In this 'Cath Lab Guide to Coronary Reactivity Testing', Dr Robert Jay Widmer (The McKinney Heart Hospital, US) outlines the rationale for performing invasive coronary reactivity testing following shared decision-making, emphasising the value of a structured, protocol-driven approach over ad hoc measurements. 

He discusses the decision to use a 6F femoral approach in this small female patient, highlighting the role of ultrasound-guided micropuncture, meticulous guiding catheter selection, and precise wire placement in the distal two-thirds of the LAD to ensure accurate thermodilution transit times. 

Dr Widmer also underscores key radiation safety practices—including use of the Rampart system and a lead-free workflow—alongside baseline LVEDP measurement and angiographic evaluation of all major epicardial vessels.
 

Key learning points:

• When to proceed to invasive coronary function testing after non-diagnostic yet persistent symptoms and inconclusive non-invasive results.
• Technical details in vascular access and guide-wire positioning that influence the accuracy of CFR and IMR data.
• How to plan the sequence of angiography, physiology, and vasoreactivity testing in advance to complete a thorough yet efficient (~30-minute) procedure.