Invasive Evaluation of Coronary Artery Disease in Severe Aortic Stenosis-A Narrative Review.

The coexistence of severe aortic stenosis (AS) and coronary artery disease (CAD) is common and presents important diagnostic and therapeutic challenges, particularly in patients being considered for transcatheter aortic valve replacement. Accurate assessment of coronary lesion significance in this setting is difficult because severe AS alters coronary haemodynamics, myocardial oxygen demand, microvascular function, and the balance between resting and hyperaemic flow. These changes may influence the interpretation of conventional physiological indices and complicate decisions regarding revascularisation. This narrative review summarises the pathophysiological interaction between severe AS and CAD and examines the contemporary evidence supporting invasive and non-invasive approaches to coronary assessment. We review the limitations and potential utility of fractional flow reserve, and non-hyperaemic pressure ratios, highlighting the frequent discordance observed between indices and the uncertainty regarding optimal thresholds in severe AS. Importantly, identification of physiologically significant lesions should be distinguished from evidence that revascularisation of these lesions improves clinical outcomes, as prospective outcome data remain limited. While recent trials support physiology-guided revascularisation in patients undergoing TAVR, outcome data remain linked primarily to conventional FFR thresholds rather than proposed AS-specific cutoffs. We also discuss emerging non-wire-based approaches, including quantitative flow ratio and computed tomography-derived fractional flow reserve, which may offer complementary value in selected patients. In addition, we examine the practical implications of coronary physiology for clinical decision-making before and after valve intervention, including the timing of percutaneous coronary intervention and the need to distinguish lesion-level diagnostic performance from evidence of clinical benefit. Current data suggest that no single modality is universally applicable and that assessment should be individualised according to lesion characteristics, clinical context, and procedural strategy. Proposed severe AS-specific thresholds for FFR and NHPR are derived from small predominantly observational studies, have not been prospectively validated against clinical outcomes and should be hypothesis-generating. A hybrid approach integrating angiographic, physiological, and computed tomography-based information may be most useful. Further prospective studies are needed to define optimal thresholds, validate management algorithms, and clarify whether physiology-guided strategies improve outcomes in severe AS.