Dynamic Cine Imaging of the Mitral Valve with 16-MDCT: A Feasibility Study

Cardiovascular imaging modalities in the diagnosis and management of rheumatic heart disease

Rheumatic heart disease (RHD) is prevalent in sub-Saharan Africa, where the capacity for diagnosis and evaluation of disease severity and complications is not always optimal. While the medical history and physical examination are important in the assessment of patients suspected to have RHD, cardiovascular imaging techniques are useful for confirmation of the diagnosis. Echocardiography is the workhorse modality for initial evaluation and diagnosis of RHD. Cardiovascular magnetic resonance is complementary and may provide additive information, including tissue characteristics, where echocardiography is inadequate or non-diagnostic. There is emerging evidence on the role of computed tomography, particularly following valve replacement surgery, in the monitoring and management of RHD. This article summarises the techniques used in imaging RHD patients, considers the evidence base for their utility, discusses their limitations and recognises the clinical contexts in which indications and imaging with various modalities are expanding.

Acute aortic syndromes and aortic emergencies

Acute aortic syndrome (AAS) and emergencies are relatively uncommon but are considered as life threatening, potentially fatal conditions. Different forms of aortic emergencies/AAS are often clinically indiscernible. Prompt and accurate diagnosis of these entities significantly influences prognosis and guides therapy. We aim to elucidate the pertinent role that radiology plays in the management of acute aortic diseases, with contrast-enhanced computed tomography angiography (CTA) being the most rapid and robust imaging technique.

Radiographic Evaluation of Valvular Heart Disease With Computed Tomography and Magnetic Resonance Correlation

Valvular heart disease is a group of complex entities with varying etiologies and clinical presentations. There are a number of imaging tools available to supplement clinical evaluation of suspected valvular heart disease, with echocardiography being the most common and clinically established, and more recent emergence of computed tomography and magnetic resonance imaging as additional supportive techniques. Yet even with these newer and more sophisticated modalities, chest radiography remains one of the earliest and most common diagnostic examinations performed during the triage of patients with suspected cardiac dysfunction. Recognizing the anatomic and pathologic features of cardiac radiography including the heart's adaptation to varying hemodynamic changes can provide clues to the radiologist regarding the underlying etiology. In this article, we will elucidate several principles relating to chamber modifications in response to pressure and volume overload as well as radiographic appearances associated with pulmonary fluid status and cardiac dysfunction. We will also present a pattern approach to optimize analysis of the chest radiograph for valvular heart disease, which will help guide the radiologist down a differential diagnostic pathway and create a more meaningful clinical report.

Quantitative Assessment of Mitral Apparatus Geometry Using Dual-Source Computed Tomography in Mitral Regurgitation

To quantitatively assess the geometric changes in mitral valve apparatus in mitral regurgitation (MR) by dualsource computed tomography (DSCT) and to analyze its impact on MR.The study subjects consisted of 20 controls, 20 patients with mild MR, and 30 patients with moderate to severe MR, all of whom underwent DSCT. The geometric parameters of the mitral valve were measured by CT and compared among the 3 groups. The correlations between DSCT measurements and MR severity were also analyzed.As regurgitation worsened, our results showed progressive enlargements of the mitral annular area, anteroposterior diameter, and mitral valve tenting area at the central level. Moreover, a higher mitral valve sphericity index and longer distance between the heads of the papillary muscles reflected a more outward displacement of the papillary muscles. The mitral annular area and tenting area at the central level had strong correlations with regurgitation severity.DSCT is available to quantitatively assess mitral valve morphology and provide additional information regarding its geometry. The mitral annular area and tenting area at the central level were the strongest determinants of MR severity.

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.

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.

Quantification of mitral regurgitation on cardiac computed tomography: comparison with qualitative and quantitative echocardiographic parameters

PURPOSE

To assess whether cardiac computed tomographic angiography (CCTA) can quantify the severity of chronic mitral regurgitation (MR) compared to qualitative and quantitative echocardiographic parameters.

MATERIALS AND METHODS

Cardiac computed tomographic angiography was performed in 23 patients (mean ± SD age, 63 ± 16 years; range, 24-86 years) with MR and 20 patients without MR (controls) as determined by transthoracic echocardiography. Multiphasic reconstructions (20 data sets reconstructed at 5% increments of the electrocardiographic gated R-R interval) were used to analyze the mitral valve. Using CCTA planimetry, 2 readers measured the regurgitant mitral orifice area (CCTA ROA) during systole. A qualitative echocardiographic assessment of severity of MR was made by visual assessment of the length of the regurgitant jet. Quantitative echocardiographic measurements included the vena contracta, proximal isovelocity surface area, regurgitant volume, and estimated regurgitant orifice (ERO). Comparisons were performed using the independent t test, and correlations were assessed using the Spearman rank test.

RESULTS

All controls and the patients with MR were correctly identified by CCTA. For patients with mild, moderate, or severe MR, mean ± SD EROs were 0.16 ± 0.03, 0.31 ± 0.08, and 0.52 ± 0.03 cm² (P < 0.0001) compared with mean ± SD CCTA ROAs 0.09 ± 0.05, 0.30 ± 0.04, and 0.97 ± 0.26 cm² (P < 0.0001), respectively. When echocardiographic measurements were graded qualitatively as mild, moderate, or severe, strong correlations were seen with CCTA ROA (R = 0.89; P < 0.001). When echocardiographic measurements were graded quantitatively, the vena contracta and the ERO showed modest correlations with CCTA ROA (0.48 and 0.50; P < 0.05 for both). Neither the proximal isovelocity surface area nor the regurgitant volume demonstrated significant correlations with CCTA ROA.

CONCLUSIONS

Single-source 64-slice CCTA provides a strong agreement with qualitative echocardiographic parameters but only a moderate correlation with quantitative echocardiographic parameters of chronic MR. Cardiac computed tomographic angiography slightly overestimates mild MR while slightly underestimating severe MR.

Mitral valve morphology assessment: three-dimensional transesophageal echocardiography versus computed tomography

BACKGROUND

Advances in the minimally invasive mitral valve repair techniques increase the demands on accurate and reliable morphologic assessment of the mitral valve using three-dimensional imaging modalities. The present study compared mitral valve geometry measurements obtained by three-dimensional transesophageal echocardiography (TEE) to those obtained with multidetector row computed tomography (MDCT) used as a standard reference.

METHODS

Clinical preoperative MDCT and intraoperative three-dimensional TEE were performed in 43 patients (mean age 81.0 ± 7.7 years) considered for transcatheter valve implantation procedure. Various measurements of mitral valve geometry were obtained from three-dimensional TEE datasets using mitral valve quantification software, and compared with those obtained from MDCT images using multiplanar reformation planes.

RESULTS

Moderate and severe mitral regurgitation was present in 48.9% of patients. There was good agreement in mitral valve geometry measurements between three-dimensional TEE and MDCT without significant overestimation or underestimation and tight 95% limits of agreement. For linear dimensions, angles and areas, the 95% limits of agreement were less than 1 cm, less than 15 degrees, and less than 2 cm(2), respectively. In addition, the intraclass correlation coefficients were more than 0.8 for all parameters. Finally, the measurements were highly reproducible, with low intraobserver and interobserver variability (nonsignificant overestimation or underestimation and narrow 95% limits of agreement).

CONCLUSIONS

The present study demonstrates the accuracy and clinical feasibility of the assessment of the mitral valve geometry with three-dimensional TEE that is comparable to the MDCT measurements. Three-dimensional TEE and MDCT provide accurate and complementary information in the evaluation of patients with mitral valve disease. Its potential incremental clinical value in the field of transcatheter mitral repair procedures needs further assessment in the future studies.

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.

Chronic mitral regurgitation detected on cardiac MDCT: differentiation between functional and valvular aetiologies

OBJECTIVE

To determine whether cardiac computed tomography (MDCT) can differentiate between functional and valvular aetiologies of chronic mitral regurgitation (MR) compared with echocardiography (TTE).

METHODS

Twenty-seven patients with functional or valvular MR diagnosed by TTE and 19 controls prospectively underwent cardiac MDCT. The morphological appearance of the mitral valve (MV) leaflets, MV geometry, MV leaflet angle, left ventricular (LV) sphericity and global/regional wall motion were analysed. The coronary arteries were evaluated for obstructive atherosclerosis.

RESULTS

All control and MR cases were correctly identified by MDCT. Significant differences were detected between valvular and control groups for anterior leaflet length (30 +/- 7 mm vs. 22 +/- 4 mm, P < 0.02) and thickness (3.0 +/- 1 mm vs. 2.2 +/- 1 mm, P < 0.01). High-grade coronary stenosis was detected in all patients with functional MR compared with no controls (P < 0.001). Significant differences in those with/without MV prolapse were detected in MV tent area (-1.0 +/- 0.6 mm vs. 1.3 +/- 0.9 mm, P < 0.0001) and MV tent height (-0.7 +/- 0.3 mm vs. 0.8 +/- 0.8 mm, P < 0.0001). Posterior leaflet angle was significantly greater for functional MR (37.9 +/- 19.1 degrees vs. 22.9 +/- 14 degrees , P < 0.018) and less for valvular MR (0.6 +/- 35.5 degrees vs. 22.9 +/- 14 degrees, P < 0.017). Sensitivity, specificity, and positive and negative predictive values of MDCT were 100%, 95%, 96% and 100%.

CONCLUSION

Cardiac MDCT allows the differentiation between functional and valvular causes of MR.

On the multiscale modeling of heart valve biomechanics in health and disease

Theoretical models of the human heart valves are useful tools for understanding and characterizing the dynamics of healthy and diseased valves. Enabled by advances in numerical modeling and in a range of disciplines within experimental biomechanics, recent models of the heart valves have become increasingly comprehensive and accurate. In this paper, we first review the fundamentals of native heart valve physiology, composition and mechanics in health and disease. We will then furnish an overview of the development of theoretical and experimental methods in modeling heart valve biomechanics over the past three decades. Next, we will emphasize the necessity of using multiscale modeling approaches in order to provide a comprehensive description of heart valve biomechanics able to capture general heart valve behavior. Finally, we will offer an outlook for the future of valve multiscale modeling, the potential directions for further developments and the challenges involved.

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.

Evaluation of cardiac valves using multidetector CT

Cardiac CT is an accurate and reasonable alternative modality for valvular imaging. It is used primarily for the evaluation of coronary artery disease; however, important information regarding valvular anatomy and function can be derived from CT. Calcification is a common CT finding in various valvular abnormalities and carries important diagnostic and prognostic value. In addition, valvular morphology, stenosis, and regurgitation also are detected on contrast enhanced scans, with good correlation with trans-thoracic echocardiography and other techniques.

Assessment of mitral valve anatomy and geometry with multislice computed tomography

OBJECTIVES

The purpose of the present study was to assess the anatomy and geometry of the mitral valve by using 64-slice multislice computed tomography (MSCT).

BACKGROUND

Because it yields detailed anatomic information, MSCT may provide more insight into the underlying mechanisms of functional mitral regurgitation (FMR).

METHODS

In 151 patients, including 67 patients with heart failure (HF) and 29 patients with moderate to severe FMR, 64-slice MSCT coronary angiography was performed. The anatomy of the subvalvular apparatus of the mitral valve was assessed; mitral valve geometry, comprising the mitral valve tenting height and leaflet tethering, was evaluated at the anterolateral, central, and posteromedial levels.

RESULTS

In the majority of patients, the anatomy of the subvalvular apparatus was highly variable because of multiple anatomic variations in the posterior papillary muscle (PM): the anterior PM had a single insertion, whereas the posterior PM showed multiple heads and insertions (n = 114; 83%). The assessment of mitral valve geometry demonstrated that patients with HF with moderate to severe FMR had significantly increased posterior leaflet angles and mitral valve tenting heights at the central (44.4 degrees +/- 11.9 degrees vs. 37.1 degrees +/- 9.0 degrees, p = 0.008; 6.6 +/- 1.4 mm/m(2) vs. 5.3 +/- 1.3 mm/m(2), p < 0.0001, respectively) and posteromedial levels (35.9 degrees +/- 10.6 degrees vs. 26.8 degrees +/- 10.1 degrees, p = 0.04; 5.4 +/- 1.6 mm/m(2) vs. 4.1 +/- 1.2 mm/m(2), p < 0.0001, respectively), as compared with patients with HF without FMR. In addition, a more outward displacement of the PMs, reflected by a higher mitral valve sphericity index, was observed in patients with HF with FMR (1.4 +/- 0.3 vs. 1.2 +/- 0.3, p = 0.004). Mitral valve tenting height at the central level and mitral valve sphericity index were the strongest determinants of FMR severity.

CONCLUSIONS

MSCT provides anatomic and geometric information on the mitral valve apparatus. In patients with HF with moderate to severe FMR, a more pronounced tethering of the mitral leaflets at the central and posteromedial levels was demonstrated using MSCT.

Noncoronary applications of cardiac multidetector row computed tomography

Multidetector row computed tomography (MDCT) has a high diagnostic accuracy to evaluate coronary artery stenoses. Additionally, the 4-dimensional aspect of cardiac MDCT allows a comprehensive evaluation of cardiac structure and function. Left ventricular volumes and systolic function can be accurately assessed with MDCT, and imaging of myocardial infarction is a promising application of cardiac MDCT. In addition, MDCT may provide anatomical visualization of heart valves. Also, evaluation of anatomy of the pulmonary veins and cardiac venous system render MDCT a valuable tool for the cardiologist performing electrophysiological procedures. In this article, the role of MDCT in the noninvasive evaluation of cardiac structure and function is discussed. An overview of the wide range of noncoronary applications of cardiac MDCT is provided, focusing on the assessment of left ventricular function, valvular heart disease, and cardiac venous anatomy.

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.

Temporal trends in utilization of cardiac computed tomography

BACKGROUND

Appropriate, inappropriate, and uncertain indications for the use of cardiac computed tomography (CT) were defined by a multisociety document in 2006. We sought to compare the appropriateness of cardiac CT examinations before and after these criteria were published.

METHODS

We retrospectively evaluated all patients presenting for cardiac CT examinations in the first 3 months of 2006 and 2007 at a large academic medical center and an unaffiliated large cardiology group private practice. The indication for the examinations were determined from the patients' medical records. The examinations were then classified as "appropriate," "inappropriate," or "uncertain," based on appropriateness criteria. Examinations that did not fall into any of these categories were classified as "uncategorized."

RESULTS

We evaluated a total of 1409 patients (64.9% men; mean age, 57.6 +/- 13.4 years). The proportion of appropriate CT examinations increased from 69.5% during the study period in 2006 to 78.5% in 2007 (P = 0.001). A corresponding decrease was observed in inappropriate CT examinations from 11.5% in 2006 to 4.6% in 2007 (P = 0.001). No change was observed in the number of CT examinations that were deemed uncertain (12.7% in 2006, and 13.3% in 2007; P = NS).

CONCLUSION

The number of CT examinations considered appropriate increased during the study period, whereas the number of inappropriate examinations decreased. Cardiologists were more likely than noncardiologists to order examinations that were appropriate during the study period.

Evaluation of temporal windows for coronary artery bypass graft imaging with 64-slice CT

Temporal windows providing the best image quality of different segments and types of coronary artery bypass grafts (CABGs) with 64-slice computed tomography (CT) were evaluated in an experimental set-up. Sixty-four-slice CT with a rotation time of 330 ms was performed in 25 patients (four female; mean age 59.9 years). A total of 84 CABGs (62 individual and 22 sequential grafts) were evaluated, including 28 internal mammary artery (33.3%), one radial artery with sequential grafting (2.4%), and 54 saphenous vein grafts (64.3%). Ten data sets were reconstructed in 10% increments of the RR-interval. Each graft was separated into segments (proximal and distal anastomosis, and body), and CABG types were grouped according to target arteries. Two readers independently assessed image quality of each CABG segment in each temporal window. Diagnostic image quality was found with good inter-observer agreement (kappa=0.62) in 98.5% (202/205) of all graft segments. Image quality was significantly better for saphenous vein grafts versus arterial grafts (P<0.001) and for distal anastomosis to the right coronary compared with other target coronary arteries (P<0.05). Overall, best image quality was found at 60%. Image quality of proximal segments did not significantly vary with the temporal window, whereas for all other segments image quality was significantly better at 60% compared with other temporal windows (P<0.05). Sixty-four-slice CT provides best image quality of various segments and types of CABG at 60% of the RR-interval.

Image quality of the aortic and mitral valve with CT: relative versus absolute delay reconstruction

RATIONALE AND OBJECTIVE

The purpose of this study was to compare image quality and artifacts of 16-detector row CT imaging of the aortic and mitral valve when performing ECG-gated synchronization using relative and absolute reconstructions.

MATERIALS AND METHODS

Cardiac CT was performed in 22 consecutive patients; 20 data sets per RR interval were reconstructed with relative and absolute reconstructions. Mean and variability of heart rate during data acquisition were noted. Two readers assessed contrast media-related artifacts, calcification-related artifacts, ECG gating-related artifacts, and image quality in parallel and perpendicular planes.

RESULTS

Contrast media-related and calcification-related artifacts similarly occurred with both reconstruction techniques. ECG gating-related artifacts occurred in both valves more often with relative reconstructions than with absolute reconstructions (p = .001). Image quality was significantly better for absolute reconstructions for the open aortic cusp surface (p = .014) and edge (p = .008) in both planes, and of the closed mitral valve leaflets (p = .003) and apposition zone (p = .003) in perpendicular planes. Occurrence of ECG gating-related artifacts in both valves significantly correlated (p = .01) with heart rate variability for relative reconstructions, whereas no correlation was found using the absolute technique.

CONCLUSION

Absolute reconstructions allow CT imaging of the aortic and mitral valve with fewer artifacts and are less sensitive to heart rate variability as compared to relative reconstructions.

Visualization Techniques in Computed Tomographic Coronary Angiography

Cardiac computed tomography (CT) scans can produce enormous datasets (>3,000 images), making traditional axial image interpretation un-workable. Previously existing and new techniques including multiplanar reformats, volume rendering, maximum intensity projections, curved multiplanar reformats, and "4D" (time-resolved) methods have all been used to increase diagnostic accuracy and reduce interpretation times. The methods and applications of these techniques to cardiac anatomy will be reviewed and discussed with an eye toward practical film interpretation.