery, but fortunately they don’t arise very often. As technology and knowledge advance, these operations get safer and safer all the time. Each individual operation has its own particular problems, but many of these are anticipated, and allowed for when calculating individual risks. There are some complications that can occur with any cardiac procedure (see box).
Many of these problems can be attributed to the period of time spent on the heart–lung machine. Although it is a wonderful invention, without which cardiac surgery would barely exist, it is not a normal physiological environment for the body, and some organs may suffer from it.
Problems coming off the heart–lung machine
The machine takes over the function of your heart and lungs for a variable period of time, while you have your surgery. When the surgery is finished, the heart and lungs need to be started up again, so that the mechanical support can be withdrawn. Usually this is not a problem, but if the heart is quite poorly, it may not be able to start up strongly enough straight away. If this is the case, there are two ways in which the heart can be given some support. The first is with strong, specialised drugs, and the second is with mechanical devices. The most common of these devices is called an intra-aortic balloon pump (balloon pump for short). Less commonly used are ventricular assist devices (VADs).
The drugs that are usually used either increase the force with which the heart muscle contracts, or increase the blood pressure. The balloon pump sits inside the aorta, and eases the work that the heart has to do to create an adequate blood pressure as well as improving the blood flow down the coronary arteries.
If you return to the ICU with either of these means of support, the plan is to ease down their influence gradually over the next few days while the heart recovers, until they can be taken away completely.
There are two main reasons for bleeding excessively after your operation. One is that the components of the blood that cause it to clot are not working properly. This can be fixed by giving these components artificially through drips.
The second is that there is bleeding from small blood vessels that have been cut during the operation, but which have remained hidden when the surgeon was finishing the operation. The only solution to this is for you to go back to theatre so the surgeon can stop these vessels bleeding. This problem affects between two and five patients in every 100. An important part of all heart operations is to leave one or more drains in the chest cavity at the end of the operation. This allows blood to escape so it does not build up and put pressure on the heart, and allows accurate measurement of blood loss. These drains come out of small holes just below your chest scar.
A small number of patients have a stroke while they are having their operation. This means that the blood supply to a part of the brain has been interrupted, either because a blood vessel has become blocked by a clot or because a blood vessel bursts and causes bleeding into the surrounding tissue.
Other patients may suffer from a stroke resulting from the presence of severe atherosclerotic disease (furring up) of the main blood vessels that supply the brain. Patients who are known to have this disease usually have an ultrasound of these blood vessels in their neck to see whether anything needs to be done before their heart surgery. It is very difficult to predict who may be affected in this way, so everybody is warned. It may be a small stroke from which the person completely recovers, or it may be a severe one. How serious the outcome is depends on the amount and exact location of the damage.
It is not uncommon for a patient to be slow to wake up after heart surgery, or to be violent and confused. This results partly from the effects of the heart–lung machine and partly from the effects of the anaesthetic. This is not the same as a stroke, and a full recovery is normally reached after a few days. Nevertheless, it can be quite disturbing for the relatives, and reassurances from the doctors and nurses are often required.
A severe stroke may result in paralysis down one side of the face or body. This may be permanent, or the person may recover to a degree, with the help of physiotherapy.
A small number of people will experience this problem after their operation, but it is usually slightly easier to predict the individuals who face an increased risk than it is with strokes. People with poor kidney function before the operation are more likely to have this failure, and once again this is probably related to time on the heart–lung machine. If you develop kidney failure after the operation, you may have to spend a few days on a kidney machine until they start working again.
This is a much more common problem, and usually occurs once you have come off the ventilator and started breathing for yourself again. Lying down for a long period of time, as you do when you have an operation, and staying in bed afterwards, causes sputum to build up in your lungs.
As a result some areas of the lungs may collapse. This is particularly likely in smokers, especially those who have smoked right up until their operation. For this reason it is extremely dangerous to smoke in the couple of days before surgery. Chest infections are treated by vigorous physiotherapy, and antibiotics if an infection develops. Sometimes, however, if things do not improve, you may need to go back on the ventilator for a short period of time.
Unfortunately, these are not as rare as they might be and every possible precaution is taken to avoid them. Minor ones tend to heal on their own if treated with antibiotics and meticulous wound care. Major ones can be a real problem, and may even prevent the breastbone from healing. In this case, one or more extra operations are required to clean the infected tissue away and re-close the wound. Overweight people, people with diabetes, people with breathing problems and people on steroids are more likely to develop complications of wound healing.
There is a relatively new technique now available for treating deep-seated infections in both chest and leg wounds. It involves a specialised sponge being inserted into the wound (often in the operating theatre), which is then connected to a powerful suction machine. This machine is often small and portable, allowing ease of movement around the ward. The sponge usually needs to be changed every three days until the infection has settled, after which time the wound can be closed. Sponge treatment of deep wounds is much more comfortable for the patient and has revolutionised the treatment of such conditions.