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.
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
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
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…