Abstract:
Catheter-based coronary angiography is the gold standard for the diagnosis of coronary artery disease (CAD). From preprocedure assessment to the acquisition of images to the postprocedural follow-up, care must be taken at each step to maximize high-quality data collection with minimal patient risk and discomfort. Optimal angiographic imaging is the result of a series of linked steps. This chapter will review each of these steps to ensure that the reader is able to obtain the best data upon which a clinical decision can be made for each patient.
Keywords:
coronary angiography, ventriculography, angiogram technique, fundamentals of coronary angiography, left heart catheterization
Catheter-based coronary angiography is the gold standard for the diagnosis of coronary artery disease (CAD). From preprocedure assessment to the acquisition of images to the postprocedural follow-up, care must be taken at each step to maximize high-quality data collection with minimal patient risk and discomfort. Optimal angiographic imaging is the result of a series of linked steps. Failure of any link breaks the imaging chain and may cause loss of all or part of the data. The chain begins with positioning the patient on the table, followed by vascular access, catheter placement, correct imaging views, contrast injection during acquisition of the images, display of the images for review, and finally the analysis and archiving of the digital images. The major causes of poor angiograms include factors specific to the patient (size, medical devices/hardware that interfere with imaging), angiographic technique, equipment-related problems, and optical and digital imaging system issues ( Box 3.1 ).
Patient factors
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Size
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Movement
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Hardware (pacemaker, Harrison rods, multiple surgery with clips, silicone prosthesis)
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Anatomic conditions (scoliosis, scarred lungs, large heart [fluid])
Angiographer factors
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Poor catheter seating (wrong catheter shape or size, anomalous origin, subselective cannulation)
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Poor contrast opacification (weak injection, volume too small, diluted contrast material)
Equipment factors
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X-ray generator problems (high heat, quantum mottle, too high kilovoltage, too short or too long pulse width)
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X-ray tube problems (anode pitting, wrong focal spot, beam geometry, proximity to image intensifier, poor collimation)
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Digital imaging program malfunction
Biologic factors
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Variation in contrast medium concentration, which is reduced during diastole due to increased blood flow, can cause subtle vessel border defining issues due to incomplete contrast mixture encountered with large diameter native vessel or bypass grafts.
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Hyperviscosity and hyperosmolality of contrast can shift tissue water into capillaries and affect imaging quality. Nonionic, Isosmotic can improve this diagnostic accuracy.
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Motion blurring can result from the movements of coronary arteries during the cardiac can affect imaging especially in distal vessels.
Indications
Coronary angiography is widely used to evaluate patients with known or suspected CAD. Angiography may be combined with the measurement of left ventricular (LV) pressures (left heart catheterization) and/or the evaluation of LV systolic function and wall motion (left ventriculography). The decision to perform a left heart catheterization and left ventriculography is left to the discretion of the operator and the patient’s primary physician.
All catheterization laboratory personnel should recognize the importance of preprocedure assessment and be aware of the indications why the patient is having the procedure performed. As a measure of quality within the laboratory, appropriate documentation should describe the indications for the procedure and, ideally, should reference the indication category from the American College of Cardiology/Society for Cardiovascular Angiography and Interventions (ACC/SCAI) appropriate use criteria (AUC) document. Using the AUC, patient indications that fall in the uncertain (U) or inappropriate (I) categories can be addressed before the procedure occurs because the AUC categories do not address all individual patient level decision-making. AUCs are intended as guiding documents. The AUC will aid in justifying the final clinical decision and indication for a procedure after discussion about treatment and patient goals. Furthermore, the SCAI has developed a smart phone application (available through the SCAI website, www.scai.org ). After answering a few short questions, the app can display the indication category for any individual patient.
Patient preparation for coronary angiography
Before proceeding with cardiac catheterization, informed consent must be obtained from all patients and/or family. It is critical to confirm this documentation prior to the procedure and the administration of conscious sedation to ensure the procedure is performed in concordance with the patient’s wishes and hospital policies.
Medications that are part of a catheterization laboratory routine for CAD evaluations and other patient’s clinical conditions are continued unless they might interfere with the technique of the procedure (i.e., continuation of novel/direct oral anticoagulants or warfarin). The administration of other antiplatelet medications including clopidogrel, prasugrel, or ticagrelor before the ascertainment of coronary anatomy is to be guided by individual laboratory protocols and any anticipated need for surgery.
Coronary angiography
The goal of coronary angiography is to visualize the coronary arteries, branches, collaterals, and anomalies with enough detail to make a precise diagnosis and plan for the treatment of CAD. With percutaneous coronary interventions (PCIs; e.g., stents), the coronary angiographer must demonstrate the precise location of disease relative to major and minor side branches and any associated vascular anomalies, such as thrombi, calcifications, or aneurysms. For the performance of PCI, visualization of vessel bifurcations, vessel tortuosity, origin of side branches, the portion of the vessel proximal to a significant lesion, and specific lesion characteristics (e.g., length, eccentricity and calcium) is crucial. The routine coronary angiographic views should visualize the origin and course of the three major vessels and their branches in at least two different planes. Because coronary anatomy varies widely, appropriate angiographic projections must be modified for each patient. In the case of a total vessel occlusion (also called chronic total occlusion [CTO]), the distal vessel should be visualized as clearly as possible by opacifying the contralateral coronary artery and collateral vessel pathways. CTO angiograms require extended cineangiographic imaging runs that are long enough to visualize late collateral vessel filling with appropriate panning across the heart. The features of the proximal segment, the distal cap (point of occlusion), and length of the occluded segment help determine the suitability for CTO revascularization strategy. CTO PCI starts with a careful review of the coronary angiogram that, in nearly all cases, should be performed using dual injection. Procedural plans are then made based on the lesion angiographic characteristics.
Angiographic catheters
The initial choice of catheters for coronary angiography depends on the approach (radial or femoral access) and physician preferences. Regardless of approach, the angiographic catheter is advanced over a J-wire (or other angled tip or soft/floppy tipped wire) to the aortic root under fluoroscopic guidance. Engagement of the left main coronary artery (LMCA) can be performed in anterior-posterior (AP) or left anterior oblique (LAO), whereas engagement of the right coronary artery (RCA) is performed in LAO. Regardless of the catheter or the artery, coaxial alignment of the catheter with the artery should be obtained by subtle movement of the catheter while carefully observing the catheter tip pressure waveform on the hemodynamic monitor. Before contrast injection through the catheter, operators must pay careful attention to the catheter tip pressure waveform, which can indicate obstruction or malpositioning of the catheter. A waveform that shows dampening or ventricularization ( Fig. 3.1 ) suggests that the catheter may be placed into a small side branch (e.g., conus) or up against a plaque or is touching left main (LM) roof where injection might lead to ventricular fibrillation and/or dissection. Care also must be taken to notice deep seating of the catheter, which may lead an operator to miss an ostial lesion beyond which the catheter has moved. During contrast injection into the coronary tree, the operator should note an adequate contrast reflux back into the aorta to see whether an ostial lesion is present. Many laboratories routinely administer intracoronary nitroglycerin to prevent or to resolve catheter-induced spasm that can mimic stenosis. Catheter-induced spasm is typically more common in the RCA than the LCA.
X-ray imaging
For all catheterization laboratories, the x-ray source is under the table, and the image intensifier (II) is directly above the patient. The source and flat-panel detector in fully digital laboratories ( II In older labs ) move in opposite directions in an imaginary circle around the patient who is positioned in the center. The body surface of the patient facing the observer determines the specific view. This relationship holds true regardless of whether the patient is supine, standing, or rotated ( Fig. 3.2 ).
Angiographic nomenclature
AP position: The detector is directly over the patient with the beam traveling perpendicularly back to front (i.e., from posterior to anterior) to the patient lying flat on the x-ray table.
RAO position: The detector is on the right side of the patient. A, Anterior; O, oblique.
LAO position: The detector is on the left side of the patient.
Note: Think of the oblique view as turning the left or right shoulder forward (anterior) to the camera (II).
Cranial: The detector is tilted toward the head of the patient.
Caudal: The detector is tilted toward the feet of the patient.
Angiographic projections made simple: An easy way to understand oblique views
Trainees in the catheterization laboratory need to understand coronary angiograms and how the arteries change position with specific angulations. The following section illustrates how the heart and the coronary arteries move in the different projections. The changing positions can be easily remembered by using the left hand as a representation of the coronary tree as it sits over the heart and changes position with different angulations while the right or left shoulder is rotated toward the detector to duplicate LAO and RAO views.
The cardiac silhouette in left anterior oblique and right anterior oblique
The heart is the size of a fist ( Fig. 3.3 ) and is shaped like an ice cream cone, with the tip toward the sternum. The open hand is positioned as it would be seen in an AP projection. When the left shoulder is moved forward (LAO projection), the hand is seen more on end; that is, the heart is made shorter and rounder in the LAO ( Fig. 3.4 A). When the right shoulder is moved forward (RAO projection), the hand is seen in profile; that is, the heart is made longer with the tip extending to the left chest wall. These two movements of the hand in the LAO and RAO remind you how the heart should look in each projection, whether seen on a plain chest x-ray or on fluoroscopy or ventriculography during cardiac catheterization (see Fig. 3.4 B).
The left coronary arteries: Left anterior oblique views
By placing the left-hand fingers over the clenched right fist, the index finger becomes the left anterior descending (LAD) artery and runs over the knuckles, which represent the anterior interventricular groove ( Fig. 3.5 ). The middle finger is spread lying on the finger joints and represents the circumflex (CFX) artery. The thumb runs horizontal to the wrist joint and represents the initial course of the RCA arising from the right sinus of Valsalva.
Left coronary artery with left anterior oblique cranial and caudal angulations
In cranial angulation, the detector moves toward the head of the patient and produces a downward tilt of the LAO view, exaggerating the LM segment but keeping the relationship between LAD and CFX almost the same ( Fig. 3.6 A).
In caudal angulation, the detector moves toward the foot of the patient. This position views the coronary arteries from underneath, tipping the LAO view upward to produce a branching appearance that some refer to as the spider view. Figure 3.6 B and similar images provide a computed tomography angiography (CTA) reconstruction of the coronary arteries, with the lower panels showing a subtracted image duplicating what would be seen on traditional coronary angiography in the catheterization laboratory. The lower right panel of Figure 3.6 B shows the LAO-caudal angulation and is called the spider view for obvious reasons.
The left coronary arteries: Right anterior oblique projections
In the LAO projection (see Fig. 3.6 ), the LAD (index finger) is on the right side and the CFX (middle finger) is on the left side. When rotated over to RAO, the position of the fingers (LAD/CFX) changes the orientation such that the LAD is now on the left and the CFX is in the middle or more rightward than in the LAO view ( Fig. 3.7 A).
The RAO with caudal angulation (see Fig. 3.7 A, top left ) tips the CFX downward, separating it further from the LAD. For the RAO with cranial angulation (see Fig. 3.7 A , top right ), the CFX is tipped upward, foreshortened, and overlapped with the LAD. Cranial views are best used to see the LAD and diagonals, whereas caudal views are best to see the CFX and LM segments. Figure 3.7 B shows the angiograms of the RAO-caudal and RAO-cranial angulations.
The right coronary artery and posterior descending artery: Left anterior oblique and right anterior oblique
Using the left hand over the fist, the thumb represents the proximal part of the RCA. The RCA continues down the wrist (atrioventricular [AV] groove) to the posterior descending artery (PDA) portion of the RCA, which runs along the inferior interventricular groove. The PDA along the bottom of the heart can be represented by the index finger ( Fig. 3.8 A). In the LAO cranial angulation, the PDA runs along the bottom of the heart and is tipped downward to visualize better the length without foreshortening ( Fig. 3.8 A). In the RAO without cranial or caudal angulation, the PDA is seen lengthwise running from the base to the apex of the heart ( Fig. 3.8 A , right panels ). Figure 3.8 B shows the CTA and contrast-filled angiograms of the RCA in the LAO-cranial and RAO projections.
Using this model, it should be easy to visualize and to remember the coronary and ventriculographic images in the different oblique views with and without cranial and caudal angulations.
Left coronary artery imaging
- 1.
The AP-caudal or shallow RAO view displays the LMCA in its entire perpendicular length ( Fig. 3.9 ). In this view, the proximal segments of the LAD and left CFX arteries are displayed, but the branches are overlapped. After the LM segment, slight RAO or LAO angulation may be necessary to clear the density of the vertebrae and the catheter shaft in the thoracic descending aorta from covering the artery.
Fig. 3.9
Frames from coronary angiograms in several standard views. (A) Left coronary artery (LCA) left anterior oblique (LAO)-cranial projection; (B) LAO-caudal projection; (C) right anterior oblique (RAO)-caudal projection; (D) RAO-cranial projection; (E) right coronary artery (RCA) in LAO-cranial projection; (F) RCA in RAO-straight projection.
- 2.
The LAO-cranial view also shows the LMCA (slightly foreshortened) and the LAD and its diagonal branches. Septal (coursing to the left) and diagonal (to the right) branches are separated clearly. The CFX artery and marginal branches are foreshortened and overlapped, although the posterolateral and posterior descending branches of left-dominant circulation are displayed clearly. Deep inspiration, which moves the density of the diaphragm down and out of the field, is helpful. The LAO angle (>45 degrees) should be set so that the LAD artery course is parallel to the spine and stays in the “lucent wedge” bordered by the spine on the medial edge and the curve of the diaphragm. Imaging over the spine degrades the quality of the angiogram and moving more LAO will bring the LAD off the spine for optimal opacification. Cranial angulation tilts the LMCA down and permits a view of the LAD/CFX bifurcation. LAO-cranial angulation that is too steep or inspiration that is too shallow produces considerable overlapping with the diaphragm and liver, degrading the image.
- 3.
The RAO-caudal view shows LMCA bifurcation, perpendicular to that of the LAO-cranial angle. The origin and course of the CFX/obtuse marginal branches, ramus intermedius branch, and proximal LAD segment are seen clearly. This view is one of the two best for visualization of the CFX artery. Overlapped diagonals obscure the LAD artery beyond the proximal segment; however, the apical segment of the LAD artery is displayed clearly.
- 4.
The RAO-cranial view is used to see the origins of the diagonals along the mid and distal LAD artery. Diagonal branch bifurcations are well visualized. The diagonal branches are projected upward. The proximal LAD and CFX usually are overlapped. Marginal branches may overlap, and the CFX artery is foreshortened, but distal circumflex and left-sided posterolateral branches are well visualized in this projection.
- 5.
The LAO-caudal view (“spider” view) shows the LMCA (foreshortened) and bifurcation of the LMCA into the CFX and LAD arteries. Proximal and mid portions of the CFX artery are usually seen clearly with the origins of obtuse marginal branches. Poor image quality may be caused by an overlapping of the diaphragm and spine. Good separation of the vessel is more difficult in vertically displaced hearts, such as those in patients with chronic obstructive pulmonary disease, and more angulation is required to obtain an unobstructed view. The LAD artery is considerably foreshortened in this view.
- 6.
A lateral view (detector rotated 90 degrees, parallel with the floor) is the best view to show the mid and distal LAD arteries. The LAD and CFX arteries are well separated. Diagonals are usually overlapped. The ramus intermedius branch course is well visualized. This view best shows insertions of bypass grafts (usually LIMA) into the mid LAD artery. Occasionally, slight caudal or cranial angulation is needed to visualize the segment of interest.
Right coronary imaging
In contrast to left coronary angiography, selective engagement of the RCA requires torqueing of the catheter anteriorly and to the right ( Fig. 3.9 E,F). The catheter must be advanced to the right coronary cusp and then pulled back slowly while applying clockwise torque. A push-pull motion while torqueing the catheter will help transmit the twisting down to the catheter tip. As with cannulation of the LM, the operator should observe the pressure waveform. Damping signals engagement of the conus branch. Injection of this vessel can lead to ventricular fibrillation. Once selective coronary engagement is accomplished, intracoronary nitroglycerin is often given to prevent or to alleviate catheter-induced spasm. If spasm occurs or if an ostial lesion is suspected, a smaller-diameter catheter might be used. If selective engagement of the RCA using standard catheters is not successful, consider using special catheters, such as 3DR or no-torque RCA catheters. Anomalous positions of the RCA should be considered when one cannot find the RCA in the usual location in the right sinus of Valsalva. A high anterior takeoff of the RCA might be present. If the RCA cannot be found, a review of left coronary angiography should be examined for unsuspected collateral flow or the RCA potentially coming off the left coronary cusp.
- 1.
The LAO-cranial view shows the origin of the RCA, the entire length of the mid RCA, and the PDA bifurcation (crux) (see Figs. 3.4 and 3.5 ). Cranial angulation tilts the PDA down to see vessel contour and to reduce foreshortening. Deep inspiration is necessary to clear the diaphragm. The PDA and posterolateral branches are slightly foreshortened in this view.
- 2.
The RAO view (no cranial or caudal angulation is generally necessary) shows the mid RCA and the length of the PDA and posterolateral branches. Septal branches coursing upward from the PDA, supplying occluded LAD artery via collaterals, may be clearly identified. The posterolateral branches are overlapped and may need the addition of a cranial view.
- 3.
The AP-cranial view shows the origin of the RCA. The mid segment is foreshortened. However, this is the best view to display the posterior descending and posterolateral branches of a dominant RCA system as well as the size of a collateralized LAD artery.
- 4.
The lateral view also shows the RCA origin (especially in patients with more anteriorly oriented orifices) and mid RCA. The PDA and posterolateral branches are foreshortened.
Technical note: Because of individual variations in anatomy, small (1 to 2 mL) test injections during patient inspiration help the operator obtain the appropriate oblique and axial (cranial/caudal) angulations and setup for panning.
Bypass graft angiography
In patients who have undergone coronary artery bypass graft (CABG) surgery, review of the operative report is important. The number and type of grafts should be noted, particularly if there are arterial grafts and they are in situ (right internal mammary artery [RIMA] or left internal mammary artery [LIMA]) or harvested (often radial artery). The proper technique to engage these grafts depends on the type of graft.
Left internal mammary angiography
Selective injection of the LIMA is required for any patient who had this graft used for CABG (typically to the LAD). The LIMA is a branch of the left subclavian artery and is most easily accessed using the left radial approach. From the femoral approach, selective intubation of the left subclavian in an LAO projection ( Fig. 3.10 ) using an internal mammary (IM) catheter can be performed after passing the catheter into the subclavian artery over a J-wire. Marked tortuosity of the proximal subclavian artery may require a soft-tipped atraumatic wire (Wholey, Versacore or Terumo Glidewire) to permit passage of the IM catheter into the subclavian artery. There is also an IM catheter that often permits easier cannulation of the LIMA. Any pressure gradient between aortic and subclavian arteries should be noted because a subclavian artery stenosis with an LIMA can lead to anterior wall ischemia (coronary-subclavian steal syndrome). Subclavian stenosis can be stented with high success and low procedural complication rates. Selective LIMA engagement can be performed in AP, RAO, or LAO (usually easiest in RAO). Turning the patient’s head to the right or left can sometimes assist in LIMA intubation. When selective angiography of the LIMA is not possible because of extreme tortuosity, nonselective injection of the left subclavian artery can be obtained with the brachial artery occluded with a blood pressure cuff inflated to suprasystolic pressure.
The best views for imaging the LIMA-LAD graft are the same as those used for evaluation of the LAD (i.e., RAO- and LAO-cranial projections). The lateral view is especially useful to visualize LIMA-LAD anastomosis and may help determine whether scar tissue has formed tacking the LIMA to the sternum, a finding important to surgeons planning a reoperation with a second sternotomy.
Right internal mammary coronary angiography
The RIMA is a branch of the right subclavian artery that arises from the innominate artery. Selective angiography of the RIMA is required when this vessel has been used as an arterial bypass graft (typically to the RCA). Use of the right radial approach permits easiest canalization of the RIMA, whereas the femoral approach can be challenging, especially in an older patient with an elongated aorta (type III aortic arch). From the femoral approach, the innominate must be engaged using an IM catheter in the LAO projection followed by advancing a J-wire into the subclavian artery ( Fig. 3.10 D). Care must be taken not to wire the right common carotid, which is the other major branch of the innominate. Engagement of the RIMA can be performed in AP projection or LAO. Head positioning or caudal arm movement sometimes assists in selective RIMA intubation.
Saphenous graft angiography
Locating saphenous vein graft (SVG) ostia can be challenging and blind movement up and down an atheromatous arch can be risky, which underscores the need to know preprocedurally how many aortotomies where made. Sometimes, surgeons place graft markers (clips or rings) near the SVG ostium, permitting easier future angiography although these markers may not be exactly at the graft opening. Classically, the orientation of SVGs from lowest (caudal) to highest (cranial) has been RCA, LAD, diagonals, and then obtuse marginals.
Coronary artery SVGs are visualized in at least two views (LAO and RAO). It is important to show the aortic anastomosis, body of the graft, distal anastomosis ( Fig. 3.11 ), distal runoff, and collateral channels. The optimal view of graft-vessel anastomosis is usually seen in the view that depicts the native vessel best. Stumps of occluded SVGs should be recorded for future reference.
General strategy for coronary artery bypass graft angiography
Following native LCA and RCA angiography and visualization of missing or reciprocally filled vessel segments, the operator proceeds to SVG angiography using key views for specific coronary artery segments and taking into account the subsequent need to determine contingency views or addition of special views.
- 1.
SVG to RCA (lowest): This graft is best engaged in an LAO projection and travels downward, paralleling the RCA. It can be easily cannulated with a multipurpose (MP) catheter or Judkins right (JR) catheter. Other catheters useful for this type of graft include a right coronary bypass (RCB) graft catheter or an Amplatz right modified (AR mod) catheter. The best views for these grafts are LAO cranial, RAO, and AP cranial.
- 2.
SVG to LAD (second lowest, above RCA): The LAD SVG graft typically originates from the anatomic leftward aspect of the anterior aorta and is best engaged in RAO using a JR4 (Judkins right, 4 cm), left coronary bypass (LCB), or Amplatz left (AL) catheter. The best views for a LAD graft are lateral, RAO cranial, LAO cranial, and AP (the lateral view is especially useful to visualize the anastomosis to the LAD).
- 3.
SVG to diagonal: Diagonal SVGs are also best visualized in the RAO projection and using the same catheters as those used for SVG to LAD. Often, a slight clockwise rotation from an inferior graft permits the JR4 to engage this graft. The best views for SVGs to diagonal are LAO cranial and RAO cranial.
- 4.
SVG to obtuse marginal (highest SVG on the aorta): SVG marginal grafts are best engaged in RAO projections using a JR4, LCB, or AL catheter. The best views for an SVG to obtuse marginal are caudal (LAO to RAO).
Right gastroepiploic artery
Because of the strong patency of arterial grafts, some surgeons graft the RCA or PDA using the right gastroepiploic artery (GEA). The right GEA, a branch of the gastroduodenal artery, originates from the common hepatic artery, which is one of the three main branches from the celiac trunk. If the operative report is not available, use of this graft should be considered if median sternotomy extends inferiorly into the abdominal cavity or numerous surgical clips extend up from the abdominal cavity to the inferior wall of the heart. Selective angiography of these grafts requires special technique. It is recommended that only operators familiar with peripheral anatomy and angiography perform GEA angiography because it requires knowledge of the vessel anatomy and selective canalization of the GEA. First, the celiac trunk (located anterior and inferiorly directed) must be engaged using specialized peripheral catheters, such as the Cobra (Cook Medical, Bloomington, IN) or Simmons Sidewinder. Anticoagulation with heparin or bivalirudin is recommended, given the need for subbranch vessel wiring. Once the celiac trunk is engaged, an angioplasty style wire (typically, 0.018 or 0.014 inches) should be passed through the common hepatic to the gastroduodenal and then to the GEA using roadmap imaging. Over this wire, a smaller 4-F or 5-F catheter (Terumo straight glide catheter) or transit catheter (0.035-inch Quickcross [Spectranetics]) can be advanced to perform selective GEA graft angiography. Care must be exerted not to cause vessel dissection. The prophylactic administration of nitroglycerin should prevent vessel spasm.
Contrast media injection techniques: Power versus hand injection
Contrast medium, a viscous, iodinated solution used to opacify the coronary arteries, can be injected either by hand through a multivalve manifold or by a variable rate power injector. For hand injections, flow rates are usually 2 to 4 mL/s with volumes of 2 to 6 mL in the RCA and 7 to 10 mL in the LCA. Operators should keep the tip of the syringe pointed down (handle raised up) so that any small bubbles float up and are not injected into the circulatory system ( Fig. 3.12 ). The use of disposable manifolds, syringes, and tubing is cost effective and safe.
Power injection of contrast media is as safe as hand injections, with operator-controlled rate and volume injections producing excellent opacification. Coronary power injectors use sterile hand controls, permitting precise operator touch-sensitive variable volume injectors (ACIST Medical Systems; Bracco Research USA; Medrad, Inc.), and a computer touch screen allows precise contrast delivery settings ( Fig. 3.13 ). The system is especially helpful for small-diameter catheters (<5 F). In addition, it is also highly cost effective with the large contrast reservoir. Typical settings for power injections are as follows:
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RCA: 6 mL at 3 mL/s; maximal 450 psi
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LCA: 10 mL at 4 mL/s; maximal 450 psi
Cineangiographic frame rates
Images may be acquired at different frame rates but a frame rate of 15 frames/s is most commonly used. In some pediatric cases or if the heart rate is greater than 95 beats/min, the rate of 60 frames/s may be used. In many adult laboratories, 7.5 to 15 frames/s is standard and reduces radiation dosage to patient and staff.
Panning techniques
Most laboratories use x-ray image screen sizes (e.g., 8 inches in diameter or less) that may preclude having the entire coronary artery course visualized without panning over the heart to include the late filling portions of the arterial segments and any collateral filling. In addition, in most views, some degree of panning is necessary to identify regions that are not seen from the initial setup position. Some branches may unexpectedly appear later from collateral filling or other unusual arterial input sources. Imaging runs should be long enough to see contrast in the cardiac veins, which is generally long enough to pan to see late-filling collateralized coronary vessels.
Angiographic view setup keys
Panning motion that is too fast or overshoots the image targets causes information to be lost. The key to accurate, optimal coronary cineangiography (that is, obtaining the most information for the least amount of movement) is the initial setup of the catheter on the fluoroscope screen. Figure 3.14 shows the catheter–LM artery setup keys for LAO views in the straight AP, cranial, and caudally angled projections. When the patient is positioned correctly and the setup key followed, only minimal panning is necessary to obtain the information. In the LAO view, the operator pans down the LAD artery then rightward to identify collaterals going to the RCA. If the CFX is occluded, then leftward panning will include collaterals going to the distal CFX artery. For the RCA, in the LAO position, the operator pans downward and to the left toward the LAD artery. This visualizes late-filling collaterals from the right coronary system to the LAD artery. These motions are shown in Figure 3.14 .
In RAO projections for the LCA and RCA, the operator pans downward to the apex to identify late-filling, left-to-left, or right-to-left collaterals. The initial setup keys for catheter tip position on the fluoroscope, summarized in Table 3.1 , help the operator include all crucial information for coronary angiography.
Collateral circulation
The opacification of a totally or subtotally (99%) occluded vessel from antegrade or retrograde filling is defined as collateral filling. The collateral circulation is graded angiographically in Table 3.2 .
| Grade | Collateral Appearance |
|---|---|
| 0 | No collateral circulation |
| 1 | Very weak (ghost-like) reopacification |
| 2 | Reopacified segment, less dense than the feeding vessel, and filling slowly |
| 3 | Reopacified segment as dense as the feeding vessel and filling rapidly |
It is useful but difficult to establish the exact size of the recipient vessel. The operator determines whether the collateral circulation is ipsilateral (e.g., same-side filling, proximal RCA to distal RCA collateral supply) or contralateral (e.g., opposite-side filling, LAD artery to distal RCA collateral supply) and identifies exactly which region is affected by collateral supply and stenoses in the artery feeding the collateral artery. He or she notes whether the opacification is forward (anterograde) or backward (retrograde). This evaluation is important for making decisions regarding which vessels might be protected or lost during coronary angioplasty.
Usefulness of biplane coronary angiography
Simultaneous biplane cineangiography, although uncommonly used, provides accurate images from two different simultaneous points of view and is advantageous in performing complete coronary or ventriculography with reduced contrast volumes and radiation exposure. Biplane angiography is most useful for the pediatric population and those patients with need for reduced contrast load (e.g., patients with renal failure).
The value of biplane information must be balanced against the difficulty of use. The traditional biplane coronary angiography setup required the patient’s heart to be in the exact center of the two planes (the isocenter) and then the AP and lateral planes were rotated from vertical or horizontal to orthogonal projections (i.e., perpendicular imaging planes, LAO cranial, and RAO caudal; Fig. 3.15 ). This setup often resulted in more difficulties than it solved, in that panning in one plane moved the heart out of the field of the other plane. Alternatively, setting up the biplane using concordant imaging views (i.e., with both C-arms in the same direction), such as using cranially angled LAO and RAO projections and then moving both C-arms to caudally angled LAO and RAO projections (see Fig. 3.15 ), makes biplane angiography simple, quick, and effective. In this way, angiographic information is not lost when panning because the heart moves in a similar direction, albeit from the opposite side (but not cranial vs. caudal). With the concordant biplane setup, contrast use is halved, radiation dose reduced, and procedure time shortened. Although biplane coronary angiography is not generally considered critical for routine studies, if the laboratory has biplane capability, this form of angiography can improve procedure times, contrast use, and information quality.
Rotational coronary angiography
To avoid radiation exposure and reduce consumption of contrast dye, some institutions use rotation of the C-arm during coronary angiography. Rotational coronary angiography has been established for noncoronary angiographic procedures, particularly in the diagnosis and treatment of cerebrovascular disease. Rotational angiography, like biplane, is dependent upon the placement of the patient in an isocenter position. Various vendors have distinct programs that permit the attainment of images across a cranial or caudal plane while injecting contrast or in the case of dual-axis rotational angiography, complete assessment of the left coronary system with a single injection. Rotational angiography has been shown to reduce radiation, contrast, and procedural time. The critical aspects of rotational angiography are proper patient positioning because panning is not possible and proper coronary injection. The use of power injectors is recommended in order to maintain a consistent injection to provide adequate opacification.
Coronary angiographic catheters
The femoral arterial catheterization technique initially performed by Dr. Melvin Judkins continues to bear his name and has been highly successful because of its simplicity and ease of use with preshaped catheters ( Fig. 3.16 ). As discussed earlier, operators using the radial artery for access can use a different array of specially designed catheters. Regardless of the vascular access, all catheters are inserted with a J-tipped guidewire. This J-wire is advanced into the ascending thoracic aorta under fluoroscopic guidance. The catheter follows the guidewire to the central position. When the catheter tip has reached the desired location in the aorta, the guidewire is removed and the catheter is aspirated (2 to 3 mL of blood), flushed, and connected to the pressure manifold. The guidewire or catheter tip should always be visible on the fluoroscopy screen when the catheter or guidewire is manipulated.
Judkins-type coronary catheters
Judkins catheters have preshaped curves and tapered end-hole tips. The Judkins left (JL) coronary catheter has a double curve. The length of the segment between the primary and secondary curve determines the size of the catheter (i.e., 3.5, 4, 5, or 6 cm). The proper size of the JL catheter is selected depending on the length and width of the ascending aorta and the approach. A JL3.5 is best from the right radial while a JL4 is best from the left radial, which mirrors the femoral approach with respect to catheter selection. In a small person with a small aorta, a 3.5-cm catheter is appropriate, whereas in a large person or in an individual with an enlarged or dilated ascending aorta (e.g., as a result of aortic stenosis, regurgitation, or Marfan syndrome), a 5-cm or 6-cm catheter may be required ( Fig. 3.17 ).
The ingenious design of the JL catheter permits cannulation of the LCA without any major catheter manipulation. The catheter tip follows the ascending aortic border and falls into the LM coronary ostium, often with an abrupt jump. In the words of its inventor, from the femoral approach “the [Judkins] catheter knows where to go if not thwarted by the operator.” Because of the ease of seating in most patients, the slow advance of the catheter under fluoroscopic control will prevent rapid engagement into an unexpected LM narrowing.
A JL4 catheter fits most adults with the catheter tip aligned parallel with the long axis of the LM coronary trunk. A smaller (3.5 cm) catheter in the same patient angles upward and a larger (5 cm) catheter angles downward into the coronary cusp. When the coronary ostium cannot be seated correctly or placed in a stable position, the catheter should be replaced with a better-fitting catheter rather than aggressively manipulated into the coronary artery ( Fig. 3.18 ). A slight rotation of the catheter may be necessary to improve alignment of the catheter tip with the LM coronary trunk.
The JR coronary catheter is sized by the length of the secondary curve and is available in 3.5-cm, 4-cm, and 5-cm sizes. In most cases, the 4-cm catheter is adequate. The JR catheter is advanced into the ascending aorta (usually with LAO projection) with the tip directed caudally ( Fig. 3.19 ).
The RCA can be entered in most cases by one of two maneuvers:
- 1.
Advance the catheter into the right coronary cusp and rotate the catheter 45 to 90 degrees clockwise as the tip is pulled back 2 to 3 cm. As the right coronary orifice is engaged, the fluoroscope shows rotation of the tip toward the right coronary cusp and downward motion of the catheter.
- 2.
Advance the catheter tip to 2 to 4 cm above the valve. When the catheter is rotated clockwise for 45 to 90 degrees, the tip rotates toward the right cusp and descends approximately 1 to 2 cm, engaging the right coronary ostium from above.
If the coronary ostium is not engaged, the maneuvers are repeated, starting at a slightly different level each time. A brief contrast media injection into the right coronary cusp may help the operator direct the catheter. A slight but firm push-pull motion on the catheter is necessary to translate rotational motion at the hub down to the tip.
If stored rotational energy is not released by a small counter rotation after seating, the catheter may spring out of the right coronary ostium when the patient takes a deep breath. After seating, the operator checks for pressure damping associated with ostial stenosis or conus branch cannulation.
Amplatz-type catheters
The left Amplatz-type catheter is a preshaped half-circle with the tapered tip extending perpendicular to the curve ( Fig. 3.20 ). Amplatz catheter sizes (left 1, 2, and 3 and right 1 and 2) indicate the diameter of the tip curve. In most normal-sized adults, no. 2 left and no. 1 right (modified) Amplatz catheters give satisfactory results. In the LAO projection, the tip is advanced into the left aortic cusp. Further advancement of the catheter causes the tip to move upward into the LM aortic trunk. It may be necessary to push Amplatz catheters down to move the tip up and out of the ostium to disengage the catheter from the LM ostium. If the catheter is pulled instead of being advanced, the tip moves downward and into the LM or CFX artery. Unwanted deep cannulation of the CFX artery might tear this branch or the LM aortic trunk. The incidence of coronary dissection is higher with Amplatz catheters than with Judkins-type catheters.
