Risk estimation and the prevention of cardiovascular disease: A national clinical guideline

1     Introduction

1.1 THE NEED FOR A GUIDELINE

Cardiovascular disease (CVD) is an umbrella term that describes a range of conditions caused by blood clots (thrombosis) or build up of fatty deposits inside an artery that cause the artery to harden and narrow (atherosclerosis). The main underlying causes of CVD are coronary heart disease (CHD), stroke, peripheral arterial disease (PAD) and aortic disease.

Cardiovascular disease will directly affect the majority of the Scottish population at some point in their life. In 2014, a fifth of adults aged 16 and over had any CVD condition or diabetes. Both incidence and prevalence of CVD are higher amongst men, the elderly and in deprived areas of Scotland.

Recent estimates of disease incidence show that rates are falling and, although the reasons for this decline are complex, improvements in diet and a reduction in smoking rates are significant factors. Between 2005/6 and 2014/5 the age-sex standardised incidence rate for CVD has fallen by 12% in men and nearly 16% in women, driven by a significant fall in CHD incidence and a smaller decline in stroke rates.2,3  (ISD Scotland. Personal communication, 21 July 2016).

Cardiovascular disease has a multifactorial aetiology with a number of potentially modifiable risk factors. The classical Framingham risk factors, age, sex, cigarette smoking, blood pressure, total cholesterol and high density lipoprotein (HDL) cholesterol have proved consistent risk factors in every population studied. Various ethnic groups

may display differences in population baseline risk.4 Scotland’s minority ethnic population is small, but growing. At the 2011 census around 4% of the country’s 5.3 million people were from minority ethnic backgrounds, double the proportion from the previous census in 2001.

Of particular relevance to the Scottish context, are the effects of socioeconomic status on the risk of developing CVD. The incidence and mortality rates from acute myocardial infarction in those aged under 65 are higher in deprived areas than in more affluent areas.

Recognising CVD as a continuum challenges the traditional concepts of primary and secondary prevention, with healthcare professionals adopting a ‘high-risk’ approach to prevention.   In fact, most CVD cases occur in the large number of individuals at lower levels of absolute risk.  High-risk approaches have been facilitated both by the availability of scoring systems to estimate absolute risk (rather than the traditional use of single risk factors) and by the advent of several treatments, principally statins and blood pressure reducing drugs, which produce marked and apparently independent reductions in CVD risk in high-risk subjects.

The guideline has attempted to devise effective strategies for the reduction of CVD that take a combined approach using both ‘high risk’ and population approaches.

1.1.1 UPDATING THE EVIDENCE

This guideline updates SIGN 97 to reflect the most recent evidence.

Where no new evidence was identified to support an update, text and recommendations are reproduced verbatim from SIGN 97. The original supporting evidence was not re-appraised by the current guideline development group.

1.2 REMIT OF THE GUIDELINE

1.2.1 OVERALL OBJECTIVES

This guideline deals with the management of cardiovascular risk both primary prevention, defined as the potential for intervention prior to the disease presenting through a specified event, and secondary prevention, defined as the potential for intervention after an event has occurred. The guideline group has tried to consider CVD as a continuum from the preclinical to the end stage disease, potentially offering different opportunities to intervene, both prior to, and after an event, so creating the potential to alter the outcome of the disease process. The group believes that it is more relevant to consider an individual in terms of whether they have a high or low risk of cardiovascular events rather than in terms of primary or secondary prevention.

The guideline provides recommendations on estimation of cardiovascular risk and interventions to reduce this risk in people with and without established CVD. The guideline does not make specific recommendations for the management of people with chronic heart failure, acute coronary syndrome, stable angina or cardiac arrhythmias which are contained within other SIGN guidelines.  Cardiac rehabilitation is the subject of a further SIGN guideline which is currently under development.