Adult Cardiac surgery is surgery on the heart and the large blood vessels in the chest in patients above the age of 16 years. It is most often done to treat complications of narrowings of the coronary arteries due to ‘hardening’ of the blood vessels. It is also practiced to treat disease of the heart valves caused by infection, rheumatic heart disease, calcification and narrowing, or when the valves become stretched up and start to leak.
Coronary Artery Bypass Grafting
Coronary artery bypass grafting surgery remains the commonest heart operation undertaken in the UK. The heart muscle is highly specialised and pumps blood around the body – it has to work very hard and to do so it receives its energy from oxygen rich blood through blood vessels called coronary arteries. In patients with heart disease these blood vessels may become narrowed through a process that involves hardening and thickening of the arteries (called atherosclerosis). This can restrict the amount of blood entering the heart. When the heart muscle does not get enough oxygen-rich blood supply, a patient may suffer with the symptoms of angina (which is usually chest pain, chest tightness or shortness of breath). On occasions the blood vessels may become completely blocked and cause a heart attack (also called a myocardial infarction).
When there are serious or multiple narrowing’s or blockages of the coronary arteries, patients can often benefit from coronary artery bypass surgery, which is undertaken by cardiac surgeons.
Coronary artery bypass graft surgery involves taking an artery of vein from elsewhere in the body and attaching (grafting) it to the diseased artery above and below the point of narrowing. This allows the blood to flow around (bypass) the blockage and reach the heart muscle without restriction.
In other circumstances blockages may be treated by stretching them open with a balloon and a wire frame called a stent. These procedures are undertaken by cardiologists through small incisions in the groin or arm (so called percutaneous coronary intervention, or PCI for short). Far more patients used to be treated by coronary artery surgery than percutaneous coronary intervention. Now more patients are treated by coronary intervention than surgery. Recent internationally accepted guidelines have given clear recommendations about which patients are best treated by coronary artery surgery and which by PCI. We expect that when these guidelines have been put into practice they will lead to an increase in the overall number of patients who receive coronary artery surgery. This is because, for many patients, coronary artery surgery has been shown to be a more effective way of treating the symptoms of angina and prolonging life than PCI or treatment with medicines alone.
It is good that patients with coronary artery disease have a series of possible treatment options open to them. As well as coronary artery surgery and PCI there is also the option of continued management with medicines alone, which may offer relief or control of symptoms without exposing patients to the risk or inconvenience of a hospital admission or an operation. Some groups of patients, such as those who are in the process of undergoing a heart attack, are best treated by a PCI – in this situation a successful procedure is associated with much better outcomes for patents and coronary artery surgery is not really an option. In other groups such as those with tight narrowings in all the major coronary arteries and some previous damage to the heart muscle, coronary artery bypass surgery is usually the best option as it leads to better life expectancy and better relief of symptoms that either on-going medical management or PCI. There is a further group of patients in which either PCI or CABG surgery may be considered; CABG will often be associated with better long-term relief of symptoms and a longer life expectancy, but a slightly higher risk from the procedure and a longer recovery time. PCI will involve a smaller operation and faster recovery but will be associated with a higher rate of symptom recurrence and no increase in life expectancy. We would recommend that patients with coronary artery disease who do not fall clearly into one of the categories for definitely PCI or definitively surgery, should be discussed through a multi-disciplinary meeting which includes cardiologists who do PCI and surgeons who do CABG, and that any recommendations from the meeting should be discussed in detail with the patient and their carers to enable patient choice and ‘shared decision-making’ to take place.
The heart has four valves, which open and close to regulate the flow of blood through different parts of the heart, as well as ensuring that it only travels in one direction. The aortic and mitral valves are on the left side of the heart and the pulmonary and tricuspid valves are on the right.
A condition called valvular heart disease can cause these valves to either become narrowed or leaky. Narrowing of a valve (stenosis) prevents blood flowing properly though it, whilst a leaky valve allows blood to flow in the wrong direction. In both cases the result is that the heart cannot get enough blood in the areas that it is needed. If surgery is required to restore the flow of blood through these valves a patient will either have their valve(s) repaired or replaced.
Valve replacement surgery is the replacement of one or more of the heart valves with either an artificial heart valve, which can be made from a combination of metal and carbon (a mechanical valve) or a ‘bioprosthesis’ (a valve that is made from animal tissues or a human cadaver). If a valve can be repaied this may involve separating fused flaps, removing, reshaping or adding tissue.
In adult cardiac surgery, three valves are commonly repaired or replaced: the aortic, mitral and tricuspid valves.
The aortic valve sits at the outlet of the heart at the base of the major blood vessel called the aorta. This valve opens when the heart pumps, to let the blood out, and then closes as the heart refills, to prevent the blood from flowing back from the aorta into the heart again. The aortic valve is one a series of valves in the heart that ensure that blood only flows in one direction around the body, ensuring that the heart works efficiently.
The aortic valve may become narrowed (which is called aortic stenosis) or it may start to leak (aortic regurgitation). When it is narrowed the heart has to work harder to pump the blood around the body. This in turn causes the heart muscle to become thicker and less effective. This can lead to symptoms of chest pain, shortness of breath, dizziness and occasionally sudden death. The only effective treatment for aortic stenosis is replacement of the aortic valve. When the aortic valve leaks severely it can cause the heart muscle to stretch up, and patients may develop shortness of breath and heart failure. The only treatment for severe aortic regurgitation that causes these symptoms is replacement or repair of the valve.
Mitral Valve Repair
The mitral valve may be affected by a disease where the valve leaflets become floppy and stretch up, causing the valve to leak. In other circumstances the heart muscle may stretch up, which can again cause the mitral valve to leak. It is also possible that infections may affect the valve (also called endocarditis), which may destroy the valve leaflets and cause the valve to leak. In many of these stuations it may be appropriate to repair, rather than replace, the mitral valve.
In general the valve is repaired by a combination of different surgical techniques which may involve removing bits of the valve leaflets, adding in extra artificial supports for the valve leaflets and placing a ring around the outside of the valve to reverse any valve stretching that is present. These techniques of valve repair are often very successful in fixing a mitral valve problem, but in some occasions valve replacement is the only option. Where valve repair is possible it is generally accepted to be a better and safer treatment than valve repair replacement.
Mitral Valve Replacement
The mitral valve sits between the major pumping chamber of the heart (the left ventricle) and the lungs. When blood flows back from the body to the heart it is pumped through the lungs to pick up oxygen, and then flows through the mitral valve before it is pumped back around the body again. The mitral valve may either become narrowed (mitral stenosis) or it may leak (mitral regurgitation) or both (mixed mitral valve disease).
When the mitral valve leaks or becomes narrowed, the heart initially compensates so there may be few or no symptoms in the early stages. However as things progress the commonest symptom is shortness of breath. Associated with changes in the left side of the heart, the right side of the heart may also become stretched up due to a build up of pressure either because the mitral valve is narrowed and obstructing flow, or because it is leaking causing blood to be pumped backwards through the lungs to the right heart. This may in turn lead to what is known as functional tricuspid regurgitation as the valve on the right side becomes faulty. On rare occasions the tricupsid valve itself may become narrowed or leaky on its own, and this may require surgery
An aneurysm is a localised, blood-filled balloon-like bulge in the wall of a blood vessel. An aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart. When the size of an aneurysm increases, there is a high risk of rupture, resulting in severe bleeding, other complications or death. Aneurysms can be hereditary or caused by disease, both of which cause the wall of the blood vessel to weaken.
Heart rhythm disorders
Arrhythmia surgery is mainly intended to eliminate irregilar heartbeats atrial fibrillation (AF) by using incisional scars to block abnormal electrical circuits. This required an extensive series of full-thickness incisions through the walls of both atria, a median sternotomy (vertical incision through the sternum) and cardiopulmonary bypass (heart-lung machine; extracorporeal circulation). A series of improvements were made, culminating in 1992 in the Cox maze III procedure, which is now considered to be the “gold standard” for effective surgical cure of AF.
During the past 10 years, several energy sources such as unipolar radiofrequency, bipolar radiofrequency, microwave, laser, high-intensity focused ultrasound, and cryothermia were incorporated into various devices in order to create some of the lesions of the Cox Maze-III procedure without actually cutting into the atrial walls. Microwave and Laser therapy have both been withdrawn from the market but the other devices continue to be utilized to treat atrial fibrillation surgically. Most of them, however, are used to create lesion patterns that are not as extensive as those of the Cox Maze-III procedure and have not proven to be as successful. Whether the failures when using these devices are due to a failure of the energy source or to the fact that an incomplete lesion set was employed remains an unresolved matter.