Cardiac Valve Assessment with MR Imaging and 64-Section Multi–Detector Row CT

Cardiac Computed Tomography of Native Cardiac Valves

Valvular heart disease (VHD) is a significant clinical problem associated with high morbidity and mortality. Although not being the primary imaging modality in VHD, cardiac computed tomography (CCT) provides relevant information about its morphology, function, severity grading, and adverse cardiac remodeling assessment. Aortic valve calcification quantification is necessary for grading severity in cases of low-flow/low-gradient aortic stenosis. Moreover, CCT details significant information necessary for adequate percutaneous treatment planning. CCT may help to detail the etiology of VHD as well as to depict other less frequent causes of valvular disease, such as infective endocarditis, valvular neoplasms, or other cardiac pseudomasses.

Thinner biological tissues induce leaflet flutter in aortic heart valve replacements

Valvular heart disease has recently become an increasing public health concern due to the high prevalence of valve degeneration in aging populations. For patients with severely impacted aortic valves that require replacement, catheter-based bioprosthetic valve deployment offers a minimally invasive treatment option that eliminates many of the risks associated with surgical valve replacement. Although recent percutaneous device advancements have incorporated thinner, more flexible biological tissues to streamline safer deployment through catheters, the impact of such tissues in the complex, mechanically demanding, and highly dynamic valvular system remains poorly understood. The present work utilized a validated computational fluid-structure interaction approach to isolate the behavior of thinner, more compliant aortic valve tissues in a physiologically realistic system. This computational study identified and quantified significant leaflet flutter induced by the use of thinner tissues that initiated blood flow disturbances and oscillatory leaflet strains. The aortic flow and valvular dynamics associated with these thinner valvular tissues have not been previously identified and provide essential information that can significantly advance fundamental knowledge about the cardiac system and support future medical device innovation. Considering the risks associated with such observed flutter phenomena, including blood damage and accelerated leaflet deterioration, this study demonstrates the potentially serious impact of introducing thinner, more flexible tissues into the cardiac system.

Computed Tomography of Cardiac Valves: Review

Valvular heart disease is a common clinical problem. Although echocardiography is the standard technique for the noninvasive evaluation of the valves, cardiac CT has evolved to become a useful tool in the evaluation of the cardiac structures as well. Importantly, CT allows for improved quantification of valvular calcification due to its superior spatial resolution. It may improve the detection of small valvular or perivalvular pathology or the characterization of valvular masses and vegetations. This review describes the assessment of normal and diseased heart valves by cardiac CT and discusses its strengths and weaknesses.

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.

Trends in the utilization of computed tomography and cardiac catheterization among children with congenital heart disease

Background/Purpose

Pediatric cardiac computed tomography (CT) is a noninvasive imaging modality used to clearly demonstrate the anatomical detail of congenital heart diseases. We investigated the impact of cardiac CT on the utilization of cardiac catheterization among children with congenital heart disease.

Methods

The study sample consisted of 2648 cardiac CT and 3814 cardiac catheterization from 1999 to 2009 for congenital heart diseases. Diagnoses were categorized into 11 disease groups. The numbers of examination, according to the different modalities, were compared using temporal trend analyses. The estimated effective radiation doses (mSv) of CT and catheterization were calculated and compared.

Results

The number of CT scans and interventional catheterizations had a slight annual increase of 1.2% and 2.7%, respectively, whereas that of diagnostic catheterization decreased by 6.2% per year. Disease groups fell into two categories according to utilization trend differences between CT and diagnostic catheterization. The increased use of CT reduces the need for diagnostic catheterization in patients with atrioventricular connection disorder, coronary arterial disorder, great vessel disorder, septal disorder, tetralogy of Fallot, and ventriculoarterial connection disorder. Clinicians choose either catheterization or CT, or both examinations, depending on clinical conditions, in patients with semilunar valvular disorder, heterotaxy, myocardial disorder, pericardial disorder, and pulmonary vein disorder. The radiation dose of CT was lower than that of diagnostic cardiac catheterization in all age groups.

Conclusion

The use of noninvasive CT in children with selected heart conditions might reduce the use of diagnostic cardiac catheterization. This may release time and facilities within the catheterization laboratory to meet the increasing demand for cardiac interventions.

The role of computed tomography in pre-procedural planning of cardiovascular surgery and intervention

Advances in our knowledge of cardiovascular disorders coupled with technological innovations have enabled the increased use of minimally invasive cardiovascular surgeries and transcatheter interventions, with resultant reduced morbidity and hospital stay. Three-dimensional imaging, particularly computed tomography (CT) is increasingly used for patient selection, providing a roadmap of the anatomy and identifying factors that may complicate these procedures. Advantages of CT are the rapid turnaround time, good spatial and temporal resolutions, wide field of view and three-dimensional multi-planar reconstruction capabilities. This pictorial review describes the role of CT in the pre-operative evaluation of patients undergoing cardiovascular surgeries and intervention. Main Messages • CT scan is valuable in pre-operative evaluation for cardiac surgeries • Cardiovascular structures, including bypass grafts should be located >10 mm from the sternum in patients for reoperative cardiothoracic surgeries • Knowledge of variations in pulmonary venous anatomy are essential for planning radiofrequency ablation.

CT and MR imaging of the aortic valve: radiologic-pathologic correlation

Valvular disease is estimated to account for as many as 20% of cardiac surgical procedures performed in the United States. It may be congenital in origin or secondary to another disease process. One congenital anomaly, bicuspid aortic valve, is associated with increased incidence of stenosis, regurgitation, endocarditis, and aneurysmal dilatation of the aorta. A bicuspid valve has two cusps instead of the normal three; resultant fusion or poor excursion of the valve leaflets may lead to aortic stenosis, the presence of which is signaled by dephasing jets on magnetic resonance (MR) images. Surgery is generally recommended for patients with severe stenosis who are symptomatic or who have significant ventricular dysfunction; transcatheter aortic valve implantation (TAVI) is an emerging therapeutic option for patients who are not eligible for surgical treatment. Computed tomography (CT) is an essential component of preoperative planning for TAVI; it is used to determine the aortic root dimensions, severity of peripheral vascular disease, and status of the coronary arteries. Aortic regurgitation, which is caused by incompetent closure of the aortic valve, likewise leads to the appearance of jets on MR images. The severity of regurgitation is graded on the basis of valvular morphologic parameters; qualitative assessment of dephasing jets at Doppler ultrasonography; or measurements of the regurgitant fraction, volume, and orifice area. Mild regurgitation is managed conservatively, whereas severe or symptomatic regurgitation usually leads to valve replacement surgery, especially in the presence of substantial left ventricular enlargement or dysfunction. Bacterial endocarditis, although less common than aortic stenosis and regurgitation, is associated with substantial morbidity and mortality. Electrocardiographically gated CT reliably demonstrates infectious vegetations and benign excrescences of 1 cm or more on the valve surface, allowing the assessment of any embolic complications.

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.

Cardiac CT angiography in children with congenital heart disease

Cardiac imaging plays an important role in both congenital and acquired heart diseases. Cardiac computed tomography (angiography) cCT(A) is a non-invasive, increasingly popular, complementary modality to echocardiography in evaluation of congenital heart diseases (CHD) in children. Despite radiation exposure, cCT(A) is now commonly used for evaluation of the complex CHD, giving information of both intra-cardiac and extra-cardiac anatomy, coronary arteries, and vascular structures. This review article will focus on the fundamentals and essentials for performing cCT(A) in children, including radiation dose awareness, basic techniques, and strengths and weaknesses of cCT(A) compared with cardiac magnetic resonance imaging (cMRI), and applications. The limitations of this modality will also be discussed, including the CHD for which cMRI may be substituted.

MDCT differentiation between bicuspid and tricuspid aortic valves in patients with aortic valvular disease: correlation with surgical findings

To identify multi-detector computed tomographic (MDCT) features discriminating bicuspid aortic valves (BAVs) from tricuspid aortic valves (TAVs) in patients with aortic valvular disease using surgical findings as reference. Forty-five patients underwent ECG-gated cardiac MDCT scans prior to aortic valve replacement. Morphologic patterns of aortic valves on MDCT were classified into: bicuspid without raphe (A), fused valve with a fish-mouth opening (B), fused valve without a fish-mouth opening (C), and tricuspid without fusion (D). To differentiate congenital raphe of BAV from commissural fusion of TAV, MDCT features of patterns B and C were evaluated. Diameters of the aortic root and ascending aorta between patients with BAVs and TAVs were also compared. Patterns A (n = 6) and B (n = 6) were all bicuspid, in pattern C: 8 of 26 (30.8%) were bicuspid, and pattern D (n = 7) were all tricuspid. In patterns B and C, uneven cusp size, round-shaped opening and midline calcification at leaflet fusion were strongly associated with BAVs (all, P < 0.05). The mean length of leaflet fusion in BAVs was significantly larger than in TAVs (13.5 vs. 8.7 mm, P < 0.0001), with a cutoff value of 10.3 mm providing a sensitivity of 85.7%, a specificity of 83.3%, and an area under the ROC curve of 0.90. In all patients, the mean diameter of the ascending aorta was larger in patients with BAVs than with TAVs (43.3 vs. 39.7 mm, P < 0.05). MDCT features of uneven cusp size, round-shaped opening, midline calcification, longer leaflet fusion and larger diameter of the ascending aorta can be helpful in distinguishing BAVs from TAVs.

Computed tomography evaluation of cardiac valves: a review

Electrocardiograph (ECG)-gated cardiac computed tomography (CT) angiography has great potential for the evaluation of the cardiac valves, with excellent image quality. The evidence-based, established clinical role of ECG-gated CT coronary angiography provides additional valuable information about valve morphology and function. A wide range of valve pathology, including congenital and acquired conditions, infectious endocarditis, and complications of valve replacement, can be assessed by cardiac CT imaging. Despite recent advances in CT technology, echocardiography remains the gold standard for noninvasive cardiac valve evaluation. Nevertheless, important clinical information about the valves can be obtained with coronary CT angiography examinations. Thus cardiac valve morphology and function should be routinely assessed and reported on coronary CT angiography examinations.

Planimetric measurement of the regurgitant orifice area using multidetector CT for aortic regurgitation: a comparison with the use of echocardiography

Objective

This study compared the area of the regurgitant orifice, as measured by the use of multidetector-row CT (MDCT), with the severity of aortic regurgitation (AR) as determined by the use of echocardiography for AR.

Materials and Methods

In this study, 45 AR patients underwent electrocardiography-gated 40-slice or 64-slice MDCT and transthoracic or transesophageal echocardiography. We reconstructed CT data sets during mid-systolic to enddiastolic phases in 10% steps (20% and 35-95% of the R-R interval), planimetrically measuring the abnormally opened aortic valve area during diastole on CT reformatted images and comparing the area of the aortic regurgitant orifice (ARO) so measured with the severity of AR, as determined by echocardiography.

Results

In the 14 patients found to have mild AR, the ARO area was 0.18±0.13 cm² (range, 0.04-0.54 cm²). In the 15 moderate AR patients, the ARO area was 0.36 ± 0.23 cm² (range, 0.09-0.81 cm²). In the 16 severe AR patients, the ARO area was 1.00 ± 0.51 cm² (range, 0.23-1.84 cm²). Receiver-operator characteristic curve analysis determined a sensitivity of 85% and a specificity of 82%, for a cutoff of 0.47 cm², to distinguish severe AR from less than severe AR with the use of CT (area under the curve = 0.91; 95% confidence interval, 0.84-1.00; p < 0.001).

Conclusion

Planimetric measurement of the ARO area using MDCT is useful for the quantitative evaluation of the severity of aortic regurgitation.

CT angiography of the cardiac valves: normal, diseased, and postoperative appearances

Although echocardiography remains the principal imaging technique for assessment of the cardiac valves, contrast material-enhanced electrocardiographically gated computed tomographic (CT) angiography is proving to be an increasingly valuable complementary modality in this setting. CT angiography allows excellent visualization of the morphologic features and function of the normal valves, as well as of a wide range of valve diseases, including congenital and acquired diseases, infectious endocarditis, and complications of valve replacement. The number, thickness, and opening and closing of the valve leaflets, as well as the presence of valve calcification, can be directly observed. CT angiography also permits simultaneous assessment of the valves and coronary arteries, which may prove valuable in presurgical planning. Unlike echocardiography and magnetic resonance imaging, however, CT angiography requires ionizing radiation and does not provide a direct measure of the valvular pressure gradient. Nevertheless, with further development of related imaging techniques, CT angiography can be expected to play an increasingly important role in the evaluation of the cardiac valves. Supplemental material available at http://radiographics.rsna.org/cgi/content/full/29/5/1393/DC1.

Support Vectors Machine-based identification of heart valve diseases using heart sounds

Taking into account that heart auscultation remains the dominant method for heart examination in the small health centers of the rural areas and generally in primary healthcare set-ups, the enhancement of this technique would aid significantly in the diagnosis of heart diseases. In this context, the present paper initially surveys the research that has been conducted concerning the exploitation of heart sound signals for automated and semi-automated detection of pathological heart conditions. Then it proposes an automated diagnosis system for the identification of heart valve diseases based on the Support Vector Machines (SVM) classification of heart sounds. This system performs a highly difficult diagnostic task (even for experienced physicians), much more difficult than the basic diagnosis of the existence or not of a heart valve disease (i.e. the classification of a heart sound as 'healthy' or 'having a heart valve disease'): it identifies the particular heart valve disease. The system was applied in a representative global dataset of 198 heart sound signals, which come both from healthy medical cases and from cases suffering from the four most usual heart valve diseases: aortic stenosis (AS), aortic regurgitation (AR), mitral stenosis (MS) and mitral regurgitation (MR). Initially the heart sounds were successfully categorized using a SVM classifier as normal or disease-related and then the corresponding murmurs in the unhealthy cases were classified as systolic or diastolic. For the heart sounds diagnosed as having systolic murmur we used a SVM classifier for performing a more detailed classification of them as having aortic stenosis or mitral regurgitation. Similarly for the heart sounds diagnosed as having diastolic murmur we used a SVM classifier for classifying them as having aortic regurgitation or mitral stenosis. Alternative classifiers have been applied to the same data for comparison (i.e. back-propagation neural networks, k-nearest-neighbour and naïve Bayes classifiers), however their performance for the same diagnostic problems was lower than the SVM classifiers proposed in this work.

Diagnostic accuracy of MDCT coronary angiography in patients referred for heart valve surgery

PURPOSE

The aim of our study was to evaluate the role of multidetector-row computed tomography (MDCT) in patients referred for heart valve surgery. We studied the diagnostic performance of CT coronary angiography (CTCA) compared with conventional coronary angiography (CCA) before valve surgery.

MATERIALS AND METHODS

During a 13-month period, 55 consecutive patients under evaluation for aortic (40/55) or mitral valve (15/55) disease before potential valve replacement underwent CTCA using a 64-detector-row scanner within 2 months of CCA for comparative purposes. All 17 major coronary artery segments were evaluated by one observer and compared with the reference standard. Patient-based, vessel-based and segment-based analyses of the data were performed.

RESULTS

Prevalence of significant coronary artery disease, defined as having at least one stenosis >/=50% per patient, was 36%. On a patient-based analysis, sensitivity, specificity and positive and negative predictive values were 100%, 91%, 83% and 100%, respectively.

CONCLUSIONS

The diagnostic accuracy of 64-row CTCA for ruling out the presence of significant coronary stenoses in patients undergoing valve surgery is excellent and allows CTCA to be used as a gatekeeper for invasive CCA in these patients. MDCT is a necessary preoperative examination that provides useful information for identifying potential operative complications of surgical procedures.

Computed tomography assessment of valvular morphology, function, and disease

Recent advancement in computed tomography angiography (CTA) has enabled the noninvasive delineation of cardiac valves using this method. Although echocardiography is the current standard, CTA is a valuable complementary imaging method to evaluate valvular morphology and function. In addition, CTA may contribute to the assessment of both congenital and acquired valvular heart disease, infectious endocarditis, and postsurgical complications of valve replacement.

Accuracy and reproducibility of assessing right ventricular function with 64-section multi-detector row CT: comparison with magnetic resonance imaging

BACKGROUND

Right ventricular (RV) function is very important for those patients with respiratory and cardiovascular disorders that can result in RV impairments. Because of complex geometry of the chamber, it is difficult to accurately measure the RV volumetric parameters with conventional imaging modalities. The purpose of this study was to evaluate whether the 64-MDCT can assess RV function with high accuracy and reproducibility when compared to the results with those of MRI.

METHODS

Forty-seven consecutive subjects underwent retrospectively ECG-gated 64-MDCT and MRI for assessing the ventricular function. Right ventricular end diastolic and end-systolic volume, stroke volume, and ejection fraction were measured with dedicated cardiac analysis software on 64-MDCT and compared with values measured on MRI which served as the reference standard. Agreement between two modalities was assessed with Bland and Altman analysis and linear regression analysis. Repeated measurements were performed to determine intraobserver and interobserver variability.

RESULTS

No significant differences were revealed in calculated RV volumes and EF between the two modalities. Agreement and correlation were similar for RV-EDV (0.4 ± 8.2 ml; r=0.95), RV-ESV (-0.6 ± 4.8; r=0.95), RV-SV (1.1 ± 6.7 ml; r=0.93), and RV-EF (0.9 ± 4.4; r=0.88). The difference of SV of right and left ventricle with 64-MDCT was not statistically significant (p=0.40) and good correlation was obtained (r=0.96). The variability in 64-MDCT measurements was lower than those in MRI.

CONCLUSIONS

ECG-gated 64-MDCT can assess the RV function with high accuracy and reproducibility without geometric assumptions about right ventricle.

A technical solution to avoid partial scan artifacts in cardiac MDCT

Quantitative evaluation of cardiac image data obtained using multidetector row computed tomography (CT) is compromised by partial scan reconstructions, which improve the temporal resolution but significantly increase image-to-image CT number variations for a fixed region of interest compared to full reconstruction images. The feasibility of a new approach to solve this problem is assessed. An anthropomorphic cardiac phantom and an anesthetized pig were scanned on a dual-source CT scanner using both full and partial scan acquisition modes under different conditions. Additional scans were conducted with the electrocardiogram (ECG) signal being in synchrony with the gantry rotation. In the animal study, a simple x-ray detector was used to generate a signal once per gantry rotation. This signal was then used to pace the pig's heart. Phantom studies demonstrated that partial scan artifacts are strongly dependent on the rotational symmetry of angular projections, which is determined by the object shape and composition and its position with respect to the isocenter. The degree of partial scan artifacts also depends on the location of the region of interest with respect to highly attenuating materials (bones, iodine, etc.) within the object. Single-source partial scan images (165 ms temporal resolution) were significantly less affected by partial scan artifacts compared to dual-source partial scan images (82 ms temporal resolution). When the ECG signal was in synchrony with the gantry rotation, the same cardiac phase always corresponded to the same positions of the x-ray tube(s) and, hence, the same scattering and beam hardening geometry. As a result, the range of image-to-image CT number variations for partial scan reconstruction images acquired in synchronized mode was decreased to that achieved using full reconstruction image data. The success of the new approach, which synchronizes the ECG signal with the position of the x-ray tube(s), was demonstrated both in the phantom and animal experiments.

Coronary artery CTA: imaging of atherosclerosis in the coronary arteries and reporting of coronary artery CTA findings

Invasive coronary angiography remains the standard for assessment of coronary anatomy and pathology, and for determining the extent and severity of coronary lumen obstruction in coronary artery disease. Recent advances in multidetector row computed tomography (MDCT) technology allowing noninvasive imaging of the coronary arteries has led to widespread enthusiasm for the use of noninvasive coronary angiography. A comprehensive and clinically useful MDCT study should incorporate an understanding of the patient history and reason for performance of the test, an overall assessment of study quality, and a complete description of pertinent findings. Because the majority of cardiac computed tomography (CT) studies are now being performed for the evaluation of the coronary arteries and obstructive coronary disease, a clear understanding of what the clinician wants to know from a CTA is critical to its comprehensive interpretation. In this manuscript, we provide an overview of the necessary components of CT coronary angiogram interpretation, from the point of view of the practicing invasive cardiologist.

Sixty-Four Slice CT Evaluation of Aortic Stenosis Using Planimetry of the Aortic Valve Area

OBJECTIVE

The purpose of our study was to evaluate planimetry of the aortic valve area with 64-slice CT in comparison with transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in patients with aortic stenosis.

MATERIALS AND METHODS

Thirty-six patients with aortic valve disease referred for coronary 64-slice CT angiography were examined. Planimetry of the aortic valve area with 64-slice CT was compared with TTE using the Doppler continuity equation for calculation of the aortic valve area and with planimetric measurement of the aortic valve area using TEE.

RESULTS

Planimetry of the aortic valve area with CT (1.11 +/- 0.42 cm2) showed a good correlation with TTE (1.05 +/- 0.42 cm2) (r = 0.88, p < 0.001) in 32 patients and a good correlation with TEE (1.41 +/- 1.61 cm2) (r = 0.99, p < 0.0001) in 10 patients. The mean and maximum transvalvular pressure gradients were correlated with the aortic valve area as measured with CT (r = -0.68, p = 0.0001; and r = -0.67, p = 0.0001, respectively). Beta-blockers were not given (mean heart rate, 62.5 +/- 10.7 beats per minute).

CONCLUSION

MDCT allows accurate planimetry of the aortic valve area in patients with aortic stenosis. In patients referred for 64-slice CT coronary angiography, concomitant aortic stenosis can be identified and evaluated.

Cross-Sectional Imaging Studies: What Can We Learn and What Do We Need to Know?

Rapid, noninvasive imaging approaches can provide novel diagnostic information and, when effectively interpreted and implemented in a therapeutic strategy, can simplify procedures. Endovascular therapy of thoracic and abdominal aortic disease represents a dramatic shift in treatment of thoracoabdominal aortic disease, but one that requires a change in the knowledge base regarding both the morphology and pathophysiology of aortic disease and the interaction with interventional devices. As a result, the demands on cross-sectional imaging have increased commensurately with the complexity of the therapeutic options, but advances in cross-sectional imaging have kept pace. Current computed tomography (CT) and magnetic resonance imaging (MRI) technologies provide detailed morphologic assessment, and are advancing rapidly into more sophisticated physiologic evaluation of aortic disease. These advances may more effectively triage patients to appropriate therapy, or exclude patients from unnecessary invasive procedures. The information gleaned from CT and MRI studies is critical for the vascular surgeon who wants to identify appropriate vascular territories for intervention, plan a detailed approach, and develop sophisticated surveillance strategies.