How stable is stable coronary artery disease?
As stable CAD is multifaceted, its prevalence, incidence, and prognosis have been difficult to assess, and numbers vary widely between studies, partly depending on the definition that has been applied. In addition, within the heterogeneous population of stable CAD, an individual’s prognosis can vary considerably depending on baseline clinical, functional, and anatomic characteristics. Data derived from randomized clinical trials of antianginal and secondary prevention therapies and/or revascularization, such as the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) 3 and the Second Randomized Intervention Treatment of Angina (RITA-2) 4 trials, indicate an annual mortality of 1.2–2.4%, with an annual incidence of cardiac death of 0.6–1.4%, whereas in the Reduction of Atherothrombosis for Continued Health (REACH) registry, which included stable but high-risk patients with a high prevalence of peripheral artery disease and diabetes, annual mortality was three times higher, reaching 3.8% 5.
In this issue of the journal, Bauters and colleagues present the 5-year risk of cardiovascular (CV) death of 4184 patients with stable CAD from the CORONOR registry conducted in the northernmost province of France, Nord-Pas-de-Calais, an area on the Belgium border where lifestyle habits including diet are more akin to northern Europe. Patients with previous myocardial infarction, coronary revascularization, or with documented CAD on coronary angiography were enrolled to the registry if they were free from any myocardial infarction or revascularization for at least 1 year, and they were followed for 5 years. The CORONOR study population is characterized by a mean age of 67 years with 78% male and 31% of patients with diabetes. Importantly, most cases of death in this registry were non-CV, whereas CV death risk was 1.3% a year, with heart failure and sudden death as the main causes of CV death.
As for the population of the study, the median time between the last coronary event and inclusion was 5 years; in that sense, the study population does not necessarily represent the typical population of stable CAD, but an even more ‘stable’ one that has withstood the test of time. However, patients with other comorbidities, such as cancer and severe lung disease that may potentially interfere with life expectancy and are therefore typically excluded from randomized controlled trials were not excluded from this registry, providing insight into the residual risk of CV death of a real-world, truly stable CAD population.
Cumulative 5-year CV death rate in the CORONOR registry was found to be 6.7%. At first look, this may seem like a surprising finding, as one may expect a higher risk of CV death among patients with established CAD, especially when considering the high risk of CV death using the SCORE risk assessment 6 attributed to patients with CV risk factors only, with no known CAD. According to the SCORE, the calculated 10-year risk of CV death of a 65-year-old smoker with borderline blood pressure and total cholesterol values is more than 15%, exceeding the annual risk of 1.3% presented here for the CORONOR population.
CAD remains the leading cause of death in the North America and Europe and is rapidly increasing in Asia and other areas with emerging economies. At first glance the findings from the CORONOR study appear inconsistent with this fact.