QJM Advance Access originally published online on September 20, 2005
QJM 2005 98(11):797-802; doi:10.1093/qjmed/hci123
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Redefining the coronary care unit: an observational study of patients admitted to hospital in England and Wales in 2003
From the Clinical Effectiveness and Evaluation Unit, Royal College of Physicians of London, London, UK
Address correspondence to Dr Clive Weston, Department of Cardiology, Singleton Hospital, Swansea SA2 8QA. email: cfmw{at}lycos.com
Received 23 May 2005 and in revised form 8 August 2005
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Summary |
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Background: Coronary care units were developed in the 1960s as specially equipped and staffed areas where patients with acute myocardial infarction could be monitored and offered rapid resuscitation from life-threatening arrhythmias. Awareness of the morbidity and mortality of the wider spectrum of acute coronary ischaemia was unrecognized at that time.
Aim: To examine the relative frequencies with which thrombolytic treatment and resuscitation from cardiac arrest are provided for patients with myocardial infarction in cardiac care units (CCUs), emergency departments (EDs) and other medical wards.
Design: Observational study.
Methods: We analysed records from the National Audit of Myocardial Infarction Project (MINAP) for 61 688 patients admitted to 230 acute hospitals in England and Wales during 2003, and who received a final diagnosis of myocardial infarction, for locations of initiation of thrombolytic therapy and of first cardiac arrest within hospital.
Results: Overall, 84% of 27 881 patients with ST-segment-elevation infarction, but only 42% of 30 382 patients with non-ST-elevation infarction, were admitted to a CCU. Of those receiving thrombolytic treatment for ST-elevation infarction, 68.3% of 21 595 did so in the ED. Within the first 4 h after arrival, the majority of episodes of cardiac arrest occurred in the ED: 709 (57%) vs. 488 (39%) in CCU, and 49 (4%) in medical wards.
Discussion: The traditional role of the CCU in providing early resuscitation and thrombolytic treatment for patients with ST elevation infarction has largely been devolved to the ED. The role of the CCU should be re-evaluated, and the service re-designed to provide specialist care for all presentations of acute coronary syndrome.
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Introduction |
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Coronary care units, now called cardiac care units (CCUs), were developed in the 1960s to provide a facility staffed and equipped to monitor patients with acute myocardial infarction (AMI) and respond rapidly to serious arrhythmias.1 When intravenous thrombolytic treatment entered routine clinical practice in the late 1980s, this was predominantly given in CCUs.2
Despite the introduction in some hospitals of successful ‘direct admission’ policies for patients with suspected AMI during the 1990s, most such patients were initially taken to emergency departments where assessment took place, followed by transfer for thrombolytic treatment in the CCU.2 In the late 1990s, a survey of UK hospitals found that thrombolytic therapy was available in only one third of emergency departments.3 In 2000, the National Service Framework for Coronary Heart Disease recommended that thrombolytic treatment should be available in at least 75% of emergency departments.4 Over the last 3 years, there has been a substantial national shift in the provision of thrombolytic treatment from CCU to emergency departments, associated with a remarkable reduction in the median interval between arrival in hospital and provision of reperfusion treatment.5 The move away from immediate treatment and care in the CCU is expected to continue, with greater provision of pre-hospital thrombolytic treatment and use of primary percutaneous intervention.
In the light of these changes we examined the present role of the CCU in the care of patients with AMI using data from the National Audit of Myocardial Infarction Project (MINAP) of patients admitted to all hospitals (n = 230) in England and Wales during 2003.
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Methods |
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The development, organization and early findings of MINAP have been previously described.5,6 The project uses a technological platform developed by the Central Cardiac Audit Database group7 to provide hospitals with both contemporary on-line analyses of their individual performance in the care of patients with acute coronary syndromes, and comparisons with national aggregate data. All acute hospitals in England and Wales now return data electronically on patients with AMI and, increasingly, other acute coronary syndromes. Patients recorded in MINAP are identified on the basis of clinical presentation. Patient data are entered into the MINAP data application by either nursing or clinical audit staff.
The dataset used by MINAP is part of the NHS Data Dictionary, and has the formal approval of the English Information Standards Board. It allows documentation of the process of care for acute coronary syndromes, including first cardiac arrests, providing information on date and time of arrest, place of arrest, presenting rhythm and outcome.8
Records were extracted for analysis from the live database on the in-patient care of 92 988 patients with a suspected acute coronary syndrome admitted to 230 acute hospitals in England and Wales during 2003.
Biochemical definition of AMI
During the period of data collection for this study, implementation of the biochemical redefinition of AMI9 was at an interim stage, in which some hospitals continued to use the previously established biochemical markers—creatine kinase (CK) and CK-MB—while others used one of a number of assays for troponin I or the single assay available for troponin T. The biological marker used by individual hospitals was not known. The final diagnosis was that provided by local clinicians based on their interpretation of a combination of clinical, biochemical and electrocardiographic findings.
Data and record completeness
While hospitals are encouraged to record all patients with suspected infarction, it is likely that not all cases of AMI are recorded in MINAP. Hospital episode statistics for 2003–4 recorded 74 373 episodes under ICD codes I21 and I22, compared with 61 688 recorded within MINAP over broadly the same period. We have no reason to suspect, however, that these records represent a sample that is biased in favour of one or other of the main sites in which the immediate care of AMI is performed.
When records are entered, there are error-checking routines within the data application to ensure that incongruous data entries are identified for local correction. A data completeness score for 11 mandatory fields relating to the care of ST elevation infarction is provided on-line to hospitals, and data completeness averages >90%. There is an annual data validation exercise, which is mandatory. Where data are missing from key analyses this is reported, but it was not practicable to analyse missing data as a separate category.
Statistical analysis
Categorical data are presented as percentages, and continuous data as means and standard deviations.
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Results |
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Of 92 988 admissions, 61 688 received a final diagnosis of AMI at death or discharge. Of these, the admission ward was recorded for 58 263 (94.4%), and analyses were based on this group. Of 27 881 patients with ST-elevation infarction (STEMI) where the admission ward was known, 84.5% were admitted to a CCU, compared with 42.4% with non-ST elevation infarction. Patients with non-ST-elevation infarction were equally likely to be admitted to an acute admissions facility (Table 1). The mean age of patients admitted to a CCU was lower (mean ± SD 67 ± 15 years), than those admitted to acute admissions units (73 ± 15 years) or to medical wards (75 ± 13 years). Overall only 62.6% patients with AMI were admitted to a CCU.
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Thrombolytic treatment
Of 27 881 patients with a final diagnosis of STEMI, 21 595 (77.4%) received thrombolytic treatment. Of these, 14 744 (68.3%) received treatment in the emergency department, 3233 (15%) after direct admission to CCU and 2851 (13.2%) after admission to the emergency department followed by transfer to the CCU for treatment. Another 767 (3.5%) received treatment elsewhere in hospital—usually an acute admissions facility. Of 14 744 having thrombolytic treatment in the emergency department, 13 920 (94.4%) subsequently were admitted to CCU.
Cardiac arrest
Of 61 688 patients with a final diagnosis of AMI, 4963 (8.0%) had a cardiac arrest in hospital. The site of the arrest was recorded for 4823 (97.2%). Of these, 890 (18.5%) occurred in the emergency department, 2187 (45.3%) in a CCU, and 1272 (26.4%) on a medical ward or acute admission facility. Another 474 (9.8%) occurred elsewhere in hospital. There was a slightly greater percentage of patients having a first arrest on a medical ward: 1272/19 298 (6.6%) compared with 2187/36 455 (6.0%) in a CCU.
The interval between arrival at hospital and first arrest was known for 777/890 (87.3%) occurring in the emergency department, 1986/2187 (91.1%) in a CCU, and 1113/1272 (87.5%) in medical facilities. During the first 4 h, there were 1246 arrests, of which 709 (56.9%) occurred in the emergency department, 488 (39.2%) in a CCU, and 49 (3.9%) in medical wards (Table 2). A further 68 patients had an arrest in the emergency department >4 h after admission.
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The majority of arrests in a CCU (1498/1986, 75.4%), occurred >4 h after admission, and 601/1986 (30.3%) occurred >48 h after admission (Table 3) The frequency of ventricular tachycardia and fibrillation as a presenting rhythm fell over time in both medical wards and CCUs, and were similar in distribution over time.
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The hospital outcome was known for 2046/2187 (93.6%) having an arrest on CCU, and for 1208/1272 (95%) on a medical ward. Resuscitation was not attempted for 282/2046 (13.8%) patients on a CCU, and for 374/1208 (31%) in other wards. Survival to leave hospital for those where resuscitation was attempted was 453/1764 (25.6%) arrests on CCU, and 126/834 (15.1%) on medical wards.
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Discussion |
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When CCUs were originally conceived, the high morbidity and mortality of biological-marker-positive acute coronary syndromes, including non-ST segment elevation infarction was unrecognized.10 Care for patients with acute coronary syndromes has embraced new technologies, greatly improved diagnostic and risk stratification strategies, and new therapeutic options.11,12 We therefore questioned to what extent present-day CCUs continued to fulfil their original role, and whether they were in a position to deal with the substantially larger numbers of patients with acute coronary syndromes requiring resuscitation and treatments other than thrombolytic drugs.
Every acute hospital in England and Wales has a CCU. In a survey of English hospitals in 2000, over 75% had a dedicated unit, as opposed to beds shared with intensive care or a medical ward with cardiac care beds, and of these 75% had between four and eight beds.13 The relatively small size of most CCUs reflects their initial aim—to care intensively for a limited number of patients with STEMI. Such capacity constraints make care for larger numbers of patients with other acute coronary syndromes impracticable. This has led to a dichotomy of care, with relatively small numbers of patients with STEMI receiving specialist care on well-staffed CCUs, while patients with many other manifestations of acute coronary syndrome receive care elsewhere that may be less than ideal.
In this analysis, while 84% patients with STEMI elevation infarction were admitted to a CCU, more than half of those with non-ST-elevation infarctions, who constitute the majority of all infarctions, were admitted to acute medical wards. Myocardial infarction without ST segment elevation has a high morbidity and mortality that may exceed that of STEMI, and early angiography and appropriate intervention are recommended for those with high-risk features.11,12
For the majority of ST-elevation infarctions, thrombolytic treatment was given in the emergency department, where the majority of early (within 4 h of admission) resuscitation attempts also occurred. Meanwhile, in CCU, >30% of first cardiac arrests took place >48 h after arrival in hospital, with a considerable number of patients having a first cardiac arrest >7 days after admission. There was a similar frequency of arrests presenting in VF or VT (from which successful resuscitation is more likely) on CCU and in medical wards, which fell sharply with time. On a typical CCU of limited size, patients with irreversible mechanical complications of AMI, having a poor prognosis, and a prolonged stay may prevent admission of other patients.
There was a substantial difference in the number of cardiac arrests for which resuscitation was deemed inappropriate on CCU (13.8%), and medical wards (31%). This may be, in part, accounted for by age differences between patients admitted to CCU and medical facilities.
It is common (although not necessarily good) practice not to admit patients with prognostically severe comorbidity to a CCU, and it is also likely that more aggressive resuscitation policies exist within a CCU, which will also account for some of this difference. However the overall percentage of patients with AMI having an arrest on CCU and in medical wards was similar. Although we quote survival to leave hospital after cardiac arrest for CCU and medical wards, this may not be a fair comparison, because of differences in characteristics between patients admitted to either area. It is more important to draw attention to the substantial numbers of patients who have an arrest outside of CCU. If resuscitation is deemed appropriate, then facilities and skills available should be of a consistently high quality. Such high quality care can be provided in a general ward, but in the spirit of the original coronary care unit concept, it seems more likely that a specialist area would provide the best chance of a favourable outcome. All patients deemed suitable for resuscitation and at risk of cardiac arrest should have equal opportunity of access to the same facilities.
The expansion of use of primary percutaneous intervention, presently underused in the UK, is expected to continue, and with this the role of the traditional CCU within hospitals without facilities for percutaneous intervention might further diminish as patients with STEMI are transported elsewhere.14 There is also evidence that the proportion of patients hospitalized with STEMI, as opposed to other manifestations of acute coronary syndrome, is shifting away from STEMI.15 The workload of CCU has changed in other respects. Temporary transvenous pacing is much less common since the advent of thrombolysis.16 Elective cardioversion, once a routine CCU activity, can be safely undertaken outwith the CCU for most patients.17 At the same time, the age of patients admitted to CCU has risen, and with it the incidence of co-morbidities that are likely to increase the complexity of management and the need for specialist care. The use of highly skilled and scarce CCU staff to care for patients with other (e.g. non-ST-elevation) manifestations of acute coronary ischaemia is, we believe, a logical development.
The move towards care in the emergency department has not been without its critics. The need to safeguard the professional development and career satisfaction of CCU nurses has been cited as a reason to maintain the emergency role of the CCU.18 It is difficult to defend this viewpoint without evidence that the shift of care to the emergency department has been detrimental to the care of patients.
In order to achieve equity of care across the spectrum of acute coronary syndromes physical reconfiguration of the traditional ‘stand-alone’ CCU will be required, particularly where hospitals do not have an adequate number of additional cardiac beds adjacent to an existing CCU.19 Where these beds do not exist, consideration should be given to the development of larger units offering facilities that reflecting the diverse nature of the clinical needs of patients with acute coronary syndromes. This does not imply a requirement for more beds; rather, a single facility bringing together patients with all manifestations of acute coronary ischaemia, to replace potentially inconsistent care provided on different medical wards. This has particular merit in terms of patient safety, consistency of care, and clinical governance, and will also facilitate closer involvement of cardiologists in the care of patients.
Weaknesses of this study
MINAP is a long-term national audit project, and data have been extracted from the database for the purposes of this observational study. Cases were identified on clinical presentation, and thus it is possible that cases presenting in an atypical fashion could be missed, and not recorded in MINAP. This would reflect on the work pattern of both the emergency department and CCU, and there is no reason to believe that a systematic bias might occur to favour one or other unit. The majority of patients admitted to hospital with infarction (about 85%) are admitted via the emergency department. It is possible that patients arresting and dying shortly after admission might fail to be entered into MINAP, but there is no way of knowing whether they were destined to be treated in the emergency department or in the CCU, had they survived. Thus the data can only examine care of those who survived long enough to be recorded in the MINAP database. It is not possible to determine the likely number of missing data involved, as there is no robust alternative with which to make a comparison. It is very likely that not all cases admitted to 230 hospitals were recorded in the MINAP database, but we consider that the large numbers recorded here provide a robust picture of the process of care provided to patients with infarction.
We believe that completeness of recording of patients admitted to CCU is very high. We cannot be so certain about patients admitted elsewhere. The great majority will be patients with non-ST-elevation infarction. Some may not be recorded, with the implication that the number of patients with infarction not cared for in a cardiac facility is greater than we have recorded here. This will vary between hospitals, depending on resources directed towards data collection.
Finally the biochemical definition of myocardial infarction, which does not yet have any national consistency, will have resulted in some variation in definition of patients with non-ST-elevation infarction but not STEMI. Some, usually with lesser degrees of troponin release, may have received a final diagnosis of troponin-positive acute coronary syndrome.
Overall we believe that these reservations will not have had a significant impact on the central gist of our argument, which is two-fold: recognition of the need for better (consistent) care for patients admitted to general medical wards with acute coronary syndromes, and the diminishing value of cardiac care units as presently constituted.
Conclusions
Our data show that the original purpose of the CCU has largely been devolved to the emergency department. The service needs to be re-designed to meet the requirements of all patients with acute coronary syndromes, and should no longer be focused on the needs of a select patient group. These findings and proposals should not be seen as a threat to skilled CCU staff, but an opportunity to offer their skills to a wider group of patients.
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Acknowledgments |
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We thank all those participating in the National Audit of Myocardial Infarction Project (MINAP) and especially those staff responsible for data collection. The National Audit of Myocardial Infarction is funded by the Healthcare Commission.
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