Cardiovascular Imaging A handbook for clinical practice - Part 4 docx

TEE is also superior to TTE in the detection of pacemaker lead vegetations.1limita-A negative TEE examination has a very high negative predictive value for IE in patients with native hea

Transesophageal echocardiography (TEE) overcomes many of these tions and has been shown in many studies to be far superior to TTE for the iden-tification of vegetations (Table 7.1) The higher resolution of TEE, multiplanecapabilities, and proximity to the valves explain the better sensitivity of TEE indetecting vegetations compared with TTE in both native valve IE (90–100%)and prosthetic valve IE (86–94%).1,3,8TEE allows a complete assessment of veg-etation characteristics, such as location, size, and number of vegetations (Fig.7.4) TEE is also superior to TTE in the detection of pacemaker lead vegetations.1

limita-A negative TEE examination has a very high negative predictive value for IE

in patients with native heart valve (over 90%).3The rare false-negative resultsmay be related to an incomplete TEE examination, TEE performed very early in

Echocardiography in infective endocarditis 79

Table 7.1 Comparative value of transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in the diagnosis of valvular vegetations.

Transthoracic echo Transesophageal echo Prostheses Sensitivity Specificity Sensitivity Specificity

the infectious process before the development of vegetations, or vegetationsthat are too small to be detected or have already embolized Careful multiplaneTEE examination might reduce the likelihood of false-negative results.

In patients with prosthetic valves, false-negative results are more prone tooccur, possibly because of incomplete visualization, presence of artifacts, andinterference In these patients, a negative TEE does not completely exclude thediagnosis of IE

Although TEE specificity for IE vegetations is high (88–100%), possible positive findings may occur in certain situations Underlying native valvular ab-normalities such as myxomatous mitral valve disease, non-specific valvularthickening, Lambl’s excrescences, or fibroelastomas may mimic vegetations.Echocardiography does not permit differentiation between active versus healedvegetations or between bacterial versus non-bacterial thrombotic vegetations,such as those observed in systemic lupus erythematosus, antiphospholipid syn-drome, or marantic endocarditis In patients with prosthetic valve, commonfindings such as sutures or prosthetic strands should not be confused with veg-etations Distinction between vegetations and prosthetic thrombus is often impossible, and other prosthetic abnormalities such as bioprosthetic leaflet degeneration can be also difficult to differentiate from vegetations

false-Detection of abscesses and perivalvular complications

Aortic location, prosthetic valve IE, and staphylococcal infection are the bestpredictive factors for IE associated perivalvular complications TEE is stronglyindicated in these high-risk patients to identify perivalvular complications Thepresence and size of vegetations do not seem helpful in predicting perivalvularextension of the infection.9Abscesses may extend into contiguous tissue, espe-cially the mitral–aortic intervalvular fibrosa, resulting in the formation of cavi-ties, pseudoaneurysms, and fistulas Mitral annular abscesses are less frequent,and almost always in patients with mitral prostheses

Echocardiographically, these abscesses appear as a perivalvular region of creased thickness (greater than 10 mm) and reduced echo-density, without ev-idence of flow with color Doppler (Fig 7.5) A pseudoaneurysm is defined as apulsatile, echo-free, perivalvular cavity with flow communicating with the car-diovascular lumen A fistula is defined as a color Doppler tract communicatingtwo adjacent cardiac chambers (Fig 7.6).9

in-The superiority of TEE over TTE in the diagnostic of periannular tions is well established.9,10Only approximately 25% of paravalvular abscessesare detected by TTE, whereas sensitivity and specificity are very high with TEE(87% and 95%, respectively, in the Daniel series10) Combined with spectraland color Doppler techniques, TEE can also identify the abnormal communicat-ing flow in pseudoaneurysms and fistulae TEE also provides information aboutthe localization and extension of paravalvular abscesses Intervalvular fibrosaabscesses and pseudoaneurysms are more frequently detected by TEE than byTTE

complica-False-positive and false-negative TEE results may occur in some cases

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Echocardiography in infective endocarditis 81

Figure 7.5 Transesophageal echocardiography demonstrating a region of reduced echo density with no flow in the periannular aortic ring (arrows) Abscess was confirmed on surgery LA, left atrium; LV, left ventricle; LVOT, left ventricular outflow tract.

Figure 7.6 Transesophageal echocardiography demonstrating perforation of an aneurysm of the anterior mitral leaflet (left) secondary to infection of the mitral–aortic intervalvular fibrosa in an aortic endocarditis Color flow Doppler shows the large eccentric jet of mitral regurgitation through the perforation (right) LA, left atrium; LV, left ventricle; RV, right ventricle.

Abscesses may be missed when they are too small Diagnostic accuracy of TEE isbetter for pseudoaneurysms than for abscesses.9Although periannular compli-cations are frequent in patients with prosthetic valve IE, their identification —even with TEE — may be challenging Prostheses, especially mechanical valves,may create confusing images because of artifacts and shadows of the prostheticmaterial and eccentric color Doppler jets Anterior aortic abscesses may bemissed with TEE in patients with prosthetic valves.

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Figure 7.7 Transesophageal echocardiography (TEE) showing a large vegetation attached to the tip of non-coronary aortic valve with complete prolapse of the cusp.

Case Presentation (Continued)

TEE showed a large vegetation attached to the tip of the non-coronary aortic valve with complete prolapse of the cusp (Fig 7.7) Severe aortic regurgitation was confirmed with color flow Doppler (Fig 7.8) A large abscess was observed at the level of the posterior aortic root, with no flow (Fig 7.9a) This abscess

extended to the subaortic region of mitral–aortic intervalvular fibrosa (Fig 7.9b) The patient underwent cardiac surgery the same day At the time of

surgery, there was complete destruction of the non-coronary aortic valve, with multiple vegetations The periannular abscess, extending to the intervalvular fibrosa, was confirmed The patient underwent aortic valve replacement with a homograft and exclusion of the abscess.

Cultures of the aortic valves grew coagulase-negative Staphylococcus which

responded to 6 weeks of rifampicin and oxacillin therapy The patient did well after 6 weeks of treatment.

New valvular dysfunction

The assessment of valvular regurgitation is based on a comprehensive tion of both TTE and TEE, coupled with pulsed, color flow, and continuous waveDoppler This allows a complete evaluation of underlying valve disease, mecha-nism, and severity of valvular regurgitation

utiliza-In typical situations, diagnosis of acute, severe, valvular regurgitation isstrongly suggested by the mechanisms of valve dysfunction, destruction, or per-foration, with flail leaflet, associated with typical Doppler findings of severe re-gurgitation Valvular perforation, especially in the aortic position is associatedwith an adverse outcome TTE can detect or suggest valvular perforation in IE,but TEE better defines this complication

Identification of new paraprosthetic regurgitation is a major graphic finding in patients suspected of having IE Because of its superiority indetermining the spatial location of regurgitant jets, TEE is the modality of choicefor the diagnosis of paravalvular regurgitation However, small intraprostheticregurgitant jets, present in the majority of normal prostheses, should not beconfused with paraprosthetic leakage

echocardio-Prognosis of infective endocarditis

Echocardiography provides important prognostic information in patients with

IE that can help medical or surgical decisions

Prognosis related to the presence and size of the vegetations

The presence and morphology of echocardiographically documented tions are associated with a higher rate of complications in IE Several studies

vegeta-Echocardiography in infective endocarditis 83

Figure 7.8 Confirmation of severe aortic regurgitation with color flow Doppler.

by the Duke criteria, patients with vegetations larger than 10 mm had a 60% cidence of emboli, while severely mobile vegetations larger than 15 mm had an

in-Figure 7.9 Transesophageal echocardiogram (TEE) showing a large abscess at the level

of the posterior aortic root: (a) with no flow; (b) with extension to the subaortic region

of mitral–aortic intervalvular fibrosa.

83% incidence of emboli.11Embolism before initiation of antimicrobial ment, or increase in vegetation size during treatment, may also predict later em-bolism.12A high incidence of embolic events is also observed in patients withright heart IE.11The indication for early surgery in patients with large vegeta-tions should be discussed individually for each patient Although large andhighly mobile vegetations, especially on the mitral valve, are more prone to embolize, indications for surgery should not be purely based on echocardio-graphic parameters,1,13but should also take into account the causative agent,the presence of complications such as heart failure, the feasibility of valve repair, and the extracardiac condition of the patient.

treat-Early detection of complications

Periannular extension of the infection is associated with more complications,poor clinical outcome, and frequent need for surgery.9

Early and accurate identification of periannular extension or prosthetic hiscence in patients suspected of having IE are critical for appropriate patientmanagement and surgical decisions Surgical repair is more difficult when thesecomplications are diagnosed at too late a stage

de-Evaluation of hemodynamic consequences of valvular regurgitation

Besides the identification and quantification of valvular regurgitation, diography allows evaluation of their hemodynamic consequences Acute, se-vere aortic or mitral regurgitation with signs of ventricular failure is associatedwith an adverse outcome and requires early surgical management

echocar-When acute regurgitation is superimposed on chronic regurgitation, pretation of echocardiographic data may be more difficult

inter-A major role of echocardiography in prognostic evaluation is the tion of the causes and severity of congestive heart failure Chamber size, segmental and global wall motion, ejection fraction, and left ventricular andpulmonary artery pressures should be defined and monitored during follow-

identifica-up Although no or moderate left ventricular dilatation favors acute tion, left ventricular enlargement and left ventricular dysfunction may bepresent in both acute and chronic situations Assessment of the progression ofthe impact of regurgitation on left ventricular volumes and function, along withclinical evaluation, is needed for adequate timing of intervention

regurgita-Guidelines for the use of echocardiography in suspected or definite infective endocarditis

The diagnostic value of echocardiography in suspected IE differs according tothe pretest probability of the disease.14Although TTE is often performed to ex-clude IE in patients with low probability of IE, it has been shown that echocar-diography has a low diagnostic yield and low impact on clinical management inthese patients.14In addition, false-positive results are more likely to occur inthese situations Thus, it could be recommended to perform echocardiography(especially TEE) only in patients with a reasonable probability of the disease In-

Echocardiography in infective endocarditis 85

deed, recent ACC/AHA and ESC recommendations have emphasized the needfor a selective approach to TEE in suspected IE (Fig 7.10):1,13

• When TTE images are of good quality and prove to be negative and there isonly a low clinical suspicion of IE, endocarditis is unlikely, TEE is not necessary,and other diagnoses should be considered.13In patients with a high or interme-diate probability of IE, TEE should be performed if TTE is negative or inconclu-sive, or in patients with prosthetic valves Negative predictive value is very high(95%) when both TTE and TEE are negative.1

• When TTE is positive, use of TEE is recommended if complications are pected, or in high-risk patients (prosthetic valve, previous endocarditis, con-genital heart disease, staphylococcal IE), or before surgery.1,13

• If TTE and TEE results remain negative, but clinical condition still leads to picion of IE, in the absence of an alternative source of infection, TEE should berepeated within 1 week.13

sus-More generally, skilled operators and good-quality images are required toavoid imaging pitfalls As often as possible, abnormal findings should be com-pared with previous examinations, especially in the postoperative period, toavoid false-positive results Repeated examinations should be performed in difficult cases to follow the progression of images The time interval betweenTEE studies should be individualized according to clinical, bacteriologic, andechocardiographic findings

86 Chapter 7

Figure 7.10 Algorithm for the use of echocardiography in suspected infective

endocarditis (Modified from Bayer et al [1998]1and Graupner et al [2002].9 )

Echocardiography has a major role in the diagnosis, risk stratification, andmanagement of patients with IE Identification of vegetations, early detection

of complications, identification of valvular dysfunction and their

hemodynam-ic consequences are important information provided by echocardiography thatcan help in risk stratification and clinical decision-making

References

1 Bayer AS, Bolger AF, Taubert KA, et al Diagnosis and management of infective

endo-carditis and its complications Circulation 1998;98:2936–48.

2 Durack DT, Lukes AS, Bright DK New criteria for diagnosis of infective endocarditis:

utilization of specific echocardiographic findings Duke Endocarditis Service Am J

endo-transthoracic and the transesophageal approach J Am Coll Cardiol 1989;14:631–8.

5 Shively BK, Gurule FT, Roldan CA, Leggett JH, Schiller NB Diagnostic value of esophageal compared with transthoracic echocardiography in infective endocarditis.

trans-J Am Coll Cardiol 1991;18:391–7.

6 Daniel WG, Mugge A, Grote J, et al Comparison of transthoracic and transesophageal

echocardiography for detection of abnormalities of prosthetic and bioprosthetic

valves in the mitral and aortic positions Am J Cardiol 1993;71:210–5.

7 Shapiro SM, Young E, De Guzman S, et al Transesophageal echocardiography in

di-agnosis of infective endocarditis Chest 1994;105:377–82.

8 Daniel WG, Mugge A, Grote J, et al Comparison of transthoracic and transesophageal

echocardiography for detection of abnormalities of prosthetic and bioprosthetic

valves in the mitral and aortic positions Am J Cardiol 1993;71:210–5.

9 Graupner C, Vilacosta I, SanRoman J, et al Periannular extension of infective

endo-carditis J Am Coll Cardiol 2002;39:1204–11.

10 Daniel WG, Mugge A, Martin RP, et al Improvement in the diagnosis of abscesses associated with endocarditis by transesophageal echocardiography N Engl J Med

1991;324:795–800.

11 Di Salvo G, Thuny F, Rosenberg V, et al Endocarditis in the elderly: clinical,

echocar-diographic, and prognostic features Eur Heart J 2003;24:1576–83.

12 Vilacosta I, Graupner C, San Roman JA, et al Risk of embolization after institution of

antibiotic therapy for infective endocarditis J Am Coll Cardiol 2002;39:1489–95.

13 Horstkotte D, Follath F, Gutschik E, et al Guidelines on prevention, diagnosis and

treatment of infective endocarditis executive summary: the task force on infective

endocarditis of the European Society of Cardiology Eur Heart J 2004;25:267–76.

14 Lindner JR, Case RA, Dent JM, Abbott RD, Scheld WM, Kaul S Diagnostic value of echocardiography in suspected endocarditis: an evaluation based on the pretest prob-

ability of disease Circulation 1996;93:730–6.

Echocardiography in infective endocarditis 87

Section two Coronary artery disease

C H A P T E R 8

Coronary imaging and screening

Koen Nieman and Pim J de Feyter

Introduction

Non-invasive imaging of the coronary arteries was first demonstrated by netic resonance imaging (MRI) in the early 1990s Since these first images, the capabilities of cardiac MRI have rapidly developed, even though cardiac MRIhas proven most useful for functional assessments and infarct imaging Parallel

mag-to these developments, computed mag-tomography (CT) has evolved inmag-to a reliablecardiac imaging modality Electron beam CT, followed by multislice spiral CThave proven able to provide high-resolution imaging of the coronary lumen aswell as the diseased coronary artery wall The time has come to determine therole of non-invasive coronary imaging, merely as an alternative to conven-tional angiography, or a complementary addition to non-invasive functional imaging

Magnetic resonance imaging

Of the currently applied non-invasive coronary imaging techniques, MRI is themost attractive in terms of patient safety, because it does not require potentiallynephrotoxic contrast media or radiation High-resolution images of the heartcan be obtained in any orientation, and with excellent tissue differentiation.MRI is a tomographic imaging technique based on the behavior of protons(hydrogen nuclei) in a magnetic field After excitation by a radiofrequency (RF)pulse, protons will emit an RF signal over a short period of time while they re-turn to their aligned position The time required for complete relaxation de-pends on the physical and biochemical environment of the proton, which isexploited by MRI to create images using various pulsing sequence designs MRI

is recognized as an important tool in cardiovascular medicine for imaging of diovascular morphology, myocardial perfusion, and myocardial viability It isconsidered the gold standard for ventricular function assessment.1

car-Magnetic resonance coronary angiography

Coronary imaging by MRI was first demonstrated in the early 1990s Using

var-91

ious 2D and 3D, breath-hold and free-breathing acquisition protocols, tive disease in the coronary arteries and bypass grafts can be visualized (Fig.8.1) Although initial reports were very promising, comparative studies withnumerous MRI techniques against conventional coronary angiography haveshown that lesions can be detected in the proximal coronary artery segmentswith a reasonable sensitivity and specificity, which remained at 38–93% and42–97%, respectively.2Despite steady technologic advancement, MRI has notyet reached a level of robustness that allows high-quality imaging of the entirecoronary artery tree with sufficient spatial resolution, temporal resolution, andcontrast-to-noise Additional limitations include the long examination times,inability to scan and/or evaluate patients with implanted metal objects,ECG–signal distortion during scanning, suppression of signal from fat tissue,and motion artifacts resulting from averaging of data that was acquired overseveral heart cycles.1

obstruc-Magnetic resonance plaque imaging

MRI can express numerous biochemical properties of the tissue being gated, which make this modality ideal for tissue differentiation By exposingatherosclerotic tissue to different pulse sequences that focus on different bio-chemical parameters, various plaque components can be identified, includingfibrous or lipid tissue, calcium, and thrombus Most of these experiences havebeen acquired in larger vessels, namely the carotid arteries and the aorta Inthese vessels accurate measurements of the plaque size can be performed,which allows monitoring of plaque progression or regression.3High-resolutioncoronary plaque imaging is a challenging and time-consuming procedure andonly limited coronary sections can be imaged within a reasonable examinationtime

investi-92 Chapter 8

Figure 8.1 Cardiac magnetic resonance imaging (MRI) Volume- rendered MR angiogram showing a venous bypass graft arising from the aortic root along the anterior surface of the heart, with anastomoses to branches of the left coronary artery, which are not well seen.

Electron-beam computed tomography

Electron-beam computed tomography (EBCT) is a fast CT technology, cally designed for imaging of the heart Because of the lack of mechanicallymoving parts, the time to acquire one image can be as short as 50 ms The acqui-sition of images is prospectively triggered by the ECG Based on the interpreta-tion of the recorded ECG trace, the scan is initiated during the predicted diastolicphase of the next heart cycle

specifi-Non-enhanced imaging of coronary calcium

The presence of calcium in the cardiovascular system is possible with any X-raymodality, as well as ultrasound and MRI Without the use of contrast media, CT

is able to detect small atherosclerotic calcifications in the coronary arteries.Since the early 1990s, EBCT has been used for the detection and quantification

of coronary calcium

By detecting calcium in the coronary arteries, the evidence for sis is compelling An exceptional cause for vessel wall calcification is Möncke-berg media sclerosis However, the inability to detect calcium does not excludethe possibility of non-calcified atherosclerotic plaque being present It has beenshown extensively that the calcium score is not useful as an reliable indicator ofobstructive coronary artery disease.4While calcification of the individual lesionmay indicate plaque stability, it has been proven that the age-adjusted amount

atherosclero-of coronary calcium is correlated to the occurrence atherosclero-of coronary events It holdsadditional predictive value over the traditional risk factors for the long-term risk

of developing symptomatic coronary artery disease Whether widespreadscreening of asymptomatic individuals for coronary calcium is desirable re-mains a matter of debate Selective use in those with an intermediate coronaryrisk, to determine whether intensive risk factor modification and medical inter-vention is warranted, has been suggested.5The use of non-enhanced EBCT as atriage tool has been explored, to exclude coronary involvement in patients withacute chest pain at the emergency department In a relatively small study nocoronary events occurred in those without coronary calcium in the period afterthey visited the hospital.6However, because the absence of coronary calciumdoes not exclude coronary plaque (rupture), particularly in young patients,these studies had little influence on clinical practice

EBCT coronary angiography

Minimally invasive imaging of the coronary lumen by EBCT is possible by injecting iodinated contrast medium into a peripheral vein A number of com-parative studies with conventional angiography have been performed since

1997 In most studies, assessment was limited to the proximal and middle nary segments After exclusion of segments or vessels with non-diagnosticimage quality (10–28%), the sensitivity and specificity to detect significantcoronary artery disease was in the range 74–92% and 63–94%, respectively(Fig 8.2).4Contrast-enhanced EBCT has also been used to detect bypass graft

coro-Coronary imaging and screening 93