Correctness of multi-detector-row computed tomography for diagnosing mechanical prosthetic heart valve disorders using operative findings as a gold standard

Cardiac computed tomography in infective endocarditis: "bridging the detection gap"

Infective Endocarditis (IE) remains a significant health challenge. Despite an increasing awareness, mortality is high and has remained largely unchanged over recent decades. Early diagnosis of IE is imperative and to assist clinicians several diagnostic criteria have been proposed. The best known are the Duke criteria. Originally published in 1994, these criteria have undergone significant modifications. This manuscript provides a timeline of the successive changes that have been made over the last 30 years. Changes which to a large degree have reflected both the evolving epidemiology of IE and the proliferation and increasing availability of advanced multi-modality imaging. Importantly, many of these changes now form part of societal guidelines for the diagnosis of IE. To provide validation for the incorporation of cardiac computed tomography (CT) in current guidelines, the manuscript demonstrates a spectrum of pictorial case studies that re-enforce the utility and growing importance of early cardiac CT in the diagnosis and treatment of suspected IE.

Usefulness of cardiac computed tomography in prosthetic heart valve dysfunction

BACKGROUND

Prosthetic heart valve (PHV) dysfunction is a serious complication. Echocardiography remains the first-line imaging investigation to assess PHV dysfunction. However, the role of Computed Tomography (CT) scanning in this type of case has not been thoroughly studied yet. The objective of our study was to determine if cardiac Computed Tomography (CT) had a potentially complementary role to play alongside echocardiography in diagnosing the mechanism of prosthetic valve dysfunction.

METHODS AND RESULTS

This prospective cohort study was conducted on 54 patients with suspected PHV dysfunction. All patients underwent routine diagnosis work-up (transthoracic and transesophageal echocardiography) and additional cardiac CT. Cardiac CT showed findings that were not detected by echocardiography in seven patients (12%) namely aortic pannus (5) and pseudoaneurysm (2). An underlying thrombus was detected by echocardiography and missed by cardiac CT in 15 patients (27%). However, in these thrombotic cases, cardiac CT contributed to the functional evaluation of leaflets.

CONCLUSION

This study demonstrates that an integrated approach including transthoracic, transesophageal echocardiography and computed tomography is useful in patients with suspected PHV dysfunction. While computed tomography is more accurate in the diagnosis of pannus formation and periannular complications, echocardiography is superior at detecting thrombus.

Non coronary applications of cardiac computed tomography: A review

Acquired heart diseases including valvular pathologies and conduction abnormalities, along with coronary artery disease make cardiovascular disease one of the major causes of mortality and morbidity worldwide. Advances in cardiac computed tomography (CCT) have led to markedly improved image quality for assessment of several coronary and noncoronary cardiac abnormalities. With the latest versions of CT scanners, image acquisition can be completed within a few seconds, in a single breath hold and with much less radiation exposure, thus making CT an even more attractive diagnostic tool with its high temporal and excellent spatial resolution. Additional advantages are its noninvasive nature, wide availability, fast image acquisition and ability to provide additional data about the cardiac structure, function, valvular motion, and presence or absence of valvular vegetation, mass or intracardiac thrombus. These factors can result in change in management in many valvular pathologies pre- and post-intervention, and in electrophysiological procedures. The goal of this article is to review applications of cardiac CT in non-coronary indications including valvular assessment, pulmonary vein isolation procedure, and left atrial appendage evaluation for its transcatheter occlusion.

Infective endocarditis - A review of current therapy and future challenges

Etiological, microbiological and epidemiological factors changed over time, but mortality rates remain high in infective endocarditis (IE). Healthcare-associated IE is nowadays responsible for a significant proportion of cases due to increasing numbers of cardiac devices. Cardiac implantable electronic devices, transcatheter aortic valve replacement, and percutaneous valve repair are meanwhile used, especially in old and sick patients. In suspected IE modified Duke criteria, integrating clinical results, imaging, and biomarkers are traditionally applied. Newer imaging technologies such as multi-slice computed tomography, photon-emission computed tomography, and magnetic resonance imaging might add value to conventional echocardiography in diagnosis and management of IE. Treatment consists of long-term antibiotic therapy, infectiological source control and/or cardiac surgery. Recently, antibiotic parenteral outpatient regimens and partial oral treatment strategies were shown to shorten hospital stays in patients suffering from IE. However, it remains unclear how to best select patients for partial oral therapy. This review describes new trends in diagnosing, imaging, and treating IE in a changing patient collective with particular focus on patients with implantable cardiac devices.

Extent of Subprosthetic Pannus after Aortic Valve Replacement: Changes Over Time and Relationship with Echocardiographic Findings

Purpose

This study aimed to evaluate changes of subprosthetic pannus on cardiac CT and determine its relationship to echocardiographic findings in patients with mechanical aortic valve replacement (AVR).

Materials and Methods

Between April 2011 and November 2017, 17 AVR patients (56.8 ± 8.9 years, 12% male) who showed pannus formation on CT and had undergone both follow-up CT and echocardiography were included. The mean interval from AVR to the date of pannus detection was 10.5 ± 7.1 years. In the initial and follow-up CT and echocardiography, the pannus extent and echocardiographic parameters were compared using paired t-tests. The relationship between the opening angle of the prosthetic valve and the pannus extent was evaluated using Pearson correlation analysis.

Results

The pannus extent was significantly increased on CT (p < 0.05). The peak velocity (3.9 ± 0.8 m/s vs. 4.2 ± 0.8 m/s, p = 0.03) and mean pressure gradient (36.4 ± 15.5 mm Hg vs. 42.1 ± 15.8 mm Hg, p = 0.03) were significantly increased. The mean opening angles of the mechanical aortic leaflets were slightly decreased, but there was no statistical significance (73.1 ± 8.3° vs. 69.4 ± 12.1°, p = 0.12). The opening angle of the prosthetic leaflets was inversely correlated with the pannus extent (r = −0.57, p < 0.001).

Conclusion

The pannus extent increases over time, increasing transvalvular peak velocity and the pressure gradient. CT can be used to evaluate the pannus extent associated with hemodynamic changes that need to be managed by surgical intervention.

Imaging for structural heart procedures: focus on computed tomography

The success and continued rapid clinical integration of transcatheter valve technologies relies on imaging modalities to guide safe and effective device deployment. In particular, cardiac imaging, using both echocardiography and CT, is an integral resource for the multidisciplinary team. These modalities can provide valuable insight for the proceduralist at each stage of transcatheter-based valve insertion, as they can be used reliably to define the anatomy of interest and its relationship to surrounding structures, determine accurate device sizing, assess patients for valve-in-valve procedures, and screen for adverse features or procedural contraindications. We provide an overview of some of the key aspects of the use of CT and echocardiography in the context of transcatheter aortic valve replacement (TAVR), as well as transcatheter mitral valve replacement (TMVR).

Recommendations on nuclear and multimodality imaging in IE and CIED infections

In the latest update of the European Society of Cardiology (ESC) guidelines for the management of infective endocarditis (IE), imaging is positioned at the centre of the diagnostic work-up so that an early and accurate diagnosis can be reached. Besides echocardiography, contrast-enhanced CT (ce-CT), radiolabelled leucocyte (white blood cell, WBC) SPECT/CT and [¹⁸F]FDG PET/CT are included as diagnostic tools in the diagnostic flow chart for IE. Following the clinical guidelines that provided a straightforward message on the role of multimodality imaging, we believe that it is highly relevant to produce specific recommendations on nuclear multimodality imaging in IE and cardiac implantable electronic device infections. In these procedural recommendations we therefore describe in detail the technical and practical aspects of WBC SPECT/CT and [¹⁸F]FDG PET/CT, including ce-CT acquisition protocols. We also discuss the advantages and limitations of each procedure, specific pitfalls when interpreting images, and the most important results from the literature, and also provide recommendations on the appropriate use of multimodality imaging.

A whole-heart motion-correction algorithm: Effects on CT image quality and diagnostic accuracy of mechanical valve prosthesis abnormalities

BACKGROUND

We aimed to determine the effect of a whole-heart motion-correction algorithm (new-generation snapshot freeze, NG SSF) on the image quality of cardiac computed tomography (CT) images in patients with mechanical valve prostheses compared to standard images without motion correction and to compare the diagnostic accuracy of NG SSF and standard CT image sets for the detection of prosthetic valve abnormalities.

METHODS

A total of 20 patients with 32 mechanical valves who underwent wide-coverage detector cardiac CT with single-heartbeat acquisition were included. The CT image quality for subvalvular (below the prosthesis) and valvular regions (valve leaflets) of mechanical valves was assessed by two observers on a four-point scale (1 = poor, 2 = fair, 3 = good, and 4 = excellent). Paired t-tests or Wilcoxon signed rank tests were used to compare image quality scores and the number of diagnostic phases (image quality score≥3) between the standard image sets and NG SSF image sets. Diagnostic performance for detection of prosthetic valve abnormalities was compared between two image sets with the final diagnosis set by re-operation or clinical findings as the standard reference.

RESULTS

NG SSF image sets had better image quality scores than standard image sets for both valvular and subvalvular regions (P < 0.05 for both). The number of phases that were of diagnostic image quality per patient was significantly greater in the NG SSF image set than standard image set for both valvular and subvalvular regions (P < 0.0001). Diagnostic performance of NG SSF image sets for the detection of prosthetic abnormalities (20 pannus and two paravalvular leaks) was greater than that of standard image sets (P < 0.05).

CONCLUSION

Application of NG SSF can improve CT image quality and diagnostic accuracy in patients with mechanical valves compared to standard images.

Assessment of Mitral Paravalvular Leakage After Mitral Valve Replacement Using Cardiac Computed Tomography

Background—

The diagnostic performance of cardiac computed tomography (CT) for detection of paravalvular leakage (PVL) after mitral valve replacement has not been investigated in a large population. We aimed to investigate the diagnostic accuracy of CT for diagnosis of mitral PVL using surgical findings as the standard reference and to compare the diagnostic performance of CT with those of transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE).

Methods and Results—

A total of 204 patients with previous mitral valve replacement who underwent cardiac CT were retrospectively included. The presence of mitral PVL was analyzed on CT, TTE, and TEE. In 78 patients who underwent redo-surgery, diagnostic performance for the detection of PVL for CT, TTE, and TEE were compared with surgical findings as the standard reference. The location of mitral PVL on CT and TEE was compared with surgical findings. Mitral PVL was present in 18.1% (37/204) on CT, in 16.2% (32/198) on TTE, and in 42.6% (29/68) on TEE. On the surgical field, PVL was identified in 41.0% (32/78). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for detection of PVL were 96.9%, 97.8%, 96.9%, 97.8%, and 97.4% for CT; 81.3%, 95.6%, 92.9%, 87.8%, and 89.6% for TTE; and 96.2%, 95.8%, 96.2%, 95.8%, and 96.0% for TEE. CT and TEE identified the correct location of PVL in 75.9% (22/29) and 85.6% (19/23).

Conclusions—

Cardiac CT may have better diagnostic accuracy compared with TTE for the detection of mitral PVL and may be comparable to TEE for the detection and localization of PVL.

Artificial aortic valve dysfunction due to pannus and thrombus - different methods of cardiac surgical management

INTRODUCTION

Approximately 60 000 prosthetic valves are implanted annually in the USA. The risk of prosthesis dysfunction ranges from 0.1% to 4% per year. Prosthesis valve dysfunction is usually caused by a thrombus obstructing the prosthetic discs. However, 10% of prosthetic valves are dysfunctional due to pannus formation, and 12% of prostheses are damaged by both fibrinous and thrombotic components. The authors present two patients with dysfunctional aortic prostheses who were referred for cardiac surgery. Different surgical solutions were used in the treatment of each case.

CASE STUDY 1

The first patient was a 71-year-old woman whose medical history included arterial hypertension, stable coronary artery disease, diabetes mellitus, chronic obstructive pulmonary disease (COPD), and hypercholesterolemia; she had previously undergone left-sided mastectomy and radiotherapy. The patient was admitted to the Cardiac Surgery Department due to aortic prosthesis dysfunction. Transthoracic echocardiography revealed complete obstruction of one disc and a severe reduction in the mobility of the second. The mean transvalvular gradient was very high. During the operation, pannus covering the discs' surface was found. A biological aortic prosthesis was reimplanted without complications.

CASE STUDY 2

The second patient was an 87-year-old woman with arterial hypertension, persistent atrial fibrillation, and COPD, whose past medical history included gastric ulcer disease and ischemic stroke. As in the case of the first patient, she was admitted due to valvular prosthesis dysfunction. Preoperative transthoracic echocardiography revealed an obstruction of the posterior prosthetic disc and significant aortic regurgitation. Transesophageal echocardiography and fluoroscopy confirmed the prosthetic dysfunction. During the operation, a thrombus growing around a minor pannus was found. The thrombus and pannus were removed, and normal functionality of the prosthetic valve was restored.

CONCLUSIONS

Precise and modern diagnostic methods facilitated selection of the treatment method. However, the intraoperative view also seems to be crucial in individualizing the surgical approach.

Multimodality Imaging Assessment of Prosthetic Heart Valves

Echocardiography and fluoroscopy are the main techniques for prosthetic heart valve (PHV) evaluation, but because of specific limitations they may not identify the morphological substrate or the extent of PHV pathology. Cardiac computed tomography (CT) and magnetic resonance imaging (MRI) have emerged as new potential imaging modalities for valve prostheses. We present an overview of the possibilities and pitfalls of CT and MRI for PHV assessment based on a systematic literature review of all experimental and patient studies. For this, a comprehensive systematic search was performed in PubMed and Embase on March 24, 2015, containing CT/MRI and PHV synonyms. Our final selection yielded 82 articles on surgical valves. CT allowed adequate assessment of most modern PHVs and complemented echocardiography in detecting the obstruction cause (pannus or thrombus), bioprosthesis calcifications, and endocarditis extent (valve dehiscence and pseudoaneurysms). No clear advantage over echocardiography was found for the detection of vegetations or periprosthetic regurgitation. Whereas MRI metal artifacts may preclude direct prosthesis analysis, MRI provided information on PHV-related flow patterns and velocities. MRI demonstrated abnormal asymmetrical flow patterns in PHV obstruction and allowed prosthetic regurgitation assessment. Hence, CT shows great clinical relevance as a complementary imaging tool for the diagnostic work-up of patients with suspected PHV obstruction and endocarditis. MRI shows potential for functional PHV assessment although more studies are required to provide diagnostic reference values to allow discrimination of normal from pathological conditions.

Measurement of Opening and Closing Angles of Aortic Valve Prostheses In Vivo Using Dual-Source Computed Tomography: Comparison with Those of Manufacturers' in 10 Different Types

Objective

The aims of this study were to compare opening and closing angles of normally functioning mechanical aortic valves measured on dual-source computed tomography (CT) with the manufacturers' values and to compare CT-measured opening angles according to valve function.

Materials and Methods

A total of 140 patients with 10 different types of mechanical aortic valves, who underwent dual-source cardiac CT, were included. Opening and closing angles were measured on CT images. Agreement between angles in normally functioning valves and the manufacturer values was assessed using the interclass coefficient and the Bland-Altman method. CT-measured opening angles were compared between normal functioning valves and suspected dysfunctioning valves.

Results

The CT-measured opening angles of normally functioning valves and manufacturers' values showed excellent agreement for seven valve types (intraclass coefficient [ICC], 0.977; 95% confidence interval [CI], 0.962-0.987). The mean differences in opening angles between the CT measurements and the manufacturers' values were 1.2° in seven types of valves, 11.0° in On-X valves, and 15.5° in ATS valves. The manufacturers' closing angles and those measured by CT showed excellent agreement for all valve types (ICC, 0.953; 95% CI, 0.920-0.972). Among valves with suspected dysfunction, those with limitation of motion (LOM) and an increased pressure gradient (PG) had smaller opening angles than those with LOM only (p < 0.05).

Conclusion

Dual-source cardiac CT accurately measures opening and closing angles in most types of mechanical aortic valves, compared with the manufacturers' values. Opening angles on CT differ according to the type of valve dysfunction and a decreased opening angle may suggest an elevated PG.

Reliability, Agreement, and Presentation of a Reference Standard for Assessing Implanted Heart Valve Sizes by Multidetector-Row Computed Tomography

The implanted prosthetic heart valve (PHV) size is vital for the evaluation of suspected PHV dysfunction and in case of reoperation or valve-in-valve transcatheter approaches. The labeled size is not always known, and discrepancies exist between manufacturers' labeled sizes and true sizes. Reproducible methods for noninvasive PHV size assessment are lacking. We determined the reliability and agreement of PHV size measurements using multidetector-row computed tomography (MDCT) and provide reference values of MDCT measurements compared with manufacturer specifications. In vitro, 15 different PHV types in available sizes (total n = 63) were imaged. In vivo, available MDCT acquisitions of patients with PHVs were retrospectively gathered in 2 centers, and 230 patients with 249 PHVs were included. Inner valve area and area-derived diameter were measured in all PHVs. For mechanical PHVs, the inner diameter was also measured. Data were analyzed using the intraclass correlation coefficient and Bland-Altman plots and related to manufacturer specifications. Measurements could be obtained for all PHV types, except the Björk-Shiley (n = 7) because of severe valve-related artifacts hampering the image quality. Intrarater and interrater reliability was excellent for biological and mechanical PHVs (intraclass correlation coefficients ≥0.903). Agreement was good for all measurements with an overall maximal mean difference (95% confidence interval) of -2.61 mm(2) (-37.9 to 32.7), -0.1 mm (-1.1 to 1.0), and 0 mm (-0.4 to 0.3) for valve area, area-derived diameter, and inner diameter, respectively. MDCT reliably discriminated consecutive PHV sizes as labeled by the manufacturer because the absolute ranges for the measurements never overlapped. In conclusion, MDCT allows assessment of the implanted PHV size with excellent reliability and agreement and can discriminate between PHV sizes for contemporary prostheses. MDCT can be used to noninvasively identify the manufacturer-labeled PHV size.

Korean guidelines for the appropriate use of cardiac CT

The development of cardiac CT has provided a non-invasive alternative to echocardiography, exercise electrocardiogram, and invasive angiography and cardiac CT continues to develop at an exponential speed even now. The appropriate use of cardiac CT may lead to improvements in the medical performances of physicians and can reduce medical costs which eventually contribute to better public health. However, until now, there has been no guideline regarding the appropriate use of cardiac CT in Korea. We intend to provide guidelines for the appropriate use of cardiac CT in heart diseases based on scientific data. The purpose of this guideline is to assist clinicians and other health professionals in the use of cardiac CT for diagnosis and treatment of heart diseases, especially in patients at high risk or suspected of heart disease.

ECG-gated MDCT after aortic and mitral valve surgery

OBJECTIVE

The purpose of this article is to review the utility of ECG-gated MDCT in evaluating postsurgical findings in aortic and mitral valves. Normal and pathologic findings after aortic and mitral valve corrective surgery are shown in correlation with the findings of the traditionally used imaging modalities echocardiography and fluoroscopy to assist in accurate noninvasive anatomic and dynamic evaluation of postsurgical valvular abnormalities.

CONCLUSION

Because of its superior spatial and adequate temporal resolution, ECG-gated MDCT has emerged as a robust diagnostic tool in the evaluation and treatment of patients with postsurgical valvular abnormalities.

Multidetector-row computed tomography allows accurate measurement of mechanical prosthetic heart valve leaflet closing angles compared with fluoroscopy

PURPOSE

The purpose of this study was to compare multidetector-row computed tomography (MDCT) leaflet restriction measurements with fluoroscopy measurements in commonly used mechanical prosthetic heart valves (PHVs).

METHODS

Four mechanical PHVs (ON-X, Carbomedics, St. Jude, and Medtronic Hall) were imaged in a pulsatile model using fluoroscopy and 64-detector-row computed tomography. Five image acquisitions of each PHV without (1) and with (4) restricted leaflet closure were made. Three observers measured closure angles on fluoroscopy and MDCT. Data were analyzed using intraclass correlation coefficient (ICC) and Bland-Altman plots.

RESULTS

Interobserver agreement was high in restricted and non-restricted leaflets on both modalities (ICCs >0.995). MDCT and fluoroscopy showed high agreements (ICCs >0.989). Median MDCT closure angle measurements differed at most -2 to +2 degrees from fluoroscopy in the restricted and -1 to +2 degrees in the non-restricted leaflets.

CONCLUSIONS

MDCT allows measurement of leaflet motion with a maximal median discrepancy of 2 degrees. Both MDCT and fluoroscopy detect restricted leaflet closure with great accuracy.

The impact of a new model-based iterative reconstruction algorithm on prosthetic heart valve related artifacts at reduced radiation dose MDCT

To assess the impact of hybrid iterative reconstruction (IR) and novel model-based iterative reconstruction (IMR) and dose reduction on prosthetic heart valve (PHV) related artifacts and objective image quality. One transcatheter and two mechanical PHVs were embedded in diluted contrast-gel, inserted in an anthropomorphic phantom and imaged stationary with retrospectively ECG-gated computed tomography. Eight acquisitions were obtained of each PHV at 120 kV, 600 mAs (routine), 300 and 150 mAs (reduced dose). Data were reconstructed with filtered back projection (FBP), IR and IMR. Hypodense and hyperdense artifact volumes were quantified using two threshold filters. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Artifact volumes differed significantly between reconstruction algorithms for all PHVs (P < 0.005). Compared to FBP, IR decreased overall hypodense and hyperdense artifact volumes; at 150 mAs by 53 and 20 % (IR) and 67 and 23 % (IMR), respectively and significantly increased SNR and CNR at all doses (P < 0.012). Even at reduced dose, IMR resulted in higher image quality than routine dose FBP and IR. Iterative reconstruction and particularly IMR significantly reduce PHV-related artifacts and improve objective image quality in non-pulsatile conditions, even in reduced-dose images. Also, this study suggests that IMR allows for more radiation dose reduction in comparison to hybrid IR while maintaining high image quality.

Imaging of cardiac valves by computed tomography

This paper describes "how to" examine cardiac valves with computed tomography, the normal, diseased valves, and prosthetic valves. A review of current scientific literature is provided. Firstly, technical basics, "how to" perform and optimize a multislice CT scan and "how to" interpret valves on CT images are outlined. Then, diagnostic imaging of the entire spectrum of specific valvular disease by CT, including prosthetic heart valves, is highlighted. The last part gives a guide "how to" use CT for planning of transcatheter aortic valve implantation (TAVI), an emerging effective treatment option for patients with severe aortic stenosis. A special focus is placed on clinical applications of cardiac CT in the context of valvular disease.

CT-scan images preprocessing and segmentation to improve bioprosthesis leaflets morphological analysis

The visualization of bioprosthesis leaflet morphology might help to better understand the underlying mechanism of dysfunction in degenerated aortic bioprosthesis. Because today such visualization of bioprosthesis leaflet morphology is intricate to impossible with other imaging techniques, we hypothesized that the processing of multi-detector CT images would allow better visualization of the prosthetic valve leaflets after biological aortic valve replacement. The purpose of our study was to prospectively evaluate patients with a degenerated aortic bioprosthesis, waiting for reoperation, by using 64-slice CT to evaluate prosthetic leaflets morphology. A semi-automatic segmentation of pre-operative tomodensitometric images was conducted, using 2 different implementations of the region growing algorithm. Here we report all segmentation steps (selection of the region of interest, filtering, segmentation). Studied degenerated aortic bioprostheses were represented by two Carpentier-Edwards Supra Annular Valve (porcine leaflets), one Edwards Perimount (pericardial leaflets) and one Medtronic Mosaic (porcine leaflets). Both segmentation methods (Isotropic Region Growing and Stick Region Growing) allowed a semi-automatic segmentation with 3D reconstruction of all bioprosthetic components (stent, leaflets, degeneration/calcifications). Explanted bioprosthesis CT images were also processed and used as reference. Segmentation results were compared by means of quantitative criteria. Semi-automatic segmentation using region growing algorithm seems to provide an interesting approach for the morphological characterization of degenerated aortic bioprostheses. We believe that in the next future CT scan images segmentation may play an important role to better understand the mechanism of dysfunction in failing aortic bioprostheses. Moreover, bioprostheses 3D reconstructions could be integrated into preoperative planning tools to optimize valve-in-valve procedure.

Organized Prosthetic Tricuspid Valve Thrombosis Treated Successfully with Medical Treatment

Prosthetic valve thrombosis (PVT) can be a life-threatening complication that requires immediate treatment. We present a case of 57-year-old woman with tricuspid PVT who was definitely diagnosed by multi-detector-row computed tomography limited with echocardiography. The patient was treated successfully with an alternative approach using low molecular weight heparin bridging therapy followed by intensifying anticoagulation alone.

Evaluation of the aortic and mitral valves with cardiac computed tomography and cardiac magnetic resonance imaging

Cardiac computed tomography (CT) produces high-quality anatomical images of the cardiac valves and associated structures. Cardiac magnetic resonance imaging (MRI) provides images of valve morphology, and allows quantitative evaluation of valvular dysfunction and determination of the impact of valvular lesions on cardiovascular structures. Recent studies have demonstrated that cardiac CT and MRI are important adjuncts to echocardiography for the evaluation of aortic and mitral valvular heart diseases (VHDs). Radiologists should be aware of the technical aspects of cardiac CT and MRI that allow comprehensive assessment of aortic and mitral VHDs, as well as the typical imaging features of common and important aortic and mitral VHDs on cardiac CT and MRI.

CT attenuation measurements are valuable to discriminate pledgets used in prosthetic heart valve implantation from paravalvular leakage

OBJECTIVES

Sutures with polytetrafluorethylene (PTFE) felt pledgets are commonly used in prosthetic heart valve (PHV) implantation. Paravalvular leakage can be difficult to distinguish from PTFE felt pledgets on multislice CT because both present as hyperdense structures. We assessed whether pledgets can be discriminated from contrast-enhanced solutions (blood/saline) on CT images based on attenuation difference in an ex vivo experiment and under in vivo conditions.

METHODS

PTFE felt pledgets were sutured to the suture ring of a mechanical PHV and porcine aortic annulus, and immersed and scanned in four different contrast-enhanced (Ultravist®; 300 mg jopromide ml(-1)) saline concentrations (10.0, 12.0, 13.6 and 15.0 mg ml(-1)). Scanning was performed on a 256-slice scanner with eight different scan protocols with various tube voltage (100 kV, 120 kV) and tube current (400 mAs, 600 mAs, 800 mAs, 1000 mAs) settings. Attenuation of the pledgets and surrounding contrast-enhanced saline were measured. Additionally, the attenuation of pledgets and contrast-enhanced blood was measured on electrocardiography (ECG)-gated CTA scans of 19 patients with 22 PHVs.

RESULTS

Ex vivo CT attenuation differences between the pledgets and contrast-enhanced solutions were larger by using higher tube voltages. CT attenuation values of the pledgets were higher than contrast-enhanced blood in patients: 420±26 Hounsfield units (mean±SD, range 383-494) and 288±41 Hounsfield units (range 202-367), respectively.

CONCLUSIONS

PTFE felt pledgets have consistently higher attenuation than surrounding contrast-enhanced blood. CT attenuation measurements therefore may help to differentiate pledgets from paravalvular leakage, and detect paravalvular leakage in patients with suspected PHV dysfunction.

Cardiac computed tomography for valve disease

Heart valve disease and coronary heart disease are very prevalent in the general population and often coincide in the same patient. Cardiac computed tomography (CT) makes it possible to noninvasively rule out coronary disease before valve surgery and to potentially avoid invasive heart catheterization in 66% to 75% of patients. The same imaging test provides abundant anatomic and functional information that complements the information from echocardiography, making it possible to characterize the etiology of the valve disease and its repercussions on the heart and aorta, as well as to quantify the severity of disease affecting the valves of the left side of the heart. In this article, we describe the anatomy of the heart valves and the technical requisites of cardiac CT for the study of the valves. We go on to explore the usefulness of CT in the preoperative study of the coronary arteries and in the morphological and functional characterization of valve disease, with special emphasis on the valves of the left side of the heart.

ECG-gated computed tomography: a new role for patients with suspected aortic prosthetic valve endocarditis

OBJECTIVES

The aim of this prospective study was to investigate the agreement in findings between ECG-gated CT and transoesophageal echocardiography (TEE) in patients with aortic prosthetic valve endocarditis (PVE).

METHODS

Twenty-seven consecutive patients with PVE underwent 64-slice ECG-gated CT and TEE and the results were compared. Imaging was compared with surgical findings (surgery was performed in 16 patients).

RESULTS

TEE suggested the presence of PVE in all patients [thickened aortic wall (n = 17), vegetation (n = 13), abscess (n = 16), valvular dehiscence (n = 10)]. ECG-gated CT was positive in 25 patients (93 %) [thickened aortic wall (n = 19), vegetation (n = 7), abscess (n = 18), valvular dehiscence (n = 7)]. The strength of agreement [kappa (95 % CI)] between ECG-gated CT and TEE was very good for thickened wall [0.83 (0.62-1.0)], good for abscess [0.68 (0.40-0.97)] and dehiscence [0.75 (0.48-1.0)], and moderate for vegetation [0.55 (0.26-0.88)]. The agreement was good between surgical findings (abscess, vegetation and dehiscence) and imaging for ECG-gated CT [0.66 (0.49-0.87)] and TEE [0.79 (0.62-0.96)] and very good for the combination of ECG-gated CT and TEE [0.88 (0.74-1.0)].

CONCLUSION

Our results indicate that ECG-gated CT has comparable diagnostic performance to TEE and may be a valuable complement in the preoperative evaluation of patients with aortic PVE.

Artifact reduction strategies for prosthetic heart valve CT imaging

Multislice CT evaluation of prosthetic heart valves (PHV) is limited by PHV-related artifacts. We assessed the influence of different kV settings, a metal artifact reduction filter (MARF) and an iterative reconstruction algorithm (IR) on PHV-induced artifacts in an in vitro model. A Medtronic-Hall tilting disc and St Jude bileafet PHV were imaged using a 64-slice scanner with 100 kV/165 mAs, 120 kV/100 mAs, 140 kV/67 mAs at an equal CTDI(vol). Images were reconstructed with (1) filtered back projection (FBP), (2) IR, (3) MARF and (4) MARF and IR. Hypo- and hyperdense artifacts volumes (mean mm(3) ± SD) were quantified with 2 thresholds (≤-50 and ≥175 Hounsfield Units). Image noise was measured and the presence of secondary artifacts was scored by 2 observers independently. Mean hypodense artifacts for the Medtronic-Hall/St Jude valve (FBP) were 966 ± 23/1,738 ± 21 at 100 kV, 610 ± 13/991 ± 12 at 120 kV, and 420 ± 9/634 ± 9 at 140 kV. Compared to FBP, hypodense artifact reductions for IR were 9/8 %, 10/7 % and 12/6 % respectively, for MARF 92 %/84 %, 89/81 % and 86/77 % respectively; for MARF + IR 94/85 %, 92/82 %, and 90/79 % respectively. Mean hyperdense artifacts for the Medtronic-Hall/St Jude valve were 5,530 ± 48/6,940 ± 70 at 100 kV, 5,120 ± 42/6,250 ± 53 at 120 kV, and 5,011 ± 52/6,000 ± 0 at 140 kV. Reductions for IR were 2/2 %, 2/3 % and 3/4 % respectively, for MARF were 9/30 %, 0/25 %, 5/22 % respectively, MARF + IR 12/32 %, 4/27 % and 7/25 % respectively. Secondary artifacts were found in all MARF images. Image noise was reduced in the IR images. In vitro PHV-related artifacts can be reduced by increasing kV despite maintaining identical CTDI(vol). Although MARF is more effective than IR, it induces secondary artifacts.

Prospective ECG triggering reduces prosthetic heart valve-induced artefacts compared with retrospective ECG gating on 256-slice CT

OBJECTIVES

Multidetector computed tomography (MDCT) has diagnostic value for the evaluation of prosthetic heart valve (PHV) dysfunction but it is hampered by artefacts. We hypothesised that image acquisition using prospective triggering instead of retrospective gating would reduce artefacts related to pulsating PHV.

METHODS

In a pulsatile in vitro model, a mono- and bileaflet PHV were imaged using 256 MDCT at 60, 75 and 90 beats per minute (BPM) with either retrospective gating (120 kV, 600 mAs, pitch 0.2, CTDI(vol) 39.8 mGy) or prospective triggering (120 kV, 200 mAs, CTDI(vol) 13.3 mGy). Two thresholds (>175 and <-45HU), derived from the density of surrounding structures, were used for quantification of hyper- and hypodense artefacts. Image noise and artefacts were compared between protocols.

RESULTS

Prospective triggering reduced hyperdense artefacts for both valves at every BPM (P = 0.001 all comparisons). Hypodense artefacts were reduced for the monoleaflet valve at 60 (P = 0.009), 75 (P = 0.016) and 90 BPM (P = 0.001), and for the bileaflet valves at 60 (P = 0.001), 90 (P = 0.001) but not at 75 BPM (P = 0.6). Prospective triggering reduced image noise at 60 (P = 0.001) and 75 (P < 0.03) but not at 90 BPM.

CONCLUSIONS

Compared with retrospective gating, prospective triggering reduced most artefacts related to pulsating PHV in vitro.

KEY POINTS

• Computed tomographic images are often degraded by prosthetic heart valve-induced artefacts • Prospective triggering reduces prosthetic heart valve-induced artefacts in vitro • Artefact reduction at 90 beats per minute occurs without image noise reduction • Prospective triggering may improve CT image quality of moving hyperdense structures.

Coronary artery assessment by multidetector computed tomography in patients with prosthetic heart valves

OBJECTIVES

Patients with prosthetic heart valves may require assessment for coronary artery disease. We assessed whether valve artefacts hamper coronary artery assessment by multidetector CT.

METHODS

ECG-gated or -triggered CT angiograms were selected from our PACS archive based on the presence of prosthetic heart valves. The best systolic and diastolic axial reconstructions were selected for coronary assessment. Each present coronary segment was scored for the presence of valve-related artefacts prohibiting coronary artery assessment. Scoring was performed in consensus by two observers.

RESULTS

Eighty-two CT angiograms were performed on a 64-slice (n = 27) or 256-slice (n = 55) multidetector CT. Eighty-nine valves and five annuloplasty rings were present. Forty-three out of 1160 (3.7%) present coronary artery segments were non-diagnostic due to valve artefacts (14/82 patients). Valve artefacts were located in right coronary artery (15/43; 35%), left anterior descending artery (2/43; 5%), circumflex artery (14/43; 32%) and marginal obtuse (12/43; 28%) segments. All cobalt-chrome containing valves caused artefacts prohibiting coronary assessment. Biological and titanium-containing valves did not cause artefacts except for three specific valve types.

CONCLUSIONS

Most commonly implanted prosthetic heart valves do not hamper coronary assessment on multidetector CT. Cobalt-chrome containing prosthetic heart valves preclude complete coronary artery assessment because of severe valve artefacts.

KEY POINTS

• Most commonly implanted prosthetic heart valves do not hamper coronary artery assessment • Prosthetic heart valve composition determines the occurrence of prosthetic heart valve-related artefacts • Björk-Shiley and Sorin tilting disc valves preclude diagnostic coronary artery segment assessment.

Comprehensive MDCT evaluation of patients with pulmonary hypertension: diagnosing underlying causes with the updated Dana Point 2008 classification

OBJECTIVE

Pulmonary hypertension is a challenge for imagers and clinicians, with a variety of possible underlying causes, each with its own specific treatment. Although the diagnosis is based on physiologic measurements, ECG-gated MDCT can play a vital role in elucidating underlying cardiac, vascular, and pulmonary causes.

CONCLUSION

A revised system for pulmonary hypertension, the Dana Point classification, can provide a template for review of the myriad causes of this complex condition.

A novel iterative reconstruction algorithm allows reduced dose multidetector-row CT imaging of mechanical prosthetic heart valves

Multidetector-row CT is promising for prosthetic heart valve (PHV) assessment but retrospectively ECG-gated scanning has a considerable radiation dose. Recently introduced iterative reconstruction (IR) algorithms may enable radiation dose reduction with retained image quality. Furthermore, PHV image quality on the CT scan mainly depends on extent of PHV artifacts. IR may decrease streak artifacts. We compared image noise and artifact volumes in scans of mechanical PHVs reconstructed with conventional filtered back projection (FBP) to lower dose scans reconstructed with IR. Four different PHVs (St. Jude, Carbomedics, ON-X and Medtronic Hall) were scanned in a pulsatile in vitro model. Ten retrospectively ECG-gated CT scans were performed of each PHV at 120 kV, 600 mAs (high-dose CTDI_vol 35.3 mGy) and 120 kV, 300 mAs (low-dose CTDI_vol 17.7 mGy) on a 64 detector-row scanner. Diastolic and systolic images were reconstructed with FBP (high and low-dose) and the IR algorithm (low-dose only). Hypo- and hyperdense artifact volumes were determined using two threshold filters. Image noise was measured. Mean hypo- and hyperdense artifact volumes (mm³) were 1,235/5,346 (high-dose FBP); 2,405/6,877 (low-dose FBP) and 1,218/5,333 (low-dose IR). Low-dose IR reconstructions had similar image noise compared to high-dose FBP (16.5 ± 1.7 vs. 16.3 ± 1.6, mean ± SD, respectively, P = 1.0). IR allows ECG-gated PHV imaging with similar image noise and PHV artifacts at 50% less dose compared to conventional FBP in an pulsatile in vitro model.