Feasibility of Contrast Material Volume Reduction in Coronary Artery Imaging using 320-Slice Volume CT

OBJECTIVE: To assess reduced volumes of contrast agent on image quality for coronary computed tomography angiography (CCTA) by using single-beat cardiac imaging with 320-slice CT.

METHODS: Forty consecutive male patients (mean age: 55.8 years) undergoing CCTA with body weight < 85 kg, heart rate < 65 bpm, and ejection fraction > 55% were included. Image acquisition protocol was standardized (120 kV, 400 mA, and prospective ECG-triggered single-beat nonspiral CCTA). Patients were randomly assigned to one of four groups (G1: received 40 ml, G2: 50 ml, G3: 60 ml, G4: 70 ml). Groups were compared with respect to aortic attenuation, image noise, and image quality.

RESULTS: CT values (mean +/- standard deviation) in the aortic root were measured as 423 +/- 38 HU in G1, and 471 +/- 68, 463 +/- 60, and 476 +/- 78 HU in G2-4, respectively. There were no statistically significant differences in attenuation among the groups (P > 0.068). All 40 CT datasets were rated diagnostic, and image noise and image quality were not statistically different among groups.

CONCLUSIONS: Using 320-slice volume CT, diagnostic image quality can be achieved with 40 ml of contrast material in CCTA in patients with normal body weight, cardiac function, and low heart rate.

PMID: 20016900

Transcatheter Aortic Valve Implantation: Role of Multi-Detector Row Computed Tomography to Evaluate Prosthesis Positioning and Deployment in Relation to Valve Function

OBJECTIVES: Aortic regurgitation after transcatheter aortic valve implantation(TAVI) is one of the most frequent complications. However, the underlying mechanisms of this complication remain unclear. The present evaluation studied the anatomic and morphological features of the aortic valve annulus that may predict aortic regurgitation after TAVI.

METHODS: In 53 patients with severe aortic stenosis undergoing TAVI, multi-detector row computed tomography (MDCT) assessment of the aortic valve apparatus was performed. For aortic valve annulus sizing, two orthogonal diameters were measured (coronal and sagittal). In addition, the extent of valve calcifications was quantified. At 1-month follow-up after procedure, MDCT was repeated to evaluate and correlate the prosthesis deployment to the presence of aortic regurgitation.

RESULTS: Successful procedure was achieved in 48 (91%) patients. At baseline, MDCT demonstrated an ellipsoid shape of the aortic valve annulus with significantly larger coronal diameter when compared with sagittal diameter (25.1 ± 2.4 vs. 22.9 ± 2.0 mm, P < 0.001). At follow-up, MDCT showed a non-circular deployment of the prosthesis in six (14%) patients. Moderate post-procedural aortic regurgitation was observed in five (11%) patients. These patients showed significantly larger aortic valve annulus (27.3 ± 1.6 vs. 24.8 ± 2.4 mm, P = 0.007) and more calcified native valves (4174 ± 1604 vs. 2444 ± 1237 HU, P = 0.005) at baseline and less favourable deployment of the prosthesis after TAVI.

CONCLUSIONS: Multi-detector row computed tomography enables an accurate sizing of the aortic valve annulus and constitutes a valuable imaging tool to evaluate prosthesis location and deployment after TAVI. In addition, MDCT helps to understand the underlying mechanisms of post-procedural aortic regurgitation.

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Radiation Dose from Single Heartbeat Coronary CT Angiography Performed With a 320 Detector Row Volume Scanner

Purpose: To determine radiation doses from coronary computed tomographic (CT) angiography performed by using a 320-detector row volume scanner and evaluate how the effective dose depends on scan mode and the calculation method used.

Materials and Methods: Radiation doses from coronary CT angiography performed by using a volume scanner were determined by using metal-oxide-semiconductor field-effect transistor detectors positioned in an anthropomorphic phantom physically and radiographically simulation a male or female human. Organ and effective doses were determined for six scan modes, including both 64-row helical and 280-row volume scans. Effective doses were compared with estimates based on the method most commonly used in clinical literature: multiplying dose-length product (DLP) by a general conversion coefficient (0.017 or 0.014) determined from Monte Carlo simulations of chest CT by using single-section scanners and previous tissue weighting factors.

Results: Effective dose was reduced by up to 91% with volume scanning relative to helical scanning, with similar imaging noise. Effective dose, determined by using International Commission on Radiological Protection publication 103 tissue-weighting factors, was 8.2 mSv, using volume scanning with exposure permitting a wide reconstruction window, 5.8 mSv with optimized exposure and 4.4 mSv for optimized 100-kVp scanning. Estimating effective dose with a chest conversion coefficient resulted in a dose as low as 1.8 mSv, substantially underestimating effective dose for both volume and helical coronary CT angiography.

Conclusion: Volume scanning markedly decreases coronary CT angiography radiation doses compared with those at helical scanning. When conversion coefficients are used to estimate effective dose from DLP, they should be appropriate for the scanner and scan mode use and reflect current tissue-weighting factors.

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Perioperative Outcomes in Reoperative Cardiac Surgery Guided by Cardiac Multidetector Computed Tomographic Angiography

OBJECTIVES: Preoperative evaluation with contrast-enhanced multidetector computed tomographic angiography (MDCTA) is considered an “appropriate” indication based on expert consensus. We aimed to evaluate how the presurgical evaluation with MDCTA impacts the outcomes after reoperative cardiac surgery (RCS).

METHODS: We retrospectively studied 364 patients undergoing RCS between 2004 and 2008, including 137 referred for MDCTA. High-risk CT findings were defined as the presence of right ventricle or aorta <10 mm from the sternum or a bypass graft <10 mm from the sternum crossing the midline. The primary clinical end point was the composite of perioperative death, myocardial infarction (MI), stoke, and hemorrhage-related reoperation. Secondary end points included surgical procedural variables and the perioperative volume of bleeding and of red blood cell (RBC) transfusion.

RESULTS: Baseline clinical characteristics were similar between the 2 groups. Individuals referred for MDCTA showed a trend toward a lower incidence of the composite primary end point (17.5% vs 24.2%, P = .13), primarily related to a significantly lower incidence of perioperative MI (0% vs 5.7%, P = .002). Multidetector computed tomographic angiography was also associated with shorter perfusion (90 vs 110 minutes, P = .002), cross clamp time (63 vs 75 minutes, P = .003), and total time in intensive care unit (103 vs 148 hours, P = .04), and a lower volume of postoperative RBC transfusion (627 vs 824 mL, P = .09). These differences remained significant after adjustment for the Society of Thoracic Surgeons score and the performing surgeon.

CONCLUSIONS: The use of MDCTA before RCS was associated with shorter perfusion and cross clamp time, shorter intensive care unit stays, and less frequent perioperative MI.

PMID: 20152230

Evaluation of Coronary CTA Appropriateness Criteria in an Academic Medical Center

OBJECTIVES: The aim of this study was to evaluate published appropriateness criteria for CT angiography (CTA) at the authors’ academic medical center.

METHODS: Two observers independently reviewed the medical records of 251 patients who had undergone dual-source coronary CTA from June 1 to December 31, 2007. Patients were assigned to indications from 1 of 7 tables from the American College of Cardiology Foundation and ACR Appropriateness Criteria. Agreement between the two observers was assessed using kappa statistics. Disagreements were resolved by consensus panel. The final numbers of appropriate, uncertain, inappropriate, and not classifiable indications were recorded.

RESULTS: Indications for testing were classified as appropriate in 69 patients (27%), inappropriate in 42 patients (17%), and uncertain in 25 patients (10%). One hundred fifteen indications for coronary CTA (46%) were not classifiable. Analysis of interobserver variability for overall appropriateness yielded a kappa value of 0.31, which was considered to indicate fair agreement.

CONCLUSION: The results of this study suggest that a significant proportion (46%) of the coronary CTA studies performed at the authors’ institution are for indications that are not covered by the published appropriateness criteria. Modifications to these criteria could help decrease the number of studies that are not classifiable. Physician education could decrease the number of inappropriate studies.

PMID: 20142087

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). 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).

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Reference Values for Right Ventricular Volumes and Ejection Fraction With Real-Time Three-Dimensional Echocardiography: Evaluation in a Large Series of Normal Subjects

OBJECTIVES: The quantification of right ventricular (RV) size and function is of diagnostic and prognostic importance. Recently, new software for the analysis of RV geometry using three-dimensional (3D) echocardiographic images has been validated. The aim of this study was to provide normal reference values for RV volumes and function using this technique.

METHODS: A total of 245 subjects, including 15 to 20 subjects for each gender and age decile, were studied. Dedicated 3D acquisitions of the right ventricle were obtained in all subjects.

RESULTS: The mean RV end-diastolic and end-systolic volumes were 49 ± 10 and 16 ± 6 mL/m2 respectively, and the mean RV ejection fraction was 67 ± 8%. Significant correlations were observed between RV parameters and body surface area. Normalized RV volumes were significantly correlated with age and gender. RV ejection fractions were lower in men, but differences across age deciles were not evident.

CONCLUSIONS: The current study provides normal reference values for RV volumes and function that may be useful for the identification of clinical abnormalities.

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Expert Review Document on Methodology, Terminology, and Clinical Applications of Optical Coherence Tomography: Physical Principles, Methodology of Image Acquisition, and Clinical Application for Assessment of Coronary Arteries and Atherosclerosis

Optical coherence tomography (OCT) is a novel intravascular imaging modality, based on infrared light emission, that enables a high resolution arterial wall imaging, in the range of 10-20 microns. This feature of OCT allows the visualization of specific components of the atherosclerotic plaques. The aim of the present Expert Review Document is to address the methodology, terminology and clinical applications of OCT for qualitative and quantitative assessment of coronary arteries and atherosclerosis.

PMID: 19892716

Neglected Cardiovascular Diseases in Africa

Several medical conditions that affect the cardiovascular system are restricted to, or affect predominantly Africans. They can be considered neglected diseases because, despite affecting considerable numbers of people, they have not been the subject of systematic research or structured control programs and did not benefit from translation of knowledge obtained in other areas of human knowledge. Their epidemiology and natural history are often incompletely described, and the etiology and pathogenesis are unclear, leading to little or no improvement in medical care for patients, and absence of effective preventive measures for their control.

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Characteristics and Clinical Significance of Late Gadolinium Enhancement by Contrast-Enhanced Magnetic Resonance Imaging in Patients With Hypertrophic Cardiomyopathy

BACKGROUND: Myocardial late gadolinium enhancement (LGE) on contrast-enhanced magnetic resonance imaging (CE-MRI) of patients with hypertrophic cardiomyopathy (HCM) has been suggested to represent intramyocardial fibrosis and, as such, an adverse prognostic risk factor. We evaluated the characteristics of LGE on CE-MRI and explored whether LGE among patients with HCM was associated with genetic testing, severe symptoms, ventricular arrhythmias, or sudden cardiac death (SCD).

METHODS: Four hundred twenty-four patients with HCM (age 55+/-16 years [range 2 to 90], 41% females), without a history of septal ablation/myectomy, underwent CE-MRI (GE 1.5 Tesla). We evaluated the relation between LGE and HCM genes status, severity of symptoms, and the degree of ventricular ectopy on Holter ECG. Subsequent SCD and appropriate implanted cardioverter defibrillator (ICD) therapies were recorded during a mean follow-up of 43+/-14 months (range 16 to 94).

RESULTS: Two hundred thirty-nine patients (56%) had LGE on CE-MRI, ranging from 0.4% to 65% of the left ventricle. Gene-positive patients were more likely to have LGE (P<0.001). The frequencies of New York Heart Association class >3 dyspnea and angina class >or=3 were similar in patients with and without LGE (125 of 239 [52%] versus 94 of 185 [51%] and 24 of 239 [10%] versus 18 of 185 [10%], respectively, P=NS). LGE-positive patients were more likely to have episodes of nonsustained ventricular tachycardia (34 of 126 [27%] versus 8 of 94 [8.5%], P<0.001), had more episodes of nonsustained ventricular tachycardia per patient (4.5+/-12 versus 1.1+/-0.3, P=0.04), and had higher frequency of ventricular extrasystoles/24 hours (700+/-2080 versus 103+/-460, P=0.003). During follow-up, SCD occurred in 4 patients, and additional 4 patients received appropriate ICD discharges. All 8 patients were LGE positive (event rate of 0.94%/y, P=0.01 versus LGE negative). Two additional heart failure-related deaths were recorded among LGE-positive patients. Univariate associates of SCD or appropriate ICD discharge were positive LGE (P=0.002) and presence of nonsustained ventricular tachycardia (P=0.04). The association of LGE with events remained significant after controlling for other risk factors.

CONCLUSIONS: In patients with HCM, presence of LGE on CE-MRI was common and more prevalent among gene-positive patients. LGE was not associated with severe symptoms. However, LGE was strongly associated with surrogates of arrhythmia and remained a significant associate of subsequent SCD and/or ICD discharge after controlling for other variables. If replicated, LGE may be considered an important risk factor for sudden death in patients with HCM.

PMID: 19850699

The Absence of Coronary Calcification Does Not Exclude Obstructive Coronary Artery Disease or the Need for Revascularization in Patients Referred for Conventional Coronary Angiography

OBJECTIVES: This study was designed to evaluate whether the absence of coronary calcium could rule out 50% coronary stenosis or the need for revascularization. The latest American Heart Association guidelines suggest that a calcium score (CS) of zero might exclude the need for coronary angiography among symptomatic patients.

METHODS: A substudy was made of the CORE64 (Coronary Evaluation Using Multi-Detector Spiral Computed Tomography Angiography Using 64 Detectors) multicenter trial comparing the diagnostic performance of 64-detector computed tomography to conventional angiography. Patients clinically referred for conventional angiography were asked to undergo a CS scan up to 30 days before.

RESULTS: In all, 291 patients were included, of whom 214 (73%) were male, and the mean age was 59.3 ± 10.0 years. A total of 14 (5%) patients had low, 218 (75%) had intermediate, and 59 (20%) had high pre-test probability of obstructive coronary artery disease. The overall prevalence of 50% stenosis was 56%. A total of 72 patients had CS = 0, among whom 14 (19%) had at least 1 50% stenosis. The overall sensitivity for CS = 0 to predict the absence of 50% stenosis was 45%, specificity was 91%, negative predictive value was 68%, and positive predictive value was 81%. Additionally, revascularization was performed in 9 (12.5%) CS = 0 patients within 30 days of the CS. From a total of 383 vessels without any coronary calcification, 47 (12%) presented with 50% stenosis; and from a total of 64 totally occluded vessels, 13 (20%) had no calcium.

CONCLUSIONS: The absence of coronary calcification does not exclude obstructive stenosis or the need for revascularization among patients with high enough suspicion of coronary artery disease to be referred for coronary angiography, in contrast with the published recommendations. Total coronary occlusion frequently occurs in the absence of any detectable calcification. (Coronary Evaluation Using Multi-Detector Spiral Computed Tomography Angiography Using 64 Detectors [CORE-64]; NCT00738218)

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Validation of a New Contrast Material Protocol Adapted to Body Surface Area for Optimized Low-Dose CT Coronary Angiography With Prospective ECG-Triggering

OBJECTIVES: In patients with large total blood volume contrast material (CM) dilution decreases coronary attenuation in CT coronary angiography (CTCA). As increased blood volume is well paralleled by body surface area (BSA) we assessed a BSA-adapted CM protocol to compensate for dilution effects.

METHODS: Low-dose CTCA with prospective ECG-triggering was performed in 80 patients with a BSA-adapted CM bolus ranging 40-105 ml and injection rate ranging 3.5-5.0 ml/s for a BSA of <1.70 to >2.5 m(2). Eighty control patients matched for BSA who had previously undergone routine CTCA with a fixed CM protocol of 80 ml at 5 ml/s served as reference group. The average vessel attenuation from the proximal right (RCA) and the left main coronary artery (LMA) was assessed. Correlation of BSA with vessel attenuation was assessed in both groups.

RESULTS: BSA-matching of all patients was successful (BSA-adapted group 1.98 +/- 0.15 m(2), range 1.66-2.39 m(2) versus reference group 1.98 +/- 0.17 m(2), range 1.59-2.38 m(2); P = 0.74). Mean CM bolus was significantly smaller in the BSA-adapted versus the reference group (70.9 +/- 14.1 vs. 80.0 +/- 0 ml, P < 0.001). There was no correlation in the BSA-adapted group (r = -0.07, P = 0.53, SEE = 0.15), while coronary attenuation was inversely related to BSA in the reference group (r = -0.59, P < 0.001, SEE = 0.14).

CONCLUSIONS: We have successfully validated a BSA-adapted contrast material protocol which results in a comparable coronary contrast enhancement independent of individual BSA. This was achieved despite a significant reduction in the overall contrast material amount.

PMID: 20131006

Clinical Feasibility of a Fully Automated 3D Reconstruction of Rotational Coronary X-Ray Angiograms

OBJECTIVES: Although fixed view x-ray angiography remains the primary technique for anatomic imaging of coronary artery disease, the known shortcomings of 2D projection imaging may limit accurate 3D vessel and lesion definition and characterization. A recently developed method to create 3D images of the coronary arteries uses x-ray projection images acquired during a 180 degrees C-arm rotation and continuous contrast injection followed by ECG-gated iterative reconstruction. This method shows promise for providing high-quality 3D reconstructions of the coronary arteries with no user interaction but requires clinical evaluation.

METHODS: The reconstruction strategy was evaluated by comparing the reconstructed 3D volumetric images with the 2D angiographic projection images from the same 23 patients to ascertain overall image quality, lesion visibility, and a comparison of 3D quantitative coronary analysis with 2D quantitative coronary analysis.

RESULTS: The majority of the resulting 3D volume images were rated as having high image quality (66%) and provided the physician with additional clinical information such as complete visualization of bifurcations and unobtainable views of the coronary tree. True-positive lesion detection rates were high (90 to 100%), whereas false-positive detection rates were low (0 to 8.1%). Finally, 3D quantitative coronary analysis showed significant similarity with 2D quantitative coronary analysis in terms of lumen diameters and provided vessel segment length free from the errors of foreshortening.

CONCLUSIONS: Fully automated reconstruction of rotational coronary x-ray angiograms is feasible, produces 3D volumetric images that overcome some of the limitations of standard 2D angiography, and is ready for further implementation and study in the clinical environment.

PMID: 20118152

ASCI 2010 Appropriateness Criteria For Cardiac Computed Tomography: A Report of the Asian Society of Cardiovascular Imaging Cardiac Computed Tomography and Cardiac Magnetic Resonance Imaging Guideline Working Group

In Asia, the healthcare system, populations and patterns of disease differ from Western countries. The current reports on the criteria for cardiac CT scans, provided by Western professional societies, are not appropriate for Asian cultures. The Asian Society of Cardiovascular Imaging, the only society dedicated to cardiovascular imaging in Asia, formed a Working Group and invited 23 Technical Panel members representing a variety of Asian countries to rate the 51 indications for cardiac CT in clinical practice in Asia. The indications were rated as ‘appropriate’ (7-9), ‘uncertain’ (4-6), or ‘inappropriate’ (1-3) on a scale of 1-9. The median score was used for the final result if there was no disagreement. The final ratings for indications were 33 appropriate, 14 uncertain and 4 inappropriate. And 20 of them are highly agreed (19 appropriate and 1 inappropriate). Specifically, the Asian representatives considered cardiac CT as an appropriate modality for Kawasaki disease and congenital heart diseases in follow up and in symptomatic patients. In addition, except for some specified conditions, cardiac CT was considered to be an appropriate modality for one-stop shop ischemic heart disease evaluation due to its general appropriateness in coronary, structure and function evaluation. This report is expected to have a significant impact on the clinical practice, research and reimbursement policy in Asia.

PMID: 20094917

Meta-analysis: Noninvasive Coronary Angiography Using Computed Tomography Versus Magnetic Resonance Imaging

OBJECTIVES: Two imaging techniques, multislice computed tomography (CT) and magnetic resonance imaging (MRI), have evolved for noninvasive coronary angiography. To compare CT and MRI for ruling out clinically significant coronary artery disease (CAD) in adults with suspected or known CAD.

METHODS: MEDLINE, EMBASE, and ISI Web of Science searches from inception through 2 June 2009 and bibliographies of reviews. Prospective English- or German-language studies that compared CT or MRI with conventional coronary angiography in all patients and included sufficient data for compilation of 2 × 2 tables. 2 investigators independently extracted patient and study characteristics; differences were resolved by consensus.

RESULTS: 89 and 20 studies (comprising 7516 and 989 patients) assessed CT and MRI, respectively. Bivariate analysis of data yielded a mean sensitivity and specificity of 97.2% (95% CI, 96.2% to 98.0%) and 87.4% (CI, 84.5% to 89.8%) for CT and 87.1% (CI, 83.0% to 90.3%) and 70.3% (CI, 58.8% to 79.7%) for MRI. In studies that included only patients with suspected CAD, sensitivity and specificity of CT were 97.6% (CI, 96.1% to 98.5%) and 89.2% (CI, 86.0% to 91.8%). Covariate analysis yielded a significantly higher sensitivity for CT scanners with more than 16 rows (98.1% [CI, 97.0% to 99.0%]; P < 0.050) than for older-generation scanners (95.6% [CI, 94.0% to 97.0%]). Heart rates less than 60 beats/min during CT yielded significantly better values for sensitivity than did higher heart rates (P < 0.001). Few studies investigated coronary angiography with MRI. Only 5 studies were direct head-to-head comparisons of CT and MRI. Covariate analyses explained only part of the observed heterogeneity.

CONCLUSIONS: For ruling out CAD, CT is more accurate than MRI. Scanners with more than 16 rows improve sensitivity, as do slowed heart rates.

PMID: 16442907