Quantification of Aortic Valve Calcification Using Multislice Spiral Computed Tomography

Quantification of Aortic Valve Calcification in Contrast-Enhanced Computed Tomography

Background: The goal of our study is to evaluate a method to quantify aortic valve calcification (AVC) in contrast-enhanced computed tomography for patients with suspected severe aortic stenosis pre-interventionally. Methods: A total of sixty-five patients with aortic stenosis underwent both a native and a contrast-enhanced computed tomography (CECT) scan of the aortic valve (45 in the training cohort and 20 in the validation cohort) using a standardized protocol. Aortic valve calcification was semi-automatically quantified via the Agatston score method for the native scans and was used as a reference. For contrast-enhanced computed tomography, a calcium threshold of the Hounsfield units of the aorta plus four times the standard deviation was used. Results: For the quantification of aortic valve calcification in contrast-enhanced computed tomography, a conversion formula (691 + 1.83 x AVCCECT) was derived via a linear regression model in the training cohort. The validation in the second cohort showed high agreement for this conversion formula with no significant proportional bias (Bland-Altman, p = 0.055) and with an intraclass correlation coefficient in the validation cohort of 0.915 (confidence interval 95% 0.786-0.966) p < 0.001. Conclusions: Calcium scoring in patients with aortic valve stenosis can be performed using contrast-enhanced computed tomography with high validity. Using a conversion factor led to an excellent agreement, thereby obviating an additional native computed tomography scan. This might contribute to a decrease in radiation exposure.

Sex differences in aortic valve calcification in severe aortic valve stenosis: association between computer tomography assessed calcification and valvular calcium concentrations

AIMS

The aims of this study were to investigate the correlation and sex differences between total valve calcium, valve calcium concentration, and aortic valve calcification (AVC) in explanted valves from patients with severe aortic valve stenosis undergoing aortic valve replacement (AVR).

METHODS AND RESULTS

Sixty-nine patients with severe aortic stenosis (AS) scheduled for elective AVR underwent echocardiography and cardiac computed tomography (CT) prior to surgery (AVCin vivo) and CT of the explanted aortic valve (AVCex vivo). Explanted valves were prepared in acid solution, sonicated, and analysed with Arsenazo III dye to estimate total valve calcium and valve calcium concentration. Median AVCex vivo was 2082 (1421-2973) AU; mean valve calcium concentration was 1.43 ± 0.42 µmol Ca2+/mg tissue; median total valve calcium 156 (111-255) mg Ca2+, and valve calcium density 52 (35-81) mg/cm2. AVC displayed a strong correlation with total valve calcium (R2 = 0.98, P < 0.001) and a moderate correlation with valve calcium concentration (R2 = 0.62, P < 0.001). Valvular calcium concentration was associated with sex, aortic valve area, and mean gradient. After adjusting for age and estimated glomerular filtration rate, sex and mean gradient remained associated with valve calcium concentrations.

CONCLUSION

AVC score provides a strong estimate for total valve calcium but to a lesser degree calcium concentration in the valve tissue of patients with severe AS. Females presented lower valvular calcium concentrations than males irrespective of AS severity, adding evidence and providing support to the important point that sex differences in valvular calcium concentration in AS does not reflect valvular size.

Incidental Cardiac Findings in Non-Electrocardiogram-gated Thoracic Computed Tomography of Intensive Care Unit Patients: Assessment of Prevalence and Underreporting

PURPOSE

Cardiac findings frequently remain unreported on non-electrocardiogram (ECG)-gated computed tomography (CT). Although the clinical relevance of such findings may be limited in a general patient population, they may have significant impact in intensive care patients. Thus, the purpose of this study was to evaluate the prevalence, underreporting, and clinical relevance of incidental cardiac findings in intensive care unit (ICU) patients.

MATERIALS AND METHODS

Non-ECG-gated chest CT examinations of ICU patients were retrospectively analyzed for incidental cardiac findings. The findings were classified into 3 categories (A to C): category A findings, which carry potential for risk to life; category B findings, which have a potential for significant morbidity; category C findings, which have a possible effect on prognosis.

RESULTS

A total of 500 patients who underwent non-ECG-gated thoracic CT examinations were included. Of the 500 patients, 403 presented with 1443 cardiac findings. Of all cardiac findings, 37% were described in the initial written report. Sixty category A findings were detected, of which 48% were not mentioned in the report. Six hundred forty category B findings were detected, of which 77% were not described in the report. The remaining 743 findings were classified as category C, 55% of which were not reported in the report.

CONCLUSIONS

The prevalence as well as the rate of underreporting of incidental cardiac findings in non-ECG-gated chest CT of ICU patients is very high. The results of this study underscore the importance of dedicated training for assessment of cardiac structures and conditions, which may be detected on non-ECG-gated chest CT.

Grading of aortic stenosis severity: a head-to-head comparison between cardiac magnetic resonance imaging and echocardiography

AIM

To prospectively evaluate the accuracy of cardiac magnetic resonance (cMR) imaging for the assessment of aortic valve effective orifice area (EOA) by continuity equation and anatomical aortic valve area (AVA) by direct planimetry, as compared with transthoracic (TTE) and transesophageal (TEE) two-dimensional (2D) echocardiography, respectively.

METHODS AND RESULTS

A total of 31 patients (21 men, 10 women, mean age 69 ± 10 years) with moderate-to-severe aortic stenosis (AS) diagnosed by TTE and scheduled for elective aortic valve replacement, underwent both cMR and TEE. AVA by cMR was obtained from balanced steady-state free-precession cine-images. EOA was computed from phase-contrast MR flow analysis. AVA at cMR (0.93 ± 0.42 cm²) was highly correlated with TEE-derived planimetry (0.92 ± 0.32 cm²) (concordance correlation coefficient, CCC = 0.85). By excluding 11 patients with extensively thickened and heavily calcified cusps, the CCC increased to 0.93. EOA at cMR (0.86 ± 0.30 cm²) showed a strong correlation with TTE-derived EOA (0.78 ± 0.25 cm²) (CCC = 0.82).

CONCLUSIONS

cMR imaging is an accurate alternative for the grading of AS severity. Its use may be recommended especially in patients with poor transthoracic acoustic windows and/or in case of discordance between 2D echocardiographic parameters.

Annular Rupture During Transcatheter Aortic Valve Implantation: Predictors, Management and Outcomes

Transcatheter aortic valve implantation (TAVI) is the treatment of choice in patients with symptomatic severe aortic stenosis who are either inoperable or at high risk for conventional surgical aortic valve replacement. Recent data have also shown favourable outcomes in patients deemed to be at intermediate operative risk, which expands the application of this novel technology. Despite its success, TAVI has been associated with rare life-threatening complications. Of these, aortic annular rupture is considered to be the most devastating. Advances in pre-procedural screening and patient selection have reduced the incidence of annular rupture. When this complication occurs, early recognition and prompt management are essential. This article is intended to provide a comprehensive review of the predictors, management and clinical outcomes of aortic annular rupture.

An insight into transcatheter aortic valve implantation-a perspective from multidetector-computed tomography

Transcatheter aortic valve implantation (TAVI) has now become an acceptable alternative to surgical aortic valve replacement for patients with severe aortic stenosis at high risk. The early enthusiasm for this technology has not diminished but rather has developed at an unprecedented rate over the last decade. Alongside the developments in implantation technique, transcatheter design, and postprocedural care, cardiac imaging modalities have also had to concurrently evolve to meet the perpetual demand for lower peri- and postprocedural complication rates. Although transthoracic and transesophageal echocardiography remain vital in patient's selection and periprocedural guidance, there is now emerging evidence that indicates that multidetector-computed tomography (MDCT) may also have an equally important role to play. The aim of the current review is to examine the modern role of MDCT in assessing patients with aortic stenosis being considered for TAVI.

Sex differences in aortic valve calcification measured by multidetector computed tomography in aortic stenosis

BACKGROUND

Aortic valve calcification (AVC) is the intrinsic mechanism of valvular obstruction leading to aortic stenosis (AS) and is measurable by multidetector computed tomography. The link between sex and AS is controversial and that with AVC is unknown.

METHODS AND RESULTS

We prospectively performed multidetector computed tomography in 665 patients with AS (aortic valve area, 1.05±0.35 cm(2); mean gradient, 39±19 mm Hg) to measure AVC and to assess the impact of sex on the AVC-AS severity link in men and women. AS severity was comparable between women and men (peak aortic jet velocity: 4.05±0.99 versus 3.93±0.91 m/s, P=0.11; aortic valve area index: 0.55±0.20 versus 0.56±0.18 cm(2)/m(2); P=0.46). Conversely, AVC load was lower in women versus men (1703±1321 versus 2694±1628 arbitrary units; P<0.0001) even after adjustment for their smaller body surface area or aortic annular area (both P<0.0001). Thus, odds of high-AVC load were much greater in men than in women (odds ratio, 5.07; P<0.0001). Although AVC showed good associations with hemodynamic AS severity in men and women (all r>0.67; P<0.0001), for any level of AS severity measured by peak aortic jet velocity or aortic valve area index, AVC load, absolute or indexed, was higher in men versus women (all P≤0.01).

CONCLUSIONS

In this large AS population, women incurred similar AS severity than men for lower AVC loads, even after indexing for their smaller body size. Hence, the relationship between valvular calcification process and AS severity differs in women and men, warranting further pathophysiological inquiry. For AS severity diagnostic purposes, interpretation of AVC load should be different in men and in women.

Clinical indications for cardiac computed tomography. From the Working Group of the Cardiac Radiology Section of the Italian Society of Medical Radiology (SIRM)

Cardiac computed tomography (CCT) has grown as a useful means in different clinical contexts. Technological development has progressively extended the indications for CCT while reducing the required radiation dose. Even today there is little documentation from the main international scientific societies describing the proper use and clinical indications of CCT; in particular, there are no complete guidelines. This document reflects the position of the Working Group of the Cardiac Radiology Section of the Italian Society of Radiology concerning the indications for CCT.

Aortic annulus dimensions and leaflet calcification from contrast MSCT predict the need for balloon post-dilatation after TAVI with the Medtronic CoreValve prosthesis

AIMS

We compared the measurement of aortic leaflet calcification on contrast and non-contrast MSCT and investigated predictors of the need for balloon post-dilatation after TAVI.

METHODS AND RESULTS

In 110 patients, who had TAVI with a Medtronic CoreValve prosthesis (MCS) for symptomatic aortic stenosis, calcification of the aortic root was measured on non-contrast MSCT (conventionally) and on contrast MSCT (signal attenuation >450 Houndsfield units). Calcium volume was underestimated on contrast- when compared to non-contrast MSCT: median (IQ-range)=759 (466 to 1295) vs. 2016 (1376 to 3262) and the difference between the two methods increased with higher calcium volumes (correlation coefficient r=0.90). Calcium mass was only slightly underestimated on contrast vs. non-contrast MSCT: median (IQ-range)=441 (268 to 809) vs. 555 (341 to 950) and there was no association between the differences and increasing calcium mass (r=0.17). Balloon post-dilatation was performed for significant aortic regurgitation after TAVI in 11 of 110 patients. When compared to controls, the patients who required balloon post-dilatation had higher aortic leaflet calcium on contrast CT (p<0.01), higher aortic annulus diameters (p<0.01) and higher annulus to prosthesis area ratio (p=0.01). ROC curves demonstrated that aortic root or aortic leaflet calcium measured on either contrast- or non-contrast MSCT showed excellent discrimination for the requirement of balloon post-dilatation (area under ROC >0.80 for all), whereas the discriminatory value of aortic annulus dimensions was moderate (area under ROC=0.69) and that of prosthesis to annulus ratio was poor (area under ROC=0.36).

CONCLUSIONS

Dense aortic leaflet calcification measured on contrast MSCT discerned well the need for balloon post-dilatation after TAVI with an MCS for significant PAR. Non-contrast MSCT may no longer be needed to quantify aortic root calcium before TAVI.

Correlation of Device landing zone calcification and acute procedural success in patients undergoing transcatheter aortic valve implantations with the self-expanding CoreValve prosthesis

OBJECTIVES

The aim of this study was to assess the influence of amount and distribution of calcifications of the aortic valve and the left ventricular outflow tract on the acute procedural outcome of patients undergoing transcatheter aortic valve implantation (TAVI).

BACKGROUND

Transcatheter aortic valve implantation is a new percutaneous technique especially for elderly, high-risk patients with significant aortic valve stenosis (AS). After TAVI, post-interventional paravalvular aortic regurgitations (PAR) can occur, which is believed to be related partially to valve calcifications.

METHODS

We prospectively analyzed 100 symptomatic patients with severe AS scheduled for TAVI with the CoreValve ReValving (Medtronic, Minneapolis, Minnesota) prosthesis. In all patients, a native and contrast-enhanced multislice cardiac computed tomography was performed pre-interventionally. Calcification load of the valve and the adjacent outflow tract was estimated by the Agatston Score (AgS), and the amount and distribution of calcification was semi-quantitatively assessed and graded on a 1 to 4 scale (device "landing zone" calcification score [DLZ-CS]). Aortography was performed to evaluate the PAR pre-interventionally, after initial device release (PAR0) and after termination of the procedure (PAR1). Transthoracic echocardiography was performed 2 weeks after implantation (PAR2).

RESULTS

The AgS and DLZ-CS showed a significant correlation with the grade of PAR0 (AgS: r = 0.329, p = 0.001; DLZ-CS: r = 0.356, p < 0.001), PAR1 (AgS: r = 0.254, p = 0.011; DLZ-CS: r = 0.240, p = 0.016), and PAR2 (AgS: r = 0.341, p = 0.001; DLZ-CS: r = 0.300, p = 0.002). Both scores (AgS and DLZ-CS) showed a significant positive correlation (r = 0.858, p < 0.001).

CONCLUSIONS

Calcification in the CoreValve device "landing zone" shows a significant positive correlation to PAR after TAVI. Furthermore, the need for "second maneuvers" (i.e., post-dilation after initial device release) can be predicted by these calcification scores (AgS and DLZ-CS).

Cardiac CT for the differentiation of bicuspid and tricuspid aortic valves: comparison with echocardiography and surgery

OBJECTIVE

The purpose of this study is to evaluate the diagnostic performance of CT, compared with that of echocardiography and surgery, for differentiating between bicuspid and tricuspid aortic valves.

MATERIALS AND METHODS

Forty-seven patients with bicuspid valve and 47 patients with tricuspid aortic valve underwent retrospectively ECG-gated dual-source CT and echocardiography. Thirty-four (72%) of the 47 patients with bicuspid aortic valve underwent valve surgery. Two independent blinded observers assessed the CT image quality of the aortic valve during diastole and systole on a 4-point scale, determined which phase allowed the differentiation of valve type, distinguished between tricuspid and bicuspid aortic valves, and assessed for the presence of a raphe. Diagnostic performance of CT was determined using echocardiography and surgery as the reference standard.

RESULTS

According to echocardiography and surgery, seven (15%) of the 47 bicuspid aortic valves had no raphe, and 40 (85%) had a raphe. CT image quality was diagnostic (i.e., scores of 1-3) in all 94 patients in both diastole and systole. Among patients with bicuspid aortic valve and no raphe, differentiation between tricuspid and bicuspid aortic valves could be performed in diastole in 100% (7/7) of cases. Among patients with bicuspid aortic valve and raphe, differentiation was possible only in systole in 5% (2/40) of cases and when combining diastole and systole in 95% (38/40) of cases. In three bicuspid aortic valves with raphe, the valve was misclassified by CT as tricuspid aortic valve. Overall sensitivity and specificity of CT for the diagnosis of bicuspid aortic valve were 94% and 100%.

CONCLUSION

CT is highly accurate for differentiation between bicuspid and tricuspid aortic valves. For bicuspid aortic valves without raphe, diastolic reconstructions are sufficient, whereas in those with a raphe, additional reconstructions in systole are required.

Association of aortic valve calcification to the presence, extent, and composition of coronary artery plaque burden: from the Rule Out Myocardial Infarction using Computer Assisted Tomography (ROMICAT) trial

BACKGROUND

Aortic valve calcification (AVC) is associated with cardiovascular risk factors and coronary artery calcification. We sought to determine whether AVC is associated with the presence and extent of overall plaque burden, as well as to plaque composition (calcified, mixed, and noncalcified).

METHODS

We examined 357 subjects (mean age 53 +/- 12 years, 61% male) who underwent contrast-enhanced electrocardiogram-gated 64-slice multidetector computed tomography from the ROMICAT trial for the assessment of presence and extent of coronary plaque burden according to the 17-coronary segment model and presence of AVC.

RESULTS

Patients with AVC (n = 37, 10%) were more likely than those without AVC (n = 320, 90%) to have coexisting presence of any coronary plaque (89% vs 46%, P < .001) and had a greater extent of coronary plaque burden (6.4 vs 1.8 segments, P < .001). Those with AVC had >3-fold increase odds of having any plaque (adjusted odds ratio [OR] 3.6, P = .047) and an increase of 2.5 segments of plaque (P < .001) as compared to those without AVC. When stratified by plaque composition, AVC was associated most with calcified plaque (OR 5.2, P = .004), then mixed plaque (OR 3.2, P = .02), but not with noncalcified plaque (P = .96).

CONCLUSION

Aortic valve calcification is associated with the presence and greater extent of coronary artery plaque burden and may be part of the later stages of the atherosclerosis process, as its relation is strongest with calcified plaque, less with mixed plaque, and nonsignificant with noncalcified plaque. If AVC is present, consideration for aggressive medical therapy may be warranted.

NiTinol-based cutting edges for endovascular heart valve resection: first in-vitro cutting results

Machining of shape memory alloys based on Nitinol (NiTi) creates difficulties due to its ductility and severe strain hardening. In this experiment, different cutting edges and grinding parameters were tested to optimize cutting results on NiTi-based blades intended for endovascular heart valve resection. The cutting procedure was performed using two counter-rotating circular NiTi blades of different diameter. A rotating/punching process should be performed. Different shapes (glazed, waved, and saw tooth), different grinding techniques (manual, manual grinder, and precise milling cutter) and additionally various velocities (50 and 200 rpm) were tested on specific test specimens. Cutting forces were measured and cutting quality was examined using digital microscopy. Preliminary tests with rotating blades showed superior results using cutting edges for the punching process (150 N vs. 200 N; n=7). In a second step special test specimens were tested. Maximum cutting-force was 265 N+/-20 N (mean+/-SD; n=7). Subsequently different shapes were tested at 50 and 200 rpm using the rotating/punching method regarding alternate grinding techniques. Cutting forces were 27 N+/-7.7 N for glazed blades (n=7) at 50 rpm and 18 N+/-4.7 N at 200 rpm, waved blades (n=7) required a maximum force of 18 N+/-5 N at 50 rpm and 11 N+/-3.3 N at 200 rpm, whereas saw tooth blades (n=7) needed 17 N+/-12.7 N at 50 rpm and 9 N+/-1.2 N at 200 rpm. Precise cutting quality was only seen when using glazed blades sharpened under accurate conditions with a high-speed milling cutter. Although shape memory alloys based on Nitinol are difficult to process, and well-defined grinding parameters do not exist, acceptable results can be reached using high-speed milling cutters. Best cutting quality can be observed by using glazed blades, performing a rotating/punching process at high velocities. Lower cutting forces can be observed by using other shape-types, however this leads to lower cutting quality. Therefore, further investigations on blade-machining and velocity-testing seem to be necessary to create optimal cutting results.

Interaction of age with lipoproteins as predictors of aortic valve calcification in the multi-ethnic study of atherosclerosis

BACKGROUND

Previous epidemiologic studies have shown that low-density lipoprotein is an independent risk factor for prevalent aortic valve calcification (AVC); however, to our knowledge, the interactions between plasma lipoprotein concentrations and age on the relative risks (RRs) for AVC prevalence and severity have not been examined in a large, racially and ethnically diverse cohort.

METHODS

Using stepwise RR regression, the relationships of baseline fasting lipid levels and lipoprotein levels to baseline prevalence and severity of AVC were determined in 5801 non-statin-using participants in the Multi-Ethnic Study of Atherosclerosis (MESA).

RESULTS

In age-stratified, adjusted analyses, the low-density lipoprotein-associated RRs (95% confidence intervals) for prevalent AVC were higher for younger compared with older participants (age 45-54 years, 1.69 [1.19-2.39]; age 55-64 years, 1.48 [1.24-1.76]; age 65-74 years, 1.09 [0.95-1.25]; and age 75-84 years, 1.16 [0.99-1.36]; P interaction = .04]. There was a similar, significant interaction of age with total cholesterol-associated RR for prevalent AVC (P interaction = .04). In contrast, total- to high-density lipoprotein cholesterol ratio RRs were similar across all age strata (P interaction = .68). At multivariate analyses, no lipoprotein parameter was associated with AVC severity.

CONCLUSIONS

In this racially and ethnically diverse, preclinical cohort, low-density lipoprotein was a risk factor for AVC only in participants younger than 65 years, whereas the total cholesterol/high-density lipoprotein cholesterol ratio was associated with a modest increased risk of AVC across all ages. These findings may have important implications for the efficacy of and targets for dyslipidemia therapies in calcific aortic valve disease.