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Coronary angiography
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
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