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Health Evidence Bulletins - Wales

Coronary Heart Disease

Introduction 

The original series Protocols for Investment in Health Gain were written in the early 1990s to suggest areas where the introduction, or more widespread use, of certain practices could lead to worthwhile improvements in health for the people of Wales.  Subsequently, the Health Evidence Bulletins Wales project was instigated in 1996 to review these documents and provide summaries or statements of the best current evidence with a precise indication of the strength of the evidence and its sources for each statement1. This Bulletin updates the Health Evidence Bulletin: Cardiovascular Diseases2 and has been specifically developed to support the implementation of the Wales National Service Framework for coronary heart disease, Tackling CHD in Wales: Implementing Through Evidence3

The statements represent a methodical summary of the evidence in this area found through a formal literature search across a wide range of sources.   The evidence has been critically appraised using internationally accepted methods, compiled into this document under the direction of public health and clinical specialists, and reviewed by a multidisciplinary team who are directly involved in patient care and with members of the public4. The information in this document and the Project Methodology are also available electronically, via the Health of Wales Information Service (http://www.wales.nhs.uk/hebw) and the Internet (http://hebw.cardiff.ac.uk).

The convention used in this document to indicate the type of evidence  is5: 

‘Type I evidence’ -  at least one good systematic review

 (including at least one randomised controlled trial).

‘Type  II evidence’ - at least one good randomised controlled trial

‘Type III evidence’ - well designed interventional studies without randomisation

‘Type IV evidence’ - well designed observational studies

‘Type V evidence’ - expert opinion; influential reports and studies

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The use of evidence type rather than evidence hierarchy has been chosen deliberately.   Every attempt has been made to find the best available evidence within each topic.  Information from high quality intervention studies is included whenever possible but observational evidence is also cited where relevant.  By valuing evidence from randomised controlled trials more highly than observational studies there is a danger that interventions with limited effectiveness might be judged to be more worthy than those based on observation. Similarly, those observational studies that clearly prove effectiveness (and make a randomised trial unethical) might be undervalued.

In addition, for interventions designed to influence human behaviour and social interactions at the population level, classical experimental designs such as the randomised controlled trial are often impractical. Other, complementary, research methods are therefore often used, such as qualitative ones, which can provide insights into people’s experiences and into the social contexts that strengthen, support or diminish health and health-determining behaviour. 

Information assigned as Type V evidence may include expert opinion and important reports or recommendations that should also be highly regarded.

Although the statements are deliberately brief, statistically significant quantitative information has been provided where possible using the units of measure provided in the cited publication(s).  Issues of cost-effectiveness or cost-benefit are considered where evidence is available.  For guidelines an indication is given as to whether they are based on a systematic review (evidence based guidelines) and/or developed via the consensus of an expert panel (expert consensus guidelines).  Recommendations for further research are given in italics.

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The Coronary Heart Disease Health Evidence Bulletin

The following information sources were systematically searched in the preparation of this Bulletin:  Medline, Premedline, Embase, CINAHL, Evidence Base, HMIC, Science Citation Index, EBM Reviews (including the Cochrane Library), National Research Register, New Zealand Guidelines Group, National Institute for Clinical Excellence (NICE), SIGN Guidelines, SIGLE, TRIP, Clinical Evidence, Welsh Assembly Government web-site, Specialist Societies and Colleges (eg the British Cardiac Society, American College of Cardiology/American Heart Association, European Society of Cardiology).  

Specific search filters were used to search for systematic reviews and randomised controlled trials across all topic areas4.  Randomised controlled trials with less than 100 participants were normally excluded unless a smaller trial was the best available evidence within a subject area.   Specific searches, for all types of evidence, were then carried out for topics where evidence from randomised controlled trials was not available or feasible.  A comprehensive literature search across all topics was carried out covering publications from 1998-July 2002 to update the literature searches carried out for the Cardiovascular Diseases bulletin2.  Update searches were carried out in the Cochrane Database of Systematic Reviews 2003 Issue 1 and Clinical Evidence January 2003 for all topics.  In addition, all the information sources listed above were searched in July-October 2003 for specific topics and publications as recommended by the critical appraisal and review groups.  Full details of all the search strategies used are available from the Project Office6.   

All topics in Tackling CHD3 have been included.  However, the large bodies of research relating to specific groups of patients only (eg those with diabetes) or to the detail of techniques and interventions during surgery have not been covered.  Some ongoing multi-centre studies are included for information if they recruited more than 300 subjects.

This Bulletin is designed to summarise the best current evidence to support the development of implementation tools such as guidelines and care pathways at national and local levels.   It is also anticipated that the document will be of interest to all professionals involved in delivering services for people with, or at risk from, coronary heart disease, in keeping abreast of the large and increasing body of literature in this field. Some of the conclusions reached in this bulletin will inevitably be controversial. Every effort has been made to include the best evidence within a subject area. Readers who are aware of any important studies that have been overlooked are encouraged to contact the project team6.

While every effort is made to avoid errors in these summaries, the statements are intended to act as signposts to reliable sources of evidence, not as guidelines for the management of patients.  It is hoped that this bulletin will facilitate evidence-based practice, which involves “integrating individual expertise with the best available external evidence from systematic research”7.

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December 2003

1   http://hebw.cardiff.ac.uk
2   Cardiff:  Welsh Office, 1998 http://hebw.cardiff.ac.uk/cardio/pdfcardio.pdf [accessed 19.12.03]
3   Cardiff: National Assembly for Wales, July 2001.  http://www.wales.nhs.uk/publications/coronary-heart-disease-e.pdf [accessed 19.12.03]
4   Weightman AL, Barker J, Lancaster J.  Health Evidence Bulletins Wales.   Project Methodology 4.  Cardiff: University of Wales College of Medicine, 2001.  http://hebw.cardiff.ac.uk/projectmethod/METHOD4.PDF [accessed 19.12.03]
5   This table is adapted from the Bandolier system (derived from the work at McMaster University, Canada) using the NHS Centre for Reviews and Dissemination criteria for a systematic review.  See http://www.jr2.ox.ac.uk/Bandolier/band6/b6-5.html [accessed 19.12.03] and the Database of Abstracts of Reviews of Effectiveness (DARE) in the Cochrane Library.
6   Health Evidence Bulletins Wales.  Division of Information Services. University of Wales College of Medicine, Cardiff CF14 4XN.  Email: MannMK@cardiff.ac.uk
7   Sackett DL, Richardson WS, Rosenberg W, Haynes RB. Evidence-based Medicine. How to Practice and Teach EBM.  Edinburgh: Churchill Livingstone, 1997.

 Glossary of Abbreviations used in this Bulletin

ACE inhibitors   Angiotensin Converting Enzyme Inhibitors
A&E      Accident & Emergency
AF         Atrial fibrillation
AMI   Acute Myocardial Infarction
BACR       British Association for Cardiac Rehabilitation 
BCS        British Cardiac Society
BHF    British Heart Foundation
BMI      Body Mass Index
BNP        B-type Natriuretic Peptide
BP   Blood pressure
CABG   Coronary Artery Bypass Graft 
CHD        Coronary Heart Disease
CHF          Congestive Heart Failure
CI           Confidence Interval
CPR        Cardio Pulmonary Resuscitation
CRP     C Reactive Protein
CVD         Cardiovascular disease
CVS   Cardiovascular system
DBP       Diastolic Blood Pressure
ECG      Electro Cardiograph/Cardiogram
ERG        External Reference Group
GP   General Practitioner
Hb   Haemoglobin
HDA      Health Development Agency
HTA   Health Technology Assessment
IHD    Ischaemic Heart Disease
IV          Intravenous
LDL       Low Density Lipoprotein
LR   Likelihood ratio
LVAD      Left Ventricular Assist Device
MRI   Magnetic Resonance Imaging
NHANES     National Health and Nutrition Examination Survey
NHS   National Health Service
NICE   National Institute for Clinical Excellence
NNT       Number Needed to Treat
NRT           Nicotine Replacement Therapy
NSAIDS           Non-steroidal anti-inflammatory drugs
NSF   National Service Framework
OR Odds Ratio
PTCA   Percutaneous Transluminal Coronary Angioplasty
QALY   Quality Adjusted Life Year
SBP        Systolic Blood Pressure
SPECT    Single Photon Emission Computed Tomography

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Health Evidence Bulletins: Wales, Duthie Library, UWCM, Cardiff CF14 4XN. e-mail: mannmk@cf.ac.uk