This document discusses potential pitfalls in coronary pressure assessment during fractional flow reserve (FFR) measurements. It identifies technical issues like loose connections, improper zeroing or equalization, drift, and inadequacies of the recording system. Procedural problems are also outlined such as issues with guide catheter size, engagement, flushing, or side holes as well as wire-related problems. Insufficient hyperemic stimulation can also lead to underestimation of lesions. Recognizing possible sources of error is important to performing reliable FFR measurements.

1. Pitfalls in coronary pressure
assessment
Zsolt Piróth MD FESC
Gottsegen György Hungarian Institute of Cardiology
3rd
Physiology for Coronary Intervention Workshop
Sarasota, Nov. 29, 2018

2. „Coronary pressure never lies”
if you know
What to ask
How to set the right question
Koolen JJ et al., CCI 2008

3. Potential problems
Technical issues:
• loose connection, leak in guide connections
• improper zero, equalization
• drift
• „cursor” location
• inadequacy of the recording system
Procedural problems:
• guide catheter related (size, sidehole, deep engagement, flush)
• wire related (introducer needle, accordion)
• insufficient hyperemia (drug, dose, administration)
Patient subsets:
• ostial, diffuse disease, serial lesions
• microvascular disease
• LVH, exercise-induced vasoconstriction
• extreme tortuosity

4. Loose connection

5. Zeroing issues - height of transducer
Based on K. G. Oldroyd, TCT 2009
I. Transducer ↑  Pa↓
II. Correct height
III. Transducer ↓  Pa↑
∆h 13 mm  1 mmHg error
II. I. III.

6. Equalization – introducer needle

7. Equalization – introducer needle

8. Equalization – introducer needle
K. G. Oldroyd, TCT 2009; B. de Bruyne ETP 2011

9. Equalization – introducer needle
K. G. Oldroyd, TCT 2009; B. de Bruyne ETP 2011

10. Pressure distal (Pd)
- blood pressure distal to the lesion (pw)
Pressure arterial (Pa)
- aortic pressure (conventional transducer)
Equalization
Pd
Pa

11. Drift vs true gradient
Drift
• identical morphology
• aortic notch in the distal curve
• equal gradient throughout systole
and diastole
True gradient
• different morphology
• distal pressure ventricularised
• at rest:
– predominantly diastolic gradient
– no or small systolic gradient
• at hyperemia:
– increase of diastolic gradient
– also some systolic gradient

12. Faulty measurement of Pa
Change in the height of the transducer
Capillary forces in the guiding catheter
Large introducer needle left in the Y connector
Wedging of the guiding catheter
Guiding catheter with side holes
Automated contrast machine
Faulty measurement of Pd
Microscopical air bubbles in the sensor capsule
Change of temperature (room → blood)
Blood / saline at the electrical connection
What causes drift?
Preventable
with training

13. Drift vs true gradient
If drift is suspected:
• re-equalisation
• pressure-pull back curve with correction
• during PCI consider placing a 2nd
wire before
removing pw

14. Cursor location
Don’t place blind trust in
computer assisted
measurements!

15. Inadequacy of the recording system
Nico H. J. Pijls, Brussels, 2008
Mean pressure should be averaged on a beat-to-beat basis; take the lowest value

16. Potential problems
Technical issues:
• loose connection, leak in guide connections
• improper zero, equalization
• drift
• „cursor” location
• inadequacy of the recording system
Procedural problems:
• guide catheter related (size, sidehole, deep engagement, flush)
• wire related (introducer needle, accordion)
• insufficient hyperemia (drug, dose, administration)
Patient subsets:
• ostial, diffuse disease, serial lesions
• microvascular disease
• LVH, exercise-induced vasoconstriction
• extreme tortuosity

17. Size of guiding
3 mm
3 mm
3 mm 1.98 mm
2.31 mm
2.64 mm77 %
59 %
43 %
Area stenosis8F
7F
6F
Nico H. J. Pijls, Educational Training Program ESC, 2007

18. Deep seated guiding

19. Unseated guide

20. Damping of the aortic pressure

21. Guiding with sideholes
Pc ≠ Pa
Nico H. J. Pijls, Educational Training Program ESC, 2007
Pd
Pc
Pa

22. Guiding with sideholes
Nico H. J. Pijls, Educational Training Program ESC, 2007
iv Adenosineiv Adenosineiv Adenosine

23. Guiding catheter related problems
Large guiding
• size of guiding - ostial disease, narrow ostium
• insufficient hyperemia
 smaller F size, avoid guiding being sucked
 disengage, iv Adenosine
Guiding with sideholes
• unreliable aortic pressure measurement
 avoid SH guiding
 iv Adenosine, withdraw guiding from ostium
Inadequate flushing
• pressure artefacts
 thorough flushing

24. Capillary forces of the contrast
Pc ≠ Pa
Nico H. J. Pijls, Brussels, 2008

25. Guidewire related problems
Whipping artifact
pw sensor hits the coronary wall
spikes appear in the waveform
 move the wire

26. Guidewire related problems
Accordion effect
in tortuous vessels
pseudo-stenosis
 remove wire
B. de Bruyne The Accordion Phenomenon, Circulation. 2008; 118: e677-e678

27. Insufficient hyperemia
K. G. Oldroyd, TCT 2009
Insufficient hyperemia
Underestimation of gradient
Overestimation of FFR
Underestimation of lesion severity

28. Choice of hyperemic stimuli - pitfalls
IV Adenosine:
• infuse through central vein
• high volume infusion pump
• check infusion, pump system and lines
• incorrect dose mix or dilution
• avoid Valsalva maneuver during infusion
Intracoronary route:
• guiding catheter position - failure to seat
• guiding catheter side-holes
• too quick
• flow obstruction
• incorrect dose mix or dilution

29. Potential problems
Technical issues:
• loose connection, leak in guide connections
• improper zero, equalization
• drift
• „cursor” location
• inadequacy of the recording system
Procedural problems:
• guide catheter related (size, sidehole, deep engagement, flush)
• wire related (introducer needle, accordion)
• insufficient hyperemia (drug, dose, administration)
Patient subsets:
• ostial, diffuse disease, serial lesions
• microvascular disease
• LVH, exercise-induced vasoconstriction
• extreme tortuosity

30. Non-ischemic FFR despite tight stenosis
Physiologic explanations:
• Stenosis hemodynamically nonsignificant despite
angiographic appearance
• Small perfusion territory, old MI, little viable tissue, small
vessel
• Abundant collaterals
• Severe microvascular disease (rarely affecting FFR)
Interpretable explanations:
• Other culprit lesion
• Chest pain of noncardiac origin
Actual false negative FFR:
• Acute phase of ST elevation myocardial infarction
• Exercise-induced spasm
Nico H. J. Pijls, Educational Training Program ESC, 2009

31. How to avoid pitfalls
• know your system
• train your team
• follow the same procedural steps each time
• be consistent in your decisions

32. Conclusions
• FFR measurement is a straightforward procedure
• There are however some pitfalls that are
• avoidable
• recognizable
• easy to resolve
• Negative FFR is almost always a true negative

33. Thank you for your attention!
Pitfalls - if recognised - can make you
even stronger…