Case of the Month. Prize-winning Poster. Quantification of left ventricular volumes using three-dimensional echocardiographic speckle tracking: comparison with MRI Eur Heart J Radiation dose exposure of computed tomography coronary angiography: comparison of dual-source, slice and slice CT Heart T2-weighted magnetic resonance imaging to assess myocardial oedema in ischaemic heart disease Heart Am J Roentgenol w A method for calcium quantification by means of CT coronary angiography using multidetector CT: very high correlation with agatston and volume scores Eur Radiol Automatic selection of optimal systolic and diastolic reconstruction windows for dual-source CT coronary angiography Eur Radiol Prognostic value of computed tomography coronary angiography in patients with suspected coronary artery disease: a month follow-up study Eur Radiol Evaluation of coronary artery calcium screening strategies focused on risk categories: The Dallas Heart Study Am Heart J Remodelling of the aortic root in severe tricuspid aortic stenosis: implications for transcatheter aortic valve implantation Eur Radiol Prognostic and accuracy data of multidetector CT coronary angiography in an established clinical service Clin Radiol Myocardial infarcts were induced by occlusion of the mid LAD with an inflated coronary angioplasty balloon as previously described in detail Five animals did not survive the infarct procedure.
Two animals died during the early follow-up in the first 4 days post-MI and 4 animals died between week 8 and 12 post-MI. Twenty-two animals were enrolled in the study. The thirteen animals randomized to cell therapy received bone-marrow derived porcine mesenchymal stem cells MSCs. MSCs were obtained, isolated, and expanded as previously described 6. Trypan blue staining was performed to attest viability of thawed MSC lots before injection.
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Myocardial injections were performed as previously described in detail 5 , 6. MDCT images were acquired at two time-points, prior to randomization at week 12 post-MI and 12 weeks after the intra-myocardial injection procedure at week Each animal was scanned with electrocardiographic monitoring using a 0. Data acquisition for LV-function parameters and LV-volumes were initiated manually at a threshold value of HU in the descending aorta. Additional 90 ml iodixanol were given intravenously after first-pass acquisitions, and delayed contrast enhancement images were acquired 10 minutes after initial contrast delivery; ml of iodixanol 0.
All raw data were reconstructed at contiguous 0. Endo- and epicardial borders of the LV were defined in all 10 contiguous slices and each end-diastolic and end-systolic frame was determined to calculate LVEF, end-diastolic LV volume, end-systolic LV volume, LV stroke volume, and LV remodeling parameters.
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The temporal resolution based on gantry rotation of all MDCT acquisitions was ECG editing to account for arrhythmias were performed when necessary. Infarct size was defined as infarct mass as percentage of LV-mass. A total of six to eight contiguous short—axis slices were prescribed to cover the entire LV, from base to apex. Delayed contrast enhanced MRI images were acquired in the same location as the short axis cine-images. Inversion recovery time was adjusted as needed to null the normal myocardium To evaluate LVEF, LV-volumes and myocardial mass endo- and epicardial borders were defined each in the end-diastolic and end-systolic frame in 25 to 30 contiguous slices, and LV parameters and volumes were calculated.
The temporal resolution of the cine MR images was Infarct size, determined by infarct mass as a percentage of LV-mass and infarct volume in de-MR images, were defined with the same threshold method described for de-MDCT analysis. Twenty-two animals were enrolled in this study 12 weeks post-MI After randomization, animals in both groups were of similar age One placebo and two MSC treated animals were excluded from analysis due to poor imaging quality caused by motion artifacts at week Infarct size, defined as infarct mass as percentage of LV-mass, was reduced in all MSC treated animals at week 24 while it increased in all animals in the placebo group Figure 1.
We observed a mean expansion of Delayed contrast enhanced images were reconstructed in the short axis at 4 mm slice thickness. Panel B and D show the slices of the placebo A and MSC C case, respectively, with a computer-generated mask depicting the infarct area in red. Cardiac MDCT demonstrated that the decrease in infarct size resulted in The complete data is presented in table 2.
Bland-Altman analysis revealed a slight overestimation by 1. Infarct size decreased by mean values of 4. The changes between the in placebo and MSC treated animals were also detected with both imaging modalities. Our results suggest that MDCT imaging reliably assesses end-diastolic LV volumes, LVEF, infarct size, and infarct volumes with delayed contrast acquisitions; it is able to access the effect of intra-myocardial delivered cell therapy compared to placebo.
These findings confirm previous studies that used MRI to evaluate the therapeutic potential of intra-myocardial delivered MSC in HF subjects with chronic infarct scars 6 , This study introduces MDCT imaging as an alternative cardiac imaging technique to determine efficacy of novel myocardial therapeutics. MDCT has the capability to distinguish between viable and non-viable myocardium with delayed contrast-enhancement for the detection of acute and chronic infarct scar, and has recently been reported in animal experiments and human studies; however, it is still considered an investigative technique 9 — 11 , 16 , After intravenous delivery, iodine-based contrast agents accumulate in myocardial tissue damaged by MI.
The discrimination between viable and nonviable myocardium result from increased attenuation values caused by the accumulation of iodine molecules in the infarct area detected by MDCT. This is in contrast to enhancement mechanisms by MRI that rely on alteration of the contrast media via interactions with water molecules 9.
The infarct sizes detected by de-MDCT in this study are significantly smaller than matching MRI values; these results are in accordance with previously published data for acute and chronic MI 16 , The extent of contrast enhancement detected by MRI has been shown to predict the response to medical treatment in HF patients Reduction of infarct size has been noted with de-MRI following myocardial cell therapy in animal studies and patients 4 — 6 , 22 , Thus, quantification of infarct size and infarct volume by de-MDCT could be a valuable surrogate end point allowing the prediction of response to therapy.
Delayed contrast enhanced MDCT currently offers the highest spatial resolution for transmural characterization of infarct scars, and this can be particularly helpful in guiding intra-myocardial delivery of cell-based therapies. An akinetic segment might be deemed nonviable by nuclear techniques caused by limited spatial resolution, but shows some viability in de-MDCT, which increases the likelihood that this segment will eventually recover with therapeutic intervention Cardiac function with MDCT is accomplished with intravenous injection of iodine-based contrast agents for opacification of the blood pool to delineate the borders of the ventricle and application of retrospective ECG-gated protocols, to record the complete cardiac cycle during the R-R-interval.
Temporal resolution, based on gantry rotation, has been reported to be less than ms with single-source systems and further to 83ms with dual-source MDCT technology 7. Our results are in accordance with studies comparing single-source and dual-source slice MDCT— with MRI showing small differences between both modalities and narrow Bland-Altman windows 25 — In our study, we observed good correlation coefficients for end-diastolic LV-volumes and LVEF and we are able to confirm the linear relationship between both volumetric imaging techniques for LV-function and LV remodeling parameters making both tomographic imaging methods interchangeable for LV function and LV-volumes assessment.
Human trials, using a variety of cell-therapy approaches, have used improvements in LVEF as an end-point 3. Compared with volumetric changes, using LVEF as an end-point has the advantage of denoting a survival difference and is an accepted surrogate measure for mortality MDCT can be safely performed in patients with metallic implants, such as pacemakers; defibrillators; and prostheses; who are inappropriate candidates for MRI.
Although MRI is considered the reference standard for cardiac function and myocardial viability— based on the accuracy and reproducibility of measurements— the duration of cardiac MRI acquisitions with multiple prolonged breath-holds are required to obtain adequate data sets, are time consuming, and impossible in patients with claustrophobia.
MDCT imaging is fast and offers good temporal and excellent spatial resolution; however, MDCT acquisitions require iodinated contrast agents and involve radiation exposure. In order to translate cardiac function and viability assessment with MDCT into clinical trials standardized low-dose protocols are needed; especially, to minimize overall radiation exposure as follow—up studies are required for outcome assessment. In the latest generation of MDCT scanners, ECG-gated tube current modulations are commonly applied in retrospective acquisitions for evaluation of cardiac function 7.
Low-dose delayed contrast-enhancement protocols have been reported 9. We have recently described a prospectively gated protocol for high-resolution de-MDCT imaging that lowers radiation dose by an order of magnitude Cardiac CT perfusion is based on the same first-pass principle as MRI 14 which has been used to evaluate cell therapy 5. Cardiac MDCT is poised to offer a comprehensive evaluation of novel myocardial therapeutics.
This animal study was conducted without any medical therapy given to patients currently post-MI.click here
Article - Cardiac MDCT: Utility in delineating morphology and function
Therefore, the chronic MIs expanded and the infarct size increased in the placebo group consistent with results from a clinical study using non-invasive imaging techniques conducted in the early s With modern medical therapy decrease in infarct size is anticipated in chronic MI as shown in a recent MRI study Although these limitations are evident in the current study, the goal of this study was to demonstrate the usefulness of using MDCT to evaluate the effect of myocardial therapies.
However, there are some limitations that may affect the transfer of the reported MDCT protocols and results to application in human trials. First, the animals presented had elevated heart rates which are usually considered a relative contraindication for MDCT. While the reported MDCT protocols proved reliable even under these unfavorable conditions, it has to be considered that patients with an elevated heart rate above 60—70bpm may receive negative chronotropic medication in order to reduce the heart rate for coronary CT angiography.
In addition to revealing the pulmonary vein anatomy and morphology of the LA, it is also important for the electrophysiologist to determine the location of the esophagus with respect to the LA prior to beginning a catheter-guided ablation procedure for AF. The authors emphasized that the target sites during catheter ablation of AF may often fall within this region of contact and suggested that the presence of a fat pad around the esophagus insulates it from thermal injury.
Therefore, using CT to identify patients who do not have this fat pad prior to the procedure could be beneficial. Evaluating the morphology of the coronary venous anatomy Figure 4 is also of interest to the clinician.
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Knowledge of the coronary venous anatomy can help guide multiple therapies, including catheter placement in the coronary sinus for ablation procedures, 17 placement of left ventricular LV or biventricular pacing devices in patients with heart failure, 18,19 and the determination whether the venous system can be used to bypass coronary artery stenoses for percutaneous in situ coronary venous arterialization 20 or used for retroperfusion therapy. Clear delineation of cardiac morphology is also imperative for the cardiac surgeon in cases of repeat sternotomy.
Elahi et al 25 examined the complication rate in patients who underwent repeat sternotomy. They found complications directly attributable to repeat sternotomy in 21 These included minor injuries to the aorta 4. Most notably, there was uncontrollable hemorrhage from a tear in the aorta 0. The overall mortality in the repeat sternotomy group in the literature has been as high as After undergoing sternotomy, the anterior mediastinal anatomy may be distorted by fibrosis.
Major injuries may result in sternal re-entry due to inadvertent laceration of the heart, coronary arteries, or great vessels. Injury to implanted saphenous vein grafts has been reported and can result in massive intraoperative hemorrhage, myocardial ischemia, and infarction 27 Figure 5. The lack of adequate retrosternal space is one of the main risk factors for sternal re-entry.
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If there is increased risk of damage to retrosternal structures during sternotomy, the femoral vessels are commonly isolated prior to the procedure. Partial cardiopulmonary bypass using the femoral artery and vein is subsequently used to decompress the cardiac chambers and cool the patient circulatory arrest prior to sternal division. The presence of pseudoaneurysms Figure 7 or the enlargement or anterior displacement of the RV may be indications for peripheral bypass.
In patients with congenital heart disease, detecting coronary artery anomalies prior to operative intervention is also imperative. In patients with cardiac disorders, a desirable test to measure function is one that can provide quick, accurate, reproducible, and noninvasive high-quality images to determine the severity of cardiac impairment and evaluate the efficacy of treatment. Conventional ventriculography to measure cardiac function, while often considered the gold standard, is an expensive and invasive modality performed during angiography.
However, it is limited by the geometric assumptions that are made from projectional images.
This can lead to the inability to evaluate regions of the heart where there are complex irregular shape changes. Transthoracic ECG TTE is widely used, as it can provide accurate measurements of ventricular volumes and mass as a cost-effective 33 bedside cardiac evaluation tool. With its multiplanar nature and high spatial and contrast resolution, MRI is likely the noninvasive standard of reference for the qualitative assessment of ventricular volumes, EF, and mass.
Electrocardiographic-gated SPECT offers the ability of combining 3-dimensional 3D assessments of LV volumes and consecutively calculated function parameters.