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Background and aims: The lysosomal cysteine proteases cathepsin B and S have been implicated in the atherosclerotic process. The present paper investigates the association between serum levels of cathepsin B and S and cardiovascular events and mortality in patients with stable coronary heart disease. Methods: The CLARICOR trial is a randomised, placebo-controlled trial investigating the effect of clarithromycin versus placebo in patients with stable coronary heart disease. The outcome was time to either a cardiovascular event or all-cause mortality. The placebo group was used as discovery sample and the clarithromycin group as replication sample: n = 1998, n = 1979; mean age (years) 65, 65; 31%, 30% women; follow-up for 10 years; number of composite outcomes n = 1204, n = 1220; respectively. We used a pre-defined multivariable Cox regression model adjusting for inflammation, established cardiovascular risk factors, kidney function, and use of cardiovascular drugs. Results: Cathepsin B was associated with an increased risk of the composite outcome in both samples after multivariable adjustment (discovery: multivariable ratio (HR) per standard deviation increase 1.12, 95% confidence interval (CI) 1.05–1.19, p < 0.001, replication; HR 1.14, 95% CI 1.07–1.21, p < 0.001). There was no significant association between cathepsin S and the composite outcome in either the discovery or replication sample after multivariable adjustment (p>0.45). Secondary analyses suggest that cathepsin B was predominantly associated with mortality rather than specific cardiovascular events. Conclusions: Cathepsin B, but not serum cathepsin S, was associated with an increased risk of cardiovascular events in patients with stable coronary heart disease. The clinical implications of our findings remain to be established.

Pregnancy associated plasma protein-A (PAPP-A) is a potential new marker for vulnerable plaques in the coronary arteries only examined in stable coronary disease (CAD) in patients undergoing coronary angiography. Here we address the prognostic value of serum PAPP-A in unselected stable CAD patients.Blood samples were drawn at study entry. Serum PAPP-A values ≥4mIU/L were considered elevated. Mortality and non-fatal myocardial infarction was prospectively registered. The primary outcome was the composite outcome of myocardial infarction and all-cause mortality, secondary outcomes were all-cause mortality and myocardial infarction.Patients (n=4243) were followed for a median of 2.8 years. In a Cox analysis, elevated PAPP-A was significantly related to the composite outcome of myocardial infarction and death (HR 1.99, 95% CI 1.62-2.45, p0.0005), all-cause mortality (HR 2.42, 1.92-3.06, p0.0005), and myocardial infarction (HR 1.40, 1.01-1.94, p=0.046). After Holm's correction, the latter significance disappeared. After adjustment for risk factors and medication at entry, elevated PAPP-A remained significantly related to the composite outcome (HR 1.51, 1.22-1.86, p0.0005) and all-cause mortality (HR 1.68, 1.32-2.13, p0.0005).In patients with stable CAD elevated serum PAPP-A seems promising as aid in identifying patients at high risk for death.