Sachin S. Goel and Samir R. Kapadia
Over the last two decades, interventional cardiology has rapidly expanded in the field of coronary and noncoronary structural interventions such as valve repair, transcatheter valve replacement, septal defect closure, etc. Coronary angiography is the gold standard for assessing coronary anatomy; however, sometimes it does not provide information about the physiologic or functional significance of a stenotic lesion, and neither does it adequately assess the severity and extent of atherosclerotic plaque in the vessel wall. Fractional flow reserve (FFR) has emerged as an excellent tool for assessing the physiologic impact of a lesion, and intracoronary imaging with intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have shown promise in assessing the atherosclerotic plaque and the response of the coronary vessel wall to percutaneous coronary intervention (PCI). Integration of information from various imaging modalities such as fluoroscopy, cineangiography, echocardiography, and computed tomography (CT) is critical for safety and success of structural cardiac interventions. In this chapter, we first highlight the role of functional imaging in the catheterization laboratory by means of FFR and the role of intracoronary imaging with IVUS and OCT and then discuss structural cardiac anatomy using various imaging techniques and their utility in guiding different structural interventions.
PHYSIOLOGIC ASSESSMENT OF CORONARY ARTERY DISEASE IN THE CATHETERIZATION LABORATORY
The goals of treatment in patients with coronary artery disease (CAD) are reduction in symptoms and risk of myocardial infarction (MI) and improvement in survival. The randomized prospective COURAGE (Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation) trial showed that revascularization with PCI does not reduce the risk of MI or improve survival in patients with stable CAD when added to optimal medical therapy (OMT).1 Presence of myocardial ischemia is a risk factor for adverse clinical outcome in patients with CAD, and concurrently, PCI was shown to reduce major adverse events in the subset of COURAGE population with significant ischemia on stress testing.2 The observed lack of benefit of PCI in all comers with stable CAD is likely due to the lack of correlation of severity of coronary stenosis, as assessed by coronary angiography, with the degree of ischemia or hemodynamic significance of coronary stenosis.3 In addition, PCI has occasional complications, which can affect long-term outcomes. Coronary angiography provides a two-dimensional (2-D) image of the three-dimensional (3-D) vessel lumen, which coupled with vessel overlap, tortuosity and eccentricity of lesions, often makes it very difficult for the angiographer to assess the functional or physiologic impact of a lesion despite multiple views. This can be assessed most accurately by means of a noninvasive stress test or an invasive physiologic test that can be performed in the catheterization laboratory, namely FFR.
Fractional Flow Reserve
FFR is defined as the ratio of maximal blood flow in a stenotic artery to normal maximal flow.4 It can be measured during coronary angiography by passing a 0.014-inch pressure sensor angioplasty wire through a guiding catheter into the coronary artery. The wire’s pressure signal is first matched with the aortic pressure (Pa) and then the lesion in question is crossed with the wire. Coronary hyperemia is then induced, usually with intravenous adenosine. The pressure in the coronary artery distal to the stenotic lesion (Pd) and Pa are continuously recorded, and FFR is calculated as the ratio Pd/Pa at maximal hyperemia (Fig. 46.1).
FIGURE 46.1 A: Coronary angiogram demonstrating intermediate severity lesion (50% to 60% stenosis) in the mid-LAD. B: FFR demonstrating a value of 0.88 indicating hemodynamically insignificant stenosis.
FFR in a normal coronary artery equals 1.0. An FFR value of 0.80 or less indicates hemodynamically significant coronary stenosis with an accuracy of >90%.5
In contrast to noninvasive myocardial perfusion imaging studies, FFR is a vessel-specific index of ischemia and hence more specific and has better spatial resolution. In the DEFER study, 325 patients underwent FFR of an intermediate coronary lesion prior to planned PCI. Patients with FFR ≥ 0.75 were randomized to deferral of PCI (Defer group, n = 91) or performance of PCI (Perform group, n = 90).6 If FFR was ≤0.75, patients PCI was performed as planned (Reference group; n = 144). At 5 years of followup, the event-free survival was similar in the Defer and Perform groups (80% vs. 73%, p = 0.52). In addition, the composite rate of death and MI was not different in the Defer and Perform groups (3.3% vs. 7.9%, p = 0.21).6 Similarly, in patients with multivessel CAD, nonrandomized studies have shown that FFR-guided PCI is associated with favorable outcomes and lower cost when compared to angiographically guided PCI without a physiologic assessment by FFR.7,8
These studies led to the large, prospective, multicenter, randomized FAME trial (FFR versus Angiography in Multivessel Evaluation), to compare FFR-guided PCI compared to conventional angiographically guided PCI in patients with multivessel CAD.9
In the FAME study, 1,005 patients with multivessel CAD were randomly assigned to undergo PCI with drug-eluting stent (DES), guided by angiography alone or PCI guided by an abnormal FFR ≤ 0.80. The mean SYNTAX score was 14.5 in each group, indicating low-intermediate risk patients.
The 1-year combined primary endpoint of death, MI, and repeat revascularization was lower at 13.2% in the FFR-guided PCI group compared to 18.3% in the angiography-guided PCI group (p = 0.02). In addition, the FFR-guided PCI group had less death or MI (7.3% vs. 11.1%, p = 0.04), fewer stents used per patient (1.9 ± 1.3 vs. 2.7 ± 1.2, p < 0.001), less use of contrast (272 mL vs. 302 mL, p < 0.001) and lower procedural cost ($5,332 vs. $6,007, p < 0.001).
The exact mechanism of benefit in the FFR-guided PCI arm of the FAME trial is not known; however, it appears to support the well-recognized fact that the most important prognostic indicator for adverse outcome in patients with CAD is the presence and extent of ischemia.10 It is possible that FFR-guided PCI results in a net clinical benefit as the reduction in ischemia by PCI outweighs the risks of PCI (stent thrombosis, restenosis) due to fewer implanted stents. The beneficial effects of FFR-guided PCI were maintained out to 2 years on follow-up in the FAME study.11 The purpose of the randomized FAME II trial is to compare outcomes of FFR-guided PCI plus OMT versus OMT alone in patients with stable CAD.
CORONARY INTRAVASCULAR IMAGING
Coronary angiography, which provides a luminogram, does not provide information about the atherosclerotic plaque in the vessel wall and often underestimates the severity and extent of atherosclerosis. Over the last two decades, IVUS has evolved as adjunct to coronary angiography and provides valuable information about the vessel wall with several research and clinical applications. Recently, infrared light-based imaging technology such as OCT has emerged, which provides significantly improved image resolution compared to IVUS.
Intravascular Ultrasound
The IVUS equipment consists of a special transducer mounted catheter and a console to reconstruct and display the image. Current IVUS catheters range from 2.6 to 3.5 French (Fr) in size and can be advanced through a conventional 6-Fr guide catheter over a 0.014-inch angioplasty guidewire. There are two types of IVUS catheters, phased array and rotating transducer. High ultrasound frequencies (20 to 40 MHz) are employed resulting in excellent axial and lateral resolution. Intravenous heparin and intracoronary nitroglycerin are routinely administered before performing IVUS. Subsequently, the angiographer retracts the transducer manually or with a motorized pullback device. Images are obtained and recorded digitally for analysis during pullback, using side branches visualized with both angiography and ultrasound, as landmarks to facilitate interpretation. IVUS is a safe procedure with few documented complications. Coronary spasm is the most frequent complication (1% to 3%) and this responds well to intracoronary nitroglycerin. Major complications including dissection or vessel occlusion are rare (<0.5%).
Normal Coronary Anatomy by IVUS
In normal coronaries, a standard IVUS image usually shows the vessel wall as a trilaminar structure, consisting of the intima, media, and adventitia (Fig. 46.2), due to visualization of two strong acoustic interfaces by ultrasound, the leading edge of the intima (at the interface between the blood-filled lumen and the endothelium) and the external elastic membrane (EEM, located at the media–adventitia interface). The lumen shows swirling echoes from circulating blood elements and this “blood speckle” helps identify dissection planes.
FIGURE 46.2 Normal coronary artery anatomy by IVUS. Yellow color represents intima; black color represents media; red color represents blood-filled lumen. (Reproduced from Tuzcu EM, Bayturan O, Kapadia S. Invasive imaging: Coronary intravascular ultrasound: a closer view. Heart. 2010;96:1318–1324, with permission from BMJ Publishing Group Ltd.)
Characterization of Atherosclerosis by IVUS
IVUS studies have shown that atherosclerosis is much more extensive and severe than what is apparent on coronary angiography. Atherosclerotic plaques can range in appearance from soft or hypoechoic plaques that have high lipid content to bright echogenic plaques that have more fibrous and calcified components. A more detailed analysis of plaque composition is possible using IVUS-derived virtual histology (IVUS-VH), which has good histopathologic validation and is based on spectral analysis of radiofrequency signals. Using IVUS-VH, atherosclerotic plaque is color coded into different types based on lipid, fibrous, and calcium content. Studies have shown a greater proportion of lipid and necrotic core with a thin fibrous cap in patients presenting with acute coronary syndrome.12 Another interesting concept revealed by IVUS studies is arterial remodeling (positive or negative), which refers to changes in arterial dimensions associated with the development of atherosclerosis. Positive or expansive remodeling refers to increase in the lumen area in the initial stages of atherosclerosis due to expansion of the EEM area with plaque deposition.13 This may explain the discrepancy between IVUS findings of significant plaque and normal or mildly abnormal coronary “luminogram” by angiography. It has been shown that lesions associated with expansive remodeling are prone to rupture and lead to acute coronary syndromes.14 IVUS studies have also demonstrated the other kind of remodeling, referred to as negative remodeling or arterial shrinkage, which is more common in stable CAD.15 It has been implicated in restenosis following balloon angioplasty. Precise quantitation of the extent of atheroma at different time points using IVUS has been instrumental in understanding the natural history of atherosclerosis as well as the impact of cholesterol-lowering drugs in reducing the progression of atherosclerosis16 and even its regression.17
The first large prospective, randomized multicenter IVUS trial of statins, the REVERSAL (Reversal of Atherosclerosis with Aggressive Lipid Lowering) study, randomly assigned patients to receive a moderate lipid-lowering regimen consisting of 40 mg of pravastatin or an intensive lipid-lowering regimen consisting of 80 mg of atorvastatin.16 With significantly greater reductions in LDL and CRP levels, the intensive lipid-lowering regimen halted the progression of coronary atherosclerosis as assessed by IVUS, compared to the moderate lipid-lowering regimen.
The prospective ASTEROID study (A Study to Evaluate the Effect of Rosuvastatin on Intravascular Ultrasound-Derived Coronary Atheroma Burden) evaluated coronary atherosclerosis by IVUS before and after 24 months of intensive lipid-lowering therapy with 40 mg/d of rosuvastatin.17 With a lowering in mean LDL-C to 61 mg/dL and an elevation in HDL-C by 14.7%, significant reduction in atheroma burden was observed by IVUS, consistent with regression of coronary atherosclerotic plaque.
Applications of IVUS in the Catheterization Laboratory
It is common to encounter lesions on angiography that are of uncertain significance such as angiographically moderate stenosis (50% to 70%), difficult to assess sites such as ostial or bifurcation lesions, left main trunk disease, intraluminal filling defects, and hazy lesions. Unlike FFR, specific threshold criteria for intervention by IVUS have not been prospectively validated.
A minimal luminal area of 3 to 4 mm2 by IVUS correlates with a significant reduction in FFR for a native coronary artery18 and a minimal luminal area of <6 to 7.5 mm2 usually indicates a significant lesion in the left main trunk.19,20
Cardiac allograft vasculopathy is known to be associated with a poor outcome in heart transplant patients. IVUS allows assessment of early plaque accumulation before luminal stenosis develops, thus recognizing silent vasculopathy, which has been identified as a powerful predictor of subsequent adverse outcomes in transplant recipients.21 IVUS has several important applications before, during, and after PCI.
Pre-PCI IVUS allows assessment of plaque distribution, especially whether the lesion involves or spares the ostium of the vessel that may help with optimal balloon and stent positioning. The presence and distribution of calcification can be assessed with IVUS.
Stent undersizing is a well-known predictor of stent thrombosis,22 and IVUS can help with selecting the optimal stent size based on vessel and lumen size.
IVUS has provided pivotal insights into the effect of various interventional techniques on the arterial wall. It was first shown by Colombo et al.23 that high pressure stent deployment by IVUS guidance resulted in better stent expansion, complete apposition, and prevention of subacute thrombosis. With bare metal stents (BMS), IVUS studies have shown that larger in-stent lumen area was associated with lower restenosis and target vessel revascularization rates.24 Although the rates of instent restenosis are much lower in the DES era, IVUS studies have clearly demonstrated that underexpansion of DES (Fig. 46.3) is the predominant mechanism leading to DES restenosis.25 A postdeployment minimal stent area of 5 mm2 has been shown to decrease the likelihood of angiographic restenosis.25
FIGURE 46.3 IVUS demonstrating unopposed coronary stent struts. (Reproduced from Tuzcu EM, Bayturan O, Kapadia S. Invasive imaging: Coronary intravascular ultrasound: a closer view. Heart. 2010;96:1318–1324, with permission from BMJ Publishing Group Ltd.)
Even though cessation of dual antiplatelet therapy is the most important mechanism in DES thrombosis, incomplete stent expansion remains a risk factor and IVUS can be used poststent deployment to assess adequacy of deployment and apposition. In addition, late stent malapposition, in which stent struts are no longer adjacent to the vessel wall late following stent implantation, was shown to be four times higher in DES compared to BMS in a recent meta-analysis.26 This was found to be associated with late and very late stent thrombosis. IVUS can also be very useful in identifying and guiding the management of complications following stent placement such as dissection, which has been shown to increase the rate of restenosis.
IVUS has played a pivotal role in clinical trials studying progression and regression of coronary atherosclerosis. Adverse events following PCI such as instent restenosis and stent thrombosis correlate with IVUS findings.
Optical Coherence Tomography
OCT is an emerging intracoronary imaging modality that uses backscattering of infrared light to obtain high-resolution tissue images. It is similar in principle to IVUS but uses light rather than acoustic waves. Current OCT systems consist of an optical fiber, a proximal low pressure occlusion balloon catheter, and an OCT imaging system console. Important differences compared to IVUS are that an occlusion balloon is needed proximal to the area of interest that is being imaged, in addition to continuous infusion of Ringer lactate or iodinated contrast media when using nonocclusion technique, to remove blood from the imaging field. An OCT image at the site of a previously placed stent is shown in Figure 46.4.
FIGURE 46.4 OCT at a site of previously placed coronary stent demonstrating (A) blood-filled coronary lumen, (B) catheter, (C) stent struts, (D) intimal thickening, (E) ring artifact, (F) a branch vessel.
Applications of OCT
As noted above, atheromas with a thin fibrous cap are thought to be more vulnerable to plaque rupture, leading to acute coronary syndromes. Ex vivo and in vivo studies have shown OCT to be a potentially complimentary technique to IVUS in characterization of atherosclerotic plaques,27,28 providing the potential for fibrous cap plaque measurement and identification of vulnerable plaque. Late stent thrombosis in patients with DES has been shown to be associated with delayed healing and poor endothelialization with incomplete stent strut coverage and apposition.26,29 OCT has shown higher sensitivity compared to IVUS in assessment of incomplete stent apposition and stent coverage.30 Studies are ongoing to assess the impact of information gauged by these newer intravascular imaging techniques on patient outcomes.
IMAGING FOR STRUCTURAL CARDIAC INTERVENTIONS
Fluoroscopy
Left Ventriculogram
A left ventriculogram is often performed to assess for presence of left ventricle (LV) wall motion abnormalities, degree of mitral regurgitation, presence of ventricular septal defect, and LV thrombus. It is typically performed with a pigtail catheter, in the 30-degree right anterior oblique (RAO) projection. Anterior and inferior walls of the LV and the apex are seen in this view (Fig. 46.5A). Anterior and posterior mitral valve leaflets are seen from the side in a longitudinal plane along with the inflow portion of the ventricle. This relationship is critical to recognize when performing mitral valve intervention when devices have to be advanced coaxially in the inflow (e.g., Inoue balloon). Adding steeper RAO angulation (45 degrees) moves the left atrium away from the spine and enables assessment of severity of mitral regurgitation. The lateral wall and septum are best assessed in a 60-degree LAO projection (Fig. 46.5B). Various segments of the mitral valve leaflets (A1, A2, A3 and P1, P2, P3) can be assessed in this view. The orientation of the aortic valve cusps (right, left, and noncoronary) can be assessed in the RAO and LAO projections as shown in Figure 46.5A,B.
FIGURE 46.5 Left ventriculogram. (Top panels). RAO 30-degree view of the LV in diastole and systole. The aortic valve (open arrow) with three leaflets (RCC blue, NCC white, and LCC with red lines), mitral valve (solid white arrow), and the papillary muscles (solid black arrows) are shown. In diastole (A), the mitral valve is open and there is clearance of contrast as the blood enters the LV from left atrium. Anterior and posterior leaflets are seen separate in diastole (left panel). In systole (B), the mitral valve is closed and the aortic valve is open (right panel). In this view, anterior, apex, and the inferior walls can be assessed. Left ventriculogram (Bottom panels). LAO 60-degree view of the LV in diastole (C) and systole (D). Open arrow shows the aortic valve with three leaflets (RCC blue, NNC white, and LCC with red lines) and solid white arrow shows the mitral valve. In diastole, the mitral valve is open and there is clearance of contrast as the blood without contrast enters the LV from left atrium. Anterior and posterior leaflets are seen separate in diastole. In this view, the lateral and the septal walls of the LV can be assessed. AV, aortic valve; AML, anterior mitral leaflet; LCC, left coronary cusp; NCC, noncoronary cusp; PML, posterior mitral leaflet; Ant PM, anterolateral papillary muscle; Post PM, posterolateral papillary muscle; RAO, right anterior oblique; RCC, right coronary cusp. (Reprinted from Shishehbor M, Kapadia SR. Imaging for intracardiac intervention. In: Topol EJ, ed. Textbook of Interventional Cardiology, 5th ed. Philadelphia: Saunders Elsevier; 2008, with permission.)
Right Ventriculogram
The inflow and outflow tracts of the right ventricle (RV) are at right angles to each other. Right ventriculogram is typically performed in anteroposterior and lateral projection with the catheter (pigtail or National Institutes of Health [NIH]) positioned in the mid cavity with a high rate of injection (>25 mL/s). Right ventriculogram can be used to assess the pulmonary valve, the tricuspid valve, and right ventricular outflow tract obstruction (Fig. 46.6).
FIGURE 46.6 Anteroposterior and lateral view of the RV with the pigtail catheter in the right ventricular outflow tract. Note doming of the pulmonic valve as shown by the black arrows. (Reprinted with permission from Shishehbor M, Kapadia SR. Imaging for intracardiac intervention. In: Topol EJ, ed. Textbook of Interventional Cardiology. 5th ed. Philadelphia: Saunders Elsevier; 2008).
Right Atrial Angiogram
Right atrial angiogram, typically performed with a pigtail or NIH catheter and a rapid injection, is used to evaluate the interatrial septum (IAS) and the structures seen are shown in Figure 46.7. This procedure can be useful during transseptal puncture and transcatheter patent foramen ovale (PFO) or atrial septal defect (ASD) closure.
FIGURE 46.7 Anteroposterior (top panel) and lateral (bottom panel) view of a right atrial angiogram. Left panel is dextro phase, right panel is levo phase, and the mid panel is these two phases superimposed on each other. SVC, superior vena cava; IVC, inferior vena cava; RA, right atrium; LA, left atrium; AO, aorta; RV, right ventricle; PA, pulmonary artery; NCC, non-coronary cusp; antL MV, anterior leaflet of the mitral valve. (Reprinted from Shishehbor M, Kapadia SR. Imaging for intracardiac intervention. In: Topol EJ, ed. Textbook of Interventional Cardiology, 5th ed. Philadelphia: Saunders Elsevier; 2008, with permission.)
Pulmonary Angiogram
Pulmonary angiography is the gold standard imaging modality for diagnosing pulmonary embolism. In addition, it is used to assess a variety of other conditions such as pulmonary valve stenosis, pulmonary artery stenosis, anomalous pulmonary venous return, and pulmonary arteriovenous malformations. Most commonly, multi–side hole pigtail or NIH catheter is used with high injection rate (40 mL/s; Fig. 46.8).
FIGURE 46.8 Normal pulmonary angiogram in the anteroposterior view. A: Shows the pulmonary artery trunk and the left and right pulmonary arteries and their branches. B: Shows opacification of the left atrium in levo phase. Digital subtraction is used to visualize the pulmonary veins (solid white arrows). PA, pulmonary artery; LA, left atrium. (Reprinted with permission from Shishehbor M, Kapadia SR. Imaging for intracardiac intervention. In: Topol EJ, ed. Textbook of Interventional Cardiology, 5th ed. Philadelphia: Saunders Elsevier; 2008, with permission.)
Left Atrial Angiogram
Left atrial angiogram is rarely performed by direct injection, but LA is frequently seen on the levo phase of the right-sided angiogram or pulmonary angiogram. Pulmonary artery angiogram performed in the anteroposterior (AP) and lateral views can be useful to visualize the LA and assess pulmonary vein drainage prior to ASD closure (see Fig. 46.8, right panel). Direct injection in the left atrial appendage (LAA) can be performed to evaluate the anatomy prior to percutaneous closure.
Aortography
Ascending aortography is performed to evaluate aortic valve disease and the ascending aorta. It has become particularly important with the advent of transcatheter aortic valve replacement (TAVR). Aortogram is performed in the RAO (30 degrees) and LAO (40 degrees) projections with a multi–side hole pigtail catheter positioned just 2 to 3 cm above the sinuses of Valsalva and a high rate of injection (20 mL/s for 2 to 3 seconds). Various anatomical relationships are important to recognize on fluoroscopy. Visualization of the aortic valve plane is critical for optimal valve positioning during TAVR (Fig. 46.9). In the RAO projection, the right coronary cusp (RCC) is the most anterior located cusp and the noncoronary cusp (NCC) is the most posterior located cusp with the left coronary cusp (LCC) in between the RCC and NCC (see Fig. 46.9). In the LAO projection, the LCC is well visualized (closest to the lateral wall of the ventricle), whereas the NCC and RCC are superimposed on one another with NCC lying slightly below RCC (see Fig. 46.9). In order to achieve alignment of the aortic valve cusps during TAVR, a slight caudal angulation is needed in the RAO projection, and cranial angulation is needed in the LAO projection. Preprocedural CT imaging of the aortic root also helps define accurate angiographic planes for valve implantation during TAVR.31Fluoroscopy is also important in recognizing other important anatomic features such as the relation of the NCC with the IAS for transseptal puncture, superior vena cava for intracardiac echocardiography (ICE) imaging, and anterior leaflet of the mitral valve for antegrade interventions, which are shown in the PA view on RA angiogram (see Fig. 46.7).
FIGURE 46.9 Aortic root angiography and alignment of the aortic valve plane for transcatheter aortic valve implantation. Views are LAO 40 degrees with 20 degrees caudal and RAO 20 degrees with 20 degrees caudal. NCC, noncoronary cusp; LCC, left coronary cusp; LAO, left anterior oblique; RAO, right anterior oblique; RCC, right coronary cusp. (Reprinted with permission from Shishehbor M, Kapadia SR. Imaging for intracardiac intervention. In: Topol EJ, ed. Textbook of Interventional Cardiology, 5th ed. Philadelphia: Saunders Elsevier; 2008, with permission.)
Transesophageal Echocardiography
Transesophageal echocardiography (TEE) provides high-resolution images and has become an integral part of structural cardiac interventional procedures including balloon mitral valvuloplasty, TAVR, transcatheter mitral valve repair, and occasionally, closure of interatrial communications. TEE can be performed relatively safely in the catheterization laboratory in supine position with judicious use of short-acting sedatives and posterior pharyngeal suction, without general anesthesia. The common positions for the TEE transducer are the upper mid esophagus, mid esophagus, and transgastric positions. The common views include the 0, 40 to 60, 90, and 120 degrees.
Intracardiac Echocardiography
ICE provides excellent images without the associated patient discomfort and airway issues, as may occur with TEE. In some situations, ICE can produce better images compared to TEE, for example, the posterior and inferior part of the IAS where TEE probe is too close to that area and the pulmonary valve and apical portion of the interventricular septum due to their anterior position. In addition, using ICE obviates the need for an imaging cardiologist in the catheterization laboratory. In our catheterization laboratory, we use the 8 F or 11 F probes with phased array system, which is capable of color Doppler imaging and allows imaging comparable to TEE, to guide our structural heart interventions. ICE is mainly used to assess the IAS and pulmonary veins during transcatheter PFO or ASD repairs, transseptal puncture, and for aortic and mitral valve interventions in some cases.32 In the electrophysiology laboratory, ICE is very useful during catheter ablation procedures for arrhythmias.
Multidetector Computed Tomography
Multidetector computed tomography (MDCT) is playing an increasingly important role in screening patients for structural cardiac interventions, particularly TAVR.33 It is useful in assessing several characteristics of the aortic valve and its surrounding anatomy such as (a) severity and location of calcification, (b) aortic annulus dimensions, (c) plane of the aortic annulus, (d) assessment of sinotubular junction, (e) distance of the coronary ostia from the aortic cusp margin and the length of the leaflets, and (f) aortic and iliofemoral anatomy. In addition, fusion of preprocedural MDCT with intraprocedural 3-D CT and routine fluoroscopic images in the catheterization laboratory has been shown to be feasible, allowing for improved guidance and manipulation of catheters and devices, with potential for increased safety and efficacy.34
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QUESTIONS AND ANSWERS
Questions
1. A 68-year-old woman with history of hypertension, hyperlipidemia, and diabetes mellitus presents with symptoms of intermittent exertional chest discomfort for the last 3 weeks. Coronary angiogram reveals 70% to 80% stenosis in the mid left anterior descending (LAD) and a 50% to 60% stenosis in the proximal right coronary artery (RCA). What is the most appropriate next best step?
a. Proceed with percutaneous coronary intervention (PCI) on the mid-LAD and proximal RCA.
b. Perform fractional flow reserve (FFR).
c. Stop the procedure and perform exercise stress test.
d. Refer the patient for coronary artery bypass grafting to the LAD and RCA.
2. The above patient had FFR of 0.88 across the proximal RCA lesion and 0.72 across the mid-LAD lesion. What is the most appropriate next step?
a. PCI on the LAD and RCA
b. PCI on the RCA only
c. PCI on the LAD only
d. Medical management
3. In patients being referred for transcatheter aortic valve replacement (TAVR), multidetector computed tomography (MDCT) is useful in assessing which of the following?
a. Dimensions of the aortic root
b. To determine coaxial angles for optimization of valve implantation
c. Distance of the coronary ostia from the aortic cusp margin and the length of the aortic valve leaflets
d. Aortic and iliofemoral anatomy
e. All of the above
4. Which of the following is NOT true regarding coronary intravascular ultrasound (IVUS)?
a. Coronary spasm is the most frequent complication of IVUS, and this responds well to intracoronary nitroglycerin.
b. In the drug-eluting stent (DES) era, a postdeployment minimal stent area of >5 mm2 by IVUS has been shown to decrease the likelihood of angiographic restenosis.
c. Stent undersizing is a well-known predictor of stent thrombosis, and IVUS can help with choosing the optimal stent size based on vessel and lumen size.
d. IVUS has played a very important role in understanding the natural history of atherosclerosis and the impact of cholesterol-lowering drugs in reducing the progression of atherosclerosis and even its regression.
e. A minimal luminal area of <8 mm2 by IVUS correlates with a significant reduction in FFR for a native coronary artery.
5. The left ventriculogram shown above (Top—systole, Bottom—diastole) depicts which of the following?
a. Severe mitral regurgitation
b. Ventricular septal rupture
c. Inferobasal left ventricular aneurysm
d. Left ventricular thrombus
e. Left ventricular free wall rupture
6. A 65-year-old man with history of hypertension, hyperlipidemia, and diabetes mellitus, presenting with severe substernal crushing chest pain, undergoes coronary angiography that reveals a hazy lesion in the RCA as shown below. IVUS is performed to investigate the cause of haziness. The IVUS image on the right (B) demonstrates which of the following?
a. Ulcerated plaque
b. Severe calcification
c. Coronary dissection
d. Coronary arterial remodeling
e. Air embolism
Answers
1. Answer B: This patient has a severe lesion in the mid-LAD and an intermediate lesion in the RCA. Based on the FAME trial, a strategy of measuring FFR in patients with multivessel coronary disease undergoing PCI and stenting lesions only with FFR ≤ 0.80 was found to reduce the rate of death, nonfatal myocardial infarction (MI), and repeat revascularization on follow-up. The functional significance of the RCA lesion must first be determined and this can be easily performed while in the catheterization laboratory using FFR, and there is no need to stop the procedure and perform an exercise stress test.
2. Answer C: Deferring PCI in patients with stable angina and normal FFR yields excellent event-free survival, and the risk of cardiac death or MI related to that lesion is <1% per year and not decreased with stenting (DEFER trial). Treating only the clearly ischemic lesion, that is, the LAD, is the best strategy in this case.
3. Answer E: MDCT is very useful in assessing all of the above.35
4. Answer E: A minimal luminal area of 3 to 4 mm2 by IVUS correlates with a significant reduction in FFR for a native coronary artery. A minimal luminal area of <6 to 7.5 mm2 usually indicates a significant lesion in the left main trunk. All other statements are true.
5. Answer C: The left ventriculogram clearly demonstrates an aneursym of the inferobasal left ventricular wall.
6. Answer A: The IVUS image demonstrates an ulcerated plaque, which is responsible for the haziness in the distal RCA.