Multimodality imaging assessment of mitral annular disjunction in mitral valve prolapse.

OBJECTIVE: Mitral annular disjunction (MAD) is an abnormality linked to mitral valve prolapse (MVP), possibly associated with malignant ventricular arrhythmias. We assessed the agreement among different imaging techniques for MAD identification and measurement. METHODS: 131 patients with MVP and significant mitral regurgitation undergoing transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) were retrospectively enrolled. Transoesophageal echocardiography (TOE) was available in 106 patients. MAD was evaluated in standard long-axis views (four-chamber, two-chamber, three-chamber) by each technique. RESULTS: Considering any-length MAD, MAD prevalence was 17.3%, 25.5%, 42.0% by TTE, TOE and CMR, respectively (p<0.05). The agreement on MAD identification was moderate between TTE and CMR (κ=0.54, 95% CI 0.49 to 0.59) and good between TOE and CMR (κ=0.79, 95% CI 0.74 to 0.84). Assuming CMR as reference and according to different cut-off values for MAD (≥2 mm, ≥4 mm, ≥6 mm), specificity (95% CI) of TTE and TOE was 99.6 (99.0 to 100.0)% and 98.7 (97.4 to 100.0)%; 99.3 (98.4 to 100.0)% and 97.6 (95.8 to 99.4)%; 97.8 (96.2 to 99.3)% and 93.2 (90.3 to 96.1)%, respectively; sensitivity (95% CI) was 43.1 (37.8 to 48.4)% and 74.5 (69.4 to 79.5)%; 54.0 (48.7 to 59.3)% and 88.9 (85.2 to 92.5)%; 88.0 (84.5 to 91.5)% and 100.0 (100.0 to 100.0)%, respectively. MAD length was 8.0 (7.0-10.0), 7.0 (5.0-8.0], 5.0 (4.0-7.0) mm, respectively by TTE, TOE and CMR. Agreement on MAD measurement was moderate between TTE and CMR (ρ=0.73) and strong between TOE and CMR (ρ=0.86). CONCLUSIONS: An integrated imaging approach could be necessary for a comprehensive assessment of patients with MVP and symptoms suggestive for arrhythmias. If echocardiography is fundamental for the anatomic and haemodynamic characterisation of the MV disease, CMR may better identify small length MAD as well as myocardial fibrosis.

Assessment of myocardial fibrosis by late gadolinium enhancement imaging and biomarkers of collagen metabolism in chronic rheumatic mitral regurgitation.

BACKGROUND: In chronic rheumatic mitral regurgitation (CRMR), involvement of the myocardium in the rheumatic process has been controversial. Therefore, we sought to study the presence of fibrosis using late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) and biomarkers of collagen turnover in CRMR. METHODS: Twenty-two patients with CRMR underwent CMR and echocardiography. Serum concentrations of matrix metalloproteinase- 1 (MMP-1), tissue inhibitor of MMP-1 (TIMP- 1), MMP-1-to-TIMP-1 ratio, procollagen III N-terminal pro-peptide (PIIINP) and procollagen type IC peptide (PIP) were measured. RESULTS: Four patients had fibrosis on LGE-CMR. PICP and PIIINP concentrations were similar to those of the controls, however MMP-1 concentration was increased compared to that of the controls (log MMP-1 3.5 ± 0.7 vs 2.7 ± 0.9, p = 0.02). There was increased MMP-1 activity as the MMP-1-to- TIMP-1 ratio was higher in CRMR patients compared to the controls ( -1.2 ± 0.6 vs -2.1 ± 0.89, p = 0.002). CONCLUSIONS: Myocardial fibrosis was rare in CRMR patients. CRMR is likely a disease characterised by the predominance of collagen degradation rather than increased synthesis and myocardial fibrosis.

Diagnostic accuracy of electrocardiographic P wave related parameters in the assessment of left atrial size in dogs with degenerative mitral valve disease.

The purpose of this research was to compare the accuracy of newly described P wave-related parameters (P wave area, Macruz index and mean electrical axis) with classical P wave-related parameters (voltage and duration of P wave) for the assessment of left atrial (LA) size in dogs with degenerative mitral valve disease. One hundred forty-six dogs (37 healthy control dogs and 109 dogs with degenerative mitral valve disease) were prospectively studied. Two-dimensional echocardiography examinations and a 6-lead ECG were performed prospectively in all dogs. Echocardiography parameters, including determination of the ratios LA diameter/aortic root diameter and LA area/aortic root area, were compared to P wave-related parameters: P wave area, Macruz index, mean electrical axis voltage and duration of P wave. The results showed that P wave-related parameters (classical and newly described) had low sensitivity (range=52.3 to 77%; median=60%) and low to moderate specificity (range=47.2 to 82.5%; median 56.3%) for the prediction of left atrial enlargement. The areas under the curve of P wave-related parameters were moderate to low due to poor sensitivity. In conclusion, newly P wave-related parameters do not increase the diagnostic capacity of ECG as a predictor of left atrial enlargement in dogs with degenerative mitral valve disease.

Assessment of mitral apparatus in patients with acute inferoposterior myocardial infarction and ischaemic mitral regurgitation with two-dimensional echocardiography from anatomically correct imaging planes.

BACKGROUND: Ischaemic mitral regurgitation (IMR) is associated with adverse prognosis after myocardial infarction (MI) as a result of left ventricular remodelling and geometric deformation of the mitral apparatus (MA). AIM: The aim of this study was to assess MA from anatomically correct imaging planes in acute inferoposterior MI and IMR. METHODS: Ninety-three patients with no structural cardiac valve abnormalities and the first acute inferoposterior MI were prospectively enrolled into the study. Two-dimensional transthoracic echocardiography for MA assessment was performed within 48 h of presentation after reperfusion therapy. Based on the degree of mitral regurgitation (MR), patients were divided into either a no significant MR (NMR) group (n = 52 with no or mild, grade 0-I MR) or an IMR group (n = 41 with grade ≥ 2 MR). The control group consisted of 45 healthy individuals. RESULTS: Ischaemic MR was related with dilatation of the left ventricle chambers, decrease in ejection fraction, increase in mitral annulus diameter and area, and changes in subvalvular apparatus when compared with the NMR group or healthy individuals. CONCLUSIONS: Ischaemic MR in acute inferoposterior MI is related with worse lesions in MA geometry that cause insufficiency of mitral valve function.

Discordance between echocardiography and MRI in the assessment of mitral regurgitation severity: a prospective multicenter trial.

BACKGROUND: The decision to undergo mitral valve surgery is often made on the basis of echocardiographic criteria and clinical assessment. Recent changes in treatment guidelines recommending surgery in asymptomatic patients make the accurate assessment of mitral regurgitation (MR) severity even more important. OBJECTIVES: The purpose of this study was to compare echocardiography and magnetic resonance imaging (MRI) in the assessment of MR severity using the degree of left ventricular (LV) remodeling after surgery as the reference standard. METHODS: In this prospective multicenter trial, MR severity was assessed in 103 patients using both echocardiography and MRI. Thirty-eight patients subsequently had isolated mitral valve surgery, and 26 of these had an additional MRI performed 5 to 7 months after surgery. The pre-surgical estimate of regurgitant severity was correlated with the postoperative decrease in LV end-diastolic volume. RESULTS: Agreement between MRI and echocardiographic estimates of MR severity was modest in the overall cohort (r = 0.6; p < 0.0001), and there was a poorer correlation in the subset of patients sent for surgery (r = 0.4; p = 0.01). There was a strong correlation between post-surgical LV remodeling and MR severity as assessed by MRI (r = 0.85; p < 0.0001), and no correlation between post-surgical LV remodeling and MR severity as assessed by echocardiography (r = 0.32; p = 0.1). CONCLUSIONS: The data suggest that MRI is more accurate than echocardiography in assessing the severity of MR. MRI should be considered in those patients when MR severity as assessed by echocardiography is influencing important clinical decisions, such as the decision to undergo MR surgery.

P wave area for quantitative electrocardiographic assessment of left atrial remodeling.

BACKGROUND: Left atrial (LA) dilation provides a substrate for mitral regurgitation (MR) and atrial arrhythmias. ECG can screen for LA dilation but standard approaches do not assess LA geometry as a continuum, as does non-invasive imaging. This study tested ECG-quantified P wave area as an index of LA geometry. METHODS AND RESULTS: 342 patients with CAD underwent ECG and CMR within 7 (0.1±1.4) days. LA area on CMR correlated best with P wave area in ECG lead V1 (r = 0.42, p<0.001), with lesser correlations for P wave amplitude and duration. P wave area increased stepwise in relation to CMR-evidenced MR severity (p<0.001), with similar results for MR on echocardiography (performed in 86% of patients). Pulmonary arterial (PA) pressure on echo was increased by 50% among patients in the highest (45±14 mmHg) vs. the lowest (31±9 mmHg) P wave area quartile of the population. In multivariate regression, CMR and echo-specific models demonstrated P wave area to be independently associated with LA size after controlling for MR, as well as echo-evidenced PA pressure. Clinical follow-up (mean 2.4±1.9 years) demonstrated ECG and CMR to yield similar results for stratification of arrhythmic risk, with a 2.6-fold increase in risk for atrial fibrillation/flutter among patients in the top P wave area quartile of the population (CI 1.1-5.9, p = 0.02), and a 3.2-fold increase among patients in the top LA area quartile (CI 1.4-7.0, p = 0.005). CONCLUSIONS: ECG-quantified P wave area provides an index of LA remodeling that parallels CMR-evidenced LA chamber geometry, and provides similar predictive value for stratification of atrial arrhythmic risk.

Mitral apparatus assessment by delayed enhancement CMR: relative impact of infarct distribution on mitral regurgitation.

OBJECTIVES: This study sought to assess patterns and functional consequences of mitral apparatus infarction after acute myocardial infarction (AMI). BACKGROUND: The mitral apparatus contains 2 myocardial components: papillary muscles and the adjacent left ventricular (LV) wall. Delayed-enhancement cardiac magnetic resonance (DE-CMR) enables in vivo study of inter-relationships and potential contributions of LV wall and papillary muscle infarction (PMI) to mitral regurgitation (MR). METHODS: Multimodality imaging was performed: CMR was used to assess mitral geometry and infarct pattern, including 3D DE-CMR for PMI. Echocardiography was used to measure MR. Imaging occurred 27 ± 8 days after AMI (CMR, echocardiography within 1 day). RESULTS: A total of 153 patients with first AMI were studied; PMI was present in 30% (n = 46 [72% posteromedial, 39% anterolateral]). When stratified by angiographic culprit vessel, PMI occurred in 65% of patients with left circumflex, 48% with right coronary, and only 14% of patients with left anterior descending infarctions (p <0.001). Patients with PMI had more advanced remodeling as measured by LV size and mitral annular diameter (p <0.05). Increased extent of PMI was accompanied by a stepwise increase in mean infarct transmurality within regional LV segments underlying each papillary muscle (p <0.001). Prevalence of lateral wall infarction was 3-fold higher among patients with PMI compared to patients without PMI (65% vs. 22%, p <0.001). Infarct distribution also impacted MR, with greater MR among patients with lateral wall infarction (p = 0.002). Conversely, MR severity did not differ on the basis of presence (p = 0.19) or extent (p = 0.12) of PMI, or by angiographic culprit vessel. In multivariable analysis, lateral wall infarct size (odds ratio 1.20/% LV myocardium [95% confidence interval: 1.05 to 1.39], p = 0.01) was independently associated with substantial (moderate or greater) MR even after controlling for mitral annular (odds ratio 1.22/mm [1.04 to 1.43], p = 0.01), and LV end-diastolic diameter (odds ratio 1.11/mm [0.99 to 1.23], p = 0.056). CONCLUSIONS: Papillary muscle infarction is common after AMI, affecting nearly one-third of patients. Extent of PMI parallels adjacent LV wall injury, with lateral infarction-rather than PMI-associated with increased severity of post-AMI MR.

Cell maceration scanning electron microscopy and computer-derived porosity measurements in assessment of connective tissue microstructure changes in the canine myxomatous mitral valve.

Canine myxomatous mitral valve disease is associated with changes in the valve extracellular matrix (ECM). The aim of this study was to examine the use of cell macerated scanning electron microscopy (CMSEM) in evaluating ECM changes in a small sample of valves and to quantify these changes using computer-aided image analysis of sample porosity (a measure of structural disorganisation and collagen loss). The distinct layered structure of the de-cellularised matrix could be seen in the normal valve and there were marked changes in layers and ECM organisation as the disease progressed. Clearly visible and quantifiable, statistically significant changes were found in valve porosity across the entire leaflet thickness and particularly in the valve mid and distal zones. All of these changes are presumed to affect the mechanical function of the valve. In conclusion, CMSEM with computed image analysis can be used to visualise and measure tissue structural changes in a quasi-3-dimensional manner in normal and diseased tissues.

Clinical assessment of systolic myocardial deformations in dogs with chronic mitral valve insufficiency using two-dimensional speckle-tracking echocardiography.

OBJECTIVE: The objective of this study was to clinically assess myocardial deformations in dogs with chronic mitral valve insufficiency (CMVI) using two-dimensional speckle-tracking echocardiography (2D-STE). ANIMALS: 87 dogs with CMVI. METHODS: Dogs were placed into 1 of 3 classes, based on the International Small Animal Cardiac Health Council classification. In addition, 20 weight- and age-matched healthy dogs were enrolled as controls. The dogs were examined for myocardial deformations using 2D-STE, and strain and strain rate in the longitudinal, circumferential, and radial directions were evaluated. RESULTS: Class II and III dogs had higher circumferential strain than class I dogs (P = 0.002 and P = 0.001, respectively) and controls (P < 0.001 and P < 0.001, respectively). Class III dogs had higher radial strain than class I dogs (P = 0.001) and controls (P < 0.001). Class III dogs had higher radial strain rate than class I dogs (P = 0.006) and controls (P = 0.001). Other deformations, including longitudinal deformations, were not significantly different between classes of CMVI or between CMVI dogs and controls. CONCLUSIONS: In the clinical progression of CMVI in dogs, myocardial deformations, as assessed by 2D-STE, differed according to myocardial contractile direction. Thus, assessments of multidirectional myocardial deformations may be important for better assessment of clinical cardiac function in dogs with CMVI.

Incremental role of three-dimensional transesophageal echocardiography in the assessment of mitral-aortic intervalvular fibrosa abscess.

We report a case of an elderly patient in whom live/real time three-dimensional transesophageal echocardiography (3DTEE) provided definitive diagnosis of mitral-aortic intervalvular fibrosa abscess. This could not be done by two-dimensional transthoracic echocardiography (2DTTE) and two-dimensional transesophageal echocardiography (2DTEE). 3DTEE was also helpful in ruling out associated mitral valve endocarditis, which was initially suspected by 2DTEE leading to a mitral valve sparing surgery. Thus, 3DTEE provided incremental information over 2DTTE and 2DTEE in this patient.

Echocardiographic assessment of canine degenerative mitral valve disease.

Degenerative mitral valve disease (MVD), the most common acquired heart disease in small-sized dogs, is characterized by valvular degeneration resulting in systolic mitral valve regurgitation (MR). Worsening of MR leads to several combined complications including cardiac remodeling, increased left ventricular filling pressure, pulmonary arterial hypertension, and myocardial dysfunction. Conventional two-dimensional, M-mode, and Doppler examination plays a critical role in the initial and longitudinal assessment of dogs affected by MVD, providing information on mitral valve anatomy, MR severity, left ventricular (LV) size and function, as well as cardiac and vascular pressures. Several standard echocardiographic variables have been shown to be related to clinical outcome. Some of these markers (e.g., left atrium to aorta ratio, regurgitation fraction, pulmonary arterial pressure) may also help in identifying asymptomatic MVD dogs at higher risk of early decompensation, which remains a major issue in practice. However, both afterload and preload are altered during the disease course. This represents a limitation of conventional techniques to accurately assess myocardial function, as most corresponding variables are load-dependent. Recent ultrasound techniques including tissue Doppler imaging, strain and strain rate imaging, and speckle tracking echocardiography, provide new parameters to assess regional and global myocardial performance (e.g., myocardial velocities and gradients, deformation and rate of deformation, and mechanical synchrony). As illustration, the authors present new data obtained from a population of 91 dogs (74 MVD dogs, 17 age-matched controls) using strain imaging, and showing a significant longitudinal systolic alteration at the latest MVD heart failure stage.

Functional valve assessment: the emerging role of cardiovascular magnetic resonance.

The prevalence of valvular heart disease is increasing along with the life span of the population. In assessing individuals with valve disease, echocardiography is the primary imaging modality used by clinicians both for initial assessment and for longitudinal evaluation. Information regarding valve morphology and function, cardiac chamber size, wall thickness, ventricular function, and estimates of pulmonary artery pressures can be readily obtained and integrated to formulate an assessment of valve disease severity. In some instances, body habitus or the presence of coexisting lung disease may result in suboptimal acoustic windows on echocardiography, which may lead to technically difficult studies. Additionally, in some patients, information from clinical history and physical examination or other diagnostic tests may be discordant with echocardiographic findings. In these instances, there is a significant clinical role for cardiovascular magnetic resonance (CMR). The diagnostic capabilities of CMR have increased substantially over the past 20 years due to hardware and software advances. Today, CMR has a number of unique advantages over other imaging modalities - primarily, it provides a view of the entire heart without limitations from inadequate imaging windows or body habitus. Furthermore, CMR can obtain imaging data in any imaging plane prescribed by the scan operator, which makes it ideal for accurate investigation of all cardiac valves - aortic, mitral, pulmonic, and tricuspid. In addition, CMR for valve assessment is noninvasive, free of ionizing radiation, and in most instances does not require contrast administration. Since a comprehensive review of the role of CMR in all valve lesions is beyond the scope of this article, we will focus on the most common valvular indication for performance of clinical CMR techniques and an overview of selected validation and reproducibility studies. The objectives of a comprehensive CMR study for evaluating mitral insufficiency are threefold: 1) to provide insight into the mechanism of mitral insufficiency, and 3) to discern the consequences of the lesions including the effects on left ventricular (LV) volume, LV systolic function, and left atrial volumes. In most instances this information can be obtained without the need for intravenous contrast agents (gadolinium). Therefore, CMR can be performed even in patients with severe renal failure.

Three-dimensional echocardiography for assessment of mitral valve regurgitation.

PURPOSE OF REVIEW: Estimation of severity has become a significant predictor of outcomes and a pivotal factor in the management of mitral regurgitation. The flow convergence formula has become one of the most important quantitative methods for valve regurgitation in echocardiography. Nevertheless, it has many assumptions leading to over or underestimations. With recent development of a much improved three-dimensional volumetric imaging, there have been efforts in trying to overcome these two-dimensional limitations using three-dimensional approaches. Hence, this review is mainly focused on three-dimensional color flow and techniques of quantifying the severity of mitral regurgitation using three-dimensional echocardiography. RECENT FINDINGS: Investigators have found that imaging the proximal flow convergence region (PFCR) and measuring the vena contracta area are highly feasible. The shape of the PFCR may vary, being a hemisphere, prolate or oblate hemispheroid, or hemi-ellipsoid, based on these findings; three-dimensional formulas have a stronger correlation, less underestimation and better accuracy than the two-dimensional proximal isovelocity surface area method. Direct measurements of the effective regurgitant orifice are also feasible and serve as an alternative to hemodynamic formulas. SUMMARY: Three-dimensional echocardiography has made major advances with the three-dimensional matrix transesophageal echo and will be a clinically viable tool as probe technology and software evolve.

Echocardiographic and histological assessment of age-related valvular changes in normal rats.

Aging is associated with morphologic and functional alterations of the rat's left ventricle. However, the time-course of valvular function and morphology in normal aging rats has not yet been studied. For this purpose, 30 male Wistar rats (318 +/- 5g, 10 weeks old) underwent serial echocardiograms for 58 weeks under sodium pentobarbital 50 mg/kg IP anesthetization followed by necropsy. Histopathology was also performed in two additional groups of 10 rats at 10 and 30 weeks of age. Regurgitations were considered as any retrograde flow on 2-D or M-mode color Doppler echocardiography. Tricuspid regurgitation was already found at 10 weeks of age and became more frequent with age. Pulmonary, mitral and aortic regurgitation was seldom observed at 10 weeks but became more frequent after 30 weeks. For the mitral and aortic valve, this was also associated with an increase in valvular thickness because of nodular or segmental myxoid leaflet changes. The severity of valvular regurgitations did not increase with age. In conclusion, aging leads to morphologic and functional valvular changes in normal rats. This is important when investigating models of valvular heart disease in small animals.

Towards comprehensive assessment of mitral regurgitation using cardiovascular magnetic resonance.

Cardiovascular magnetic resonance (CMR) is increasingly used to assess patients with mitral regurgitation. Its advantages include quantitative determination of ventricular volumes and function and the mitral regurgitant fraction, and in ischemic mitral regurgitation, regional myocardial function and viability. In addition to these, identification of leaflet prolapse or restriction is necessary when valve repair is contemplated. We describe a systematic approach to the evaluation of mitral regurgitation using CMR which we have used in 149 patients with varying etiologies and severity of regurgitation over a 15 month period. Following standard ventricular cine acquisitions, including 2, 3 and 4 chamber long axis views and a short axis stack for biventricular function, we image movements of all parts of the mitral leaflets using a contiguous stack of oblique long axis cines aligned orthogonal to the central part of the line of coaptation. The 8-10 slices in the stack, orientated approximately parallel to a 3-chamber view, are acquired sequentially from the superior (antero-lateral) mitral commissure to the inferior (postero-medial) commissure, visualising each apposing pair of anterior and posterior leaflet scallops in turn (A1-P1, A2-P2 and A3-P3). We use balanced steady state free precession imaging at 1.5 Tesla, slice thickness 5 mm, with no inter-slice gaps. Where the para-commissural coaptation lines curve relative to the central region, two further oblique cines are acquired orthogonal to the line of coaptation adjacent to each commissure. To quantify mitral regurgitation, we use phase contrast velocity mapping to measure aortic outflow, subtracting this from the left ventricular stroke volume to calculate the mitral regurgitant volume which, when divided by the left ventricular stroke volume, gives the mitral regurgitant fraction. In patients with ischemic mitral regurgitation, we further assess regional left ventricular function and, with late gadolinium enhancement, myocardial viability. Comprehensive assessment of mitral regurgitation using CMR is feasible and enables determination of mitral regurgitation severity, associated leaflet prolapse or restriction, ventricular function and viability in a single examination and is now routinely performed at our centre. The mitral valve stack of images is particularly useful and easy to acquire.

Assessment of coronary sinus anatomy between normal and insufficient mitral valves by multi-slice computertomography for mitral annuloplasty device implantation.

INTRODUCTION: Latest techniques enable positioning of devices into the coronary sinus (CS) for mitral valve (MV) annuloplasty. We evaluate the feasibility of non-invasive assessment to determine CS anatomy and its relation to MV annulus and coronary arteries by multi-slice CT (MSCT) in normal and insufficient MV. METHODS: Fifty patients (33 males, 17 females, age 67+/-11 years) were studied retrospectively by 64-MSCT scans for anatomical criteria regarding CS and its relation to MV annulus and circumflex artery (CX). We included 24 patients with severe mitral insufficiency and 26 with no MV disease. Diameter of MV, of proximal and distal ostium of CS, length and volume of CS, angle between anterior interventricular vein (AIV) and CS, caliber change of CX before, under/over and after CS were analysed. Different anatomical correlations were demonstrated: distance of MV annulus to CS, CX to CS. RESULTS: Diameter of proximal CS ostium was significantly larger in insufficient MV compared to normal MV (11+/-2.8 mm vs 9.9+/-2.5 mm; p<0.024). CS was significantly longer in patients with insufficient MV (125.4+/-17 mm vs 108.9+/-18 mm; p<0.003) with also significant differences in volume of CS (p<0.039). Significant difference in annulus diameter, 46.1+/-6mm (insufficient MV) versus 39.5+/-7.5 mm, p<0.004 was observed. Angle CS-AIV was 103.5+/-29 degrees (range 52 degrees -144 degrees ) in insufficient valves versus 118.2+/-24.5 degrees (range 73 degrees -166 degrees ) in normal valves with a tendency to higher angles in normal valves (p=0.06). Distance of MV annulus to CS measured 16+/-4.1/14.2+/-3.6 mm (insufficient/normal MV) without significant difference between groups. In 15 patients CX ran under CS. Eighty-four percent of these patients (13/15) show a decrease in CS caliber in the area of intersection. In 14 patients CS ran over and in one patient the diameter of the CS at intersecting region was smaller. In 16 patients no direct point of contact was visible, in five patients CX to CS positioning was not evaluable. CONCLUSION: There is a significant anatomic difference between normal and insufficient MV, which might be the basis for any interventional approaches through the CS. Exact measurements of all structures and its anatomic correlations are possible with MSCT, which allows pre-interventional planning.