ECG-Gated Dual-Source CT for Detection of Left Atrial Appendage Thrombus in Patients Undergoing Catheter Ablation for Atrial Fibrillation

OBJECTIVES: Left atrial ablation is increasingly used to treat patients with symptomatic atrial fibrillation (AF). Prior to ablation, exclusion of left atrial appendage (LAA) thrombus is important. Whether ECG-gated dual-source computed tomography (DSCT) provides a sensitive means of detecting LAA thrombus in patients undergoing percutaneous AF ablation is unknown. Thus, we sought to determine the utility of ECG-gated DSCT in detecting LAA thrombus in patients with AF.

METHODS: A total of 255 patients (age 58 +/- 11 years, 78% male, ejection fraction 58 +/- 9%) who underwent ECG-gated DSCT and transesophageal echocardiography (TEE) prior to AF ablation between February 2006 and October 2007 were included. CHADS2 score and demographic data were obtained prospectively. Gated DSCT images were independently reviewed by two cardiac imagers blinded to TEE findings. The LAA was either defined as normal (fully opacified) or abnormal (under-filled) by DSCT.

RESULTS: An under-filled LAA was identified in 33 patients (12.9%), of whom four had thrombus confirmed by TEE. All patients diagnosed with LAA thrombus using TEE also had an abnormal LAA by gated DSCT. Thus, sensitivity and specificity for gated DSCT were 100% and 88%, respectively. No cases of LAA filling defects were observed in patients <51 years old with a CHADS2 of 0.

CONCLUSIONS: In patients referred for AF ablation, thrombus is uncommon in the absence of additional risk factors. Gated DSCT provides excellent sensitivity for the detection of thrombus. Thus, in AF patients with a CHADS2 of 0, gated DSCT may provide a useful stand-alone imaging modality.

PMID: 20809409

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

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

Dipyridamole Stress and Rest Myocardial Perfusion by 64-Detector Row Computed Tomography in Patients With Suspected Coronary Artery Disease

OBJECTIVES: Recently, stress myocardial computed tomographic perfusion (CTP) was shown to detect myocardial ischemia. Our main objective was to evaluate the feasibility of dipyridamole stress CTP and compare it to single-photon emission computed tomography (SPECT) to detect significant coronary stenosis using invasive conventional coronary angiography (CCA; stenosis >70%) as the reference method.

METHODS: Thirty-six patients (62 +/- 8 years old, 20 men) with previous positive results with SPECT (<2 months) as the primary inclusion criterion and suspected coronary artery disease underwent a customized multidetector-row CT protocol with myocardial perfusion evaluation at rest and during stress and coronary CT angiography (CTA). Multidetector-row computed tomography was performed in a 64-slice scanner with dipyridamole stress perfusion acquisition before a second perfusion/CT angiographic acquisition at rest. Independent blinded observers performed analysis of images from CTP, CTA, and CCA. All 36 patients completed the CT protocol with no adverse events (mean radiation dose 14.7 +/- 3.0 mSv) and with interpretable scans.

RESULTS: CTP results were positive in 27 of 36 patients (75%). From the 9 (25%) disagreements, 6 patients had normal coronary arteries and 2 had no significant stenosis (8 false-positive results with SPECT, 22%). The remaining patient had an occluded artery with collateral flow confirmed by conventional coronary angiogram. Good agreement was demonstrated between CTP and SPECT on a per-patient analysis (kappa 0.53). In 26 patients using CCA as reference, sensitivity, specificity, and positive and negative predictive values were 88.0%, 79.3%, 66.7%, and 93.3% for CTP and 68.8, 76.1%, 66.7%, and 77.8%, for SPECT, respectively (p = NS).

CONCLUSIONS: In conclusion, dipyridamole CT myocardial perfusion at rest and during stress is feasible and results are similar to single-photon emission CT scintigraphy. The anatomical-perfusion information provided by this combined CT protocol may allow identification of false-positive results by SPECT.

PMID: 20643238

Aortic Stiffness Independently Predicts Exercise Capacity in Hypertrophic Cardiomyopathy: A Multimodality Imaging Study

PMID:

Carotid Atherosclerosis Does Not Predict Coronary, Vertebral, or Aortic Atherosclerosis in Patients With Acute Stroke Symptoms

OBJECTIVES: The purpose of this study was to determine whether significant atherosclerotic disease in the carotid arteries predicts significant atherosclerotic disease in the coronary arteries, vertebral arteries, or aorta in patients with symptoms of acute ischemic stroke.

METHODS: Atherosclerotic disease was imaged using CT angiography in a prospective study of 120 consecutive patients undergoing emergent CT evaluation for symptoms of stroke. Using a comprehensive CT angiography protocol that captured the carotid arteries, coronary arteries, vertebral arteries, and aorta, we evaluated these arteries for the presence and severity of atherosclerotic disease. Significant atherosclerotic disease was defined as >50% stenosis in the carotid, coronary, and vertebral arteries, or >4 mm thickness and encroaching in the aorta. Presence of any and significant atherosclerotic disease was compared in the different types of arteries assessed.

RESULTS: Of these 120 patients, 79 had CT angiography examinations of adequate image quality and were evaluated in this study. Of these 79 patients, 33 had significant atherosclerotic disease. In 26 of these 33 patients (79%), significant disease was isolated to 1 type of artery, most often to the coronary arteries (N=14; 54%). Nonsignificant atherosclerotic disease was more systemic and involved multiple arteries.

CONCLUSIONS: Significant atherosclerotic disease in the carotid arteries does not predict significant atherosclerotic disease in the coronary arteries, vertebral arteries, or aorta in patients with symptoms of acute ischemic stroke. Significant atherosclerotic disease is most often isolated to 1 type of artery in these patients, whereas nonsignificant atherosclerotic disease tends to be more systemic.

PMID: 20595672

Diabetes: Prognostic Value of CT Coronary Angiography: Comparison With a Nondiabetic Population

OBJECTIVES: To evaluate the prognostic value of multidetector computed tomographic (CT) coronary angiography in a diabetic population known to have or suspected of having coronary artery disease (CAD) compared with that in nondiabetic individuals.

METHODS: Institutional review board approval and patient informed consent were obtained. Three hundred thirteen patients with type 2 diabetes mellitus (DM) and 303 patients without DM underwent unenhanced 64-detector row CT, at which a calcium score was obtained, followed by CT angiography. Multidetector CT coronary angiograms were retrospectively classified as normal, showing nonobstructive CAD (<50% luminal narrowing), or showing obstructive CAD (>50% luminal narrowing). During follow-up after CT angiography, major events (cardiac death, nonfatal myocardial infarction, and unstable angina requiring hospitalization) and total events (major events plus coronary revascularizations) were recorded for each patient. Cox proportional hazards analysis and Kaplan-Meier analysis were used to compare survival rates.

RESULTS: In the group of 313 patients with DM, there were 213 men, and the mean age was 62 years +/- 11 (standard deviation). In the group of 303 patients without DM, there were 203 men, and the mean age was 63 years +/- 11. The mean number of diseased segments (5.6 vs 4.4, P = .001) and the rate of obstructive CAD (51% vs 37%, P < .001) were higher in patients with DM. Patients were followed up for a mean of 20 months +/- 5.4 (range, 6-44 months). At multivariate analysis, DM (P < .001) and evidence of obstructive CAD (P < .001) were independent predictors of outcome. Obstructive CAD remained a significant multivariate predictor for both patients with DM and patients without DM. In both patients with DM and patients without DM with absence of disease, the event rate was 0%. The event rate increased to 36% in patients without DM but with obstructive CAD and was highest (47%) in patients with DM and obstructive CAD.

CONCLUSIONS: In both patients with DM and patients without DM, multidetector CT coronary angiography provides incremental prognostic information over baseline clinical variables, and the absence of atherosclerosis at CT coronary angiography is associated with an excellent prognosis. Multidetector CT coronary angiography might be a clinically useful tool for improving risk stratification in both patients with DM and patients without DM.

PMID: 20574086

Low-Dose Prospective ECG-Triggering Dual-Source CT Angiography in Infants and Children With Complex Congenital Heart Disease: First Experience

OBJECTIVE: To explore the clinical value of low-dose prospective ECG-triggering dual-source CT (DSCT) angiography in infants and children with complex congenital heart disease (CHD) compared with transthoracic echocardiography (TTE).

METHODS: Thirty-five patients (mean age: 16 months, range: 2 months to 6 years; male 15; mean weight: 12 kg) underwent low-dose prospective ECG-triggering DSCT angiography and TTE. Surgeries were performed in 29 patients, and conventional cardiac angiography (CCA) was performed in 8 patients. The accuracy was calculated based on the surgical and/or CCA findings. The overall imaging quality was evaluated on a five-point scale.

RESULTS: A total of 146 separate cardiovascular deformities were confirmed. DSCT missed three atrial septal defects and a patent ductus arteriosus. The accuracy of DSCT angiography and TTE was 97.3% (142/146) and 92.5% (135/146), respectively. Overall test parameters for DSCT angiography and TTE were similar (sensitivity, 97.3% vs 92.5%; specificity, 99.8% vs 99.8%). The average subjective image quality score was 4.3 +/- 0.7. The mean effective dose was 0.38 +/- 0.09 mSv.

CONCLUSIONS: Prospective ECG-triggering DSCT angiography with a very low effective radiation dose allows the accurate diagnosis of anomalies in infants and children with complex CHD compared with TTE. It has great promise to become a commonly used second-line technique for complex CHD.

PMID: 20532783

“Device Landing Zone” Calcification, Assessed by MSCT, as a Predictive Factor for Pacemaker Implantation After TAVI

OBJECTIVES: After trans-catheter aortic valve implantation (TAVI), the need for post-interventional pacemaker (PM) implantation can occur in as many as 10%-50% of cases, but it is not yet clear, how this need can be predicted. The aim of this study was to assess the possible predictive factors of post TAVI PM implantation, based on Computed Tomography (CT) measured aortic valve calcification and its distribution.

METHODS: We prospectively analyzed 81 consecutive symptomatic patients with severe AS scheduled for TAVI using the CoreValve prosthesis (Medtronic, Minneapolis, USA). In all patients, a native and contrast-enhanced multi-slice cardiac CT was performed pre-interventionally, estimating calcification load of the native valve cusps and of the adjacent outflow tract (so called “device landing zone” – DLZ) by the Agatston Score (AgS). Objective, computer-evaluated, pre-procedural ECG-analysis was performed with regards to pre-existing conduction abnormalities. Transthoracic echocardiography was performed pre and post TAVI.

RESULTS: TAVI was successful in all cases. PM implantation was deemed necessary in altogether 32 patients, out of 67 without a PM pre-TAVI (32/67, 47%). Various parameters were tested as predictors of post TAVI PM in a multivariate logistic regression analysis model.Female sex (p=0,005) and depressed EF (p=0,023) showed a significant correlation. PM implantation correlated also to the DLZ calcification, as assessed by CT (p=0,004). This model leads to an AUC (area under the ROC -receiver operator characteristics – curve) of 0,83.

CONCLUSION: Calcium amount in the CoreValve DLZ in combination with clinical data could predict the need for post TAVI PM implantation.

PMID: 20506410

Cardiovascular Imaging With Computed Tomography: Responsible Steps to Balancing Diagnostic Yield and Radiation Exposure

Cardiovascular computed tomography (CT) is at the center of the risk-benefit debate about ionizing radiation exposure to the public from medical procedures. Although the risk has been sensationalized, the cardiovascular CT community has responded to the scrutiny by increasing efforts to ensure the responsible use of this young technology. Efforts to date have primarily included the development of appropriateness criteria and the implementation of dose-lowering techniques. Still needed is the development of standards that incorporate radiation exposure optimization into scan protocol selection. Such standards must consider applied radiation in the context of the clinical indication as well as the characteristics of the patient and provide guidance with regard to specific parameter settings. This editorial viewpoint demonstrates the need for comprehensive, individualized review of the clinical scenario before performing a cardiovascular CT, as well as the need for standards. If cardiovascular CT is the appropriate test and scan parameters are optimized with respect to radiation exposure, benefit should necessarily outweigh potential risk. However, efforts to promote responsible cardiovascular CT imaging must continue to ensure this is true for every patient.

PMID: 20466351

Choosing the Optimal Wall Shear Parameter for the Prediction of Plaque Location-A Patient-Specific Computational Study in Human Right Coronary Arteries

OBJECTIVES: Average wall shear-stress (AWSS), average wall shear-stress gradient (AWSSG), oscillatory shear index (OSI) and relative residence time (RRT) are believed to predict areas vulnerable to plaque formation in the coronary arteries. Our aim was to analyze the correlation of these parameters in patients’ vessels before the onset of atherosclerosis to the specific plaque sites thereafter, and to compare the parameters’ sensitivity and positive predictive value.

METHODS: We obtained 30 patient-specific geometries (mean age 67.1 (+/-9.2) years, all with stable angina) of the right coronary artery (RCA) using dual-source computed tomography (CT) and virtually removed any plaque present. We then performed computational fluid dynamics (CFD) simulations to calculate the wall shear parameters.

RESULTS: For the 120 total plaques, AWSS had on average a higher sensitivity for the prediction of plaque locations (72+/-25%) than AWSSG (68+/-36%), OSI (60+/-30%, p<0.05), and RRT (69+/-59%); while OSI had a higher positive predict value (PPV) (68+/-34%) than AWSS (47+/-27%, p<0.001), AWSSG (37+/-23, p<0.001) and RRT (59+/-34%). A significant difference was also found between AWSSG and RRT (p<0.01) concerning PPV.

CONCLUSIONS: OSI and RRT are the optimal parameters when the number of false positives is to be minimized. AWSS accurately identifies the largest number of plaques, but produces more false positives than OSI and RRT.

PMID: 20466375

Coronary Computed Tomographic Angiography in Patients Suspected of Coronary Artery Disease: Impact of Observer Experience on Diagnostic Performance and Interobserver Reproducibility

OBJECTIVES: A high diagnostic performance of coronary computed tomographic angiography (CTA) in identifying coronary artery disease (CAD) has been shown in experienced high-volume centers. Whether this may be accomplished in centers with less CTA experience remains unknown. OBJECTIVES: We determined the diagnostic performance and interobserver reproducibility of CTA in detecting significant CAD in a center with limited experience.

METHODS: In 209 patients, CTA was performed with 64-slice or dual-source CT technology, and analyses were performed independently by 2 inexperienced observers. Significant CAD by CTA was defined as >1 stenoses >50% or >1 nonevaluable segment, whereas significant CAD by invasive quantitative coronary angiography was defined as >1 stenoses >50%. We evaluated the influence of CAD pretest probability, Agatston score (AS), heart rate (HR), and observer experience on the diagnostic sensitivity, specificity, positive (PPV) and negative predictive values (NPV), interobserver reproducibility, and duration of CTA analysis.

RESULTS: Per-patient (CAD prevalence, 35%) sensitivity was 88%-99%, specificity was 78%-82%, PPV was 68%-74%, and NPV was 92%-99%. Overall interobserver reproducibility was good (kappa = 0.65). A significant temporal improvement was observed in diagnostic specificity (observer A: 68%-89%, P = 0.007; observer B: 71%-89%, P = 0.02), and interobserver reproducibility (kappa = 0.35-0.89, P = 0.01) during the study period. Duration of analysis decreased during the study period and was positively associated with CAD pretest probability and AS.

CONCLUSIONS: Suboptimal diagnostic performance and interobserver reproducibility must be anticipated during CTA implementation. A high diagnostic sensitivity, specificity, and interobserver reproducibility were achieved after a large number of studies performed with the state-of-the-art scanner technology.

PMID: 20451487

Perceived Usefulness of Cardiac Computed Tomography as Assessed by Referring Physicians and its Effect on Patient Management

OBJECTIVES: Despite the growing use of computed tomographic angiography (CTA), the effect on patient management is less clear. We sought to determine the perceived usefulness of the results provided by CTA and to assess whether and how it influences patient management.

METHODS: Comprehensive prospective data were collected from 184 consecutive patients who presented for clinical CTA for the evaluation of coronary artery disease from March to July 2008. In addition, a detailed survey was sent to each referring physician for each patient examined to assess whether they found the results of the CTA useful and whether it had any influence on subsequent patient management. Of 184 CTA examinations, which had been ordered by 82 different providers, 108 surveys (59%) were completed by 53 different physicians. No significant differences were found in either the patient or provider characteristics for the completed versus noncompleted surveys.

RESULTS: Of the 184 CTA examinations, the severity of coronary disease detected by CTA was severe for 26%, mild to moderate in 47%, and not present in 27% of the patients. Clinicians considered the test results to be useful in virtually all cases and thought the results led to significant risk reclassification in 58% of the patients. If CTA had not been available, the clinicians indicated that they would have ordered an invasive test for 46% of the patients and noninvasive tests for 32%. After CTA, changes in medical therapies were made for 31%, invasive angiography was planned for 19%, and noninvasive testing was scheduled for 6% of the patients.

CONCLUSIONS: In conclusion, of 53 different referring clinicians from different medical specialties, CTA was considered to almost always be useful; however, the effect on subsequent medical management was more variable.

PMID: 20403474

Cost-Effectiveness of Coronary CT Angiography in Evaluation of Patients Without Symptoms Who Have Positive Stress Test Results

OBJECTIVE: Patients without symptoms who have positive stress test results are often referred for diagnostic catheter angiography in an evaluation for coronary artery disease (CAD). The purpose of this study was to use decision tree analysis to determine the cost-effectiveness and radiation dose that would result from performing coronary CT angiography (CTA) before catheterization.

METHODS: A decision tree was constructed to compare the false-negative rates, false-positive rates, costs, and radiation exposure of direct referral of patients for cardiac catheterization with the values associated with performing coronary CTA before catheterization. We assumed that patients referred for coronary CTA proceed to catheterization only when significant disease is identified. Costs for coronary CTA and diagnostic catheterization were obtained from the 2009 physician Medicare fee schedule. Sensitivity, specificity, and radiation dose were obtained by literature review.

RESULTS: Cost reduction with coronary CTA depends on the prevalence of coronary artery disease, but overall costs are reduced as long as the prevalence is less than 85%. At a 50% prevalence of coronary artery disease, performing coronary CTA before cardiac catheterization results in an average cost saving of $789 per patient with a false-negative rate of 2.5% and average additional radiation exposure of 1-2 mSv.

CONCLUSIONS: Performing coronary CTA before cardiac catheterization is a cost-effective strategy in the care of patients without symptoms who have positive stress test results when the probability that the patient has significant coronary artery disease is less than 50%. The false-negative rate with this strategy compares favorably with the false-negative rate of stress testing. The use of coronary CTA in this role can avoid many unnecessary cardiac catheterization procedures.

PMID: 20410412

Extracardiac Findings on Cardiac Computed Tomography: A Radiologist’s Perspective

There has been debate in the cardiology literature as to how to handle unexpected noncardiac findings on cardiac computed tomography examinations. From the perspective of a radiologist, all structures on the presented images should be assessed. The interpreter needs to carefully window the findings down to potentially important ones. Then the question becomes what to do next. Cardiologists who take primary responsibility for cardiac computed tomography examinations must be able to recognize noncardiac findings that require immediate action. Although infrequent, their clinical impact can be substantial. False-positive results will occur; minimizing these depends on knowledge of common trivial findings, normal variants, and customary workup and follow-up recommendations. This implies experience in interpreting structures outside the heart. Therefore, help from an experienced and decisive radiologist should maximize sensitivity for significant lesions while minimizing the number of false-positive diagnoses.

PMID: 20378072