Frequently Asked Questions


What is Adult Cardiac Surgery?

'Adult cardiac surgery' includes all procedures on patients aged 18 or over that involve the opening of the pericardium. The most common of these procedures are Aortic surgery, Coronary Artery Bypass Grafts, and Valve surgery.

Aortic surgery

The aorta is the major blood vessel leaving the heart and it carries blood to the rest of the body. The most common medical condition to affect the aorta is an aneurysm. Aneurysms are blood filled bulges in the wall of a blood vessel. As an aneurysm grows in size, it is increasingly likely to rupture, resulting in severe bleeding that can be fatal. Surgery may involve replacing the section of the aorta that has been weakened by the aneurysm.

Another condition affecting the aorta is aortic dissection. This occurs when a tear in the aorta’s inner wall causes blood to flow between the layers of the wall, forcing those layers apart. This can block the vessels that branch off from the aorta, damage the aortic valve or even tear the aorta completely open. This is a medical emergency that requires urgent surgical intervention.

Coronary Artery Bypass Graft (CABG) surgery

The coronary arteries are the vessels that deliver oxygen-rich blood to the heart muscle. Certain medical conditions can cause these vessels to become narrowed or blocked, which restricts the flow of blood into the heart muscle. This can lead to chest pain, known as angina, and heart attack.

CABG surgery involves taking an artery or 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.

Valve Surgery

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.

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's function is compromised.

If surgery is required to restore the flow of blood through these valves a patient will either have their valve(s) repaired or replaced.

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Where does the analysis for the Blue Book come from?

The analysis that you see in the Blue Book is based upon data collected by the National Adult Cardiac Surgery Audit (NACSA). Relevant hospitals submit operative data for every adult patient who has a major heart operation to a central database.

For the purposes of our analysis of patient's outcomes certain procedures are excluded because the patients who receive them are sufficiently high risk that risk adjustment cannot be applied accurately to them (see question 10 below). Please note that the procedures listed below are included in the section called 'What risk factors are important and how often do they occur?'

  • Emergency operations: Unscheduled patients with on-going refractory cardiac compromise severe enough that there cannot be any delay to surgery, irrespective of the time of day/day of the week.
  • Salvage operations: These are carried out on very sick patients who require cardiopulmonary resuscitation (CPR) on the way to the operating theatre.
  • Transplantations: Where a working heart is taken from a recently deceased organ donor and implanted into a patient whose heart is failing and unresponsive to other treatments.
  • Trauma: Where a heart is damaged by trauma (an external source) rather than disease.
  • Primary-VAD: Primary ventricular assist devices are mechanical implants that either partially or entirely replace the function of a failing heart. They are usually used whilst a patient awaits a heart transplant.

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What is the SCTS National Adult Cardiac Surgery Audit?

All operations on the heart that take place in NHS hospitals, and a number of private hospitals, are subject to close examination in the UK. For each patient who undergoes surgery, information is collected about the specifics of that patient, the operation performed and the outcomes of surgery. These data are collected together and analysed to provide information to patients to help them make choices about their care; to hospitals and surgeons, to help them improve the quality of surgery; and to regulators to enable them to ensure that all surgery is performed to a satisfactory standard. This process is called the National Adult Cardiac Surgery Audit (NACSA), and it is managed by NICOR, with clinical direction and strategy provided by the Society for Cardiothoracic surgery in GB and Ireland.

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How is data collected?

All hospitals that carry out the heart surgery procedures submit data for each operation that they carry out. This means that, before cleaning, the data that we hold is representative of ~100% of heart surgery being carried out in the UK. However, due to some records being invalid due to data entry errors, we do have to remove a small percentage of records prior to analysis.

Sometimes the data is collected directly on to computers at the time of surgery. In other hospitals the data is transcribed from the clinical notes onto a computerised database at a later time. Doctors and other staff are involved in the process. The data is then encrypted to ensure patient confidentiality is preserved and uploaded to a central computer for further analyses. This data is returned to the hospitals for validation to ensure that it is correct.

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How accurate is the data?

The level of completeness of the data that is submitted by hospitals is monitored continuously and publicly reported in both the National Adult Cardiac Surgery Database Report 2008, and the Annual Report.

Hospital's own software systems and the central database incorporate validation (checks on the data), such as range and consistency checks to maintain data quality. Analysis of data is also fed back to individual units for validation on a regular basis.

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How do I filter/customise what I see?

You can select the types of analysis that you would like to see by picking different types of operations, risk factors or hospitals from the drop down lists in each section. The table of data and the graph in that section will automatically update.

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How do I interpret the number of operations each year?

Why might procedure rates go down?

Certain procedures may decrease in number if different, less invasive techniques become available. For example if a patient is thought to be too high risk for open heart valve surgery, they may now receive a less invasive treatment called Transcatheter Aortic Valve Implantation (TAVI). This would mean less patients being recorded in the National Adult Cardiac Surgery Audit and more being entered onto the TAVI register. Similarly, a Percutaneous Coronary Intervention (PCI) may also be used instead of a Coronary Artery Bypass Graft procedure. PCI patients are recorded in the National Audit of Adult Coronary Interventions.

Why might procedure rates go up?

  1. More people needing surgery. This can be due to an ageing population or a higher proportion of people with the risk factors that lead to cardiovascular disease that requires surgical treatment.
  2. Patients are more likely to be diagnosed, referred and accepted for surgery. This is thought to be indicative of improved primary, secondary and tertiary care in the United Kingdom.

The more procedures recorded in the National Adult Cardiac Surgery Audit, the more reliable the analysis based upon the data is. Also, if the rate of surgery performed in hospitals increases more or less uniformly in different hospitals, this can be taken to show that the National Adult Cardiac Surgery Audit is capturing close to 100% of cardiac surgery patients in the UK.

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How do I interpret 'expected' and 'actual' outcomes of operations?

The chart and table you see here shows the difference between the mortality that we would expect to see based upon the characteristics of patients and the type of operations carried out.

Actual mortality is the number, after data cleaning, of patients who died for any reason before being discharged from the hospital in which they received their operation. It is important to bear in mind that the number of days that a patient stays in hospital varies, so these mortality rates do not reflect the chance of death after a set period. Whilst usually a patient who was ill enough post-operatively to die would not be discharged, some patients may be discharged to another hospital or have unexpected complications after being sent home.

A patient may also die for a reason not directly connected to the heart surgery that they have had. However, if a patient is thought likely to die from a non-related medical condition they would probably not be accepted for surgery, so the occurrence of this should be low.

The expected mortality rate should be viewed as a target, so we would hope that the actual mortality rate would be equal to or lower than this target. If actual mortality is proportionally lower than the expected mortality rate over time, this may show that the quality of heart surgery is improving.

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What is 'in-hospital mortality'?

This describes patients who died before they could be discharged from hospital. This includes patients who die during a heart operation, or die after the operation as a result of complications or a separate disease or disorder (known as co-morbidity).

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How are the expected outcomes of the operations calculated?

The expected mortality rates in this section are calculated by taking factors such as the age and gender of the patient, the condition of the heart, the presence of other illnesses and the type of surgery performed into account. In general the risk of surgery has gone up since the audit started, meaning that outcomes are expected to be worse. However the actual mortality has gone down, indicating the improving quality of care for patients with heart disease.

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What is a risk factor?

A risk factor is a characteristic of a patient that increases the likelihood of a bad outcome (like dying or having a stroke) following surgery.

The analysis that you can see in this section includes the most common risk factors that may affect a patient’s outcome after surgery. These are:

  • Age: Other risk factors tend to increase as a patient gets older. However, increasing age is an independent risk factor has been found to increase the risk of poor operative outcomes.
  • Female: Women are more likely to have a poor operative outcome than men.
  • Emergency: If a patient is admitted as an emergency their requirement for surgery has been identified at short notice and the admission to hospital was unplanned. The patient is ill enough to require surgery regardless or the time of day or day of the week.
  • Other than Isolated CABG: The patient is having a major cardiac procedure other than or in addition to Coronary Artery Bypass Graft. These types of procedures are considered to be more complex and carry a higher operative risk.

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How often is the analysis updated?

Analysis is updated with RAW data on a quarterly basis. All data displayed in the Blue Book has a one year time lag to allow time to collect, process and verify the data from all the hospitals. So analysis updated in June 2013 will be based on data up to March 2012.

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How is the data processed/cleaned?

Data cleaning involves 'mapping' some data items for records that were created using the old version of the dataset to new ones, applying logic to 'correct' data entry errors where possible, and removing records where correction isn’t practicable.

For more information on how this process is applied to the National Adult Cardiac Surgery Audit dataset prior to analysis, please see 'Dataset cleaning v7.0', which can be downloaded from the NICOR website.

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What is the time period covered by the audit?

We have been collecting data on patients undergoing adult cardiac surgery since 1996. Data collection has become more complete over time. The website contains data on patients undergoing surgery since 2001. The years we have included run by financial year (1st April to 31st March), so the year 2011 would include patients undergoing surgery between 1st April 2011 and 31st March 2012.

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How can patients be sure that their data is kept safe?

There are very strict guidelines and laws in the UK about preserving patients' confidentiality. To collect data, the audit has gained approval from the National Ethics and Confidentiality Committee of the National Information Governance Board. This independent group ensures that all organisations that handle sensitive patient level data do so in compliance with the guidelines. All of the work that is done by the Society for Cardiothoracic Surgery (including the data behind this website) is done on data that has been stripped of all patient identifiable or sensitive information, and is, therefore, completely anonymous.

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What happens a hospital with a high mortality rate is identified?

The SCTS are responsible for utilising analysis of NACSA data to monitor the performance of surgeons in the UK and Ireland. They explain the process in detail in the publication 'Maintaining Patients' Trust', which can be downloaded from

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Where can I find out about other heart disease clinical audits?

The National Institute for Cardiovascular Outcomes Research (NICOR), which manages NACSA, runs a total of seven cardiac audits and registries. These cover heart failure, heart attack, minimally invasive procedures in adults and paediatric heart surgery. You can find out more about these projects by visiting the NICOR website.

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Where can I find outcomes of surgery for specific surgeons?

Cardiac surgery outcomes for specific hospitals and surgeons are available at

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What procedures are included in "Isolated mitral valve surgery"?

Since mitral valve surgery (repair or replacement) may be done concomitantly with either tricuspid valve surgery or AF ablation - a decision made by each surgeon - we have included these procedures in this group.

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Who should I contact if I want more information?

For more information about the analysis you see on the Blue Book, please email

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