Physiology Decision Tree

This Physiology Decision Tree derived from Beltrame et. al (2021) offers clarity of diagnosis between epicardial disease, vasospastic angina & microvascular disease.

Historically, a negative physiology study with persistent chest pain would lead a physician to either try vasodilatory agents or suggest a cause non-cardiac in origin.

Using IMR & CFR synergistically with FFR or RFR, funnels the diagnosis down to a specific cause. In this case, the addition of IMR/CFR allows differentiation between coronary microvascular disease and vasospastic angina.

Treatment pathways have been devised to guide pharmacological therapy for both MVD and VSA.

Equalisation

Advance the wire.

Position the pressure sensor 2-3mm outside of the guide catheter to prepare for equalisation. The marker can be visualised on fluoroscopy

(note the colour change from wire tip to body).

Equalise Pd/Pa on the console while in this position.

Transition point visible on Fluoro

Introducer Needle

Ensure the introducer is removed before taking measurements.

Leaving the introducer in the Copilot creates an opening in the closed loop system. Backflow of blood can reduce Pa pressure by up to 5mmHg. This will directly affect the FFR measurement & more so Non-hyperaemic indices.

Contact your local representative to learn more.

PressureWire X

Ensure that the 'Connect' button is pressed on the console before turning on the wire.

PWX will blink green while establishing a connection.

The wire will turn solid green. It will automatic synchronize to the console & zero itself for use.

You are now ready to proceed.

Elevation

Ensure PWX and manifold are at the same elevation during Pa & wire zeroing.

For every inch they are apart in elevation, it introduces a 2mmHg differential.

If the environmental drift in pressure is large enough, it will result in a less than accurate measurement. This will directly impact if a PCI strategy is implemented.

Minimize wall contact = minimize dampening

Coaxial Engagement

The guide catheter tip should be positioned as luminal as possible without touching the vessel wall.

Wall contact can result in dampening of Pa pressure and poor delivery of hyperaemic agents for FFR & saline bolus for CFR/IMR.

Dampening of Pa pressure will directly effect FFR & RFR measurements.

Minimize wall contact = minimize dampening

Optimal Setup
FFR
RFR
CFR/IMR

The Optimal Setup screen aims to standardise how Cardiac Catheter laboratories setup for diagnostic Physiology. It provides suggestions that aid in minimising test variability & reducing the likelihood of wire & environmental related drift.

Click the

buttons for more information

Baseline
Induce Hyperaemia
Snapshot
Single Lesion Pullback
Tandem Lesion Pullback
Check for Drift

The wire is zeroed and equalised at the guide catheter.Lets begin our FFR by inducing hyperaemia.

Press "Induce Hyperaemia" button to administer 140μg/kg/min of IV adenosine

Adenosine Infusion Active: 140μg/kg/min

When IV adenosine infusion is active, the status is indicated above the trace.

Pd & Pa traces begin to separate as we approach maximal hyperaemia.Let's now select the lesion subset we will be performing FFR on.

Adenosine Infusion Active: 140μg/kg/min

For a static FFR, the pressure sensor should be positioned as distal as possibleto the lesion. While stationary at this point, an FFR reading should bemeasured on the console.

Note: We do not pull the wire back across the lesion for this type of measurement.(only to check for drift at the end of our measurement)

Adenosine Infusion Active: 140μg/kg/min

For a single lesion pullback, the pressure sensor should begin asdistal as possible to the lesion. Start recording the measurement by pressing 'Rec' and slowly pull the wire back across the lesion until it is 1-2mm outside the guide catheter.

As the lesion is crossed, you should notice a jump in the pressure gradient (yellow line).As we cross the lesion and move closer to the aorta, FFR will return to 1.0 (+/- 3mmHg). In this example, no drift has been introduced into the measurement.

Adenosine Infusion Active: 140μg/kg/min

For a tandem lesion pullback, the pressure sensor should begin approximately 1 cm past the distal-most lesion. Start recording the measurement by pressing 'Rec' and slowly pull the wire back across both lesion until it is 1-2mm outside the guide catheter.

As the lesions are crossed, you should notice an increase in the pressure gradient (white line).This should happen each time a lesion is encountered. As we move closer to the aorta, the FFR will return to 1.0 (+/- 3mmHg).

Adenosine Infusion Active: 140μg/kg/min

It is critical that we test for drift after each measurement.

Environmental or wire factors that interfere with pressure measurements may resultin stenting a patient that does not require PCI therapy. This can increase the probability of MACE.

In this example, the wire has been brought back to the guide and the FFR reads 1.0. No drift has interfered with our measurements.

Acceptable Drift = +/- 3mmHg

Baseline
Snapshot
Single Lesion Pullback
Tandem Lesion Pullback

For RFR, like other non-hyperaemic indices, no adenosine infusion is required.

The Pressurewire can be advanced beyond the lesion of interest without a hyperaemia inducing agent. Select one of the lesion subsets to perform an RFR measurement.

**No Adenosine required for Non-hyperaemic indices**

To perform a static RFR, the pressure sensor should be positioned as distal as possible to the lesion. While stationary at this point, an RFR reading can be measured on the console.

Note: We do not pull the wire back across the lesion for this type of measurement.

**No Adenosine required for Non-hyperaemic indices**

For a single lesion pullback, the pressure sensor should begin as distal as possible to the lesion. Slowly pull the wire back across the lesion until it is 1-2mm outside the guide catheter.

As the lesion is crossed, you should notice an increase in the pressure gradient (white line).Pd pressure will normalise, and the RFR will return to 1.0 (+/- 3mmHg) as the wire sensor moves closer to the aorta.

**No Adenosine required for Non-hyperaemic indices**

For a tandem lesion pullback, the pressure sensor should begin approximately 1 cm past the distal-most lesion. Start recording the measurement by pressing 'Rec' and slowly pull the wire back across both lesion until it is 1-2mm outside the guide catheter.

As the lesions are crossed, you should notice an increase in the pressure gradient (white line).This should happen each time a lesion is encountered. As we move closer to the aorta, the FFR will return to 1.0 (+/- 3mmHg).

Place PressureWire X as distal as possible to interface withthe microcirculation. A proximal and distal thermistor (temperature sensor) are responsible for measuring the mean transit time (Tmn) of injected saline as it perfuses the microcirculation.

The mean transit time is measured 3 times at baseline & 3 times during hyperaemia.

Press 'Inject Saline' to administer a single 3ml saline bolus

The system will measure the transit time of the first bolus across the wire thermistors. This measurement is placed in the first Rest transit time box seen above in the trace.

To continue with the second baseline saline bolus press "Inject Saline"

Press 'Inject Saline' to administer a single 3ml saline bolus

The system will measure the transit time of the second bolus across the wire thermistors. This measurement is placed in the second Rest transit time box seen above in the trace.

To continue with the third baseline saline bolus press "Inject Saline"

Press 'Inject Saline' to administer a single 3ml saline bolus

Induce Hyperaemia

The system will measure the transit time of the third bolus across the wire thermistors. This measurement is placed in the third Rest transit time box seen above in the trace.
‍
A Mean Transit Time is now calculated at rest and recorded in bold and underlined.

Let's now start our IV adenosine and perform the same 3 tests at hyperaemia.Press "Induce Hyperaemia" to proceed.

Inject Saline

The system will measure the transit time of the first bolus across the wire thermistors. This measurement is placed in the first Hyp transit time box seen above in the trace.

To continue with the second baseline saline bolus press "Inject Saline"

Press 'Inject Saline' to administer a single 3ml saline bolus

Induce Hyperaemia

The system will measure the transit time of the second bolus across the wire thermistors. This measurement is placed in the second Hyp transit time box seen above in the trace.

To continue with the second baseline saline bolus press "Inject Saline"

Press 'Inject Saline' to administer a single 3ml saline bolus

Induce Hyperaemia

The system will measure the transit time of the third bolus across the wire thermistors. This measurement is placed in the third Hyp transit time box seen above in the trace.

Once the third transit time is collected, the system will calculate the FFR, IMR & CFR automatically.

Click the "Analyse Results" button to visit the review screen.

Analyse results

Inject Saline

To perform a static RFR, the pressure sensor should be positioned as distal as possible to the lesion. While stationary at this point, an RFR reading can be measured on the console.

Note: We do not pull the wire back across the lesion for this type of measurement.

For a single lesion pullback, the pressure sensor should begin as distal as possible to the lesion. Slowly pull the wire back across the lesion until it is 1-2mm outside the guide catheter.

As the lesion is crossed, you should notice an increase in the pressure gradient (white line).Pd pressure will normalise, and the RFR will return to 1.0 (+/- 3mmHg) as the wire sensor moves closer to the aorta.

For a tandem lesion pullback, the pressure sensor should begin approximately 1 cm past the distal-most lesion. Start recording the measurement by pressing 'Rec' and slowly pull the wire back across both lesion until it is 1-2mm outside the guide catheter.

As the lesions are crossed, you should notice an increase in the pressure gradient (white line).This should happen each time a lesion is encountered. As we move closer to the aorta, the FFR will return to 1.0 (+/- 3mmHg).

Analysis

Let's use a decisions tree to determine the outcome of the IMR/CFR procedure.

What is FFR telling us?0.75 = significant

What is IMR telling us?56 = significant(IMR>25 is +ve)

What is CFR telling us?1.4 = significant(CFR<2 is +ve)

This patient has:1. An epicardial lesion requiring PCI.2. MVD - optimal pharmacology therapy will help angina.3. CFR indicates presence of flow disturbance.

Decision Tree