Electron-beam Computed Tomography Studies Research Articles

Rate of Progression and Functional Significance of Aortic Root Calcification After Homograft Versus Freestyle Aortic Root Replacement

Calcification is an important limitation after aortic root replacement. The aims were to compare the long-term degree and rate of calcification of homografts versus Medtronic freestyle aortic roots to determine the functional consequences and predictive factors. One hundred sixty-six patients were prospectively randomized to undergo homograft versus freestyle total aortic root replacement. Of those, 98 patients underwent a total of 248 electron beam computed tomography studies at 0.5, 1, 1.5, 2, 3, and 8 years. All patients underwent yearly clinical and echocardiographic follow-up. Calcium scores were measured using Agatston scoring. Mixed effects models demonstrate significantly higher calcium scores in homograft roots than freestyle at 1.5 years (P=0.02), 2 years (P=0.02), and 3 years (P=0.01), with a trend at 1 year (P=0.06) and 8 years (P=0.1). Homograft calcification occurs significantly faster than in freestyle prostheses between 6 months and 3 years after surgery (P=0.02). Calcification occurs at a similar rate thereafter up to 8 years (P=0.3). At 8 years, freedom from aortic valve dysfunction was lower in homografts than freestyle roots (P=0.06). Freedom from reoperation was 93+/-4% in the homograft group versus 100+/-0% in the freestyle group at 8 years (P=0.01). On multivariate analysis, redo surgery (P<0.001), smoking (P<0.01), atrial fibrillation (P=0.001), family history of coronary artery disease (P<0.01), and a degenerative etiology (P=0.02) were predictive of higher calcium scores. Homograft roots exhibit significantly higher calcium scores than freestyle roots because of faster early calcification.

Overview of renal bone disease: Causes of treatment failure, clinical observations, the changing pattern of bone lesions, and future therapeutic approach: Management of comorbidities in kidney disease in the 21st century: Anemia and bone disease

Divalent ions, metabolism abnormalities, and hyperparathyroid bone disease noted in patients with chronic kidney disease (CKD) develop early in the course of renal insufficiency. In the last two decades, therapy has focused mostly in treating the bone lesion as well as controlling the secondary hyperparathyroidism. However, recent large epidemiologic studies have highlighted the importance of both hyperphosphatemia and an increase in the calcium burden as major factors leading to the high mortality rate of end-stage renal disease (ESRD) patients [1–3]. Furthermore, a recent study strongly suggests the high mortality rate may be due to an increase in cardiac events [4]. In the present manuscript, the causes for the failure of the original therapeutic goals will be discussed first; the changing pattern in the bone lesions will be assessed second; and third, future therapeutic approaches will be explored, with special emphasis in early therapy and avoiding the cardiovascular abnormalities recently noted in CKD patients.

Progression of coronary arteriosclerosis as monitoring the therapeutic success of hyperlipidemia

Coronary calcium represents an integral part of coronary atherosclerosis. It results from an actively regulated process and already appears in early stages of the disease. Studies using electron-beam computed tomography (EBCT) have demonstrated that an accelerated progression of coronary calcified atherosclerosis is associated with an increased rate of clinical events. In experimental animal models, effective lowering of LDL cholesterol stops the progression of coronary calcified atherosclerosis. A number of EBCT-derived retrospective analyses have consistently reported that LDL cholesterol values are the most important factor influencing the progression of coronary calcified atherosclerosis. In high-risk patients with no clinical coronary artery disease who were not specifically treated, a mean annual progression of coronary calcium of 52% was observed. In the presence of statin drug therapy, progression ranged from -7% through 22%, depending on the LDL cholesterol levels during therapy. A preliminary prospective investigation has confirmed these results and, in particular, suggested that reaching low LDL cholesterol levels < 100 mg/dl effectively stops the progression of coronary calcified atherosclerosis. LDL cholesterol independent ("pleiotropic") effects of statin drugs could not be demonstrated by using EBCT. At present, two large prospective, randomized trials are being conducted which analyze the effects of intensified versus standard statin drug therapy on the progression of coronary calcified atherosclerosis by EBCT. Serial EBCT studies enable analysis of the interaction between therapeutic measures, progression of coronary calcified atherosclerosis and clinical course of the patients by virtue of direct visualization of the activity of coronary plaque disease. This has already been successfully implemented in small patients groups. Validation in the individual patient is pending. Prospective, randomized therapeutic trials are expected to yield valuable knowledge for clinical practice.

Optimal ECG Trigger Point in Electron-Beam CT Studies: Three Methods for Minimizing Motion Artifacts

Rationale and Objectives The authors hypothesized that electrocardiographic triggering near end systole could minimize motion artifacts in electron-beam computed tomography (CT) of the coronary artery. Materials and Methods The study included 2,660 patients who underwent coronary artery calcium scanning with electron-beam CT. Trigger times were as follows: end of T wave, 120 to 25 msec before end of T wave, 25–50 msec after end of T wave, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 90%, and 100% of R-R interval. The authors divided each group into seven subgroups according to heart rate. The percentages of cases with motion artifact in the right coronary artery were computed. Optimal trigger times were defined for each group, as well as for scan acquisitions of 250 and 200 msec. Results The optimal trigger times were as follows for heart rates of less than 50, 51–60, 61–70, 71–80, 81–90, 91–100, and more than 100 beats per minute, respectively: for 100-msec scans, 359 (27% of the R-R interval), 228 (31%), 314 (34%), 304 (38%), 289 (41%), 283 (45%), and 274 msec (48%) after the R wave; for 250-msec scans, 840 (63%), 654 (60%), 240 (26%), 224 (28%), 219 (31%), 208 (33%), and 200 msec (35%) after the R wave; and for 200-msec scans, 722 (65%), 687 (63%), 249 (27%), 248 (31%), 244 (35%), 233 (37%), and 223 msec (39%) after the R wave. Conclusion The use of these new electrocardiographic triggers before end systole yielded the lowest percentage of motion artifacts (<3% across all heart rates), much lower than for conventional triggers (51% of cases with motion artifact for 80% trigger, P < .001).

Validation of pulmonary venous obstruction by electron beam computed tomography in children with congenital heart disease

The purpose of this study was to explore the useful imaging findings of electron beam computed tomography (EBCT) for diagnosing pulmonary venous obstruction (PVO) in children with congenital heart disease. From July 1995 to March 1998, 17 children (9 girls and 8 boys, aged 7 days to 14 years and 9 months [median 3 months]) with the diagnosis of PVO were enrolled in this study. All images were obtained by EBCT at the end-diastolic phase of the cardiac cycle after administration of intravenous iodinated contrast medium. The findings of 25 EBCT studies were retrospectively analyzed by 2 radiologists and were correlated with echocardiography, angiocardiography, and surgical findings. Main findings on EBCT for PVO were (1) structural narrowing, (2) thickened interlobular septa, (3) peribronchovascular cuffing, and (4) ground-glass opacity of the alveoli. Structural narrowing along the course of the pulmonary venous drainage was the most important finding in all examinations (25 of 25). Lung parenchymal changes secondary to PVO included thickened interlobular septa (17 of 25), peribronchovascular cuffing (15 of 25), and ground-glass opacity of the alveoli (8 of 25). Thus, the combination of these findings provides very useful data for the definitive diagnosis of PVO. Characteristic electron beam computed tomographic findings can validate suspected PVO noninvasively.

Minimally invasive evaluation of coronary microvascular function by electron beam computed tomography.

We previously demonstrated that in vivo electron-beam computed tomography (EBCT)-based indicator-dilution methods provide an estimate of intramyocardial blood volume (BV) and perfusion (F), which relate as BV=aF+b radicalF, where a characterizes the recruitable (exchange) and b the nonrecruitable (conduit) component of the myocardial microcirculation. In the present study, we compared BV and F with intracoronary Doppler ultrasound-based coronary blood flow (CBF) as a method for detecting and quantifying differential responses of these microvascular components to vasoactive drugs in normal (control) and hypercholesterolemic (HC) pigs. BV and F values were obtained from contrast-enhanced EBCT studies in 14 HC and 14 control pigs. BV, F, and CBF values were obtained at baseline (intracoronary infusion of saline) and after 5 minutes each of intracoronary infusion of adenosine (100 microgram. kg(-1). min(-1)) and nitroglycerin (40 microgram/min). BV and CBF reserves in response to adenosine were attenuated in HC pigs compared with controls (90+/-36% versus 127+/-42%, P<0.03, and 485+/-182% versus 688+/-160%, P<0.01, respectively). The relationship between BV and F showed consistently lower recruitable BV in HC versus control pigs. Nonrecruitable BV reserve in response to adenosine was attenuated in HC compared with controls (77+/-20% versus 135+/-28%, P<0.001). Our findings are consistent with HC-induced impairment of intramyocardial resistance vessel function. EBCT technology allows minimally invasive evaluation of intramyocardial microcirculatory function and permits assessment of microvascular BV distribution in different functional components. This method may be of value in evaluating the coronary microcirculation in pathophysiological states such as hypercholesterolemia.

Simple single-section method for measurement of left and right atrial volumes with electron-beam CT

The authors estimated left and right atrial volumes by using a simple method of measurement with nonenhanced electron-beam computed tomography (CT). One hundred sixty-four contrast material-enhanced electron-beam CT studies were divided into two groups. Group 1, which included 104 studies, was used to develop the measurement method (i.e., the formulas) for measuring left and right atrial volumes from a nonenhanced study. Group 2 consisted of 60 studies on which the validity of the method was tested. Measurement of left and right atrial volumes was performed on all section levels by tracing the respective atrial borders for each section, then multiplying the area by section thickness and summing the resultant volumes. Calculated left and right atrial volumes were derived by using the biggest atrial area and cephalic-caudal span. The span was equal to section thickness times the number of sections in which the atria were present. Linear regression analysis formulas were acquired with the biggest atrial area and cephalic-caudal span. Left and right atrial calculated volumes were obtained with these formulas and demonstrated a significant good relation (r > .95, P < .001) and a difference of less than 11% (P < .05) in absolute values between measured and calculated volumes. Intraobserver, interobserver, and interstudy reproducibility were excellent, with less than 10% difference in absolute values. Left and right atrial volumes can be accurately estimated from a single midventricular section by using nonenhanced electron-beam CT.

Usefulness of Electron Beam Computed Tomography in Children With Heterotaxy Syndrome

Children with heterotaxy syndrome frequently have complex cardiac and noncardiac malformations requiring detailed diagnostic evaluation for management planning. Direct delineation of these structures by electron beam computed tomography (EBCT) is validated as a means of diagnosis. From July 1995 to March 1997, 32 patients (16 girls, 16 boys) with clinically impressed heterotaxy syndrome were enrolled in this study. After evaluation by echocardiography, EBCT studies were performed. Interpretation of cardiac anomalies was performed by sequential analysis based on these cross-sectional images. The diagnoses were subsequently confirmed by angiocardiography and surgical findings. Twenty-eight patients had bilateral trifurcated bronchi, and most of these (24 of 28) did not have a spleen. Four patients had bilateral bifurcated bronchi, 2 patients had polysplenia, and the other 2 patients had a lobulated single spleen. We found that laterality could be identified by EBCT in all patients. Comparison of diagnostic yield between echocardiography, catheterization, and EBCT showed that EBCT is superior to echocardiography and catheterization in demonstration of pulmonary venous anatomy and presence of a very small rudimentary ventricle. In addition, associated visceral, bronchopulmonary, mediastinal, and intracardiac anomalies could all be clearly delineated by EBCT at the same time. Thus, EBCT is a promising complementary modality for an overall understanding of heterotaxy syndrome.

Reproducibility of right and left ventricular volume measurements by electron-beam CT in patients with congestive heart failure.

The applicability and reproducibility of electron-beam computed tomography (EBCT) was tested to define left and right ventricular volumes in patients with congestive heart failure in a clinical setting. Ten patients (mean age 64 +/- 11 years) with dilated hearts and stable congestive heart failure (functional class III-IV) were studied. After determination of the individual circulation time, two serial short axis polytomographic EBCT studies were performed within a mean interval of 14.8 +/- 10 days. Following intravenous contrast administration, biventricular end-diastolic volumes (LVEDV, RVEDV), end-systolic volumes (LVESV, RVESV), and left ventricular muscle mass (LVMM) were determined using previously developed techniques. Adequate contrast opacification in both ventricular cavities was obtained in all patients at baseline and at follow-up. Values were 323.4 +/- 99.3 (mean +/- SD) and 332.6 +/- 105.4 ml for LVEDV, 249.3 +/- 75.6 and 250.5 +/- 79.3 ml for LVESV, 236.8 +/- 56.2 and 251.2 +/- 72.7 ml for RVEDV, 179.8 +/- 76.4 and 188.3 +/- 64.0 ml for RVESV, and 207.7 +/- 70.6 and 204.9 +/- 81.9 g for LVMM (p = NS, respectively, paired t-test). Linear regression analysis correlating biventricular volumes and left ventricular muscle mass measurements in the serial scans yielded r-values in the range of 0.89 to 0.95 and a small SEE. The SE of the mean differences between left and right ventricular ejection fraction measurements was 1 point, respectively. EBCT studies of ventricular volumes in patients with dilated hearts and congestive heart failure are highly reproducible and offer the potential for serial assessment of these patients in whom quantitation of ventricular volumes has been shown to be of prognostic value.

The Peripheral Intravenous Cannula: A Cause of Venous Air Embolism

Venous air embolism has been reported as a complication of invasive diagnostic and therapeutic procedures or accidental trauma. Little is known about the incidence of air embolism after minimal intravenous manipulations, such as the insertion of a peripheral intravenous cannula. Small air emboli in the central veins, central arteries, and cardiac chambers can be detected during electron-beam computed tomography studies of the chest. Electron-beam computed tomography of the chest was performed on 208 patients after the insertion of a peripheral intravenous cannula. The images were analyzed using a digital workstation. Small air embolism was visible in 10 of 208 (4.8%) patients in the following locations: the pulmonary trunk in 6 patients, the right ventricle in 2, the right atrium in 1, and the left brachiocephalic vein in 1. The embolism was asymptomatic in each patient. Although the potential risks in patients with septal defects and shunts remain unclear, caution should be taken with minimal intravenous manipulations.

The peripheral intravenous cannula: a cause of venous air embolism.

Venous air embolism has been reported as a complication of invasive diagnostic and therapeutic procedures or accidental trauma. Little is known about the incidence of air embolism after minimal intravenous manipulations, such as the insertion of a peripheral intravenous cannula. Small air emboli in the central veins, central arteries, and cardiac chambers can be detected during electron-beam computed tomography studies of the chest. Electron-beam computed tomography of the chest was performed on 208 patients after the insertion of a peripheral intravenous cannula. The images were analyzed using a digital workstation. Small air embolism was visible in 10 of 208 (4.8%) patients in the following locations: the pulmonary trunk in 6 patients, the right ventricle in 2, the right atrium in 1, and the left brachiocephalic vein in 1. The embolism was asymptomatic in each patient. Although the potential risks in patients with septal defects and shunts remain unclear, caution should be taken with minimal intravenous manipulations.

A comparison of99mTc-MIBI myocardial SPET with electron beam computed tomography in the assessment of coronary artery disease

We compared technetium-99m methoxyisobutylisonitrile (MIBI) myocardial perfusion single-photon emission tomography (SPET) (MPS) and electron beam computed tomography (EBCT) in order to assess their respective value in the detection of coronary artery disease (CAD). 99mTc-MIBI SPET (stress-resting) and EBCT studies were performed in 51 patients with suspected CAD who underwent coronary angiography (CAG). CAG showed that of the 51 patients, 36 had coronary stenosis >/=50% while 15 had normal results. A moderate positive rank correlation was found between coronary calcification detected by EBCT and MPS score (rs=0.5283, P<0.01). The concordance between EBCT and MPS for the evaluation of CAD was 72.5% (37/51). The sensitivity of EBCT in detecting CAD in 51 patients was comparable to that of MPS (81% vs 94%, NS). However, the accuracy of EBCT was lower than that of MPS (78% vs 94%, P<0.025). As regards the detection of individual coronary artery disease, there was no significant difference in sensitivity between EBCT and MPS (65% vs 75%, NS); however, the specificity and accuracy of EBCT were lower than those of MPS (specificity: 77% vs 95%, P<0.005; accuracy 71% vs 85%, P<0.005). The sensitivity, specificity and accuracy of MPS in detecting single-vessel disease were higher than those of EBCT (sensitivity: 86% vs 42%, P<0.025; specificity: 96% vs 70%, P<0.025; accuracy: 93% vs 61%, P<0.005). However, no significant differences in the sensitivity, specificity and accuracy of MPS and EBCT were found in respect of multivessel disease. 99mTc-MIBI myocardial perfusion SPET and EBCT provide different information in the assessment of CAD. The sensitivity of EBCT for the detection of CAD is comparable with that of MPS; however, the specificity and accuracy of EBCT are lower than those of MPS. More reliable results will be obtained if both myocardial perfusion SPET and EBCT are performed.

Angiographic and electron-beam computed tomography studies of retrograde cardioplegia via the coronary sinus

Retroperfusion of the coronary sinus does not provide homogeneous distribution of cardioplegic solution. The goal of this study was to analyze the distribution of flow during retrograde cardioplegic infusion in cadaveric human hearts with two different techniques of coronary sinus cannulation: (1) internal occlusion of the coronary sinus by balloon inflation and (2) external occlusion by tightening the orifice of the coronary sinus around a simple catheter. To evaluate differences between the two techniques, angiographic and electron-beam computed tomographic studies were performed. Computed digital angiography was performed on 14 hearts. Angiographic patterns varied according to type of coronary sinus cannulation. With the balloon inflation technique, the marginal vein and the anterior descending vein were perfused first; the posterior descending vein was not perfused. This vein was opacified secondarily through a venovenous anastomosis located at the apex of the heart. Backward flow into the right atrium (steal phenomenon) was demonstrated. At completion of retroperfusion, the inferior part of the septum remained poorly opacified. Conversely, angiographic findings after external occlusion of the coronary sinus revealed simultaneous injection of all venous channels. The entire septum was well opacified at completion of retroperfusion. Electron-beam computed tomographic study was performed on eight hearts with the external occlusion technique and nine with the internal occlusion technique. The computed tomographic findings confirmed the results of digital angiography. The peak myocardial enhancement and the peak rising rate of myocardial enhancement within the interventricular septum were significantly more important ( p < 0.0001) when the external coronary sinus occlusion mode was used than when the internal coronary sinus occlusion mode was used. In all hearts except one, the right ventricular wall was not opacified, regardless of the type of cannulation and the type of radiologic analysis. This study demonstrates the importance of coronary sinus cannulation technique in optimizing the protection of the interventricular septum with retrograde cardioplegic infusion. (J T HORAC C ARDIOVASC S URG 1996;112:1046-53)

800-6 Prognostic Value of Coronary Calcium Scores by Electron Beam Computed Tomography (EBCT) in Patients Undergoing Coronary Angiography: A Multicenter Study

Four hundred and fifty two patients (pts) underwent coronary angiography (CA) and EBCT at 5 different centers between April 1989 and Dec. 1993. EBCT studies were analyzed by a cardiologist, blinded to CA and clinical data, using a specialized work station. A follow-up phone survey was completed in 53%. Three other cardiologists. blinded to CA and EBCT, reviewed records for all deaths and hospital admissions for chest pain or suspected myocardial infarction. They determined that 9 CHD deaths and 6 acute infarctions had occurred in 31 ± 14 mos. The quartile EBCT score distribution for events was:QuartileRange of Scores# of Pts# of Events1(0–6)6002(6–92)6033(92–400)6064(&lt;400)606 Logistic regression including age, sex, CA findings and log (EBCT score) showed that only log (score) predicted events. EBCT coronary calcium predicts CHD events in pts undergoing angiography but pts with lower scores can also suffer events.