Anatomy of the mitral valvular complex and its implications for transcatheter interventions for mitral regurgitation.

Mitral regurgitation (MR) poses a significant clinical burden in the adult population, which is expected to increase even more with the ever prolonging life expectancies in developed countries. New technology has brought MR, once exclusively the arena of cardiac surgeons, to the attention of interventional cardiologists. A variety of device-oriented transcatheter strategies have evolved in recent years. A comprehensive understanding of mitral valvular anatomy is crucial for the selection of patients, the implementation of devices, and further refinements of these transcatheter techniques if they are eventually to produce procedural and clinical success. The aim of this review is to elucidate the morphology of the mitral valvular complex, integrating key anatomical features into the developing transcatheter options for the treatment of MR.

PMID: 20705218

Detection of Coronary Artery Anomalies by Dual-Source CT Coronary Angiography

OBJECTIVES: To retrospectively evaluate the clinical value of dual-source computed tomography (DSCT) coronary angiography in the diagnosis of coronary artery anomalies.

METHODS: A large cohort of 3625 consecutive patients, who underwent DSCT coronary angiography in our institute, was reviewed for coronary artery anomalies. All images were evaluated by two experienced readers using axial source images, multi-planar reformations (MPR), maximum intensity projections (MIP) and volume rendering (VR). Coronary artery anomalies were found in 36 patients (male 20, female 16, mean age 48 years, range 15-76 years). Of the 36 patients, 19 patients also underwent conventional coronary angiography (CCA).

RESULTS: The incidence of coronary artery anomalies was 0.99% (36/3625). Six different types of coronary artery anomalies were diagnosed by DSCT coronary angiography: (1) 11 anomalies of the right coronary artery; (2) five anomalies of the left coronary artery; (3) 10 anomalies of the left circumflex artery; (4) two single coronary artery; (5) one anomalous pulmonary origin of the coronary artery; (6) seven coronary artery fistula. Evaluation of the CCA resulted in a precise diagnosis in 53% (10/19) patients.

CONCLUSION: DSCT coronary angiography is a good diagnostic tool to examine coronary artery anomalies.

PMID: 20797468

Assessment of Subendocardial Structure and Function

The combination of high energy expenditure and the borderline adequacy of perfusion make the subendocardium uniquely vulnerable to injury.  Selective subendocardial involvement is usually a marker of subclinical disease.  Technical advances in new noninvasive imaging modalities, especially in spatial resolution, now permit qualitative and quantitative assessment of subendocardial structure, function, and perfusion.  Many newer techniques have the potential to provide superior prognostic information to current standard assessment methods.  This review describes the contemporary capabilities of multiple imaging modalities for assessment of the subendocardium, and seeks to guide the clinician regarding the information and technical deficiencies of each modality.

PMID: 20705269

Aortic Root Remodeling Over the Adult Life Course. Longitudinal Data From the Framingham Heart Study

OBJECTIVES: Aortic root remodeling in adulthood is known to be associated with cardiovascular outcomes. However, there is a lack of longitudinal data defining the clinical correlates of aortic root remodeling over the adult life course.

METHODS: We used serial routine echocardiograms in participants of the Framingham Heart Study to track aortic root diameter over 16 years in mid to late adulthood and to determine its short-term (4 years; n=6099 observations in 3506 individuals) and long-term (16 years; n=14 628 observations in 4542 individuals) clinical correlates by multilevel modeling. Age, sex, body size, and blood pressure were principal correlates of aortic remodeling in both short- and long-term analyses (all P<0.01).

RESULTS: Aortic root diameter increased with age in both men and women but was larger in men at any given age. Each 10-year increase in age was associated with a larger aortic root (by 0.89 mm in men and 0.68 mm in women) after adjustment for body size and blood pressure. A 5-kg/m(2) increase in body mass index was associated with a larger aortic root (by 0.78 mm in men and 0.51 mm in women) after adjustment for age and blood pressure. Each 10-mm Hg increase in pulse pressure was related to a smaller aortic root (by 0.19 mm in men and 0.08 mm in women) after adjustment for age and body size.

CONCLUSIONS: These longitudinal community-based data show that aortic root remodeling occurs over mid to late adulthood and is principally associated with age, sex, body size, and blood pressure. The underlying basis for these differences and implications for the development of cardiovascular events deserve further study.

PMID: 20713896

Pericardial Fat is Associated With Prevalent Atrial Fibrillation: The Framingham Heart Study

OBJECTIVES: Obesity represents an important risk factor for atrial fibrillation (AF). We tested the hypothesis that pericardial fat, a unique fat deposit in close anatomic proximity to cardiac structures and autonomic fibers, is associated with prevalent AF.

METHODS: Participants from the Framingham Heart Study underwent multidetector computed tomography from 2002 to 2005. We estimated the association between quantitative pericardial, intrathoracic and visceral adipose tissue volumes (per standard deviation of volume) with prevalent AF adjusting for established AF risk factors (age, sex, systolic blood pressure, blood pressure treatment, PR interval, and clinically significant valvular disease).

RESULTS: Of the 3217 eligible participants (mean age, 50.6+/-10.1 years; 48% women), 54 had a confirmed diagnosis of AF. Pericardial fat but not intrathoracic or visceral abdominal fat was associated with prevalent AF in multivariable-adjusted models (odds ratio per standard deviation of pericardial fat volume, 1.28; 95% confidence intervals, 1.03 to 1.58). Further adjustments for body mass index, heart failure, myocardial infarction, and intrathoracic fat volume did not materially change the association between pericardial fat and AF.

CONCLUSIONS: Pericardial fat was associated with prevalent AF even after adjustment for AF risk factors, including body mass index. If this association is replicated, further investigations into the mechanisms linking pericardial fat to AF are merited.

PMID: 20558845

Angiographic Versus Functional Severity of Coronary Artery Stenoses in the FAME Study Fractional Flow Reserve Versus Angiography in Multivessel Evaluation

OBJECTIVES: The purpose of this study was to investigate the relationship between angiographic and functional severity of coronary artery stenoses in the FAME (Fractional Flow Reserve Versus Angiography in Multivessel Evaluation) study. It can be difficult to determine on the coronary angiogram which lesions cause ischemia. Revascularization of coronary stenoses that induce ischemia improves a patient’s functional status and outcome. For stenoses that do not induce ischemia, however, the benefit of revascularization is less clear.

METHODS: In the FAME study, routine measurement of the fractional flow reserve (FFR) was compared with angiography for guiding percutaneous coronary intervention in patients with multivessel coronary artery disease. The use of the FFR in addition to angiography significantly reduced the rate of all major adverse cardiac events at 1 year. Of the 1,414 lesions (509 patients) in the FFR-guided arm of the FAME study, 1,329 were successfully assessed by the FFR and are included in this analysis.

RESULTS: Before FFR measurement, these lesions were categorized into 50% to 70% (47% of all lesions), 71% to 90% (39% of all lesions), and 91% to 99% (15% of all lesions) diameter stenosis by visual assessment. In the category 50% to 70% stenosis, 35% were functionally significant (FFR <0.80) and 65% were not (FFR >0.80). In the category 71% to 90% stenosis, 80% were functionally significant and 20% were not. In the category of subtotal stenoses, 96% were functionally significant. Of all 509 patients with angiographically defined multivessel disease, only 235 (46%) had functional multivessel disease (> coronary arteries with an FFR <0.80).

CONCLUSIONS: Angiography is inaccurate in assessing the functional significance of a coronary stenosis when compared with the FFR, not only in the 50% to 70% category but also in the 70% to 90% angiographic severity category.

PMID: 20579537

Adaptive StatisticaEstimated Radiation Dose Reduction Using Adaptive Statistical Iterative Reconstruction in Coronary CT Angiography: The ERASIR Study

OBJECTIVES: The objective of our study was to assess the impact of Adaptive Statistical Iterative Reconstruction (ASIR) on radiation dose and study quality for coronary CT angiography (CTA).

METHODS: We prospectively evaluated 574 consecutive patients undergoing coronary CTA at three centers. Comparisons were performed between consecutive groups initially using filtered back projection (FBP) (n = 331) and subsequently ASIR (n = 243) with regard to patient and scan characteristics, radiation dose, and diagnostic study quality.

RESULTS: There was no difference between groups in the use of prospective gating, tube voltage, or scan length. The examinations performed using ASIR had a lower median tube current than those obtained using FBP (median [interquartile range], 450 mA [350–600] vs 650 mA [531–750], respectively; p < 0.001). There was a 44% reduction in the median radiation dose between the FBP and ASIR cohorts (4.1 mSv [2.3–5.2] vs 2.3 mSv [1.9–3.5]; p < 0.001). After adjustment for scan settings, ASIR was associated with a 27% reduction in radiation dose compared with FBP (95% CI, 21–32%; p < 0.001). Despite the reduced current, ASIR was not associated with a difference in adjusted signal, noise, or signal-to-noise ratio (p = not significant). No differences existed between FBP and ASIR for interpretability per coronary artery (98.5% vs 99.3%, respectively; p = 0.12) or per patient (96.1% vs 97.1%, p = 0.65).

CONCLUSIONS: ASIR enabled reduced tube current and lower radiation dose in comparison with FBP, with preserved signal, noise, and study interpretability, in a large multicenter cohort. ASIR represents a new technique to reduce radiation dose in coronary CTA studies.

PMID:

Three-Dimensional and Two-Dimensional Quantitative Coronary Angiography, and Their Prediction of Reduced Fractional Flow Reserve

OBJECTIVES: We investigated whether three-dimensional (3D) and two-dimensional quantitative coronary angiography (2D-QCA) measurements differed in their accuracy in predicting reduced fractional flow reserve (FFR), and how this varied with stenosis severity and the FFR cut-off used.

METHODS:  Three-dimensional and 2D-QCA were compared in their measurements of minimum luminal area (MLA), percentage area stenosis, lesion length, minimum luminal diameter (MLD) and percentage diameter stenosis, and in their prediction of functionally significant FFR.

OBJECTIVES: In total, 63 target lesions were interrogated in 63 patients undergoing elective percutaneous coronary intervention. Of all measurements of lesion severity obtained by 3D-QCA, MLA best correlated with FFR (R = 0.63, P< 0.001), and was the most accurate predictor of FFR <0.75 (C statistic 0.86, P< 0.001). Of 2D-QCA measurements, MLD correlated best with FFR (R = 0.58, P< 0.001), and best predicted FFR <0.75 (C statistic 0.80, P<0.001). Overall, 3D-QCA showed a non-significant trend towards more accurate prediction of FFR than 2D-QCA, especially in intermediate lesions. The relationship between FFR and apparent stenosis severity was found to be curvilinear. Both 3D- and 2D-QCA were less accurate in intermediate lesions, and in predicting FFR ≤0.80 than in predicting FFR <0.75.

PMID:

Stress and Rest Dynamic Myocardial Perfusion Imaging by Evaluation of Complete Time-Attenuation Curves With Dual-Source CT

OBJECTIVES: This study sought to describe a protocol for myocardial perfusion imaging using dipyridamole stress, with 128-slice dual-source computed tomography (CT), and to assess the ability of CT myocardial perfusion imaging (MPI) to detect abnormal flow reserve and infarction in comparison with nuclear MPI (NMPI). CT MPI has not been previously described with the 128-slice dual-source CT scanner, or with the complete evaluation of dynamic time-attenuation curves of the myocardium.

METHODS: Thirty-five patients underwent a stress CT MPI protocol. Complete time-attenuation curves of the myocardium were acquired using a novel scan mode, which acquires prospectively electrocardiogram (ECG)-triggered axial images at 2 rapidly alternating positions. Myocardial blood flow (MBF) values of fixed and reversible defects obtained were compared between rest and stress. Findings on CT MPI were correlated to NMPI. Perfusion defects detected on CT were correlated to coronary stenoses detected on CT angiography (CTA) and invasive coronary angiography (ICA).

RESULTS: There was a 1.5-fold difference between stress (1.21 ± 0.31 cc/cc/min) and rest (0.82 ± 0.22 cc/cc/min) MBF in normal tissue. In reversible defects, MBF was 0.65 ± 0.21 cc/cc/min and 0.63 ± 0.18 cc/cc/min at stress and rest, respectively. In fixed defects, the MBF was 0.57 ± 0.22 cc/cc/min at stress and 0.54 ± 0.23 cc/cc/min at rest. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CT MPI for identifying segments with perfusion defects was 0.83, 0.78, 0.79, and 0.82, respectively. ICA results were available for 30 patients. Sensitivity, specificity, PPV, and NPV of CT MPI compared with ICA were 0.95, 0.65, 0.78, and 0.79, respectively. The radiation dose for CT MPI was 9.15 ± 1.32 mSv for the stress scan and 9.09 ± 1.40 mSv for the rest scan.

CONCLUSIONS: Vasodilator-stress CT MPI may be feasible in human subjects at a radiation dose similar to NMPI. It identifies areas of abnormal flow reserve and infarction with a high degree of correlation to NMPI as well as to stenoses detected in CTA and ICA.

PMID:

Analysis of Saphenous Vein Graft Lesion Composition Using Near-Infrared Spectroscopy and Intravascular Ultrasonography With Virtual Histology

OBJECTIVES: To examine the composition of saphenous vein graft (SVG) lesions using two novel modalities, near-infrared spectroscopy (NIRS) and intravascular ultrasonography with virtual histology (IVUS-VH).

METHODS: We performed NIRS and IVUS-VH imaging of 23 SVGs in 21 patients undergoing clinically-indicated angiography.

RESULTS: Mean patient and SVG age was 66+/-7 and 10+/-7 years, respectively. SVG lesion location was aorto-ostial in 8 (35%), body in 13 (57%) and distal anastomotic in 2 (9%). Compared to anastomotic lesions, body lesions had larger mean lumen area (6.4+/-1.8mm(2) vs. 4.2+/-6.4mm(2), P=0.02) but similar mean plaque burden (73+/-5% vs. 70+/-10%, P=0.66). A NIRS lipid core plaque was identified in 9 of 13 body lesions vs. 1 of 10 anastomotic lesions (69% vs. 10%, P=0.005). SVG body lesions had higher lipid core burden index (LCBI) compared to anastomotic lesions (184+/-76 vs. 49+/-54, P<0.001). By IVUS-VH, SVG lesions had high % necrotic core (28+/-10%) and % dense calcium (13+/-10%), without any significant difference between body and anastomotic sites. Older SVG age was associated with higher lesion and vessel LCBI (r=0.76 and r=0.64, respectively, P<0.001), but was not associated with IVUS-VH determined plaque composition. Higher HDL-cholesterol was associated with lower lesion LCBI (r=-0.43, P=0.04).

CONCLUSIONS: NIRS-measured lipid core plaque in SVGs increases with increasing SVG age and is infrequent in anastomotic lesions. No association was found between IVUS-VH plaque composition measurements and SVG lesion location or age.

PMID: 20673899

Functional Assessment of Coronary Artery Flow using Adenosine Stress Dual-energy CT: A Preliminary Study

OBJECTIVES: We attempted to assess coronary artery flow using adenosine-stress and dual-energy mode with dual-source CT (DE-CT).

METHODS: Data of 18 patients with suspected coronary arteries disease who had undergone cardiac DE-CT were retrospectively analyzed. The patients were divided into two groups: 10 patients who performed adenosine stress CT, and 8 patients who performed rest CT as controls. We reconstructed an iodine map and composite images at 120 kV (120 kV images) using raw data with scan parameters of 100 and 140 kV. We measured mean attenuation in the coronary artery proximal to the distal portion on both the iodine map and 120 kV images. Coronary enhancement ratio (CER) was calculated by dividing mean attenuation in the coronary artery by attenuation in the aortic root, and was used as an estimate of coronary enhancement. Coronary stenosis was identified as a reduction in diameter of >50% on CT angiogram, and myocardial ischemia was diagnosed by adenosine-stress myocardial perfusion scintigraphy.

RESULTS: The iodine map showed that CER was significantly lower for ischemic territories (0.76 +/- 0.06) or stenosed coronary arteries (0.77 +/- 0.06) than for non-ischemic territories (0.95 +/- 0.21, P = 0.02) or non-stenosed coronary arteries (1.07 +/- 0.33, P < 0.001). The 120 kV images showed no difference in CER between these two groups. Use of CER on the iodine map separated ischemic territories from non-ischemic territories with a sensitivity of 86% and a specificity of 75%.

CONCLUSIONS: Our quantification is the first non-invasive analytical technique for assessment of coronary artery flow using cardiac CT. CER on the iodine map is a candidate method for demonstration of alteration in coronary artery flow under adenosine stress, which is related to the physiological significance of coronary artery disease.

PMID: 20686853

Prospective Randomized Trial of Venous Cardiac Computed Tomographic Angiography for Facilitation of Cardiac Resynchronization Therapy

OBJECTIVES: Cardiovascular computed tomographic angiography (CTA) can visualize the coronary veins. We sought to assess the ability of CTA to facilitate resynchronization therapy (CRT) procedures using a prospective randomized single-center pilot study.

METHODS: Patients underwent CTA for characterization of cardiomyopathy prior to biventricular implantable cardiac-defibrillator implant. Randomization was performed with operator review of the CTA for coronary venous anatomy prior to CRT in one-half of the cases. Invasive coronary venous angiograms were used in all procedures. Analysis included procedure times and utilization of contrast, fluoroscopy, and guide catheters.

RESULTS: Characteristics of the 26 patients enrolled were mean age 55 +/- 11 years, male 76.9%, ischemic etiology 35%, ejection fraction 25 +/- 3%, class III congestive heart failure 100%, and QRS duration 179 +/- 29 ms. Of patients enrolled, 22 had both CTA and procedure initiation. Three patients (two with CTA review and one without CTA review) had aborted procedures due to hemodynamic issues. Analysis of the 22 patients (nine with preprocedure CTA review and 13 without CTA review) demonstrated that preprocedure review of CTA coronary venous anatomy led to significantly decreased procedure times and utilization of contrast, fluoroscopy, and guide catheters.

CONCLUSIONS: Preprocedure review of CTA coronary venous anatomy may lead to decreased procedural times and utilization of contrast, fluoroscopy, and guide catheters. These preliminary results will need to be evaluated in larger heart failure populations undergoing CRT.

PMID: 20579305

High-Pitch Dual-Source CT Angiography of the Aortic Valve-Aortic Root Complex Without ECG-synchronization

OBJECTIVES: To compare image quality and radiation dose of high-pitch computed tomography angiography(CTA) of the aortic valve-aortic root complex with and without prospective ECG-gating compared to a retrospectively ECG-gated standard-pitch acquisition.

METHODS: 120 patients(mean age 68 +/- 13 years) were examined using a 128-slice dual-source CT system using prospectively ECG-gated high-pitch(group A; n = 40), non-ECG-gated high-pitch(group B; n = 40) or retrospectively ECG-gated standard-pitch(C; n = 40) acquisition techniques. Image quality of the aortic root, valve and ascending aorta including the coronary ostia was assessed by two independent readers. Image noise was measured, radiation dose estimates were calculated.

RESULTS: Interobserver agreement was good(kappa = 0.64-0.78). Image quality was diagnostic in 38/40 patients(group A), 37/40(B) and 38/40(C) with no significant difference in number of patients with diagnostic image quality among all groups (p = 0.56). Significantly more patients showed excellent image quality in group A compared to groups B and C(each, p < 0.01). Average image noise was significantly different between all groups(p < 0.05). Mean radiation dose estimates in groups A and B(each; 2.4 +/- 0.3 mSv) were significantly lower compared to group C(17.5 +/- 4.4 mSv; p < 0.01).

CONCLUSIONS: High-pitch dual-source CTA provides diagnostic image quality of the aortic valve-aortic root complex even without ECG-gating at 86% less radiation dose when compared to a standard-pitch ECG-gated acquisition.

PMID: 20677006

Atherosclerotic Plaque Composition: Analysis With Multicolor CT and Targeted Gold Nanoparticles

OBJECTIVES: To investigate the potential of spectral computed tomography (CT) (popularly referred to as multicolor CT), used in combination with a gold high-density lipoprotein nanoparticle contrast agent (Au-HDL), for characterization of macrophage burden, calcification, and stenosis of atherosclerotic plaques.

METHODS: The local animal care committee approved all animal experiments. A preclinical spectral CT system in which incident x-rays are divided into six different energy bins was used for multicolor imaging. Au-HDL, an iodine-based contrast agent, and calcium phosphate were imaged in a variety of phantoms. Apolipoprotein E knockout (apo E-KO) mice were used as the model for atherosclerosis. Gold nanoparticles targeted to atherosclerosis (Au-HDL) were intravenously injected at a dose of 500 mg per kilogram of body weight. Iodine-based contrast material was injected 24 hours later, after which the mice were imaged. Wild-type mice were used as controls. Macrophage targeting by Au-HDL was further evaluated by using transmission electron microscopy and confocal microscopy of aorta sections.

RESULTS: Multicolor CT enabled differentiation of Au-HDL, iodine-based contrast material, and calcium phosphate in the phantoms. Accumulations of Au-HDL were detected in the aortas of the apo E-KO mice, while the iodine-based contrast agent and the calcium-rich tissue could also be detected and thus facilitated visualization of the vasculature and bones (skeleton), respectively, during a single scanning examination. Microscopy revealed Au-HDL to be primarily localized in the macrophages on the aorta sections; hence, the multicolor CT images provided information about the macrophage burden.

CONCLUSIONS: Spectral CT used with carefully chosen contrast agents may yield valuable information about atherosclerotic plaque composition.

PMID: 20668118

Hakki’s Formula for Measurement of Aortic Valve Area by Magnetic Resonance Imaging

OBJECTIVES: Hakki’s formula (simplified Gorlin formula) can be used during cardiac catheterization to calculate the stenosed cardiac valve areas and can also be adapted to magnetic resonance imaging (MRI) to measure the stenosed cardiac valve areas. We evaluated the reliability of this approach to determine the severity of aortic stenosis compared to the continuity equation using transthoracic echocardiography and planimetry using MRI.

METHODS: We included all eligible symptomatic patients with known aortic stenosis referred to our department during a 1-year period. The aortic valve area (AVA) was estimated using Hakki’s formula (MRI), planimetry (MRI), and the continuity equation (transthoracic echocardiography). The agreement among the measurement methods was analyzed using the Bland-Altman method.

RESULTS: A total of 63 patients were included (mean age 72 +/- 10 years, 35 men [56%]). The mean AVA was 0.70 +/- 0.21 cm(2) using the continuity equation (transthoracic echocardiography), 0.67 +/- 0.18 cm(2) using planimetry (MRI), and 0.64 +/- 0.21 cm(2) using Hakki’s formula (MRI). The mean difference was 0.03 cm(2) (95% limits of agreement -0.32 to 0.25) between planimetry and the continuity equation, 0.05 cm(2) (95% limits of agreement -0.40 to 0.29) between Hakki’s formula and the continuity equation, 0.02 cm(2) (95% limits of agreement -0.20 to 0.25) between Hakki’s formula and planimetry. The inter- and intraobserver reproducibility using Hakki’s formula was excellent.

CONCLUSIONS: In conclusion, measurement of the AVA using Hakki’s formula yielded similar results to those obtained using planimetry and slightly different ones from those obtained using the continuity equation. However, Hakki’s formula has the advantage of being easy to use, fast, and reproducible and can be used regardless of the status of the valve (in contrast to planimetry).

PMID: 20599011