Accuracy of Dual-Source CT in the Characterization of Non-Calcified Plaque: Use of a Colour-Coded Analysis Compared with Virtual Histology Intravascular Ultrasound

OBJECTIVE: Non-invasive assessment of plaque volume and composition is important for risk stratification and long-term studies of plaque stabilisation. Our aim was to evaluate dual-source computed tomography (DSCT) and colour-coded analysis in the quantification and classification of coronary atheroma.

METHODS: DSCT and virtual histology intravascular ultrasound (IVUS-VH) were prospectively performed in 14 patients. 22 lesions were compared in terms of plaque volume, maximal per cent vessel stenosis and percentages of fatty, fibrous or calcified components. Plaque characterisation was performed with software that automatically segments luminal or outer vessel boundaries and uses CT attenuation for a colour-coded plaque analysis.

RESULTS: Good correlation was found for percent vessel stenosis in DSCT (53+/-13%) and IVUS (51+/-14%; r(2) = 0.70). Mean volumes for entire plaque and non-calcified atheroma were 68.5+/-33 mm(3) and 56.7+/-30 mm(3), respectively, in DSCT and 60.8+/-29 mm(3) and 55.8+/-26 mm(3), respectively, in IVUS. Mean percentages of fatty, fibrous or calcified components were 28.2+/-6%, 53.2+/-9% and 18.7+/-13%, respectively, in DSCT and 29.9+/-5%, 55.3+/-12% and 14.4+/-9%, respectively, in IVUS-VH. Significant overestimation was present for the entire plaque and the volume of calcified plaque (p = 0.03; p = 0.0004). Although good correlation with IVUS was obtained for the entire plaque (r(2) = 0.76) and non-calcified plaque volume (r(2) = 0.84), correlation proved very poor and insignificant for percentage plaque composition. Interclass correlation coefficients for non-calcified plaque volume and percentages of fatty, fibrous or calcified components were 0.99, 0.99, 0.95 and 0.98, respectively, and intraclass coefficients were 0.98, 0.93, 0.98 and 0.99, respectively.

CONCLUSION: We found that using Hounsfield unit-based analysis, DSCT allows for accurate quantification of non-calcified plaque. Although percentage plaque composition proves highly reproducible, it is not correlated with IVUS-VH.

PMID: 19332517

Assessment of Myocardial Edema by Computed Tomography in Myocardial Infarction

OBJECTIVES: The aim of this study was to analyze whether cardiac computed tomography (CT) permits the assessment of myocardial edema in acute myocardial infarction (MI). Background: Several studies proved the value of detecting myocardial edema from T2-weighted cardiac magnetic resonance (CMR) for differentiating acute from chronic MI. Computed tomography is suited for depicting MI, but there are no data on CT imaging of myocardial edema. We hypothesized that areas of reduced attenuation in acute MI may correspond to edema.

METHODS: In 7 pigs (55.2 +/- 7.3 kg), acute MI was induced using a closed chest model. Animals underwent unenhanced arterial and late-phase dual source computed tomography (DSCT) followed by T2-weighted and delayed contrast-enhanced CMR. Animals were sacrificed, and the excised hearts were stained with 2,3,5-triphenyltetrazolin chloride (TTC). Size of MI, contrast-to-noise ratio, and percent signal difference were compared among the different imaging techniques with concordance-correlation coefficients (rho(c)), Bland-Altman plots, and analysis of variance for repeated measures.

RESULTS: Infarction was transmural on all slices. On unenhanced, arterial, and late-phase DSCT, mean sizes of MI were 27.2 +/- 8.5%, 20.1 +/- 6.9%, and 23.1 +/- 8.2%, respectively. Corresponding values on T2-weighted and delayed enhanced CMR were 28.5 +/- 7.8% and 22.2 +/- 7.7%. Size of MI on TTC staining was 22.6 +/- 7.8%. Best agreement was observed when comparing late-phase CT (rho(c) = 0.9356) and delayed enhanced CMR (rho(c) = 0.9248) with TTC staining. There was substantial agreement between unenhanced DSCT and T2-weighted CMR (rho(c) = 0.8629). Unenhanced DSCT presented with the lowest percent signal difference (46.0 +/- 18.3) and the lowest contrast-to-noise ratio (4.7 +/- 2.0) between infarcted and healthy myocardium.

CONCLUSIONS: Unenhanced DSCT permits the detection of myocardial edema in large acute MI. Further studies including smaller MI in different coronary artery territories and techniques for improving the contrast-to-noise ratio are needed.

PMID: 19833305

CT of Coronary Artery Disease – State of the Art

Technical innovation is rapidly improving the clinical utility of cardiac computed tomography (CT) and will increasingly address current technical limitations, especially the association of this test with relatively high levels of radiation. Guidelines for appropriate indications are in place and are evolving, with an increasing evidence base to ensure the appropriate use of this modality. New technologies and new applications, such as myocardial perfusion imaging and dual-energy CT, are being explored and are widening the scope of coronary CT angiography from mere coronary artery assessment to the integrative analysis of cardiac morphology, function, perfusion, and viability. The scientific evaluation of coronary CT angiography has left the stage of feasibility testing and increasingly, evidence-based data are accumulating on outcomes, prognosis, and cost-effectiveness. In this review, these developments will be discussed in the context of current pivotal transitions in cardiovascular disease management and their potential influence on the current role and future fate of coronary CT angiography will be examined.

PMID: 19864526

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0-T: A Comparative Study with X-Ray Angiography in a Single Center

OBJECTIVES: The purpose of this study was to prospectively evaluate the diagnostic performance of 3.0-T contrast-enhanced whole-heart coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease (CAD). Background: A slow-infusion, contrast-enhanced whole-heart CMRA approach has recently been developed at 3.0-T. The accuracy of this technique has not yet been determined among patients with suspected CAD.

METHODS: The 3.0-T contrast-enhanced whole-heart CMRA was performed in 69 consecutive patients. An electrocardiography-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used to acquire isotropic whole-heart CMRA with slow infusion of 0.2 mmol/kg gadobenate dimeglumine. The diagnostic accuracy of whole-heart CMRA in detecting significant stenoses (> or =50%) was evaluated using X-ray angiography as the reference.

RESULTS: The CMRA examinations were successfully completed in 62 patients. Acquisition time of whole-heart CMRA procedure was 9.0 +/- 1.9 min. The 3.0-T whole-heart CMRA correctly identified significant CAD in 32 patients and correctly ruled out CAD in 23 patients. The sensitivity, specificity, and accuracy of whole-heart CMRA for detecting significant stenoses were 91.6% (87 of 95), 83.1% (570 of 686), and 84.1% (657 of 781), respectively, on a per-segment basis. These values were 94.1% (32 of 34), 82.1% (23 of 28), and 88.7% (55 of 62), respectively, on a per-patient basis.

CONCLUSIONS: Contrast-enhanced whole-heart CMRA with 3.0-T allows for the accurate detection of coronary artery stenosis with high sensitivity and moderate specificity.

PMID: 19555843

Relationship Between Baseline Coronary Calcium Score and Demonstration of Coronary Artery Stenoses During Follow-Up MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES: The MESA (Multi-Ethnic Study of Atherosclerosis) is a population-based study of 6,814 men and women. We sought to analyze the relationship between the extent of coronary artery calcium (CAC) at baseline and the severity of coronary stenoses in clinically indicated coronary angiography studies during follow-up. Background: CAC is an established predictor of major cardiovascular events. Yet, the relationship between CAC and the distribution and severity of coronary artery stenoses has not been widely explored.

METHODS: All MESA participants underwent noncontrast enhanced cardiac computed tomography during enrollment to determine baseline CAC. We analyzed 175 consecutive angiography reports from participants who underwent coronary catheterization for clinical indications during a median follow-up period of 18 months. The relationship between baseline CAC and the severity of coronary stenosis detected in coronary angiographies was determined.

RESULTS: Baseline Agatston score was 0 in only 7 of 175 (4%) MESA participants who underwent invasive angiography during follow-up. When coronary arteries were studied separately, 13% to 18% of coronary arteries with >75% stenosis had 0 calcium mass scores at baseline. There was close association between baseline calcium mass score and the severity of stenosis in each of the coronary arteries (test for trend, p < 0.001). For example, mean calcium mass scores for <50%, 50% to 74%, and >75% stenosis in the left anterior descending coronary artery were 105.1 mg, 157.2 mg, and 302.2 mg, respectively (p < 0.001). Finally, there was a direct relationship between the total Agatston Score at baseline and the number of diseased vessels (test for trend, p < 0.001).

CONCLUSIONS: The majority of patients with clinically indicated coronary angiography during follow-up had detectable coronary calcification at baseline. Although there is a significant relationship between the extent of calcification and mean degree of stenosis in individual coronary vessels, 16% of the coronary arteries with significant stenoses had no calcification at baseline.

PMID: 19833306

CT-Guided Tube Pericardiostomy: A Safe and Effective Technique in the Management of Postsurgical Pericardial Effusion

OBJECTIVES: The purpose of this study was to analyze the efficacy and examine the competitive cost of CT-guided tube pericardiostomy in the management of symptomatic postsurgical pericardial effusion.

METHODS: Over a 4-year period, 36 patients with symptomatic pericardial effusion were treated with CT-guided percutaneous placement of an indwelling pericardial catheter, for a total of 39 CT-guided tube pericardiostomy procedures. Thirty-three patients (92%) had undergone major cardiothoracic surgery, and three patients (8%) had undergone minimally invasive procedures. The medical records were retrospectively reviewed for clinical presentation, surgical history, imaging studies performed, procedural details, fluid characterization, and outcome. Charge comparison was performed with the American Medical Association Current Procedural Terminology codes and information acquired from the billing department at our facility.

RESULTS: All 39 CT-guided tube pericardiostomy procedures were performed successfully without clinically significant complications. After 33 of the 39 procedures (85%), symptoms did not recur after the catheter was removed. Three of 36 patients (8%) had a recurrence of pericardial effusion. Comparison of procedure charges showed an 89% saving over intraoperative pericardial window procedures and no significant difference compared with ultrasound-guided tube pericardiostomy. Eight patients (21% of procedures) needed pleural drainage procedures, all of which were performed in the CT suite immediately after the tube pericardiostomy procedure.

CONCLUSIONS: CT-guided tube pericardiostomy is a safe and effective alternative to surgical drainage in the care of patients with clinically significant pericardial effusion after cardiothoracic surgery and has the additional benefit of substantial cost savings.

PMID: 19770301

Radiation Dose Reduction by Using 100-kV Tube Voltage in Cardiac 64-slice Computed Tomography: A Comparative Study

OBJECTIVES: To evaluate a 100-kilovoltage (kV) tube voltage protocol regarding radiation dose and image quality, in comparison with the standard 120kV setting in cardiac computed tomography angiography (CCTA).

METHODS: 103 patients undergoing retrospective ECG-gated helical 64-slice CCTA were enrolled (100kV group: 51 patients; 120kV group: 52 patients). Inclusion criteria were: (1) BMI <28kg/m(2); (2) weight <85kg; (3) coronary calcium score <300 Agatston Units (AU). Quantitative image quality parameters were calculated [image noise, contrast-to-noise ratio (CNR), intracoronary CT-attenuation (HU)]. Each coronary artery segment (AHA/ACC-16-segments-classification) was evaluated for image quality on a 4-point scale.

RESULTS: There was no statistical difference in age, gender, BMI and eff. tube current (mAs), and the use of ECG-tube current modulation (50.9% vs. 50% of patients) between both groups. 84.2% of patients in the 100kV group had zero calcium score or less than100AU, the remaining had between 100 and 300AU. The effective radiation dose was significantly lower in the 100kV group with mean 7.1mSv+/-2.4 (range, 3.4-11.1) compared to the 120kV group with 13.4mSv+/-5.2 (range, 6.3-22.7) (p<0.001) (dose reduction, 47%). In the 100kV group, the use of ECG-dependent tube current modulation reduced the radiation exposure (by 44.8%) to 5.3mSv+/-1.1 (range, 3.4-8.5mSv) (p<0.001), the dose without was 9.6mSv+/-1.1 (range, 6.3-11.1). Image noise in the coronary arteries was not different between both groups with 29.8 and 30.5SD (HU), respectively. CNR in the 100kV group was with 20.9+/-6.8 for the coronary arteries and with 19.9+/-5.9 for the aorta similar to the 120kV group. Intraluminal CT-attenuation (HU) of the coronary arteries were higher in the 100kV group (p25kg/m(2)).

CONCLUSIONS: The 100kV protocol significantly reduces the radiation dose in CCTA in patients with a low BMI <25kg/m(2) and a low calcium load while maintaining high image quality and the advantages of helical scan algorithm.

PMID: 19671491

Endovascular Abdominal Aortic Aneurysm Repair: Nonenhanced Volumetric CT for Follow-up

OBJECTIVES: To evaluate the clinical usefulness of volumetric analysis at nonenhanced computed tomography (CT) as the sole method with which to follow up endovascular abdominal aortic aneurysm repair (EVAR) and to identify endoleaks causing more than 2% volumetric increase from the previous volume determination.

METHODS: The study had institutional review board approval. Images were reviewed retrospectively in a HIPAA-compliant manner for 230 CT studies in 70 patients (11 women, 59 men; mean age, 74 years) who underwent EVAR. The scannning protocol consisted of three steps: (a) contrast material-enhanced CT angiography before endovascular stent placement, (b) contrast-enhanced CT angiography 0-3 months after repair to depict immediate complications, and (c) nonenhanced CT at 3, 6, and 12 months after repair. At each follow-up visit, immediate aortic volume analysis was performed. If the interval volumetric change was 2% or less, no further imaging was performed. If the volume increased by more than 2% on the nonenhanced CT image, contrast-enhanced CT angiography was performed immediately to identify the suspected endoleak. Confidence intervals (CIs) were obtained by using bootstrapping to account for repeated measurements in the same patients.

RESULTS: Mean volume decrease was -3.2% (95% CI: -4.7%, -1.9%) in intervals without occurrence of a clinically relevant endoleak (n = 183). Types I and III high-pressure endoleaks (n = 10) showed a 10.0% (95% CI: 5.0%, 18.2%) interval volumetric increase. Type II low-pressure endoleaks (n = 37) showed a 5.4% (95% CI: 4.6%, 6.2%) interval volumetric increase. Endoleaks associated with minimal aortic volume increase of less than 2% did not require any intervention. This protocol reduced radiation exposure by approximately 57%-82% in an average-sized patient.

CONCLUSIONS: Serial volumetric analysis of aortic aneurysm with nonenhanced CT serves as an adequate screening test for endoleak, causing volumetric increase of more than 2% from the volume seen at the previous examination.

PMID: 19703867

Prediction of All-Cause Mortality From Global Longitudinal Speckle Strain: Comparison with Ejection Fraction and Wall Motion Scoring

OBJECTIVES: Although global left ventricular systolic function is an important determinant of mortality, standard measures such as ejection fraction (EF) and wall motion score index (WMSI) have important technical limitations. The aim of this study was to compare global longitudinal speckle strain (GLS), an automated technique for measurement of long-axis function, with EF and WMSI for the prediction of mortality.

METHODS: Of 546 consecutive individuals undergoing echocardiography for assessment of resting left ventricular function, 91 died over a period of 5.2±1.5 years. In addition to Simpson biplane EF, WMSI was determined by 2 experienced readers and GLS was calculated from 3 standard apical views using 2D speckle tracking. The incremental value of EF, WMSI, and GLS to significant clinical variables was assessed in nested Cox models.

RESULTS: Clinical factors associated with outcome (model x²=20.2) were age (hazard ratio [HR], 1.46; P<0.01), diabetes (HR, 1.88; P=0.01), and hypertension (HR, 1.59; P<0.05). Although addition of EF (HR, 1.23; P=0.03) or WMSI (HR, 1.28; P<0.01) added to the predictive power of clinical variables, the addition of GLS (HR, 1.45; P<0.001) caused the greatest increment in model power (x²=34.9, P<0.001). GLS also provided incremental value in subgroups with EF >35% and those with and without wall motion abnormalities. A GLS > –12% was found to be equivalent to an EF <35 for the prediction of prognosis. Intraobserver and interobserver variations for EF and GLS were similar.

CONCLUSIONS: GLS is a superior predictor of outcome to either EF or WMSI and may become the optimal method for assessment of global left ventricular systolic function.

PMID: 19808623

Echocardiography in Percutaneous Valve Therapy: State-of-the-Art Paper

Echocardiography has played a critical role in valve reconstructive surgery and more recently in developments in percutaneous techniques for mitral valve repair and aortic valve implantation. A combination of transthoracic echocardiography and transesophageal echocardiography (TEE) provide diagnostic and screening data pre-procedure, intraprocedural guidance, and assessment of valve function and left ventricular reverse remodeling post-percutaneous valve procedures. The role of intracardiac echocardiography and live 3-dimensional TEE in percutaneous valve interventions is evolving. This review summarizes the role of echocardiography during percutaneous device-based valve procedures.

PMID: 19833314

Determinants of Significant Paravalvular Regurgitation After Transcatheter Aortic Valve: Implantation Impact of Device and Annulus Discongruence

OBJECTIVES: The aim of this study was to assess prosthesis/annulus discongruence and its impact on the occurrence of significant aortic regurgitation (AR) immediately after transcatheter aortic valve implantation (TAVI). Background: Paravalvular AR might occur after TAVI, but its determinants remain unclear.

METHODS: Comprehensive echocardiographic examinations were performed in 74 patients who underwent TAVI with a balloon expandable device. Congruence between annulus and device was appraised with the cover index: 100 x (prosthesis diameter – transesophageal echocardiography annulus diameter)/prosthesis diameter.

RESULTS: At baseline aortic valve area was 0.67 +/- 0.2 cm(2), and mean gradient was 50 +/- 15 mm Hg. The TAVI used transfemoral approach in 46 patients (62%) and transapical access in 28 (38%). Prosthesis size was 23 mm in 24 patients (34%) and 26 mm in 50 patients (66%). After TAVI, paravalvular AR was absent in 5 patients (7%), graded 1/4 in 53 (72%), 2/4 in 12 (16%), and 3/4 in 4 (5%). Occurrence of AR >or=2/4 was related to greater patient height, larger annulus, and smaller cover index (all p < 0.002) but not to ejection fraction, severity of stenosis, or prosthesis size. AR >or=2/4 was never observed in patients with aortic annulus <22 mm or with a cover index >8%. Significant improvements were observed from the first 20 cases (AR >or=2/4, 40%) to the last 54 (AR >2/4, 15%) (p = 0.02). In multivariate analysis, independent predictors of AR >2/4 were low cover index (odds ratio: 1.22; per confidence interval: 1.03 to 1.51 per 1% decrease, p = 0.02) and first versus last procedures (odds ratio: 2.24; 95% confidence interval: 1.07 to 5.22, p = 0.03).

CONCLUSIONS: Our study shows that the occurrence of AR >2/4 is related to prosthesis/annulus discongruence even after adjustment for experience. Hence, to minimize paravalvular AR, appropriate annular measurements and prosthesis sizing are critical.

PMID: 19778769

Accuracy of Computed Tomographic Angiography for Stenosis Quantification using Qantitative Coronary Angiography or Intravascular Ultrasound as the Gold Standard

OBJECTIVES: Computed tomographic angiography (CTA) is considered to have limited accuracy for quantifying exact percent diameter stenosis in coronary arteries. However, most studies evaluating CTA use quantitative coronary angiography (QCA) as the gold standard, a technique with its own limitations. We sought to determine whether CTA measurements of stenosis severity correlate better with intravascular ultrasound (IVUS) than with QCA.

METHODS: Luminal dimensions of 67 de novo coronary lesions were measured by CTA, IVUS, and QCA. IVUS was performed when lesion severity by angiography was equivocal.

RESULTS: Mean percent diameter stenosis by QCA was 51 +/- 9.8% and mean IVUS minimal luminal area was 3.8 +/- 1.8 mm(2). There was a moderate correlation between CTA minimal luminal area and IVUS minimal luminal area (r(2) = 0.41, p <0.001), but no relation between CTA and QCA measurements of minimal luminal diameter (r(2) = 0.01, p = 0.57) or diameter stenosis (r(2) = 0.02, p = 0.31). There was also no relation between IVUS minimal luminal area and QCA diameter stenosis (r(2) = 0.01, p = 0.50). When lesions with moderate or severe calcification were excluded, the correlation between CTA minimal luminal area and IVUS minimal luminal area was good (r(2) = 0.68, p <0.001).

CONCLUSIONS: In this cohort of patients with intermediate-grade lesions on cardiac catheterization, absolute measurements of stenosis severity on CTA correlated with IVUS but not with QCA. Our findings suggest that limitations of quantitative coronary angiography as a gold standard need to be considered in studies evaluating the accuracy of coronary CTA.

PMID: 19801022

On the Inappropriateness of Noninvasive Multidetector Computed Tomography Coronary Angiography to Trigger Coronary Revascularization: A Comparison with Invasive Angiography

OBJECTIVES: Our purpose was to evaluate the appropriateness of multidetector computed tomography angiography (MDCTA) as an anatomical standard for decision making in patients with known or suspected coronary artery disease. Background: Although correlative studies between MDCTA and coronary angiography (CA) show good agreement, MDCTA visualizes plaque burden and calcifications well before luminal dimensions are encroached.

METHODS: Pressure-derived fractional flow reserve (FFR) was obtained in 81 patients (116 vessels) who underwent both CA and MDCTA. Segments were visually graded for stenosis severity as: G0 = normal, G1 = nonobstructive (<50% diameter reduction), and G2 = obstructive (> or =50% diameter reduction).

RESULTS: Concordance between segmental severity scores by MDCTA and CA was good (k = 0.74; 95% confidence interval: 0.56 to 0.92). Diagnostic performance of MDCTA for detection of functionally significant stenosis based on FFR was low (sensitivity 79%; specificity 64%; positive likelihood ratio 2.2; negative likelihood ratio 0.3). Revascularization was considered appropriate in the presence of reduced FFR (< or =0.75). Decision making based on MDCTA guidance would result in revascularization in the absence of ischemia in 22% of patients (18 of 81) and inappropriate deferral in 7% (6 of 81), while revascularization in the absence of ischemia would be 16% (13 of 81) and inappropriate deferral 12% (10 of 81) with decisions guided by CA. Combined evaluation of stenosis severity using both anatomy (with either CA or MDCTA) and function (with FFR) yields the highest proportion of appropriate decisions: 90% and 91%, respectively (p = 0.0001 vs. CA only, p = 0.0001 vs. MDCTA only).

CONCLUSIONS: Similar to CA, anatomical assessment of coronary stenosis severity by MDCTA does not reliably predict its functional significance.

PMID: 19539260

First Head-to-Head Comparison of Effective Radiation Dose from Low-Dose 64-Slice CT with Prospective ECG-Triggering versus Invasive Coronary Angiography

OBJECTIVES: To compare effective radiation dose of low-dose 64-slice CTCA using prospective ECG-triggering versus diagnostic invasive coronary angiography (CA). Background: Reduction of radiation burden of multidetector computed tomography coronary angiography (CTCA) has remained an important task.

METHODS: 42 patients referred for elective invasive CA owing to suspected coronary artery disease (CAD) were prospectively enrolled to undergo a low-dose CTCA without calcium scoring within the same day before CA. Dose-area product of diagnostic invasive CA and dose-length product of CTCA were measured, converted into effective radiation dose and compared using Mann-Whitney U tests. In addition, accuracy of CTCA to detect CAD (coronary artery narrowing >50%) was assessed using invasive CA as standard of reference. On an intention-to-diagnose basis all non-evaluative vessels were included in the analysis and censored as positive.

RESTULTS: The estimated mean effective radiation dose was 8.5 (4.4) mSv (range 1.4–20.5 mSv) for diagnostic invasive CA, and 2.1 (0.7) mSv (range 1.0–3.3 mSv) for CTCA (p<0.001). 19 patients (42.9%) had no CAD by invasive CA. 40 (95.2%) patients have been correctly classified as having CAD (23/23) or no CAD (17/19). Over 97% (551/567) of segments were evaluable. Vessel-based analysis revealed sensitivity, specificity, positive and negative predictive value of 94.2% (CI 0.8% to 1.0%), 94.8% (CI 09% to 1.0%), 89.0% (CI 0.8% to 1.0%), 97.4% (CI 09% to 1.0%) and an accuracy of 94.6%.

CONCLUSIONS: Low dose CTCA allows evaluation of CAD with high accuracy, but delivers a significantly less effective radiation dose to patients compared to diagnostic invasive CA.

PMID: 19581273