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The British Cardiovascular Intervention Society was founded in 1988 and represents cardiologists and allied health care professionals with an interest in interventional cardiovascular procedures in all countries of the United Kingdom. The Society promotes education, training and research in cardiovascular intervention and develops and upholds clinical and professional standards to try to ensure that all patients being treated by PCI get the best possible care. We have therefore collected data about the way in which PCI is performed, and outcomes for patients following PCI, for many years. The data are publicly available on the Society’s web site and have focused on the performance of individual PCI centres. In recent years BCIS has collaborated with the National Institute of Cardiovascular Outcomes Research (NICOR) to collect and analyse these data.
While the main focus has been on the practice of PCI in different hospitals, in recent years we have also presented analyses of the practice of individual PCI consultant operators. In reading these analyses it is important to understand how they were generated so that their strengths and limitations can be recognised and the information seen in context.
These data have been provided by each centre and their PCI consultant operators. It is not possible for BCIS or NICOR to validate these data; their accuracy, therefore, rests with the PCI operators and the data collection personnel in the hospital where the PCI was performed.
For each PCI procedure over 100 data items are recorded. These include:
a) Information about the patient such as their age, sex and other conditions that they might be suffering from such as diabetes and hypertension.
b) The reason a patient needs to be treated by PCI. For example this might be for symptoms of stable angina or because they have presented to a hospital with sudden onset of chest pain due to a heart attack.
c) The way the PCI was performed, including the techniques employed and the equipment, stents and medications used.
d) How the patient got on after the PCI and whether there were any adverse events before they were discharged home.
|List of abbreviations|
|ACS||Acute Coronary Syndrome|
|BCIS||British Cardiovascular Intervention Society|
|CABG||Coronary Artery Bypass Grafting|
|CHD||Coronary Heart Disease|
|MACCE||Major Adverse and Cerebrovascular Event|
|NSTEMI||Non ST elevation Myocardial Infarction|
|PCI||Percutaneous Coronary Intervention|
|STEMI||ST elevation Myocardial Infarction|
All PCI procedures performed over a three year period are included in the analysis of numbers, case mix and outcomes (a rolling three year program). For analyses of delays to treatment (STEMI and NSTEMI), radial rates and interhospital transfer rates, only the most recent year’s data are included to ensure the results are as contemporaneous as possible
Clearly only data sent to NICOR can be analyzed. Almost all UK NHS hospitals have uploaded data, and some (but not all) private hospitals.
To assess survival after PCI, the Office of National Statistics provides us with independently assessed life status, by linkage using the NHS number. This analysis is therefore limited to England and Wales. The data are presented as 30 day survival. Patients who present with out of hospital cardiac arrest and require mechanical ventilation prior to PCI are excluded from the survival analyses, but there are no other exclusions (see section ‘split by syndrome’ for an explanation).
Further details are given under ‘Risk Adjusted Outcomes’.
The aim is to include all consultant PCI operators in the UK who performed PCI at any time during the 3 year period
Survival to 30 days after PCI is reported, using life status data provided by the Office of National Statistics. Factors that determine survival after PCI are often not related to the treatments given and procedures performed, but are influenced by the patient’s general state of health and the condition with which they present. For example some patients admitted with a heart attack may die because of extensive damage to the heart and in spite of excellent care including PCI. Most heart attacks are associated with a mortality of about 5%. If a patient presents with a very big heart attack and is in a state of ‘cardiogenic shock’, then in spite of excellent care and a high quality PCI procedure there is about a 50% risk of death (see below)
Nevertheless outcome will also depend on the quality of care given and the timeliness of treatment. For this reason the analysis attempts to account for the differences in how sick patients are when they present, so that what remains of the variation in outcomes might be explained by the care received.
The data are shown both for each operator and also for each PCI hospital. A skilled interventional cardiologist requires a combination of good clinical judgment and technical ability. Skills can only be maintained by performing a procedure regularly. However, there is no definite cut off below which an operator’s ability to perform high quality PCI will be reduced. BCIS recommends a minimum of 75 PCI procedures in a year (but encourages activity of over 150 procedures a year).
The figures presented here are for the consultant responsible for the PCI procedure, but under certain circumstances a lower volume operator may work with a high volume colleague (a ‘buddy’ or ‘mentor’), and that information is not captured in the data presented.
There are several possible reasons why operators maybe recorded with low procedural volumes. It may genuinely reflect their practice. They may have only been appointed as a consultant part way through the year in question (and so only a subset of their cases will be included). They may have suspended their work due to pregnancy, or by taking a sabbatical. In some cases an operator may have retired part way through the data collection period. There may be an error with data submitted, with missing procedures, or missing consultant GMC numbers associated with procedures.
If an operator has worked on multiple sites, then all data from those sites will be ascribed to that one operator. However some private hospitals have not submitted data electronically to NICOR, and these cases will not be included.
Patients need PCI for a variety of different reasons called ‘syndromes’ and these are called the ‘Indications for PCI’. The indications for PCI in each operator’s practice are shown. Below is an explanation of each of these indications.
Stable angina occurs when a coronary artery becomes progressively narrowed and blood supply to the heart muscle becomes restricted. People usually experience a tight constricting feeling across the chest which may be associated with breathlessness. It is brought on by physical exertion or stress. Patients with stable angina will have been admitted from home for a planned procedure and usually return home the same day or the following day.
Primary PCI (for ST Elevation Myocardial Infarction or STEMI)
Patients presenting with a complete blockage causing ST elevation on the ECG need immediate treatment. If the blockage persists the region of the heart muscle supplied by that artery will progressively die (myocardial necrosis). In the past patients were treated with a drug that dissolved the occlusive clot (thrombolysis), but now the majority are treated by PCI. This emergency treatment is called Primary PCI, and the number of these cases by each consultant (or hospital) is shown (in these data we have also included ‘facilitated PCI’ – where primary PCI is immediately preceded by treatment with certain other medications).
ACS (Non STEMI)
All other acute coronary syndromes (unstable angina and NSTEMI) are usually caused by a partial or intermittent blocked of the coronary artery and do not usually need to be treated immediately. Recommendations are that they are treated during the initial hospital presentation, preferably within 72 hours. These have been grouped together in this category, and labelled ‘ACS (non STEMI)’.
Shock (Patients in cardiogenic shock before the start of the PCI procedure)
In some patients, the damage caused to the heart muscle by a heart attack is so extensive that the pumping function of the heart is profoundly compromised. If the amount of blood pumped around the patient’s body falls too low, it may be insufficient to sustain the normal function of vital organs, and they begin to shut down (for example kidneys, brain and the liver). When this happens a patient is described as being in ‘cardiogenic shock’. The chances of a patient surviving this critical condition are low, even when the best possible care is provided by the cardiac team. Approximately a third to a half of all such patients will succumb. An operator who works in a hospital that sees a relatively large number of such patients will have a higher mortality irrespective of how skilled the teams are in treating such patients. These factors need to be taken into account when interpreting outcome data. The risk adjustment models attempt to correct for these differences, but all such mathematical methods have limitations (see below)
Ventilated Pre op (patients who have sustained out of hospital cardiac arrest)
Another group of patients whose mortality is high, are those whose hearts stop before they can be brought to hospital. They are said to have suffered an ‘out of hospital cardiac arrest’. While such patients often die before reaching hospital, some can be resuscitated by trained bystanders or paramedics. In this case they are usually brought into hospital by ambulance unconscious and attached to a machine to help them breathe (a ventilator). This group are described as ‘Ventilated Pre-Op’. Even if they are successfully brought to hospital the chance of survival remains poor at about 50%. It is also very difficult to predict survival at the time they arrive. For example it is not possible to know if they have already sustained irreversible brain damage (which is the organ most susceptible to damage at the time of cardiac arrest). If this is the case then even after a successful PCI to treat their heart attack, they may never regain consciousness. These cases are listed in the chart, but as there are no mathematical models yet developed to predict outcomes they have not been included in the assessment of risk adjusted outcome.
There are a few other less common reasons for performing PCI which are grouped here.
To perform PCI, a tube (catheter) needs to be inserted into the patient’s arterial system (see ‘The PCI procedure’). This can be inserted into the artery at the top of the leg (called the femoral artery), or in the wrist (called the radial artery). During the early development of PCI, before full miniaturisation of equipment, large bore tubes had to be used, and so could only be inserted into a large artery (such as the femoral). Through advances in engineering, equipment has become ever smaller, and is now thin enough to be inserted into the smaller, radial artery.
There are several advantages to using the radial artery for access. For example, unlike the femoral artery it does not have other critical structures close by that could be damaged (the femoral artery on the other hand is surrounded by the femoral vein and nerve). It is easier to compress the radial artery to stop bleeding after the tubes are removed, and if any bleeding does occur it is more obvious and so can be corrected more quickly. Furthermore the use of the radial route enables quicker mobilisation after the procedure.
Complications are lower if it is possible to use the radial rather than the femoral route, and radial access results in better long term outcomes and lower mortality. Nevertheless, the radial route is technically more challenging especially if the operator’s previous training and experience has been limited to transfemoral access.
In the public reports we give radial versus femoral access rates for all operators and PCI hospitals. However it is not possible to treat all patients using a radial approach. Some patient’s radial arteries are still too small, and some PCI techniques still require large bore equipment that cannot fit into a an average radial artery. As a result operators who attempt to use a radial route in all appropriate patients will not have 100% radial rates, but rather rates that are likely to be between about 80% and 95%.
If a patient develops an ST Elevation myocardial infarction (STEMI) and is to be treated by primary PCI, then speed is of the essence. A STEMI occurs when a blood vessel supplying the heart muscle blocks completely. In the absence of oxygen and nutrients this part of the heart muscle starts to die. The longer the vessel is blocked, the more heart muscle will die, and so this blockage must be opened as quickly as possible.
The ‘Door to Balloon’ time is a measure of how long it takes a PCI centre to treat such patients. It measures the delay between the arrival of a patient at the hospital, and the re-opening of the blocked artery using PCI. An audit standard is for this to be less than 90 minutes, aiming for less than 60 minutes in higher risk cases. The data are therefore presented as the percentage of patients who were treated within 90 minutes of arrival.
Breakdown by of route of admission
Patients experience longer delays to treatment if the first hospital to which they are admitted does not have the capability to perform PCI. It is therefore best for patients with symptoms of a possible heart attack to be taken directly to a hospital that can perform this treatment. Higher ‘direct admission’ to a PCI centre reduces delays to treatment and reduces overall time the patient needs to spend in hospital.
Data completeness and analysis
Most patient who present with an NSTEMI, need urgent, but not emergency treatment. While delays are not associated with increased mortality, they are associated with an increased rate of heart attacks while waiting for treatment, and also with prolonged hospital stay. National and international guidelines suggest that treatment should occur within 72 hours of admission.
To analyse these data we need to know about the patient’s journey through the hospital system. It is particularly important to know when they were first admitted (whether it be to a referring hospital or the PCI centre itself).
This section starts with an analysis of the completeness of the data. Only if the data are sufficiently complete for a meaningful analysis will that analysis be performed. Hospitals whose data are inadequate are encouraged to make more efforts in data collection.