The purpose of the current study is to assess complete coronary physiology (FFR, RFR, CFR, IMR, and CT-FFR) in TAVI candidates with intermediate coronary artery stenosis before and 6 months after TAVI. This aims to determine how TAVI affects coronary blood flow and coronary microcirculatory function after longer-term follow-up, and how these effects influence FFR and RFR values. In addition, it is aimed to correlate invasive functional testing (FFR and RFR) with non-invasive CT-FFR before and 6 months after TAVI.

Prospective, single center, open-label study to

1. compare coronary flow reserve (CFR), index of microvascular resistance (IMR), fractional flow reserve (FFR) and resting full cycle ratio (RFR) values before TAVI and 6 months after TAVI
2. correlate testing of microcirculatory function (IMR) with measurements of functional testing (FFR and RFR) before and six months after TAVI
3. correlate functional testing (FFR and RFR) with computed tomography (CT) derived fractional flow reserve (CT-FFR) before and six months after TAVI.

Inclusion Criteria:

• Age >18 years
• Willing to participate and able to understand, read and sign the informed consent document before the planned procedure
• Severe symptomatic aortic stenosis with indication for TAVI according to current guidelines deemed by the Heart Team
• Patients who have undergone coronary CT angiography before TAVI in which CAD could not be ruled out
• CAD in one or more native major epicardial vessels or their branches by coronary angiogram with visually assessed coronary stenosis, in which the physiological severity of the lesion is in question (typically 40-90% diameter stenosis).
• Eligible for invasive coronary angiography and functional assessment (FFR, RFR, CFR and IMR)
• Eligible for coronary CT-angiography and functional assessment (CT-FFR)

Exclusion Criteria:

• Patients whose CT-angiography was determined to be non-diagnostic/unreadable during its evaluation
• Previous coronary artery bypass grafting with patent grafts to the interrogated vessel
• Patients with severe lesions with a diameter stenosis ≥ 90%, flow-limiting lesions, or a significant left main coronary artery stenosis
• Critical coronary artery disease deemed by the Heart Team to require immediate revascularization
• Contraindication to adenosine (e.g. bronchial asthma)
• Chronic renal impairment with severe reduction of glomerular filtration rate (eGFR <30 ml/min)
• Presence of cardiogenic shock
• Participation in another interventional study involving the left heart or coronary arteries