Perivalvular Abscess and Related Complications

The natural history of perivalvular abscess has become better understood, largely because of serial echocardiographic studies in these patients who undergo surgical intervention as well in those who only receive medical treatment [27,28]. These studies have showed that perivalvular abscess is a dynamic process and is the precursor of all other perivalvular complications, including perivalvular dehiscence, pseudoaneurysm, and fistula. Furthermore, perivalvular abscess has a predilection to the aortic root.

The pathological definition of a paravalvular abscess is a region of necrosis with purulent material that does not communicate with a cardiac chamber or great vessel lumen [29]. This is mirrored by the echocardiographic definition of abscess which is a localized abnormal echolucent area within the perivalvular tissue that does not communicate with the circulation (Figure 7.6) [28]. In addition to identifying the presence of an abscess, there are a number of surgically relevant features that can be delineated using echo. These include the maximum thickness of the abscess cavity, the circumferential extent of the abscess, and involvement of surrounding structures. Long axis views of the aortic root and ascending aorta can be used to define the maximum thickness of the abscess cavity.

As the perivalvular abscess evolves, other features become evident. Echolucent space develops indicative of cavitation and communication with contiguous structures. Serial

Endocarditis Echocardiogram

Figure 7.6. A large abscess anterior to the aortic root in the transesophageal aortic short-axis (A) and long-axis (B) views. A large vegetation is present on the aortic valve which is bicuspid. B

Perivalvular Abscess

Figure 7.6. A large abscess anterior to the aortic root in the transesophageal aortic short-axis (A) and long-axis (B) views. A large vegetation is present on the aortic valve which is bicuspid. B

echo evaluation of abscesses in the setting of endocarditis has documented the development of pseudoaneurysm from abscess cavities [27,28]. Most of these pseudoaneurysms arise as a result of a connection between the aorta and the abscess cavity [28]. A pseudoa-neurysm is an echolucent space with flow originating from either the left ventricle (LV) or aorta. This appears as a pulsatile echolu-cent pouch anatomically related to the valve annulus [29]. When the pseudoaneurysm originates below the aortic annulus, the con nection is between LV and the pseudoaneurysm cavity and color flow imaging shows flow entering the cavity in systole from the LV (Figure 7.7) [30]. Using the color flow jet as a guide may help to image the LV to pseudoa-neurysm connection. The maximum dimension of LV to Aortic discontinuity on 2-D imaging can vary from 1 to 24 mm [30].

A fistula develops as a result of abscess drainage into and communication with two vascular structures. For instance, aneurysm of the mitral aortic intervalvular fibrosa may develop a

Mitral Aortic Intervalvular Fibrosa
A. 4MHZ '6__

3 12S 1S0

Figure 7.7. A pseudoaneurysm at the mitral annular intervalvular fibrosa on transesophageal echocardiography (A). Color flow imaging shows low velocity flow within the pseudoaneurysm communicating with the left ventricular outflow tract (B).

communication to the left atrium (LA) in addition to its communication with the left ventricular outflow tract, resulting in a fistula connecting the left ventricle with the left atrium. In other cases there may be LV to LA connection with no aneurysm of the interventricular fibrosa. Hemodynamically, the result of this LV to LA connection can be thought of as "supran-nular mitral regurgitation" (Figure 7.8) [31]. Even in patients who have had surgery for perivalvular abscess, perivalvular complications

are common and should be looked for in the follow-up of these patients.

The clinical factors predictive of periannu-lar complications are listed in Table 7.7 [29,32,33].

The presence of periannular complications of infective endocarditis has implications for the prognosis and may be an indication for surgical management, although most patients with perian-nular complications who have surgery do so for clinical indications such as persistent infection or

0136180

Figure 7.8. Left ventricle to left atrium fistula at the mitral annulus on transesophageal echocardiography (A). Color flow imaging shows the direction of the fistula flow from the left ventricle into the fistula (B)

(Continued)

Endocarditis

Table 7.7. Risk Factors in the Development of Perivalvular Complications

in Infective Endocarditis*

Risk factor

Relative risk

P-value

Prosthetic valve

1.88

<0.01

Aortic position

1.81

< 0.01

Coagulase negative staphylococci

1.77

< 0.05

Atrioventricular block

2.66

< 0.01

Intravenous drug use

2.5

< 0.01

*From Omani et al.,1989 [33]; San Roman et al.,1999 [32]; and Graupner

et al., 2002 [29].

heart failure due to dysfunction of the infected valve. Patients with periannular abscess have a high mortality whether or not they undergo surgery (Tables 7.8 and 7.9) [27-29,34-36]. In patients referred for surgical intervention, preop-erative echo is vital to plan the surgical intervention and provide guidance for operative risk. The range of operative procedures used to surgically manage periannular complications in patients with IE is discussed in details in Chapter 7.

The circumferential extent of abscess and the presence of a fistula have been shown to predict increased operative risk [35]. Hemodynamically significant aortic or mitral regurgitation increases operative risk in the setting of abscess [36]. Patients who survive surgery for perrianu-lar complications of endocarditis are at continued risk for cardiovascular morbidity. Perivalvular regurgitation is present in the majority of patients who have surgery for peri-annular complications of endocarditis. Patients operated on in the setting of aortic root abscess had a 78% rate of postoperative aortic regurgitation versus 26% in postoperative patients with endocarditis and no abscess [37]. Perivalvular leaks causing symptoms or impaired LV function may necessitate redo valve surgery [28]. Finally, recurrent or persistent infection can occur post operatively which in some cases requires further surgical intervention.

Transthoracic Echo

Abnormal thickness of the aortic root (>10 mm) without a cavity can be a sign of perivalvular

Table 7.8. Short- and Long-Term Mortality in Patients with Perivalvular Abscess who Received Medical Treatment Only

Reference

Sample size

Early mortality

Late mortality

Late surgery

Mean follow-up

Byrd etal.,1990 [27]

5

0

3

0

3 years

Aguado etal.,1993 [34]

10

9

ND

ND

30 days

Choussat et al.,1999 [35]

20

ND

8

ND

6 months

Chan,2002 [28]

12

0

8

3

4.5 years

TEE = transesophageal echocardiography, TTE =

transthoracic echocardiography, ND =

not determined.

Table 7.9. Short- and Long-Term Mortality in Patients with Perivalvular Abscess who Were Treated Surgically

Reference

Sample size

Early mortality

Late mortality

Late surgery

Mean F/U

Byrd etal.,1990 [27]

5

2

1

0

26 months

Aguado et a.,1993 [34]

30

8

1

4

78 months

Choussat et al., 1999 [35]

213

35/213

87

0

6 months

Chan,2002 [28]

31

6

10

8

4.5 yrs

Cosmi et al., 2004 [36]

24

ND

9

0

ND

TEE = transesophageal echocardiography, TTE = transthoracic echocardiography, ND =

not determined.

Table 7.10. Comparison of Transthoracic with Transesophageal Echocardiography in the Diagnosis of Perivalvular Abscess

References

TTE

TEE

Proportion of abscesses infecting prosthetic valves (%)

Sensitivity (%)

Specificity (%)

Sensitivity (%)

Specificity (%)

Ellis et al., 1985 [38]

86

88

ND

ND

17/22 (77)

Daniel etal.,1991 [40]

28

ND

87

ND

16/46 (35)

Aguado etal.,1993 [34]

80

85

ND

ND

13/36 (36)

Tingleff, 1995 [39]

ND

ND

100

ND

18/36(50)

Blumberg,1995 [41]

28

90

78

100

12/24 (50)

San Roman,1999 [32]

ND

ND

90

100

46/46(100)

Choussat, 1999 [35]

36

ND

80

ND

77/233(33)

Graupner, 2002 [29]

ND

ND

80

92

36/78(46)

TEE = transesophageal echocardiography, TTE =

transthoracic echocardiography, ND = not determined.

abscess [38]. At surgery, such thickening has been shown to correspond to a perivalvular abscess cavity containing purulent material [39]. Abscess cavities can be located at any point on the aortic annulus [39]. TTE may be particularly helpful for aortic root abscesses, especially anterior aortic root abscesses. Short-axis views of the aortic root and ascending aorta can determine the circumferential extent of the abscess cavity and its anatomic relation to the valve annulus. On color flow imaging of both short and long axis images, an abscess cavity will have no Doppler evidence of communication between the abscess cavity and a great vessel or cardiac chamber. The accuracy of echo in the diagnosis of abscess is summarized in Table 7.10 [29,32,34,35,38,41]. While TTE is specific for diagnosing abscess, a wide range of sensitivities have been reported. This wide range in sensitivity for TTE in detecting abscess likely reflects the highly variable pretest probability of abscess in patients making up the populations studied. The sensitivity of TTE in detecting abscess remains limited even with harmonic imaging [9]. If abscess is suspected clinically and not identified on TTE, then a TEE should be performed. The main reasons for false-negative TTEs for abscess are poor image quality and the lack of specificity of the echo features. Compared to periaortic abscess, mitral annular abscesses are even more difficult to diagnose by

TTE due to the far field nature of the mitral annu-lus resulting in suboptimal images.

Non-infectious causes of aortic root thickening include inflammatory aortitis, severe atheroma (unusual in the aortic root and ascending aorta), aortic dissection, and recent cardiac surgery [38]. A thorough knowledge of the normal anatomy and echocardiographic appearance of the atrioventricular groove is required to avoid misdiagnosing the presence of a mitral valve abscess (Table 7.11). The main cause of false-positive TTE diagnosis of abscess in the mitral position is degenerative changes of the mitral annulus such as mitral annular calcification and in its more severe form caseous calcification of the mitral annulus (Figure 7.9). The typical appearance of caseous calcification of the mitral annulus on echo is a large echodense mass with smooth borders, which on short axis images can have a semilunar shape within the

Table 7.11. Normal Structures and Conditions Involving the Atrioventricular Groove that May Mimic Mitral Annular Abscess

Loculated pericardial effusion

Prominent epicardial fat

Descending thoracic aorta

Dilated coronary sinus

Shadowing from mitral annular calcification

Dilated left circumflex coronary artery

Caseous Mitral Annular CalcificationMitral Annular Abscess
Figure 7.9. Caseous calcification at the mitral annulus can mimic annular calcifica-tion.The large, circular, echodense mass with echolucent centre is shown in the transthoracic parasternal long axis (A) and apical long-axis (B) views.

atrioventricular groove [42]. Surgical and pathological inspection reveals the contents to be a pastelike material which microscopically contains calcium and lymphocytes but no infectious organisms [42]. Clinical correlation is essential when confronted with this entity.

Aortic pseudoaneurysm has a propensity to affect the posterior aortic root and can be identified as an echo lucent space (Figure 7.10). Color flow imaging shows only low velocity to-and-fro flow within the pseudoaneurysm. A fistula is a communication with flow between two cardiac chambers or great vessels [29,32].

Fistulas can result from the development of connections within cardiac chambers and great vessels in the setting of a preexisting abscess or pseudoaneurysm. In fact, the majority of fistulas are found in the setting of other periannular complications such as abscess or pseudoaneurysm [43]. Another cause of fistula involves the progression of infection of the mitral annular intervalvular fibrosa. A fistula should be suspected when color flow imaging shows turbulent flow originating in one cardiac chamber or great vessel and terminating in a second great vessel or chamber (Figure 7.11). Patients suspected to

Figure 7.10. A large echofree cavity posterior to the aortic root in the transthoracic parasternal long axis view. Aortic pseudoa-neurysm is usually not well seen on transthoracic echocardiography.

Figure 7.10. A large echofree cavity posterior to the aortic root in the transthoracic parasternal long axis view. Aortic pseudoa-neurysm is usually not well seen on transthoracic echocardiography.

Perivavular Abcess

Figure 7.11. Turbulent flow within an echolucent structure at the mitral annulus suggestive of a fistula on transthoracic echocardiography.

Transesophageal Fistula Pics

Figure 7.11. Turbulent flow within an echolucent structure at the mitral annulus suggestive of a fistula on transthoracic echocardiography.

have perivalvular complications should undergo TEE to assess the extent and anatomic relationship of the abnormalities in relation to the adjacent cardiac structures.

Transesophageal Echo

TEE is more sensitive and specific for the detection of abscess in both the aortic and mitral positions (Table 7.10). The sensitivity of TEE ranges from 78% to 90% with a specificity from 92% to

100%. Adhering to the requirement for echolu-cency to define abscess can result in false negatives, particularly in the early stage of periannular infection [29]. Serial TEE evaluation of periannu-lar infection in patients managed medically has shown that early abscesses appear as abnormal thickening of the aortic root which subsequently cavitates (Figure 7.6). Therefore echolucency is a specific sign for abscess but may not be present in the earliest stages of abscess formation. In situations where abscess is suspected but the only finding is abnormal wall thickness, repeat imag ing with TEE may document the development of an echolucent cavity, thus increasing sensitivity to detect this complication while avoiding false positives due to non-infectious causes of increased aortic root thickness.

On TEE an aneurysm of the mitral aortic intervalvular fibrosa demonstrates systolic expansion and diastolic collapse of the interannular zone between the anterior mitral leaflet and the aortic valve [31] (Figure 7.7). Color flow imaging allows the identification and localization of holes and fistulae that may be present within the aneurysm and result in connection between LV and LA. In some cases such fistulas or holes can occur without an aneurysm, typically as a complication of aortic valve IE (Figure 7.12). In the series by Karalis et al., these complications and fistulas were correctly identified by TEE in all seven cases but by TTE in only one case [31].

Compared to TTE, TEE is more sensitive and specific for the diagnosis of pseudoaneurysm and fistula. In addition, the circumferential extent, anatomic relationship and site of communication are better delineated by TEE. As

Perivavular Abcess
A
Atrial Fistula
Figure 7.12. Large vegetations involving the mitral and tricuspid valves on trans-esophageal echocardiography (A). Color flow imaging shows the left ventricle to right atrium fistula.

with periannular abscess, TEE offers higher accuracy and more detailed imaging and is therefore recommended in all cases of known or suspected perivalvular complications.

Summary

1. Perivalvular abscess is a dynamic process and is the precursor of perivalvular abnormalities such as pseudoaneurysm and fistula.

2. TTE can diagnose aortic root abscess but rarely diagnoses mitral abscess.

3. TEE is more sensitive and specific in detecting periannular abscess, aneurysms, and fistulas.

4. Patients with periannular abscess have high short- and long-term morbidity and mortality despite surgical treatment.

Was this article helpful?

0 0
All Natural Yeast Infection Treatment

All Natural Yeast Infection Treatment

Ever have a yeast infection? The raw, itchy and outright unbearable burning sensation that always comes with even the mildest infection can wreak such havoc on our daily lives.

Get My Free Ebook


Post a comment