Sobhi Abadi

Multidetector CT angiography in the evaluation of acute mesenteric ischemia

The aim of this study was to determine the accuracy of multidetector row CT angiography in the diagnosis of acute mesenteric ischemia. Ninety-three consecutive studies on 91 patients with clinically suspected acute mesenteric ischemia underwent abdominal CT angiography as the first, and usually the sole, diagnostic procedure. CT was performed with a multidetector 16-row CT system from the level of the diaphragm to the pelvis in two phases: early arterial and late portal phase. CT examinations were reviewed by the duty radiologist. Final diagnosis was established by a senior radiologist. CTA was diagnostic in 92 studies. Mesenteric ischemia was diagnosed in 18 patients, 14 of them were of the thromboembolic type and four from the nonocclusive type. Positive CTA findings were confirmed by surgery in 13 patients and by clinical follow-up in three cases. Other reasons for abdominal pain were diagnosed by CT in 38 patients out of the remaining 74. There were two false positive and two false negative CT results, resulting in an overall accuracy of 95.6%. Multidetector CT angiography is a fast and accurate investigation for the diagnosis of acute mesenteric ischemia and in most cases can be used as the sole diagnostic procedure.

Feasibility of automatic assessment of four-chamber cardiac function with MDCT: Initial clinical application and validation

BACKGROUND The ability to perform a simultaneous analysis of ventricular and atrial volumes may provide clinically useful information for diagnosis and prognosis. We aimed to evaluate the feasibility and clinical value of a novel algorithm that performs fully automatic evaluation of the four cardiac chambers and myocardium from gated CT datasets. METHODS 50 patients were studied-Group 1: 30 consecutive unselected patients, Group 2A: 10 patients after myocardial infarction and Group 2B: 10 normal controls. Fully automatic, segmentation of the heart was performed with a model-based segmentation algorithm requiring no user input other than loading the datasets. Qualitative and quantitative evaluation of segmentation quality was performed. Left ventricular (LV) and right ventricular (RV) stroke volumes (SV) were compared. RESULTS Overall, segmentation succeeded in all patients although 11/500 (2.2%) cardiac chambers achieved poor segmentation grading. Correlation coefficients between automatic and manually derived volumes were excellent (r>0.98) for all chambers. Bland-Altman analysis showed minimal bias (-1.0ml, 0.4ml, -1.8ml) for the LV and RV, and right atria, respectively, with mild overestimation of LV myocardial volume (5.2ml). Significant, yet consistent, overestimation of left atrial volume (23.6ml) due to inclusion of proximal pulmonary veins was observed. LV and RV ejection fraction (r=0.91 and 0.98) and SV (r=0.98 and 0.99) also correlated closely with minimal bias (<2%). Most significantly, LV SV (91.0+/-21.6ml) correlated highly with RV SV (81.7+/-18.2ml, r=0.86). Outliers could usually be explained by valvular regurgitation. CONCLUSIONS Fully automatic segmentation of all cardiac chambers can be achieved with high accuracy over multiple cardiac phases, enabling reliable comprehensive evaluation of four-chamber cardiac function.

Acute renal infarction from a cardiac thrombus

Background A 53-year-old man presented to hospital 2 hours after the abrupt onset of left upper abdominal pain. He was treated with analgesics and discharged after 4 hours of observation, but presented to another hospital 2 hours later with severe left abdominal pain. His past medical history included ischemic dilated cardiomyopathy due to recurrent myocardial infarction.Investigations Physical examination, electrocardiography, laboratory investigations, contrast-enhanced computed tomography, and transesophageal echocardiography.Diagnosis Renal artery thromboembolism resulting from dilated cardiomyopathy, severely reduced cardiac function and an intracardiac thrombus.Management Anticoagulation with unfractionated heparin followed by enoxaparin and warfarin.

Direct comparison between coronary computed tomography and invasive angiography for calculation of SYNTAX score.

AIMS We aimed to test the feasibility of calculating SYNTAX score from coronary computed tomographic angiography (CCTA) compared to from invasive coronary angiography (ICA). METHODS AND RESULTS SYNTAX score was independently and blindly calculated from CCTA and from ICA in 104 patients, age 57±10, with significant (>50%) stenoses in 1.7±0.7 vessels. The level of agreement was assessed by Cohens kappa. Agreement between ICA and CCTA for conventional vessel-based analysis (presence of >50% stenosis per vessel) was substantial with kappa=0.66 and sensitivity, specificity and accuracy of 74%, 90% and 80%, respectively. The mean SYNTAX score was 14.2±10.0 by ICA and 10.3±6.9 by CCTA, with a significant underestimation of 3.9±8.2 by CCTA (p<0.001). Weighted kappa was 0.33, indicating only fair agreement. When only good quality CCTA were included, kappa improved to 0.56. Analysis of the cause of the bias showed ICA to identify more lesions per patient (2.2±1.3 vs. 1.7±1.0, p<0.001), while the mean score per lesion was not different (6.4 vs. 5.9, p=ns). CONCLUSIONS CCTA, despite having a good agreement with ICA by conventional vessel-based analysis, showed only fair agreement for the calculation of SYNTAX score, and cannot be currently used as a substitute for diagnostic ICA for this purpose.

The three-dimensional geometric relationship between the mitral valvar annulus and the coronary arteries as seen from the perspective of the cardiac surgeon using cardiac computed tomography

OBJECTIVES Mitral annuloplasty involves sewing a prosthetic ring to the mitral annulus. This involves a risk of damaging the surrounding structures in the left atrioventricular (AV) groove, particularly the left circumflex artery, which may be inadvertently sutured, causing an arterial occlusion. We have used cardiac computed tomography (CT) scans to study the three-dimensional relationship between the mitral valvar annulus and the neighbouring coronary arteries in the AV groove, and to map the distance between the arteries and the annulus. METHODS We examined cardiac CT scans of two groups of patient: 40 normal subjects, and 30 patients with left ventricular dysfunction and/or mitral regurgitation. The hinge line of the mitral valve, as well as the location of the coronary arteries within the left AV groove, was manually marked on a workstation and three-dimensional coordinates saved in digital format. Dedicated software was developed to calculate the plane of the mitral annulus, and the smallest distance between each point on the annulus and each of the left circumflex and right coronary arteries, called local minima. The global minimum for each heart is defined as the minimum of all local minima. RESULTS The global minimum for the left circumflex averaged 6.4 ± 2.1 mm, usually involving the proximal portion, just laterally to the left trigone. In three-tenths of patients, the global minimum was <5 mm. This was more common in patients with left dominance, and in the normal subjects. The major component of the line vector between the annulus and circumflex is parallel to the plane of the mitral annulus, while the perpendicular component is usually in an atrial direction. For the dominant right coronary artery (RCA), the global minimum distance to the annulus is 14.7 ± 5.7 mm. In no patient did the RCA approach to within 5 mm with respect to the mitral annulus, albeit that 13% were <10 mm. CONCLUSIONS In a significant proportion of patients, the left circumflex is in very close proximity to the annulus of the mitral valve. Knowledge of the precise three-dimensional relationships between the structures can be expected to minimize iatrogenic complications.

Novel method for real-time hybrid cardiac CT and coronary angiography image registration : visualising beyond luminology, proof-of-concept

AIMS During coronary angiography and percutaneous coronary interventions (PCI) only the lumen of the coronary vessel is imaged. The complete pathology of the vessel wall--namely the extent of calcification, structure of non-calcified plaque and lesion length--cannot be accurately determined. These can be imaged using coronary CT angiography (CTCA). We aimed to investigate the accuracy, feasibility, safety and value of a novel hybrid method encapsulating real-time registration of CTCA to coronary angiography images. The method is designed to seamlessly integrate into the routine catheterisation procedures and provide information to assist in decision making during the interventional procedure. METHODS AND RESULTS Phantoms simulating the coronary tree were used to test the accuracy and potential of co-registration of information. Precision of the imaging system was tested using radio-opaque markers and distance between bifurcations. We included patients who underwent CTCA and also underwent cardiac catheterisation. Analysis and feasibility was performed offline in the first twenty patients and online in the following 19 patients. The online CTCA and angiography co-registration was performed by the AngioCt software program. The registration result was displayed on a separate screen in the catheterisation laboratory as a three-dimensional coronary tree and a curved multi-planar reformat (MPR) view. Preclinical validation showed that the co-registration of the coronary tree is feasible, and measurements of length and diameter are precise for all standard working angulations during coronary angiography. Real-time registration was successful in all cases and aided in selection of the view that will provide the least foreshortening and no vessel overlapping, the length of balloons and stent to use and assisted in crossing chronic total occlusions (CTO). CONCLUSIONS This is the first report of a novel method for online real-time hybrid CTCA and angiography registration. In this pilot study we found that this method is feasible, accurate, and easy to use. It can be used for selecting the best working angulations for minimising foreshortening and vessel overlapping, determining stent size and location, and providing a reference vessel path and structure in cases of CTO.

Integrated SPECT/CT for assessment of haemodynamically significant coronary artery lesions in patients with acute coronary syndrome

PurposeEarly risk stratification in patients with non-ST elevation acute coronary syndromes (NSTE-ACS) is important since the benefit from more aggressive and costly treatment strategies is proportional to the risk of adverse clinical events. In the present study we assessed whether hybrid single photon emission computed tomography (SPECT)/coronary computed tomography angiography (CCTA) technology could be an appropriate tool in stratifying patients with NSTE-ACS.MethodsSPECT/CCTA was performed in 90 consecutive patients with NSTE-ACS. The Thrombolysis in Myocardial Infarction risk score (TIMI-RS) was used to classify patients as low- or high-risk. Imaging was performed using SPECT/CCTA to identify haemodynamically significant lesions defined as >50% stenosis on CCTA with a reversible perfusion defect on SPECT in the corresponding territory.ResultsCCTA demonstrated at least one lesion with >50% stenosis in 35 of 40 high-risk patients (87%) as compared to 14 of 50 low-risk patients (35%; TIMI-RS <3; p <0.0001). Of the 40 high-risk and 50 (16%) low-risk TIMI-RS patients, 16 (40%) and 8 (16%), respectively, had haemodynamically significant lesions (p = 0.01). Patients defined as high-risk by a high TIMI-RS, a positive CCTA scan or both (n = 45) resulted in a sensitivity of 95%, specificity of 49%, PPV of 35% and NPV of 97% for having haemodynamically significant coronary lesions. Those with normal perfusion were spared revascularization procedures, regardless of their TIMI-RS.ConclusionNoninvasive assessment of coronary artery disease by SPECT/CCTA may play an important role in risk stratification of patients with NSTE-ACS by better identifying the subgroup requiring intervention.

Clinical evaluation of a fully automated model-based algorithm to calculate left ventricular volumes and ejection fraction using multidetector computed tomography

Objectives: To evaluate feasibility and accuracy of a fully automatic algorithm (FAA) for calculating left ventricular volumes and ejection fraction (LVEF) from multidetector computed tomography (MDCT) studies versus a previously validated method based on Simpsons method serving as our reference standard (RS), and left ventriculography (LVG), in patients with acute chest pain (ACP). Methods: 23 patients admitted with ACP underwent ECG-gated MDCT, as well as LVG during their hospitalization. MDCT based end-diastolic, end-systolic and stroke volumes (EDV, ESV, SV) and LVEF were calculated using the RS and the FAA. Results: One patient was excluded after FAA failure to detect contours. In the remaining 22 patients, mean±SD LVEF measurements were RS 61±11%, FAA 59±11% (r = 0.91 versus RS), LVG 57±16% (r = 0.6 versus RS). In comparison to RS, FAA overestimated EDV by 10.1±8.5 ml, ESV by 7.3±6.4 ml and SV by 3.6±8.6 ml, and underestimated LVEF measurements by 2.7±4.6%, related to contour smoothing. LVEF by FAA was within 8% of RS for all patients except one. In contrast, LVG differed significantly from RS. Conclusions: The evaluated FAA obtained accurate, clinically relevant results for left ventricular volumes and LVEF relative to the RS.

Multidetector computed tomography predictors of late ventricular remodeling and function after acute myocardial infarction

BACKGROUND Despite advent of rapid arterial revascularization as 1st line treatment for acute myocardial infarction (AMI), incomplete restoral of flow at the microvascular level remains a problem and is associated with adverse prognosis, including pathological ventricular remodeling. We aimed to study the association between multidetector row computed tomography (MDCT) perfusion defects and ventricular remodeling post-AMI. METHODS In a prospective study, 20 patients with ST-elevation AMI, treated by primary angioplasty, underwent arterial and late phase MDCT as well as radionuclide scans to study presence, size and severity of myocardial perfusion defects. Contrast echocardiography was performed at baseline and at 4 months follow-up to evaluate changes in myocardial function and remodeling. RESULTS Early defects (ED), late defects (LD) and late enhancement (LE) were detected in 15, 7 and 16 patients, respectively and radionuclide defects in 15 patients. The ED area (r=0.74), and LD area (r=0.72), and to a lesser extent LE area (r=0.62) correlated moderately well with SPECT summed rest score. By univariate analysis, follow-up end-systolic volume index and ejection fraction were both significantly related to ED and LD size and severity, but not to LE size or severity. By multivariate analysis, end-systolic volume index was best predicted by LD area (p<0.05) and ejection fraction by LD enhancement ratio. CONCLUSIONS LD size and severity on MDCT are most closely associated with pathological ventricular remodeling after AMI and may thus play a role in early identification and treatment of this condition.

Quantitative Evaluation of Regional Left Ventricular Function by Multidetector Computed Tomography

Objective: Because most contemporary workstations offer quantitative analysis of regional function by multidetector computed tomography, we aimed to establish typical values for normal, hypokinetic, and akinetic regions, and to establish optimal thresholds to differentiate between normal and abnormal values. Methods: For 33 patients, quantitative regional functional parameters were compared with visual analysis by both multidetector computed tomography and echocardiography. Normal values were established to normalize for segmental variability. Optimal thresholds were established to differentiate between normal and abnormal segments by receiver operating characteristic analysis. Results: Akinetic, hypokinetic, and normokinetic segments demonstrated significant differences (P < 0.0001) for end-systolic thickness (mean [95% confidence interval], 9.4 [4.5-14.3], 11.7 [7.2-16.2], and 14.3 mm [8.2-20.3 mm]), respectively; thickening, 24% [−22% to 71%], 45% [−16% to 106%], and 82% [10%-154%]), respectively; and motion, 3.5 [−2.0 to 8.9], 6.1 [-0.2 to 12.4], and 8.5 mm [1.8-15.3 mm], respectively). Thickening performed best with area under the curve of 0.87 and sensitivity equal to specificity of 82%. Intraobserver variability was good, but interobserver variability was only moderate. Conclusions: Quantification of regional myocardial function can be performed to assist the physician in mapping left ventricular function.