The CAS study is a prospective observational cohort study investigating the effects of congenital aortic stenosis (ConAoS) on the left ventricular function and the prevalence, pattern and expanse of left ventricular hypertrophy (LVH), myocardial stiffness and myocardial fibrosis.

Congenital aortic stenosis (ConAoS) accounts for 4-8% of all congenital cardiac diagnoses. It is often caused by a bicuspid aortic valve (BAV), which has an estimated prevalence of 0.5-2% in the general population. Patients with ConAoS may remain asymptomatic, but gradual deterioration of the stenosis and the strong association of BAV with aortic dilatation contributes to important morbidity and mortality. The prevalent nature of this heart defect implies an important health problem resulting in hospitalization and (re-) interventions. As it is still largely unknown which markers predict adverse outcome, the aim of this study is to evaluate trends in imaging and biomarkers in this patient population and their relation with clinical outcome.

It is increasingly acknowledged that aortic stenosis is not only a disease of the valve, but also of the left ventricle (LV) and the aorta. In the course of disease progression, pressure overload and ventricular wall stress lead to remodeling of the LV, which eventually leads to left ventricular hypertrophy (LVH) and myocardial fibrosis. Although these processes have been described in patients with aortic stenosis, little is known about the prevalence and prognostic relevance of LVH and myocardial fibrosis in patients with ConAoS, who are often relatively young. Applying upcoming innovative imaging modalities such as high frame rate echocardiography and T1-mapping in patients with ConAoS will increase our knowledge on tissue characterization, which in turn will facilitate identifying patients at high risk for complications and rapid disease progression.

The CAS study is a clinical observational study investigating the effects of ConAoS on the left ventricular function and the prevalence, pattern and expanse of LVH, myocardial stiffness and myocardial fibrosis. Moreover, the prognostic capacity of the presence of these pathological processes will be assessed, correlating findings at baseline to clinical outcome by assessing the occurrence of cardiovascular events and all-cause mortality during 3-year clinical follow-up. The investigators will unravel biomarker and imaging predictors for myocardial dysfunction (systolic and diastolic) with specific attention for male-female differences. This newly gained knowledge will enable the investigators to improve and individualize current treatment protocols and derive novel therapeutic strategies for adult patients with ConAoS.

In order to be eligible to participate in this study, a subject must meet the following criteria:

• Aged ≥ 18 years
• Capable of understanding and signing informed consent.

Inclusion criteria for the CAS study are patients diagnosed with a valvular congenital aortic stenosis. Two groups of patients will be included:

• Patients with a prior aortic valve replacement (AVR)
• Patients without a prior AVR and with an aortic jet velocity ≥ 2.5 m/s.

Exclusion Criteria:

• Patients with severe aortic regurgitation

• Presence of any of the following contra-indications for MRI

  • Contra-indication to gadolinium based contrast media (eGFR <30 ml/min or contrast allergy)
  • Other contra-indications such as presence of pacemaker/implantable cardioverter defibrillator, severe claustrophobia or pregnancy

• Patients known with or previously treated because of aortic coarctation.

• Patients known with genetic syndromes or connective tissue disorders

The study population consists of adult ConAoS patients, who are visiting the outpatient clinic of the Erasmus MC.