Coronary Angiography: Valve and Hemodynamic Assessment

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 ).

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 ).

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.

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.

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 ).

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.

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.