Value of cardiac computed tomography angiography in pre-operative assessment of infective endocarditis

The diagnosis of infective endocarditis (IE) is challenging with up to 40% risk of mortality [1]. Early detection and accurate diagnosis is very significant for the care of patients with IE who will often require surgery along with antibiotic therapy. Transthoracic echocardiography (TTE) is typically the initial imaging study to assess valvular involvement in IE [2]. TTE offers good temporal and spatial resolution and is free of ionizing radiation. The important role of TTE in diagnosing IE has been valuable in the modified Duke criteria [3]. In contrast, cardiac computed tomography angiography (CTA), characteristically plays a supportive role in imaging assessment of complication of IE. Nonetheless, use of this modality for evaluating IE has been increasing particularly with the introduction of high resolution image acquisition [4‐9, 11]. Recently, The European Society of Cardiology joint the use of cardiac CTA in its guideline for managing of IE [10]. At our institution, patients with planned cardiothoracic surgery often undergo a cardiac CTA to assistance in preoperative planning. Characteristically, we acquire preoperative cardiac CTA for the assessment of the complication of IE, proximity of cardiovascular structures to retrosternal regions and the existence and extent of coronary artery disease. Moreover, complications associated with IE may also be assessed on these CT images, with accusations for clinical management. In the present study, we anticipated to evaluate the role of cardiac CTA in the preoperative assessment of patients with recognized IE and to compare the results of cardiac CTA with those of TTE and intraoperative findings.

Institutional Review Board approval was obtained for this retrospective review. Inclusion criteria were as follows; patients had surgically proven IE on gross examination and pathologically proven IE with positive causative organism on tissue culture and.

microscopic examination; and patients had cardiac CTA study for pre-surgical evaluation.

Exclusion criteria was the patients with negative culture and pathology findings from surgical tissue. All patients had TTE examinations. To assess true clinical performance of both.

CT and TTE imaging, we assessed only initial preoperative imaging in this investigation, to avoid bias. Imaging findings were analyzed separately based upon valve type (prosthetic and native) and anatomic position. We defined the following imaging criteria for IE complications.

A total of 24 patients with cardiac CTA scans performed during the patient’s hospitalization or within the previous week as part of preoperative assessment. The time period covers January 2015 to December 2017. The median interval between the cardiac CTA and TTE is 2 days. The median interval between cardiac CTA and surgery is 5 days. The median interval between TTE and surgery is 7 days. All study patients had surgical confirmation of IE involving the mitral and/or aortic valve, with causative organisms reviewed in each case. Cardiac CTA findings, including evidence of pseudoaneurysm, abscess, vegetation, and dehiscence were compared with TTE findings when relevant, with surgical reports used as the gold standard.

When comparing the performance of cardiac CTA and TTE, statistically significant differences were verified in the sensitivity for detection of pseudoaneurysm and abscess with cardiac CTA performing superiorly. The sensitivity and specificity for detection of vegetation and dehiscence did not differ significantly between the two groups. The findings remained unchanged when an analysis was limited to the subgroup of patients with prosthetic valve IE.(Table 1) Of the 5 patients who underwent intra-operative coronary artery bypass graft (CABG), none of them was evaluated with invasive cardiac catheterization pre-operatively.

Cardiac CTA was similar to TTE in identification of vegetation and dehiscence in the present study, although, unsurprisingly, cardiac CTA demonstrated significantly higher sensitivity for pseudoaneurysm and abscess. This is regardless of almost one-half of patients having prosthetic valves with current evidence indicating that cardiac CTA has the capability to change diagnosis/treatment with echocardiography in 20–25% of prosthetic IE cases [14]. The diagnosis of perivalvular abscess/pseudoaneurysm related with endocarditis is vital because the presence of a perivalvular abscess/pseudoaneurysm increases the mortality rate by up to 2-fold [15]. In the present study, thirteen patients (54.2%) developed an abscess/pseudoaneurysm, and cardiac CTA correctly diagnosed ten more cases with abscesses/pseudoaneurysms than echocardiography. Echocardiography can underestimate perivalvular involvement, particularly in the case of small lesions, calcified or prosthetic valves [16, 17]. In patients with problematic to characterize perivalvular extension of infection by TTE, cardiac CTA is a practical next diagnostic step with the capability to define the coronary arterial anatomy concurrently, thus avoiding a supplementary procedure such as invasive coronary catheterization and contrast exposure. Cardiac CTA discovered paravalvular abscesses that might not be perceived on TTE due to shadowing of valvular calcification or mechanical valve. Cardiac CTA can be used as a subsidiary modality for detecting infective endocarditis, predominantly in patients who cannot tolerate transesophageal echocardiography (TEE) or with a poor acoustic window. Cardiac CTA has excellent negative predictive value in low to intermediate coronary artery disease (CAD) risk patients. The evidence has been less robust in high risk patients with some studies representing a continuous high negative predictive value whereas others sustaining a high sensitivity, but a decline in NPV due to the increased prevalence of disease [18, 19]. A cost effectiveness study integrating cardiac CTA as a first line test in pre-operative coronary evaluation for non-cardiac surgery established a decreased cost associated with the work-up and perioperative period [20]. Hence, along with avoiding an invasive procedure with a low risk for adverse events, this approach may be economically practical as well. This will reliably exclude significant coronary artery disease and possibly avoid invasive cardiac catheterization with its related potential complications, and might assistance with surgical planning. There are several studies published up to the present time to support this approach of pre-operative CTA in non-cardiac along with cardiac surgery. [21] Ciolina et al. demonstrated the additional value of cardiac CTA for assessing the aortic valve in pre-operative work-up for aortic stenosis [22]. In 42 patients, cardiac CTA appropriately graded aortic valve calcification, sized the aortic annulus and sinotubular junction, perceived thoracic aortic aneurysms, and properly assessed aortic valve area while also being used to evaluate coronary artery. The capability of cardiac CTA to concurrently provide additional diagnostic information and reliably evaluate coronary artery makes it a versatile diagnostic test with significant yield in the pre-operative work-up of patients with IE and other valvular disorders. Our study has limitations that warrant address. First, the analysis was performed in a single center for selected patients who undertook surgical treatment for infective endocarditis. A selection bias may consequently have been introduced during the evaluation of the results. Furthermore, because we have collected surgically managed patients in this study, we could not include all infective endocarditis patients who were treated by medical treatment alone. Nevertheless, we have focused on the surgical findings to compare the cardiac CTA and echocardiography findings. Second, surgical inspection might not be the faultless reference standard for infective endocarditis, predominantly for small lesions. Small vegetation, leaflet perforations, or abscess/pseudoaneurysm formation might not be noticed by surgical inspection.

Finally, the radiation dose is still the primary apprehension of cardiac CTA, particularly in retrospective ECG-gating with a higher radiation dose. A prospective ECG-triggering method using dual-source CT or iterative reconstruction might be used in a future study to reduce this radiation exposure.

The sensitivities of cardiac CTA and TTE to perceive vegetation and dehiscence in patients with infective endocarditis are similar. Ten cases of abscess/pseudoaneurysm can be established by cardiac CTA alone. The greatest advantage of cardiac CTA in the setting of IE is its capability to couple the detection of complex cardiac anatomic abnormalities with coronary artery delineation. Cardiac CTA might be considered as an alternative coronary artery imaging modality in IE patients with low to intermediate risk of disease but meet guideline recommendations for coronary artery imaging.