Although adjunctive modalities (stress testing, noninvasive imaging including coronary computed angiography, coronary physiology, and intracoronary imaging) can help evaluate coronary anatomy, coronary angiography remains the most commonly used technique for assessing the presence and severity of coronary artery stenoses and for planning coronary revascularization (surgical or percutaneous).
For coronary angiography to provide accurate information about coronary anatomy, it should be performed using meticulous technique, which can help maximize the accuracy of the imaging, while minimizing the potential risks associated with the procedure.
6.1
Step 1. Ensure there is good pressure waveform
6.1.1
Goal
To ensure that the catheter tip is free and coaxial with the coronary artery ostium, not obstructing coronary flow or engaged against the arterial wall and that the catheter lumen is clear of any foreign material, such as thrombus, plaque, or air.
This is performed as described in step 6 of Chapter 5 : Coronary and Graft Engagement ( Section 5.6 ).
6.2
Step 2. Test contrast injection
6.2.1
Goal
To confirm that the tip of catheter is engaged in the coronary artery (or bypass graft) ostium. Optimally, the catheter should engage the ostium coaxially to avoid tenting which could lead to dissection.
Sometimes test injection may not be necessary if the operator is certain (based on catheter movement and “jump” motion of the catheter) that the coronary ostium is engaged.
6.2.2
How to?
- 1.
1–2 mL of contrast is injected through the catheter (that has been cleared of any thrombus, air, or debris as described in Section 5.6 .
6.2.3
What can go wrong?
6.2.3.1
Coronary artery dissection ( Section 5.6.4.3 and Section 25.2.1 and PCI Manual Online case 40 )
Causes:
- •
Suboptimal catheter engagement (e.g., deep catheter intubation, subintimal or noncoaxial intubation, or catheter positioned at the edge of or under an eccentric plaque, especially of the left main coronary artery).
- •
Ostial coronary lesion.
- •
Forceful contrast injection (usually when performed in the setting of suboptimal catheter engagement as described above).
- •
Dampened arterial waveform.
Prevention:
- •
Ensure nondampened pressure waveform (step 1 in this chapter) before injecting contrast.
- •
Ensure coaxial catheter placement.
- •
Inject contrast gently (if manual injection is used).
Treatment ( Section 25.2.1 ):
- •
STOP injecting contrast.
- •
Gentle catheter retraction.
- •
Wire through dissected coronary artery with a workhorse guidewire into the true lumen, or reenter distally using chronic total occlusion techniques. It may be necessary to select a guide catheter with a slightly different distal curve than the one that caused the dissection.
- •
Stent area of dissection. Intravascular imaging is strongly recommended to ensure complete coverage of the ostial dissection by the stent.
- •
Treat patient symptoms as appropriate.
6.2.3.2
Coronary embolization ( Section 5.5 , Section 25.2.3 )
.
6.3
Step 3. Administer intracoronary nitroglycerin
PCI Manual Online case 56 (spasm of anomalous circumflex—resolved after nitroglycerin administration)
6.3.1
Goal
To prevent and/or correct coronary spasm that could be interpreted as fixed coronary lesions and to optimize balloon and stent sizing.
6.3.2
How?
Check systolic blood pressure and administer nitroglycerin (50–200 mcg intracoronary) unless the patient has severe hypotension:
- •
>120 mmHg: administer 200 mcg nitroglycerin.
- •
100–120 mmHg: administer 100 mcg nitroglycerin.
- •
<100 mmHg: 50 mcg or no nitroglycerin (due to concern for worsening hypotension).
Nitroglycerin can be administered through the manifold or directly through the Y-connector using the introducer needle (“ nitro on a stick ”).
Alternatively, a sublingual nitroglycerin (0.4 mg) can be given.
Wait 1–2 minutes prior to coronary angiography, as it can take time (up to 2 minutes) for vasodilation to occur . A drop in systemic blood pressure is common.
As an alternative, in cases of suspected spasm that will not recede following administration of nitroglycerin, use of OCT or IVUS may help differentiate between coronary spasm and true atherosclerotic stenosis.
6.3.3
What can go wrong?
6.3.3.1
Hypotension (see Section 28.1.1 )
Causes:
- •
Vasodilatory effect of nitroglycerin.
- •
Vasodilators administered prior to angiography to facilitate radial access, such as verapamil.
- •
Acute inferior myocardial infarction with right ventricular infarction.
- •
Hypovolemia (which is possible in patients who are kept NPO before cardiac catheterization if they are not given intravenous fluids).
- •
Recent use of phosphodiesterase type 5 (PDE5) inhibitors, such as sildenafil (Viagra, within prior 24 hours), vardenafil (Levitra, within 24 hours), avanafil (Stendra, within 24 hours) and tadalafil (Cialis, within 48 hours).
- •
Vasovagal reaction to nitrates.
- •
Transducer or connection issues (pseudohypotension).
Prevention:
- •
Do not administer nitroglycerin if systemic pressure is low or if the patient is suspected to be hypovolemic, has right ventricular infarction, or has recently taken a phosphodiesterase type 5 (PDE5) inhibitor.
Treatment:
- •
Administer normal saline (often done prophylactically after nitroglycerin administration).
- •
Observe until blood pressure recovers.
- •
In severe hypotension cases, administer vasopressors, such as phenylephrine.
6.4
Step 4. Optimally position patient, image receptor, shields, and operator
6.4.1
Goal
To optimize the position of the X-ray image receptor and the patient to obtain excellent cineangiography images with the lowest possible radiation dose for both the patient and the operator.
6.4.2
How?
Patient position : the table should be placed as high as possible, while remaining comfortable and ergonomic for the operator.
Image receptor position : the image receptor should be placed as close as possible to the patient.
Image receptor angulation :
Left main: usual initial projection is AP (anteroposterior) to assess the left main ostium.
Left anterior descending artery: RAO (right anterior oblique) with some caudal and AP cranial.
Right coronary artery: usual initial projection is LAO (left anterior oblique) with cranial angulation.
Saphenous vein and radial grafts: usual initial projection is LAO.
IM grafts: usual initial projection is AP.
Shielding position : placed between patient and operator to reduce scatter radiation to the operator.
Operator position : as far as possible from the patient and X-ray tube. This can be facilitated by using a tubing extension for the manifold.
6.4.3
Challenges
6.4.3.1
Poor image quality
Causes:
- •
Large patient size.
- •
Excessive angulation.
- •
Image receptor too far from the patient.
- •
Differences in density of surrounding structures.
Prevention:
- •
Use shallower angulation, which facilitates X-ray beam penetration.
- •
Collimate to the area of interest and use filters.
Treatment:
- •
Use shallower angulation, which facilitates X-ray beam penetration.
- •
Change X-ray settings (such as frame rate and pulse rate to increase radiation dose and penetration).
6.4.4
What can go wrong?
6.4.4.1
Patient injury
Causes:
- •
Excessive movement of the image receptor.
Prevention:
- •
Caution while moving image receptor.
- •
Some X-ray systems have sensors that prevent the image receptor from hitting the patient.
Treatment:
- •
Depends on the type of injury.
6.4.4.2
Operator injury
Causes:
- •
Failure to move away from the X-ray system trajectory.
Prevention:
- •
Move away from the X-ray system moving parts.
Treatment:
- •
Depends on the type of injury—usually no specific treatment is required.
6.5
Step 5. Assess pressure and ECG
6.5.1
Goal
To ensure that there is no pressure dampening or new ECG changes before performing angiography.
6.5.2
How?
- 1.
Assess the pressure waveform, to verify that there is no dampening, ventricularization, or new hypotension. This is performed as outlined in Section 5.6 .
- 2.
Assess the ECG, to confirm that there are no new ECG changes (contrast administration may sometimes cause ST segment elevation or depression or T-wave inversion).
6.5.3
Challenges
- 1.
Poor-quality ECG signal. This may require repositioning of the electrodes.
- 2.
Poor-quality pressure signal. The transducer is flushed and the connections checked.
6.5.4
What can go wrong?
- 1.
Coronary ischemia due to catheter occluding or partially occluding antegrade coronary flow, which can lead to hypotension and arrhythmias, even ventricular fibrillation, if not corrected expeditiously. Remedy by withdrawing the catheter, and reengaging more carefully or by using a smaller French size catheter.
- 2.
Coronary dissection due to contrast injection despite ventricularization of the pressure waveform.
6.6
Step 6. Perform cineangiography
6.6.1
Goal
To record high-quality cineangiographic videos of each coronary artery in orthogonal projections, minimizing overlap.
6.6.2
How?
- 1.
The patient and image receptor are positioned optimally to allow coronary artery visualization with minimal or no panning. For example, for imaging the left coronary system in the RAO cranial projection the catheter tip should be at the left upper corner of the screen. When performing the LAO caudal (spider) projection, the catheter should be in the middle and center of the screen.
- 2.
The operator presses the cineangiography pedal.
- 3.
After 1–2 seconds (to allow visualization of any prior stent, calcium or contrast clearing from the prior injection) the assistant or operator (using a syringe or an automated system, if available) injects contrast to fully opacify the coronary artery, ensuring there is contrast reflux into the aorta. The syringe is held vertical to prevent potential bubble embolization.
- 4.
Panning is performed (if needed) to ensure imaging of all the branches and the distal portion of the injected coronary artery, as well as potential collateral filling of other vessels However, panning is best avoided as it degrades the quality of the image, especially when performing dual injection for chronic total occlusion interventions.
- 5.
Image acquisition is continued until all branches (and collateral branches in cases of contralateral or ipsilateral vessel occlusion) are opacified. Long acquisitions should be avoided except when delayed collateral filling is present.
- 6.
At the end of the injection the syringe is refilled with contrast, to facilitate the subsequent injection.
- 7.
Repeat until orthogonal projections are obtained for all coronary arteries and bypass grafts:
- a.
Left main: AP, RAO caudal, RAO cranial, LAO cranial, LAO caudal (spider).
- b.
LAD: AP or RAO cranial, RAO caudal.
- c.
RCA: LAO, LAO cranial or AP cranial, RAO.
- d.
Saphenous vein and radial grafts: LAO, RAO.
- e.
IM: AP, lateral, AP cranial or RAO cranial.
- a.
6.6.3
Challenges
6.6.3.1
Inability to fill the coronary artery
Complete filling of the coronary artery is critical for accurate interpretation of the coronary angiography. If complete filling cannot be achieved, it is best to declare that the angiogram was nondiagnostic, than provide a potentially erroneous interpretation.
Causes:
- •
Small catheter (especially 4 French).
- •
Side hole catheters.
- •
Large or ectatic coronary arteries.
- •
Poor engagement of the coronary artery.
- •
High coronary flow (e.g., in patients with severe aortic stenosis, hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, arteriovenous fistula).
- •
High contrast viscosity (isoosmolar contrast agents are more viscous than low-osmolar contrast agents).
- •
Weak injection.
- •
High left ventricular end-diastolic pressure.
Prevention and treatment:
- •
Use a catheter with larger lumen (e.g., a guide catheter instead of a diagnostic catheter or a larger French size diagnostic catheter).
- •
Avoid side hole catheters.
- •
Stronger injection, possibly using an automated injector, although manual injection allows more tailoring of the force of injection: if there is slight pressure dampening manual injection is preferred.
6.6.3.2
Catheter disengages coronary artery during injection
Causes:
- •
Poor engagement.
- •
Strong contrast injection.
- •
Insufficient catheter support relative to the required contrast injection force.
- •
Patient taking deep breaths, especially during radial procedures.
Prevention:
- •
Ensure good guide engagement with coaxial alignment prior to contrast injection.
- •
Start injection softly and increase force while injecting.
Treatment:
- •
Reengage catheter and retry.
- •
Use another catheter.
- •
Insert guidewire into coronary artery to anchor catheter.
- •
Use a guide catheter extension to better engage the coronary artery.
- •
Slowly ramp up the injection pressure.
6.6.3.3
Unable to optimally visualize some coronary segments
Causes:
- •
Poor engagement.
- •
Weak contrast injection.
- •
Overlap of coronary segments.
- •
Patient size (larger patients are more difficult to image as the X-ray has to penetrate through thicker tissue planes).
- •
Not enough angiographic views.
Prevention:
- •
Optimize coronary artery filling.
- •
Use various projections to minimize overlap of various coronary segments.
Treatment:
- •
Improve engagement (if poor visualization is due to poor filling).
- •
Use larger catheter (if poor visualization is due to poor filling).
- •
Use different projections (at least two orthogonal projections).
6.6.3.4
What can go wrong (see also Chapter 25 : Acute Vessel Closure)?
- 1.
Spasm (that is why nitroglycerin should be administered before coronary angiography unless there is a contraindication, such as hypotension) ( Section 25.2.5 ).
- 2.
Air embolization (see Chapter 5 : Coronary and Graft Engagement, step 5 Section 5.5 and Section 25.2.3.3 ).
- 3.
Thrombus or other debris embolization (see Chapter 5 : Coronary and Graft Engagement, step 5 Section 5.5 and Section 25.2.3 ).
- 4.
Dissection ( Section 25.2.1 ).
6.7
Step 7. Assess pressure and ECG
6.7.1
Goal
To ensure that there is no pressure dampening, new hypotension, or new ECG changes after each angiography run.
6.7.2
How?
- 1.
Assess the pressure waveform, to verify that there is no dampening or new hypotension.
- 2.
Assess the ECG, to confirm that there are no new ECG changes (ST segment or rhythm changes) that require treatment, such as ventricular fibrillation.
6.8
Step 8. Angiogram interpretation
6.8.1
Goal
To determine coronary flow and the presence and severity of coronary stenoses in the acquired cineangiography runs.
6.8.2
How?
The following parameters are assessed for each artery and lesion in each cineangiographic run .
6.8.2.1
Coronary flow
Coronary flow usually assessed using the TIMI (Thrombolysis in Myocardial Infarction) flow grade as follows ( Fig. 6.1 ): Grade 0 (no perfusion): There is no antegrade flow beyond the point of occlusion.
