Table 2. Challenges and pitfalls related to physiological assessment.

Patient factors
Challenges and pitfalls	Comment	Solution
Presence of significant ostial CAD	Identified with ventricularisation or “damping” pressure waveform on engagement, not assessable with some FCA modalities	Reposition guide catheter to a more proximal position, ensure coaxiality, consider downsizing guide catheter, use an additional guidewire or septal wire to control catheter tip position
Haemodynamic crosstalk in presence of tandem lesions	Sequential lesions along a vessel invariably physiologically influence the other lesions in the vessel	Consider simulated planning prior to undertaking PCI on 1 or 2 stenoses based on longitudinal vessel analysis obtained with functional coronary angiography, NHPR, or FFR
Procedural factors
Challenges and pitfalls	Comment	Solution
Pressure wire drift	Offset of pressure reading during the procedure	Repeat procedure, use drift correction/re-normalise, or use image-based technique
Pseudostenosis caused by intracoronary wires	Straightening of tortuous vessels by intra-coronary wire may generate introsusceptions with haemodynamic relevance	Consider FCA as an alternative to intracoronary pressure guidewires
Ventricularisation/damping of aortic pressure	Guiding catheter engaged abutting the vascular lumen or in significant ostial lesions	Reposition guide catheter, ensure coaxiality, consider downsizing guide catheter, equalisation of pressure guidewire is advised
Use of guide catheter with side holes	False estimate of Pa at the tip of the guiding catheter	Advise not to use catheter with side holes for intracoronary assessment. If needed for clinical reasons, ensure catheter disengagement and use of IV adenosine.
Use of guide catheter extensions	May cause ventricularisation of Pa, if introduced after pressure equalisation, may modify Pa and affect measurements	Perform pressure equalisation with extension within guide catheter, withdraw guide extension at the time of physiological assessment
Use of coronary microcatheters	If used after pressure equalisation, may modify Pa and affect measurements	Perform pressure equalisation with microcatheter within guide catheter before measurements
Wire whipping	Pressure wire signal degrading through contact with vascular lumen	Repositioning of the pressure wire often resolves this issue
Transient microvascular dysfunction associated with the procedure	Rotational atherectomy and PCI tools generating microparticles may cause transient microvascular dysfunction, affecting pressure indices	Consider FCA as an alternative to intracoronary assessment if transient microvascular dysfunction is assumed or suspected
FFR measurement in region without stable hyperaemia	Whilst the software reports the lowest physiological reading, these might not be in stable hyperaemia and therefore overestimate lesion severity	Measure FFR in stable hyperaemia, and if needed adjust measurement points manually
CAD: coronary artery disease; IV: intravenous; FCA: functional coronary angiography; FFR: fractional flow reserve; NHPR: non-hyperaemic pressure ratio; Pa: aortic pressure; PCI: percutaneous coronary intervention