In the first retrospective part of the study the investigators will conduct a data analysis of patients having received a bovine aortic graft. The investigators will analyze charts and CT / MRI at various time intervals and identify if there are signs of inflammation.

In the second prospective part the investigators will select survivors from the first part with and without inflammation signs. If they consent to participate in the study the investigators will do a blood sampling in order to perform further immunological analysis. Additionally, the investigators will examine their quality of life by QoL SF-12 questionnaire.

Part 1 Retrospective database search on subjects that received a Shelhigh graft (n= 116) and subjects that received a mechanical graft (n=50) in a similar time frame, age, gender, co-morbidities, clinical history.

Analyzing CT or MRI report at following time intervals: 3 - 6 months postoperatively, 1, 2 and 3 years postoperatively (regular check-up appointments in clinics).

Additionally, extraction of following data-set (based on availability): temperature, lab values (C-reactive protein, white blood count, Eosinophil count), pathology report and CT- / MRI- imaging in cases of re-operation.

Firstly, identify if there is a graft inflammation (positive / negative group within the bovine group).

Secondly, compare to mechanical group.

Part 2 Choose 10 + 10 patients of the bovine group (with / without immune response) and 10 of the mechanical group in order to conduct further immunological testing and comparison. The immunological testing will include measurement of immunoglobulin E and immunoglobulin G antibodies against bovine protein, as well as in vitro T cell reactivity in Interleukin 4 and interferon-gamma Elispot. These parameters will characterize whether the patient mounted an adaptive immune response against the bovine protein. In addition, the investigators will measure total immunoglobulin G4 and Interleukin-6 levels in the serum of all patients, as additional inflammation markers.

Contact patients to come into clinics for a visit, explain study. Blood sampling (1 serum and 1 EDTA) after patients consent.

Material will be sampled and sent in anonymized form via express courier to the Translational Immunology Lab at the University Hospital Basel. Samples will be processed within 24h to isolate peripheral blood mononuclear cells (PBMC) and serum. PBMC and Serum will be cryopreserved at -180°C and -80°C respectively. Samples will be analyzed in batches each including 3-5 subjects per group.

Inclusion Criteria:

• Recipients of the bovine graft or mechanical graft. For the prospective part 2: able to give informed consent by signature, age, matching characteristics and time frame.

Exclusion Criteria:

• Individuals of the patient cohort from the last 20 years who indicated that their data cannot be utilized for future research will be excluded from the study.
• Inability or any contraindications to undergo the planned investigated intervention, clinically significant concomitant diseases precluding ambulatory control in the day clinic in Bern.

Part 1: n=116 bovine (total amount of recipients of the Shelhigh graft at the investigators' institution).

50 (mechanical control)

Part 2: n= 10 (bovine with immune response) +10 (bovine without immune response) +10 (mechanical control)