Coronary Angiography: Valve and Hemodynamic Assessment


Cardiac catheterization and coronary angiography are essential tools in the diagnosis and evaluation of coronary and valvular heart disease, with several million procedures performed annually in the United States. Significant technological advances have occurred since the insertion of the first intravascular catheter by Werner Forsman in the 1920s, the first selective coronary catheterization by F. Mason Sones in 1956, and the first coronary angioplasty by Andreas Grüntzig in 1977. Today, angioplasty and stenting are the predominant modes of catheter-based intervention in all major vascular beds.

Coronary artery disease (CAD) is the leading cause of death in the United States, a statistic that has remained relatively stable over several decades despite landmark improvements in primary and secondary prevention as well as rapid catheter-based emergency management of acute coronary syndromes. Morbidity from CAD is likewise a major public health issue because of increasing numbers of survivors with resultant congestive heart failure (CHF).

Diagnostic Catheterization Techniques

Indications

The most common indications for the performance of diagnostic cardiac catheterization are to assess for the presence, extent, and severity of clinically suspected CAD, or to evaluate the severity of noncoronary valvular or myocardial disorders, particularly when a surgical or percutaneous intervention is contemplated. The decision to perform invasive coronary angiography or hemodynamic testing should be based on a careful analysis of the indications, risk-to-benefit ratio, and alternatives, to best identify patients who will benefit most from the procedure.

Contraindications

There are few absolute contraindications to cardiac catheterization other than patient refusal. The principle relative contraindications include active bleeding, severe anemia, coagulopathy, uncontrolled hypertension, significant electrolyte abnormalities, advanced renal dysfunction, active infection, decompensated heart failure precluding adequate patient positioning, and recent stroke ( Box 52-1 ).

Box 52-1
Relative Contraindications to Cardiac Catheterization and Coronary Angiography

  • Active bleeding or severe anemia

  • Severe coagulopathy

  • Advanced renal dysfunction

  • Uncontrolled hypertension

  • Significant electrolyte imbalance (e.g., severe hypokalemia)

  • Active infection or unexplained fever

  • Acute or subacute stroke

  • Decompensated heart failure preventing patient positioning or oxygenation

Complications

The overall risk of major complications resulting from diagnostic cardiac catheterization is less than 1%, although non–major vascular access site complications such as non–life-threatening bleeding or pseudoaneurysm formation can be as high as 3% with femoral artery access in patients with peripheral arterial disease. In addition, catheter manipulation in atherosclerotic vessels can lead to emboli (thrombus, atherosclerotic debris, calcium, or air) or clot formation, potentially leading to stroke, myocardial infarction, worsening renal function, or CHF ( Box 52-2 ).

Box 52-2
Possible Complications of Cardiac Catheterization

  • Death: 0.1% to 0.2%

  • Myocardial infarction: 0.1%

  • Stroke: <0.4%

  • Vascular complication: 2% to 5%

  • Severe contrast reaction: <0.2%

  • Renal failure: 1% to 30%

Coronary Angiography

Coronary angiography is performed by selective injection of the coronary arteries. In rare instances, nonselective coronary imaging or aortography can also be performed to identify ostia of native coronary arteries that are difficult to locate (predominantly those with anomalous origins) or bypass grafts.

Vascular Access

The most common access site for coronary angiography in the United States remains the femoral artery, although axillary, brachial, and radial approaches can also be used. The transradial approach to cardiac catheterization, first introduced by Lucien Campeau in 1989, is being used increasingly for diagnostic coronary angiography and percutaneous coronary interventions, primarily because of its lower bleeding rates, reduced access site complications, improved patient comfort, and reduced length of stay and hospital costs. Although adoption of radial access in the United States has been slow compared with other parts of the world, the number of procedures performed transradially increased from 3% in 2008 to more than 8% in 2011, and it is predicted to rise to more than 20% in 2015. Internationally, there are many centers that currently perform more than 95% of procedures via the transradial approach.

Challenges that are unique to the transradial approach include difficulty traversing a spastic radial artery or a tortuous radiobrachial or thoracic artery ( Fig. 52-1 ). Postprocedural permanent radial artery occlusion occurs infrequently, and it is typically clinically silent because of the dual blood supply to the hand. Radial occlusion can, however, affect future use of the radial artery as a bypass conduit. Laboratory studies have demonstrated reduced flow-mediated dilation and intimal hyperplasia, which could theoretically reduce radial artery graft patency in the radial arteries of patients who have undergone prior transradial catheterization.

FIGURE 52-1, A, Radial artery loop. B, Tortuosity of the right subclavian artery. C, Venogram of congenitally absent right superior vena cava (SVC) and persistent left SVC (arrow) performed during attempted right heart catheterization via the right antecubital vein.

The most common method of vessel cannulation is the Seldinger technique. In this technique, the vessel of interest is punctured, and a guidewire (usually an 0.035-inch J-tipped wire) is advanced into the vessel. The J-tipped wire then serves as a rail over which a dilator and sheath enter the vessel. For radial artery catheterization, a micropuncture needle with a 0.018-inch wire and a specialized radial sheath with a hydrophilic coating are used instead. Once access is obtained, the sheath acts as an entry point for passage and exchange of all catheters and devices, generally over the 0.035-inch J-tipped wire. After a catheter is advanced into the ascending aorta, the guidewire is withdrawn and the catheter is connected to a manifold system that allows, in a closed system, the ability to simultaneously inject contrast and transduce pressures at the catheter tip. The catheter is then cleared and advanced, with continuous pressure monitoring, into the ostia of the coronary artery. If the pressure waveform dampens or the catheter fails to backbleed, a significant ostial coronary artery lesion, unfavorable catheter engagement angle, catheter kinking, or entrapment of thrombus or atheroma should be suspected. Care should always be taken during engagement and injection of any coronary artery to avoid potentially fatal complications such as introduction of air, vessel dissection, intubation of a critical left main lesion, or disruption of atherosclerotic lesions.

Accurate delineation of coronary anatomy and identification of coronary stenoses is dependent on the acquisition of multiple orthogonal views to enable full visualization of all coronary segments without foreshortening or overlap. Preshaped coronary catheters are used to engage the left and right coronary arteries selectively. The choice of a specific diagnostic catheter is influenced by the site of arterial access, the size of the aortic root, and the anatomic take-off of the coronary arteries. Typically, a Judkins left 4-cm catheter (JL4) and a Judkins right 4-cm catheter (JR4) are used as the default catheters for left and right coronary angiography, respectively, via the femoral approach ( Fig. 52-2 ). Transradial coronary angiography can generally be performed using femoral catheter curves without difficulty; however, a shorter JL curve and longer JR curve may be required for a proper fit from the right radial approach. In addition, several universal catheters are also available for transradial use for both right and left coronary angiography, and often left ventriculography as well, such as the Kimny, Jacky, or Tiger catheters.

FIGURE 52-2, Representative tip configurations and catheters used in diagnostic coronary angiography: Judkins right (JR) and left (JL) catheters. The primary (upper arrow) and secondary (lower arrow) curves of the Judkins left catheter are shown; Amplatz right (AR) and left (AL) catheters; multipurpose (MP) catheter; internal mammary (IM) catheter; and left coronary bypass (LCB) catheter.

Left Coronary Angiography

Safe cannulation of the left main (LM) coronary ostium is best ensured by confirming that the pressure tracing is neither dampened nor ventricularized. The default JL4 catheter is successful in engaging the left main ostium approximately 80% of the time. If the aortic root is dilated or unusually narrow, longer or shorter catheters (JL5 or JL3.5) may be required, whereas a posterior origin of the left main is often best imaged using an Amplatz catheter.

Coronary anatomy is defined during angiography with contrast injections of 8 to 10 mL during cineangiography runs. The imaging angles used during angiography permit three-dimensional reconstruction of the coronary anatomy using orthogonal views to visualize each artery and its ostial, proximal, mid, and distal segments in multiple planes.

The left coronary system begins with the left main, which terminally bifurcates into the left anterior descending (LAD) and left circumflex (LCX) coronary arteries. In approximately one third of patients, the LM terminally trifurcates into the LAD, the LCX, and an intermediate branch (the ramus intermedius coronary artery) that supplies much of the left ventricular free wall. The LAD artery gives off septal branches as it courses down the interventricular groove and diagonal branches, which supply the anterolateral free wall of the left ventricle. The LCX, as it courses in the atrioventricular (AV) groove, gives off obtuse marginal branches that supply the lateral free wall of the left ventricle ( Fig. 52-3 ).

FIGURE 52-3, Coronary angiography of the left (A) and right (B) coronary arteries in the right anterior oblique caudal (A) and left anterior oblique cranial (B) projections. Diag, Diagonal artery; LAD, left anterior descending artery; LCX, left circumflex artery; LM, left main artery; OM, obtuse marginal artery; PDA, posterior descending artery; PLB, posterolateral branch artery; RCA, right coronary artery.

Right Coronary Angiography

The right coronary artery (RCA) is usually engaged with a JR4 catheter. The RCA courses in the interventricular groove and gives off acute marginal and right ventricular branches that supply the right ventricular free wall. The RCA terminally bifurcates at the crux of the heart to form the right posterolateral branch (PLB) and the right posterior descending artery (PDA), which supply the inferolateral segments of the left ventricle, the inferior wall, and posterior interventricular septum (see Fig. 52-3 ).

The dominance of the coronary circulation depends on which artery supplies the posterior circulation—the PDA or the PLB. Approximately 60% of the population is right-dominant (the RCA provides both of these branches), 25% is codominant (the RCA supplies the PDA and the LCX gives off the PLB), and 15% is left-dominant (the LCX provides both of these branches).

Coronary Anomalies

Several coronary anomalies ( Fig. 52-4 ) exist in addition to the typical coronary anatomy described earlier. Most are simple anatomic variants, such as dual ostia for the LAD and LCX, whereas others are congenital abnormalities, such as an anomalous origin of the LCX from the RCA. Most of these congenital anomalies have little effect on coronary circulation; however, in the case of the LM or LAD originating from the RCA or right coronary cusp and coursing posteriorly between the aorta and pulmonary artery, there is an associated increased mortality, usually secondary to arrhythmias and ischemia.

FIGURE 52-4, A, Nonselective angiogram of the left coronary sinus in an 81-year-old woman presenting with an acute inferior myocardial infarction and cardiogenic shock, demonstrating absence of coronary arteries arising from the left coronary cusp. B, Selective angiogram of the right coronary artery in the same patient revealing an anomalous origin of the left main coronary artery (LM) from the right coronary artery (RCA) and acute thrombotic occlusion of the proximal RCA. C, Angiography in the same patient after successful angioplasty of the RCA, now also demonstrating well-established collateral vessels to a severely diseased left circumflex coronary artery (LCX). D, Cardiac computed tomography angiogram three-dimensional reconstruction with virtual dissection of a similar anomalous LM arising from the RCA in a 21-year-old woman. E, Angiogram from a 54-year-old man with similar anatomy in the left anterior oblique cranial projection. The entire coronary system is visualized from a single ostium located at the right coronary sinus. The RCA and LM trunk arise together, and the LM divides into the left anterior descending (LAD) and LCX branches. RI, Ramus intermedius coronary artery.

Angiographic Projections

When performing angiography of the coronary circulation, it is critical to obtain multiple views of each vessel in various orthogonal planes to define all the segments fully and clearly. Methodical, comprehensive angiography with orthogonal angulation prevents an operator missing a significant coronary lesion, which may be evident in only one plane but not another. By convention, all views are reported with left or right angulation first, followed by the degree of cranial or caudal angulation. For example, a 30/25 left anterior oblique (LAO)/cranial view represents 30 degrees of LAO angulation with 25 degrees of cranial angulation.

All major coronary arteries lie in one of two planes: the interventricular septum or the atrioventricular groove ( Fig. 52-5 ). Standard angiographic projections are designed to display the coronary anatomy in profile in these planes. For example, the right PDA in its course along the interventricular septum and the inferior wall is best seen with the interventricular septum in its longest profile—the right anterior oblique (RAO) projection. On the other hand the LCX, which courses along the AV groove, is best visualized in the anteroposterior (AP) or RAO caudal projection, looking at the AV groove in profile.

FIGURE 52-5, Representation of coronary anatomy in relationship to the interventricular and atrioventricular valve planes as seen in two views: right anterior oblique (RAO) and left anterior oblique (LAO). Coronary branches are as follows: AcM, Acute marginal; CB, conus branch; CX, circumflex; D, diagonal; L Main, left main; LAD, left anterior descending; OM, obtuse marginal; PD, posterior descending; PL, posterolateral left ventricular; RCA, right coronary; RV, right ventricular; S, septal; SN, sinus node.

Left Main Coronary Artery

The LM coronary artery is best seen in a shallow LAO projection with slight caudal angulation to visualize its middle and distal segments optimally, and with cranial angulation to improve visualization of its proximal and ostial segments. Another helpful view is the steep LAO caudal (also called the spider view ) which lays out the terminal left main bifurcation. Unfortunately, this last view is not helpful in the case of a horizontally positioned heart, in which situation a steep RAO caudal view is substituted.

Left Anterior Descending Coronary Artery

The LAD courses anterior and inferior to the LM, enters the interventricular groove, and then travels to the apex of the heart. No single view adequately depicts the entire course of the LAD. The proximal LAD is best visualized in steep LAO projections with cranial angulation, whereas the middle and distal segments are better seen in LAO and RAO views with some caudal angulation. In some cases, when the proximal LAD is not well seen in standard views (e.g., with a horizontally oriented heart), a 30 RAO/30 cranial angle better lays out the proximal LAD and LM bifurcation.

The diagonal arteries, the major branches of the LAD, course off the LAD toward the lateral free wall of the left ventricle. The best view for most of the diagonal arteries, to include their origin and distal segments, is usually a steep LAO (50 degrees) with steep cranial (50 degrees) angulation. In some cases, there is only one diagonal branch off the LAD—sometimes referred to as a twin LAD given its large area of subtended myocardium.

Left Circumflex Coronary Artery

The LCX is best seen in caudal projections. The proximal portion of the LCX is usually imaged in the RAO caudal angulation, which also lays out the marginal arteries. An alternative view for the mid segment of the LCX and the marginal arteries is the steep LAO caudal (spider) view. In obese patients, however, this latter view can be challenging, because the x-ray has to penetrate extra tissue, resulting in a distorted, dark, or hazy image.

Right Coronary Artery

The RCA enters the anterior AV groove and courses distally. The proximal segment of the RCA is best seen in the flat LAO angulation. For optimal visualization of the ostium, a steep (50 degrees) LAO projection is preferred. The mid segment of the RCA is best seen in the LAO and flat RAO projections. The crux, or distal RCA, and the proximal portions of the right PDA and PLB arteries are best seen with an AP or slight LAO projection with 20 to 30 degrees of cranial angulation. Finally, the middle and distal segments of the right PDA are best visualized with a flat RAO projection.

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