CC8: PCI and Radi-wire FFR Flashcards
What things could make PCI complex?
-Calcified lesions
-Bifurcation lesions
-Unprotected left main coronary lesions
-Chronic total occlusions
-Ostial lesion
-Graft PCI
How can calcified lesions affect stent?
-Stent under-expansion
-Stent malapposition
What is rotablation?
-Rapidly rotating burr to modify calcium
-Increase lumen size
Downsides of rotablation
-Higher complication rate compared to shockwave
-Causes trauma to vessel
-Doesn’t collect calcium so could flow downstream
What drugs are given during rotablation and why?
Heparin
-Prevents thrombus
Nitrate
-Prevents spasm
Verapamil
-no-reflow
Shockwave balloon and its benefits
-Sonic waves aim to fracture the intra-plaque calcium
-Reduced vascular intimal injury
-Ease of use
What needs to be considered when lesion is at bifurcation?
-There is a risk of losing the side branch when atheroma/thrombus is displaced
-So 2 wires are used to allow access to side branch if needed
Techniques for treating bifurcation lesions
-Jailed wires
-Post stent optimisation technique (POT)
-Kissing balloons
How to stent left main?
-Wires down LAD and Circ
-Megatron stent used because it can be over-expanded
-Likely to have pressure drop (have metaraminol)
-Left main inflations short as possible
Megatron stent and uses
-Can expand from 3.5 to 6mm
Used for:
-Tapered vessels
-Bifurcations
-Proximal optimisation technique (POT)
Issues with ostial stenting
-Ostium may be missed
-If struts extend to aorta, makes re-engaging coronary very difficult
-Stent struts can be flared
CTO antegrade technique
-Negotiate proximal cap
-Advance length of occluded segment
-Wire exchanges over micro-catheter
-Dilate and modify (rota/shockwave)
-Stent
-IVUS
CTO retrograde technique
-Soft wire negotiated through donor artery and collaterals into distal target vessel
-At site of occlusion, soft wire exchanged over microcatheter for stiff wire
Why is it easier to cross the fibrous cap retrogradely?
-Proximal cap is likely fibro-calcific
-Proximal cap is likely to be at a side branch ostium
Risks of graft PCI?
-Mean age of patients is older
-Higher burden of other disease
-Higher risk of no-reflow
-Higher risk of perforations
What factors could make PCI complex?
Patient comorbidites
-HF
-Diabetes
-Unstable angina/NSTEMI
Complex CAD
-Multi-vessel disease
-Left main disease
-Long lesion
Haemodynamic compromise
-Low EF
-Low CO
Operator experience
-Individual skills
-Personal experience
Why do we use pressure wire?
-Used for moderate/intermediate lesions to help decide whether or not a stenosis is significant
-Comparing blood pressure before and after stenosis provides information about blood flow
How is guide catheter used in pressure wire?
-Positioned at ostium of vessel
-Pressure is measured invasively via closed fluid system to transducer
How is transducer used in pressure wire?
-Ensure transducer at patient’s heart level
-Ensure good aortic pressure trace before starting pressure wire study
How to prepare pressure wire?
-Flush wire in packaging with saline
-Ensure pressure sensor fully immersed in saline, requires 20-30ml flush
-Allow pressure sensor to stabilise in saline solution for 1 min on flat surface before zeroing wire
Describe the pressure wire
-Wire has 3cm radio-opaque tip before pressure wire sensor
-Sensor is 3cm from tip of wire
4 steps in pressure wire
Step 1: Zero transducer
Step 2: Connect wire
Step 3: Equalise pressure wire
Step 4: Advance wire beyond lesion
(pressure sensor at least 2-3cm distal to lesion)
How to introduce pressure wire
-Minimal shaping to tip of wire to prevent damage to pressure sensor
-Introducer needle helps advance and position
-But must be removed prior to any equalisation or measurements being made
How are coronary spasms prevented in pressure wire study?
-Nitrates given intra-coronary beforehand
-Ensures vessel is at maximum lumen diameter
Why do we normalise/equalise pressure wire?
-Usually a small drift between catheter and pressure wire
-Normalising/equalising allows system to adjust for any drift
-Ensure catheter is well-flushed of contrast and medications prior to equalising
What should you do if there is large difference in catheter and pressure wire pressures before equalising?
-Ensure introducer needle removed
-O ring/Y connector fully closed?
What should pressure be after equalising
1.0
-No difference between catheter and pressure wire
Equalisation in ostial lesion assessments
-For aorto-ostial lesions equalisation performed with catheter and pressure wire in the aorta
What can cause damping of aortic waveform in pressure wire study?
-A wedged guide catheter in the ostium of the right or left main vessel
What is FFR
Fractional Flow Reserve
-Adenosine given to dilate vessels and increase blood flow, inducing ‘maximum hyperaemia’
-Patients should have haemodynamic response to adenosine even if lesion is not significant
Effect of giving adenosine
-Normally small pressure increase and then decrease indicates hyperaemia achieved
-Adenosine may cause heart block
-Patients feel SOB with hyperaemia
What FFR value indicates lesion?
FFR<0.80 indicates significant lesion
FFR>0.80 no significant benefit by treating lesion
How can a significant narrowing on angiogram not be causing ischaemia?
-FFR accounts for size of perfusion area
-FFR accounts for contribution of collaterals
What is IFR/RFR?
RFR - Resting Full cycle Ratio
IFR - Instantaneous wave-free Ratio
-Non-stress measurement of intracoronary pressure difference
-Uses diastolic flow reserve and average of 3-5 beats
-Significant if <0.90
When shoudl IFR/RFR be used instead of FFR?
-When adenosine is contraindicated
E.g. In asthmatic patients
Advantages of IFR pullback?
-Provides the benefits of pullback measurements without the need for hyperaemia
-Live display of single-cycle iFR value
-Pullback assessment of multiple lesions
How to do drift check?
-After taking a measurement check the wire has not drifted (sensor error)
-Pullback wire to the position it was normalised
-Flush catheter and ensure Pd/Pa value is back to 1.0
-If value is not within 0.98-1.02, then procedure should be repeated
Reasons or drift
-Has guide catheter been adequately flushed with saline?
-Is pressure wire checked at same position as during equalisation?
-Is guiding catheter same position as during equalisation?
-Has the height of transducer changed?
-Is the introducer needle left in the Y-connector?
-Was the pressure wire prepared correctly? (placed flat and flushed with 20-30ml saline)
When can you get a reverse pressure gradient (e.g. FFR 1.04)?
-In large RCA or Circ vessels
-As wire passes distally and falls below level of transducer
-Can confirm not drift by taking pressure sensor back to ostium of catheter
What is Whipping artefact?
-Can occur when pressure sensor interacts with wall of coronary
-More likely in small vessels
What is CT FFR?
-Newer FFR technology
-Non-invasive
-Coronary CT data sent to HeartFlow for analysis
-Creates personalised 3D digital model of coronary anatomy
-Can predict new FFR value after treating lesion
What is CFR?
Coronary flow reserve
-Measures blood flow in epicardial arteries and the microvasculature
-Calculates difference in flow from resting and hyperaemia, decreases with microvascular disease
<2.5 is abnormal
What is IMR?
Index of microcirculatory resistance
-Measures the blood flow in microvasculature
-Uses FFR to correct for epicardial flow
>25 is abnormal
