Assessment of Lipoprotein(a) and Endogenous Fibrinolysis in Atherosclerotic Cardiovascular Disease/Aortic Valve Disease

The risk of a clot forming in a blood vessel, which can cause a heart attack or stroke, is determined partly by how "sticky" the blood is and partly by the effectiveness of the natural defences in the blood in dissolving any clots that start forming (clot lysis, or "fibrinolysis").

In the last few years, using new blood testing techniques, we and other groups, have shown that individuals who have less effective natural clot lysis, have a much higher risk of heart attack, stroke and death, even despite current best medications.

Therefore, we would like to find medications that can make clot lysis more effective, in such individuals, to reduce their risk of stroke and heart attack. Unfortunately, most blood thinning tablets for long term use do not improve clot lysis. Earlier, our group has shown that the anticoagulant apixaban, mildly improved clot lysis

Elevated concentration of Lp(a) in the blood is a risk factor for the development of cardiovascular disease including coronary artery disease and narrowing of the aortic valve. Lp(a) may exert its adverse effects by impairing fibrinolysis. Plasmin is an important enzyme present in blood that degrades many blood plasma proteins, including fibrin clots. Lp(a) has a high degree of homology to plasminogen (a pro-enzyme that is cleaved to form plasmin) and may cause thrombosis by competitively inhibiting t-PA-mediated plasminogen activation and tPA-mediated clot lysis. Furthermore, Lp(a) stimulates the activity of PAI-1, which is the major inhibitor of the fibrinolytic system.

Until recently, Lp(a) has been considered a non-modifiable cardiovascular risk factor as few therapies are available to sufficiently reduce Lp(a) levels. New data, however, have shown that novel cholesterol lowering treatments, namely PCSK9 inhibitors and inclisiran (a long-acting silencing RNA) can reduce Lp(a) levels by approximately 20-25%.

Given Lp(a) is a causal risk factor for cardiovascular outcomes, it is important to know if a reduction in Lp(a) can favourably modify endogenous fibrinolysis.

If Lp(a) level is directly related to the effectiveness of endogenous fibrinolysis, then medications that reduce Lp(a) (currently PCSK9i and/or inclisiran, and others in development) could be used as targeted treatment for patients who despite optimal antithrombotic therapy, demonstrate impaired endogenous fibrinolysis.

Inclusion criteria

• Male and female patients aged 18 years or over

• i) Patients identified as eligible for treatment with either a PCSK9i or inclisiran ii) Patients diagnosed with moderate or severe calcific aortic stenosis based on non-enhanced Cardiac CT scan

• Willing and able to understand the Participant Information Sheet and provide informed consent

• The patient must agree to comply with the drawing of blood samples for the assessments

• The patient does not meet any of the exclusion criteria

Exclusion criteria

• Inability to provide valid informed consent
• Male and female patients aged < 18 years of age
• The patient has, in the opinion of the investigator, significant neurological, hepatic, renal, endocrine, gastrointestinal, pulmonary, haemorrhagic, metabolic or other disease likely to confound the study requirements or analyses
• The patient has a history of substance abuse or demonstrates signs or clinical features of active substance abuse or psychiatric disease
• Alcohol consumption above recommended safe levels (i.e., more than 14 units per week) due to the potential effects of high alcohol levels on platelet reactivity
• Any illness deemed significant by the investigator during the four (4) weeks preceding the screening period of the study
• Any major bleeding diathesis or blood dyscrasia (platelets < 70 x 109/l, Hb < 8 g/dl, INR > 1.4, APTT > x 2 upper normal limit, leucocyte count < 3.5 x 109/l, neutrophil count < 1 x 109/l)
• Currently enrolled in an investigational device or non-licensed drug trial