Epicardial Adipose Tissue and Coronary Artery Plaque Characteristics

OBJECTIVE: Epicardial adipose tissue (EAT) has been implicated in the pathogenesis of coronary atherosclerosis. The association of EAT volume with type of coronary artery plaque on computed tomography angiography (CTA) is not known.

METHODS: Coronary artery calcium (CAC) scoring and EAT volume measurement were performed on 214 consecutive patients (mean age 54+/-14 years) referred for coronary CTA. CAC was performed on non-contrast images, while EAT volume, the severity of luminal stenoses, and plaque characterization were assessed using contrast-enhanced CTA images. EAT volume was also indexed to body surface area (EAT-i).

RESULTS: EAT volume correlated with age, height, body mass index (BMI), and CAC score. EAT volume increased significantly with the severity of luminal stenosis (p<0.001), and in patients with no plaques, calcified, mixed, and non-calcified plaques (62+/-33mL, 63+/-22mL, 98+/-47mL, and 99+/-36mL, respectively, p<0.001). The EAT volume was significantly larger in patients with mixed or non-calcified plaques compared to patients with calcified plaques or no plaques (all p<0.01 ). The trend remained significant after adjustment for traditional risk factors for coronary artery disease. In adjusted models EAT was an independent predictor of CAC [exp(B)=3.916, p<0.05], atherosclerotic plaques of any type [exp(B)=4.532, p<0.01], non-calcified plaques [exp(B)=3.849, p<0.01], and obstructive CAD [exp(B)=3.824, p<0.05]. The above results were unchanged after replacing EAT with EAT-i.

CONCLUSION: EAT volume was larger in the presence of obstructive CAD and non-calcified plaques. These data suggest that EAT is associated with the development of coronary atherosclerosis and potentially the most dangerous types of plaques.

PMID: 20031133

Appearance of Lipid-Laden Intima and Neovascularization After Implantation of Bare-Metal Stents

OBJECTIVES: We examined the neointimal characteristics of bare-metal stents (BMS) in extended late phase by the use of optical coherence tomography (OCT). The long-term neointimal features after BMS implantation have not yet been fully characterized.

METHODS: Intracoronary OCT observation of BMS segments was performed during the early phase (<6 months, n = 20) and late phase (>5 years, n = 21) after implantation. Internal tissue of the BMS was categorized into normal neointima, characterized by a signal-rich band without signal attenuation, or lipid-leaden intima, with marked signal attenuation and a diffuse border. In addition, the presence of disrupted intima and thrombus was evaluated. Neovascularization was defined as small vesicular or tubular structures, and the location of the microvessels was classified into peristent or intraintima.

RESULTS: Normal neointima proliferated homogeneously, and lipid-laden intima was not observed in the early phase. In the late phase, lipid-laden intima, intimal disruption, and thrombus frequently were found in comparison with the early phase (67% vs. 0%, 38% vs. 0%, and 52% vs. 5%, respectively; p < 0.05). Peristent neovascularization demonstrated a similar incidence between the 2 phases. The appearance of intraintima neovascularization was more prevalent in the late phase than the early phase (62% vs. 0%, respectively; p < 0.01) and in segments with lipid-laden intima than in nonlipidic segments (79% vs. 29%, respectively; p = 0.026).

CONCLUSIONS: This OCT study suggests that neointima within the BMS often transforms into lipid-laden tissue during an extended period of time and that expansion of neovascularization from peristent to intraintima contributes to atherosclerotic progression of neointima.

PMID:

Dose Reduction in Helical CT: Dynamically Adjustable Z-Axis X-Ray Beam Collimation

OBJECTIVE: The purpose of this study was to measure the dose reduction achieved with dynamically adjustable z-axis collimation.

METHODS: A commercial CT system was used to acquire CT scans with and without dynamic z-axis collimation. Dose reduction was measured as a function of pitch, scan length, and position for total incident radiation in air at isocenter, accumulated dose to the center of the scan volume, and accumulated dose to a point at varying distances from a scan volume of fixed length. Image noise was measured at the beginning and center of the scan.

RESULTS: The reduction in total incident radiation in air at isocenter varied between 27% and 3% (pitch, 0.5) and 46% and 8% (pitch, 1.5) for scan lengths of 20 and 500 mm, respectively. Reductions in accumulated dose to the center of the scan were 15% and 29% for pitches of 0.5 and 1.5 for 20-mm scans. For scan lengths greater than 300 mm, dose savings were less than 3% for all pitches. Dose reductions 80 mm or farther from a 100-mm scan range were 15% and 40% for pitches of 0.5 and 1.5. With dynamic z-axis collimation, noise at the extremes of a helical scan was unchanged relative to noise at the center. Estimated reductions in effective dose were 16% (0.4 mSv) for the head, 10% (0.8 and 1.4 mSv) for the chest and liver, 6% (0.8 mSv) for the abdomen and pelvis, and 4% (0.4 mSv) and 55% (1.0 mSv) for coronary CT angiography at pitches of 0.2 and 3.4.

CONCLUSIONS: Use of dynamic z-axis collimation reduces dose in helical CT by minimizing overscanning. Percentage dose reductions are larger for shorter scan lengths and greater pitch values.

PMID: 20028890

Prosthesis-Patient Mismatch After Transcatheter Aortic Valve Implantation with the Medtronic-Corevalve Bioprosthesis

OBJECTIVES: Prosthesis-patient mismatch (P-PM) is an important determinant of morbidity and mortality following open aortic valve replacement. The aims of this study were to report its incidence and determinants following transcatheter aortic valve implantation (TAVI) with the Corevalve bioprosthesis, which have—thus far—not been described.

METHODS: Patients with severe calcific aortic stenosis received TAVI with the Corevalve bioprosthesis via transfemoral route. FollowingTAVI, moderate P-PM was defined as indexed aortic valve effective orifice area (AVAi) <0.85 cm²/m² and severe P-PM as AVAi <0.65 cm²/m². Clinical, echocardiographic, and procedural factors relating to P-PM were studied. Optimal device position was defined on fluoroscopy as final position of the proximal aspect of the Corevalve stent frame 5–10 mm below the native aortic annulus. Between January 2007 and January 2009, 50 consecutive patients underwent TAVI in a single centre with the Corevalve bioprosthesis.

RESULTS: Mean age was 82.8 years (SD 5.9; 70–93) and 48% were male. P-PM occurred in 16 of 50 cases (32%). Optimal position was achieved in 50% of cases. P-PM was unrelated to age, annulus size, LVOT size, Corevalve size, aortic angulation, ejection fraction, and sex. It was inversely correlated to optimal position (Spearman rho r = –0.34, P = 0.015). Those with optimal positioning had a 16% incidence of P-PM relative to 48% of those with suboptimal positioning (Pearson x² P = 0.015).

CONCLUSIONS: The incidence of P-PM following TAVI with the Corevalve bioprosthesis is compared favourably with that seen after AVR with conventional open stented bioprostheses and its occurrence is influenced by device positioning.

PMID: 19497768

Acute Myocardial Infarction: Serial Cardiac MR Imaging Shows a Decrease in Delayed Enhancement of the Myocardium During the 1st Week After Reperfusion

OBJECTIVES: To evaluate the time course of delayed gadolinium enhancement of infarcted myocardium by using serial contrast agent–enhanced (CE) cardiac magnetic resonance (MR) images obtained during the acute, subacute, and chronic stages of infarction.

METHODS: The study protocol was reviewed and approved by the local ethics committee, and written informed consent was obtained. Seventeen patients with reperfused acute myocardial infarction (AMI) underwent cine and CE cardiac MR a median of 1, 7, 35, and 180 days after reperfusion. Infarct size determined on the basis of delayed enhancement MR imaging at different times was compared by using nonparametric tests and Bland-Altman analysis. Extent of myocardial enhancement was compared with single photon emission computed tomographic (SPECT) measures of infarct size with Spearman correlation. Regional myocardial enhancement extent and contractility were analyzed with nonparametric tests.

RESULT: Infarct size was 18.3% of total myocardial LV volume on day 1 after AMI and decreased to 12.9% on day 7, 11.3% on day 35, and 11.6% on day 180 (all P < .001). Estimated infarct size on day 7, as compared with day 1 enhancement size, declined by 57.1% within the epicardium and by 6.3% within the endocardium (both P < .001). Infarct size on day 7 showed only minor changes at subsequent imaging and yielded a high correlation with SPECT measurements of infarct size (r = 0.84). Infarct size on day 7 inversely correlated with long-term wall thickening (P < .0001) and allowed prediction of contractile function.

CONCLUSIONS: In patients with AMI and successful coronary reperfusion, the size of delayed gadolinium enhancement at CE cardiac MR imaging significantly diminished during the 1st week after infarction. Thus, timing of CE cardiac MR imaging is crucial for accurate measurement of myocardial infarct size early after AMI.

PMID:

Myocardial Tissue Tagging With Cardiovascular Magnetic Resonance

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional function that provides a detailed and comprehensive examination of intra-myocardial motion and deformation. Given the current advances in gradient technology, image reconstruction techniques, and data analysis algorithms, CMR myocardial tagging has become the reference modality for evaluating multidimensional strain evolution in the human heart. This review presents an in depth discussion on the current clinical applications of CMR myocardial tagging and the increasingly important role of this technique for assessing subclinical myocardial dysfunction in the setting of a wide variety of myocardial disease processes.

PMID: 20025732

Projected Cancer Risks from Computed Tomographic Scans Performed in the United States in 2007

OBJECTIVES: The use of computed tomographic (CT) scans in the United States (US) has increased more than 3-fold since 1993 to approximately 70 million scans annually. Despite the great medical benefits, there is concern about the potential radiation-related cancer risk. We conducted detailed estimates of the future cancer risks from current CT scan use in the US according to age, sex, and scan type.

METHODS: Risk models based on the National Research Council’s “Biological Effects of Ionizing Radiation” report and organ-specific radiation doses derived from a national survey were used to estimate age-specific cancer risks for each scan type. These models were combined with age- and sex-specific scan frequencies for the US in 2007 obtained from survey and insurance claims data. We estimated the mean number of radiation-related incident cancers with 95% uncertainty limits (UL) using Monte Carlo simulations.

RESULTS: Overall, we estimated that approximately 29, 000 (95% UL, 15 000-45 000) future cancers could be related to CT scans performed in the US in 2007. The largest contributions were from scans of the abdomen and pelvis (n = 14 000) (95% UL, 6900-25 000), chest (n = 4100) (95% UL, 1900-8100), and head (n = 4000) (95% UL, 1100-8700), as well as from chest CT angiography (n = 2700) (95% UL, 1300-5000). One-third of the projected cancers were due to scans performed at the ages of 35 to 54 years compared with 15% due to scans performed at ages younger than 18 years, and 66% were in females.

CONCLUSIONS: These detailed estimates highlight several areas of CT scan use that make large contributions to the total cancer risk, including several scan types and age groups with a high frequency of use or scans involving relatively high doses, in which risk-reduction efforts may be warranted.

PMID: 20008689

Annual Progression of Coronary Calcification in Trials of Preventive Therapies: A Systematic Review

OBJECTIVES: Coronary artery calcification (CAC) measured by computed tomography is radiographic confirmation of atherosclerosis, predicts cardiovascular events, and has been evaluated as a surrogate measure in randomized trials.

METHODS: We performed a literature search for prospective randomized trials in which CAC was measured at baseline and at 1 year or more of follow-up. We computed the weighted mean annualized rate of CAC progression for a variety of therapies tested in these trials.

RESULTS: Ten trials (n = 2612) met our criteria and were included. Electron-beam, double-helix, and multislice computed tomography were used in 6, 2, and 2 trials, respectively. Agatston (8 trials) and volumetric (2 trials) methods were used for CAC evaluation. In 5 trials in subjects with cardiovascular disease (CVD) (n = 2135; age, ~64 years; ~39% women; follow-up, ~26 months), therapies included statins (n = 1370), placebo (n = 564), and antihypertensives (n = 201). In 5 trials in subjects with chronic kidney disease (n = 477; age, ~55 years; ~34% women; follow-up, ~14 months), interventions included low-phosphorus diet (n = 29), sevelamer hydrochloride (n = 229), and calcium-based phosphate binders (n = 219). The mean (SD) weighted annualized CAC increase overall and in patients with CVD and chronic kidney disease was 17.2% (6.7%), 16.9% (5.2%), and 18.4 (11.1%), respectively (P < .001). The rate among those assigned blinded placebo was 14.6% (1.0%) (2 trials). There was no consistent or reproducible treatment effect of any therapy on this outcome measured at 1 year.

CONCLUSIONS: The 1-year change in CAC does not appear to be a suitable surrogate end point for treatment trials in patients with CVD or chronic kidney disease.

PMID: 20008688

FDG-PET Can Distinguish Inflamed From Non-Inflamed Plaque in an Animal Model of Atherosclerosis

OBJECTIVES: The presence of activated macrophages is an important predictor of atherosclerotic plaque rupture. In this study, our aim was to determine the accuracy of (18)F- fluorodeoxyglucose (FDG) microPET imaging for quantifying aortic wall macrophage content in a rabbit model of atherosclerosis.

METHODS: Rabbits were divided into a control group and two groups post aortic balloon injury: 6 months high-cholesterol diet (HC); and 3 months HC followed by 3 months low-cholesterol diet plus statin (LCS). In vivo and ex vivo microPET, ex vivo well counting and histological quantification of the atherosclerotic aortas were performed for all groups.

RESULTS: Macrophage density was greater in the HC group than the LCS group (5.1 +/- 1.4% vs. 0.6 +/- 0.7%, P = 0.001) with a trend towards greater macrophage density in LCS compared to controls (P = 0.08). There was a strong correlation across all groups between macrophage density and standardized uptake value (SUV) derived from ex vivo microPET (r = 0.95, P = 0.001) and well counting (r = 0.96, P = 0.001). Ex vivo FDG SUV was significantly different between the three groups (P = 0.001). However, the correlation between in vivo microPET FDG SUV and macrophage density was insignificant (r = 0.16, P = 0.57) with no statistical differences in FDG SUV seen between the three groups.

CONCLUSIONS: This study confirms that in an animal model of inflamed and non-inflamed atherosclerosis, significant differences in FDG SUV allow differentiation of highly inflamed atherosclerotic aortas from those stabilized by statin therapy and low cholesterol diet and controls.

PMID: 19784796

Ultra-Low-Dose Intra-Arterial Contrast Injection for Iliofemoral Computed Tomographic Angiography

OBJECTIVES: This study sought to evaluate the feasibility of using ultra-low-dose intra-arterial contrast injection for iliofemoral computed tomographic (CT) angiography to follow diagnostic cardiac catheterization.  Cardiovascular interventions such as percutaneous aortic valve replacement require transfemoral delivery of large-bore intra-arterial catheters; therefore, pre-procedural assessment of aortoiliofemoral anatomy is important. CT angiography is ideal for this purpose but requires a large volume of intravenous contrast.

METHODS: Consecutive patients requiring evaluation of aortoiliofemoral anatomy underwent conventional anteroposterior projection iliac angiography during cardiac catheterization. A pigtail catheter was left in situ in the infrarenal abdominal aorta, and patients were transferred to the CT suite. Subsequently, 10 to 15 ml of contrast diluted with normal saline was injected intra-arterially via the pigtail catheter while a spiral CT of the abdomen and pelvis was acquired. Conventional angiographic and CT images were analyzed independently to assess suitability for large-bore (7-mm-diameter) intra-arterial catheter access.

RESULTS: Excellent CT image quality was achieved in 34 of 37 patients (92%). The mean contrast dose for CT was 12 ± 2 ml. In 9 patients (24%), CT changed the assessment of femoral access feasibility. Furthermore, in another 7 patients (19%), unfavorable anatomy as shown by CT directed the avoidance of a particular side. Overall, CT findings altered the interventional approach in 16 patients (43%). There was no significant deterioration detected in renal function after coronary and CT angiography (estimated glomerular filtration rate 54.8 ± 3.8 ml/min before 53.3 ± 3.9 ml/min after, p = 0.55).

CONCLUSIONS: High-quality aortoiliofemoral CT angiography can be obtained with a technical success rate of >90% using 10 to 15 ml of contrast injected via a catheter in the abdominal aorta, and offers an alternative to conventional X-ray or CT angiography with high-volume intravenous contrast injection.

PMID: doi:10.1016/j.jcmg.2009.08.010

Feasibility of Noninvasive Assessment of Thin-Cap Fibroatheroma by Multidetector Computed Tomography

OBJECTIVES: The purpose of this study was to investigate whether multidetector computed tomography (MDCT) can noninvasively help assess thin-cap fibroatheroma (TCFA). Plaque rupture and thrombus formation play key roles in the onset of acute coronary syndrome. TCFA is recognized as a precursor lesion for plaque rupture, and MDCT angiography can potentially help identify plaques prone to rupture.

METHODS: We enrolled 105 patients with coronary artery disease (acute coronary syndromes, n = 31; stable angina pectoris, n = 74). Culprit lesions were assessed by both MDCT and optical coherence tomography (OCT). Patients were divided into a TCFA and a non-TCFA group according to OCT findings; clinical and MDCT observations were compared for 2 groups.

RESULTS: There were no differences in patients’ characteristics between the 2 groups. OCT revealed 25 TCFAs at the culprit site in 105 patients. Acute coronary syndrome was more frequent in the TCFA group than in the non-TCFA group (52% vs. 23%, p = 0.01). High-sensitive C-reactive protein was higher in the TCFA group (0.32 ± 0.32 mg/dl vs. 0.17 ± 0.16 mg/dl, p < 0.001). Positive remodeling identified by MDCT was observed more frequently in the TCFA group than in the non-TCFA group (76% vs. 31%, p < 0.001). Computed tomography attenuation value of the culprit plaque in the TCFA group was lower than that in the non-TCFA group (35.1 ± 32.3 HU vs. 62.0 ± 33.6 HU, p < 0.001). The frequency of ring-like enhancement in the TCFA group was higher than in the non-TCFA group (44% vs. 4%, p < 0.0001). The sensitivity, specificity, positive predictive value, and negative predictive value of ring-like enhancement for detecting TCFA are 44%, 96%, 79%, and 85%, respectively. By stepwise regression, the ring-like enhancement, high-sensitive C-reactive protein, and diagnosis of acute events were associated with the presence of TCFA at the culprit site.

CONCLUSIONS: MDCT can identify differences in plaque morphologies between TCFA and non-TCFA. From our results, MDCT may provide for the noninvasive assessment of vulnerable plaque.

PMID:

Impact of Primary Coronary Angioplasty Delay on Myocardial Salvage, Infarct Size, and Microvascular Damage in Patients with ST-Segment Elevation Myocardial Infarction: Insight From Cardiovascular Magnetic Resonance

OBJECTIVES: We investigated the extent and nature of myocardial damage by using cardiovascular magnetic resonance (CMR) in relation to different time-to-reperfusion intervals. Previous studies evaluating the influence of time to reperfusion on infarct size (IS) and myocardial salvage in patients with ST-segment elevation myocardial infarction (STEMI) have yielded conflicting results.

METHODS: Seventy patients with STEMI successfully treated with primary percutaneous coronary intervention within 12 h from symptom onset underwent CMR 3 +/- 2 days after hospital admission. Patients were subcategorized into 4 time-to-reperfusion (symptom onset to balloon) quartiles: 90 to 150 min (group II, n = 17), >150 to 360 min (group III, n = 17), and >360 min (group IV, n = 17). T2-weighted short tau inversion recovery and late gadolinium enhancement CMR were used to characterize reversible and irreversible myocardial injury (area at risk and IS, respectively); salvaged myocardium was defined as the normalized difference between extent of T2-weighted short tau inversion recovery and late gadolinium enhancement.

RESULTS: Shorter time-to-reperfusion (group I) was associated with smaller IS and microvascular obstruction and larger salvaged myocardium. Mean IS progressively increased overtime: 8% (group I), 11.7% (group II), 12.7% (group III), and 17.9% (group IV), p = 0.017; similarly, MVO was larger in patients reperfused later (0.5%, 1.5%, 3.7%, and 6.6%, respectively, p = 0.047). Accordingly, salvaged myocardium markedly decreased when reperfusion occurred >90 min of coronary occlusion (8.5%, 3.2%, 2.4%, and 2.1%, respectively, p = 0.004).

CONCLUSIONS: In patients with STEMI treated with primary percutaneous coronary intervention, time to reperfusion determines the extent of reversible and irreversible myocardial injury assessed by CMR. In particular, salvaged myocardium is markedly reduced when reperfusion occurs >90 min of coronary occlusion.

PMID: 19942086

Association of Traditional Cardiovascular Risk Factors with Coronary Plaque Sub-Types Assessed by 64-Slice Computed Tomography Angiography in a Large Cohort of Asymptomatic Subjects

OBJECTIVES: Although prior studies have shown that traditional cardiovascular (CV) risk factors are associated with the burden of coronary atherosclerosis, less is known about the relationship of risk factors with coronary plaque sub-types. Coronary computed tomography angiography (CCTA) allows an assessment of both, total disease burden and plaque characteristics. In this study, we investigate the relationship between traditional CV risk factors and the presence and extent of coronary plaque sub-types in a large group of asymptomatic individuals.

METHODS: The study population consisted of 1015 asymptomatic Korean subjects (53+/-10 years; 64% were males) free of known CV disease who underwent 64-slice CCTA as part of a health screening evaluation. We analyzed plaque characteristics on a per-segment basis according to the modified American Heart Association classification. Plaques in which calcified tissue occupied more than 50% of the plaque area were classified as calcified (CAP), <50% calcified area as mixed (MCAP), and plaques without any calcium as non-calcified (NCAP).

RESULTS: A total of 215 (21%) subjects had coronary plaque while 800 (79%) had no identifiable disease. Multivariate regression analysis demonstrated that increased age (per decade) and gender are the strongest predictors for the presence of any coronary plaque or the presence of at least one segment of CAP and MCAP (any plaque-age: OR 2.89; 95% CI 2.34, 3.56; male gender: OR 5.21; 95% CI 3.20, 8.49; CAP-age: OR 2.75; 95% CI 2.12, 3.58; male gender: 4.78; 95% CI 2.48, 9.23; MCAP-age: OR 2.62; 95% CI 2.02, 3.39; male gender: OR 4.15; 95% CI 2.17, 7.94). The strongest predictors for the presence of any NCAP were gender (OR 3.56; 95% CI 1.96-6.55) and diabetes mellitus (OR 2.87; 95% CI 1.63-5.08). When looking at the multivariate association between the presence of >/=2 coronary segments with a plaque sub-type and CV risk factors, male gender was the strongest predictor for CAP (OR 7.31; 95% CI 2.12, 25.20) and MCAP (OR 5.54; 95% CI 1.84, 16.68). Alternatively, smoking was the strongest predictor for the presence of >2 coronary segments with NCAP (OR 4.86; 95% CI 1.68, 14.07). Low-density lipoprotein cholesterol (LDL-C) was only a predictor for the presence and extent of mixed coronary plaque.

CONCLUSION: Age and gender are overall the strongest predictors of atherosclerosis as assessed by CCTA in this large asymptomatic Korean population and these two risk factors are not particularly associated with a specific coronary plaque sub-type. Smoking is a strong predictor of NCAP, which has been suggested by previous reports as a more vulnerable lesion. Whether a specific plaque sub-type is associated with a worse prognosis is yet to be determined by future prospective studies.

PMID: 19524922

Three Dimensional Evaluation of the Aortic Annulus using Multislice Computer Tomography: Are Manufacturer’s Guidelines for Sizing for Percutaneous Aortic Valve Replacement Helpful?

OBJECTIVES: To evaluate the effects of applying current sizing guidelines to different multislice computer tomography (MSCT) aortic annulus measurements on Corevalve (CRS) size selection.

METHODS: Multislice computer tomography annulus diameters [minimum: D(min); maximum: D(max); mean: D(mean) = (D(min) + D(max))/2; mean from circumference: D(circ); mean from surface area: D(CSA)] were measured in 75 patients referred for percutaneous valve replacement.

RESULTS: Fifty patients subsequently received a CRS (26 mm: n = 22; 29 mm: n = 28). D(min) and D(max) differed substantially [mean difference (95% CI) = 6.5 mm (5.7-7.2), P < 0.001]. If D(min) were used for sizing 26% of 75 patients would be ineligible (annulus too small in 23%, too large in 3%), 48% would receive a 26 mm and 12% a 29 mm CRS. If D(max) were used, 39% would be ineligible (all annuli too large), 4% would receive a 26 mm, and 52% a 29 mm CRS. Using D(mean), D(circ), or D(CSA) most patients would receive a 29 mm CRS and 11, 16, and 9% would be ineligible. In 50 patients who received a CRS operator choice corresponded best with sizing based on D(CSA) and D(mean) (76%, 74%), but undersizing occurred in 20 and 22% of which half were ineligible (annulus too large).

CONCLUSIONS: Eligibility varied substantially depending on the sizing criterion. In clinical practice both under- and oversizing were common. Industry guidelines should recognize the oval shape of the aortic annulus.

PMID: 19995874

CT clinical perspective: Challenges and the Impact of Future Technology Developments

Computed tomography is not the most frequent radiologic imaging procedure, but is arguably the most important in terms of clinical impact. CT is used extensively for emergencies, cardiovascular, pulmonary, gastrointestinal, endocrine, neurological, orthopedic and other applications -often as the first and only imaging procedure needed for diagnosis. The chances are very high that a patient will have a CT scan in the emergency department, as an outpatient or as an inpatient for a multitude of indications – pain, trauma, suspected infection or malignancy, and frequently to investigate symptoms such as pain, or to answer a question raised by another abnormal test, such as an EKG abnormality or ultrasound finding. Despite the universality of CT in hospitals and clinics as well as free-standing imaging centers, the technology continues to evolve with greater coverage, faster acquisition and multienergy sources or detectors. The most demanding imaging applications are cardiovascular, where complex motion and small morphologic features coexist, so imaging methods that are very satisfactory elsewhere in the body may not be successful. Clinical CT scanning consists of administering toxic materials, e.g., contrast media, often monitoring the EKG and illuminating the body with high brightness x-rays. Larger area detectors and higher acquisition rates are welcome improvements, but don’t solve all of the problems encountered with scan variability due to respiratory, random body, and cardiac motion, especially in a spectrum of patients from infant to massively obese adult sizes (< 1 kg to 250 kg or more). The challenges and pitfalls in CT will be delineated and evaluated relative to current and future technology.

PMID: 19965146