Optimal risk stratification in patients with intermediate risk based on coronary calcium
01 / 2008 - unknown
Can measurement of coronary calcification in subjects free from symptomatic CV disease but with an ?intermediate? 10-19% CV risk within 10 years help to further categorise this group according to the need for optimal preventive risk factor management?VraagstellingAt which coronary calcification level in subjects free from symptomatic CV disease but with an estimated 10-19% CV risk within 10 years is risk factor management is indicated? Research questionWhich coronary calcification level in subjects free from symptomatic cardiovascular disease but with a 10-19% risk of cardiovascular disease within 10 years indicates a group of patients whose CV risk after optimal risk factor management is similar or higher to that of subjects with a 10 year CV risk of 20% or above who also received optimal risk factor management? Background: Current Dutch guidelines on risk factor management are inconclusive as to whether or not subjects with an estimated 10 year cardiovascular (CV) risk of 10-19% as assessed by the Framingham risk score (=intermediate risk group) should receive treatment for risk factors. The inconclusiveness reflects a weighing of feasibility, costs and perceived medicalisation. Although both blood pressure and cholesterol guidelines state that drug treatment is cost effective in this group on an individual level, for the country as a whole application of the guidelines is too costly. A selection procedure to assure that those patients in the intermediate risk stratum who might benefit most, receive treatment may help to solve the dilemma. To this aim, non-invasive measurement of coronary calcification seems promising. Objective: To determine at which coronary calcification level in subjects free from symptomatic CV disease but with an estimated 10-19% CV risk within 10 years risk factor management is indicated? Design: We propose a prospective follow-up study, in which drug treatment is given to all subjects free from symptomatic CV disease, but with an estimated 10 year risk of CV events between 10% or above. Those in the intermediate (10-19%) risk group undergo non-invasive assessment of coronary calcifications using computer tomography. The primary outcome is combined incidence of CV death, non-fatal myocardial infarction and non-fatal stroke.Data analysis: CV incidence rates will be estimated by calcification level for those with intermediate risk at baseline. Calcification levels will be determined at which the intermediate risk subjects have a CV incidence rate similar to or higher than those with a 10 year risk of 20% or over (based on conventional risk assessment; according to current guidelines this group receives optimal risk factor treatment). Sample size analysis suggests that around 4000 subjects need to be enrolled.Expectation: The inference from analyses is that intermediate (10-19%) risk patients should receive risk factor treatment if their calcification is at or above the level that brings them at the same (treated) disease rates as those starting with an estimated risk of 20% or higher. The relevance is that the intermediate risk group constitutes around 36% of the 55-79 year old Dutch population. Of all CHD events in this age group, over one third occurs in the intermediate risk group. Our proposal may show that around 9% of these CHD events may be prevented using this approach.