Judd E. Reed

Nonparallel changes in global left ventricular chamber volume and muscle mass during the first year after transmural myocardial infarction in humans

OBJECTIVES This study was designed to serially assess time-dependent changes in both chamber volume and myocardial muscle mass after infarction in humans. BACKGROUND Dilation of the left ventricular chamber has been previously described after transmural myocardial infarction. METHODS Global left ventricular chamber volumes and muscle mass were quantified by using cine computed tomographic scanning in 18 patients at hospital discharge and 6 weeks, 6 months and 1 year after an initial transmural myocardial infarction (12 anterior and 6 inferior). No patient had heart failure during the initial hospital stay or on any subsequent follow-up visit. RESULTS The patients with anterior myocardial infarction (estimated infarct extent 27 +/- 2% of left ventricle) demonstrated a progressive increase in left ventricular end-diastolic volume from 148 +/- 9 ml (mean +/- SEM) at hospital discharge to 180 +/- 9 ml at 1 year after infarction (p < 0.001). However, global left ventricular muscle mass decreased significantly during the 1st 6 weeks after infarction but returned by 1 year to nearly the value determined at hospital discharge (177 +/- 13 vs. 165 +/- 10 g, p = NS). The changes in global muscle mass did not parallel the steady and progressive increases in chamber end-diastolic volume. The end-diastolic chamber volume to muscle mass ratio, an index of global left ventricular wall tension, increased steadily after hospital discharge but remained level by 1 year after infarction. The time course of changes in global end-systolic chamber volume was roughly proportional to the concomitant changes in end-diastolic volume. During this same time period, left ventricular stroke volume remained constant or improved from that determined at baseline. Global left ventricular end-diastolic and end-systolic volumes remained relatively static during the 1st year in the patient subgroup with inferior wall myocardial infarction (estimated infarct extent 10 +/- 1% of left ventricle), but global muscle (myocardial) mass initially decreased and then increased in a pattern similar, although of smaller magnitude, to that observed in patients with anterior wall myocardial infarction. CONCLUSIONS Overall, left ventricular end-diastolic and end-systolic chamber volumes increase progressively from hospital discharge to 1 year after an initial transmural myocardial infarction in patients with a moderately large anterior wall infarction but remain stable in patients with a small inferior wall infarction. Concurrently, total left ventricular muscle mass decreases significantly during the initial 6 weeks after infarction (presumed largely secondary to changes in the necrotic segments) but then returns to the hospital discharge baseline values by 1 year. These data are consistent with the late development of, at most, limited ventricular hypertrophy in the noninfarcted myocardium that occurs well after the early and progressive left ventricular chamber dilation observed in patients with a moderate to large myocardial infarction. These data, in particular as applied to patients with anterior infarction, suggest that ventricular wall tension is significantly elevated at least during the 1st year after an initial transmural myocardial infarction. These observations may explain the potential utility of agents aimed at reducing afterload or ventricular wall tension during the early convalescent phase after myocardial infarction.

Pituitary desensitization to gonadotropin- releasing hormone increases abdominal adiposity in hyperandrogenic anovulatory women

OBJECTIVE To determine whether hyperandrogenism in anovulatory women affects body fat distribution. DESIGN Prospective nonrandomized study. SETTING An academic research environment. PATIENT(S) Ten hyperandrogenic anovulatory patients and 10 healthy women matched by body mass index. INTERVENTION(S) Regional body fat analysis was performed before and after 3 months of GnRH analogue (GnRH-a) therapy. MAIN OUTCOME MEASURE(S) Body fat distribution was measured by waist-to-hip circumference ratio, single-slice computed tomography imaging (L2-3 interspace), and total body dual-energy x-ray absorptiometry. RESULT(S) Weight, body mass index, waist-to-hip circumference ratio, total body and leg fat mass, and subcutaneous adipose area were unaffected by the presence of hyperandrogenism or the use of GnRH-a therapy. Basal abdominal fat mass, abdomen-to-leg fat mass ratio, visceral adipose area, and total visceral adipose volume were comparable in both study groups. The abdominal fat mass increased in both groups during GnRH-a therapy, whereas the abdomen-to-leg fat mass ratio rose significantly only in the hyperandrogenic patients. During GnRH-a therapy, the hyperandrogenic patients demonstrated a significant increase in visceral adipose area compared with the healthy women so that total visceral adipose volume increased significantly in the former but not the latter. CONCLUSION(S) Three months of GnRH-a administration preferentially increased abdominal fat, as measured by single-slice computed tomography imaging and total body dual-energy x-ray absorptiometry, in hyperandrogenic anovulatory women.

Comparison of two different software systems for electron-beam CT-derived quantification of coronary calcification.

OBJECTIVE The growing interest in coronary calcium quantification by electron-beam CT (EBCT) has led to the development of various software systems for the analysis of EBCT raw data, but it is unknown whether these software systems yield comparable results. METHODS Two sets of EBCT scans were obtained in 73 asymptomatic patients less than 15 minutes apart. Both scans of each patient were analyzed using two different software systems, the Mayo Clinic software and the AccuImage Scoring System. The authors compared the calcium quantities yielded by the two different software systems, analyzed the interscan variability, and calculated the interobserver variability. Finally, they investigated the influence of the CT density factor inherent in the widely used Agatston score for the quantification of coronary calcium on reproducibility. RESULTS The mean score determined by the Mayo Clinic software was 14% greater than that determined by the AccuImage system. The mean difference between the two systems was 14% +/- 25%, and the median difference was 3%. The relative mean and the median difference between the two scans of one patient were 15.3% and 6% determined by the AccuImage system and 17% and 6.5% determined by the Mayo Clinic software. The interobserver reliability calculated by the Mayo Clinic software was better than that of the AccuImage system. There was a trend for better reproducibility using calcium area rather than the Agatson score. CONCLUSIONS Two different scoring systems do not necessarily yield the same result. Calcium quantities were systematically determined to be greater by one system than the other, and there were significant differences with regard to interobserver reliability. Hence, software should be tested with regard to reproducibility data, and the interpretation of calcium quantities should acknowledge which type of software was used.

Measurement of myocardial infarct size by electron beam computed tomography: a comparison with 99mTc sestamibi.

RATIONALE AND OBJECTIVES The authors sought to determine, using a variety of regional left ventricular ejection fraction (EF) and wall thickening (WTh) criteria, the applicability to measure left ventricular (LV) infarct size using electron-beam CT (EBCT) in patients as compared with technetium 99m (99mTc) sestamibi scanning as reference standard. METHODS Twelve patients (age 57 +/- 11 years) underwent 99mTc sestamibi scanning and EBCT at hospital discharge after an acute index anterior myocardial infarction. Left ventricular infarct size was defined using standard 99mTc sestamibi scanning. Regional EF and WTh were analyzed on each EBCT scan with use of a floating epicardial centroid method. In five contiguous LV tomograms, the amount of infarcted myocardium was estimated using the following EF and WTh criteria: EF < or = 35%, 30%, 25%, 20%, and WTh < or = 2 mm, 1 mm, and 0 mm. RESULTS Infarct size measured with 99mTc sestamibi was 33.3% (+/- 18.3%) (mean +/- SD, range 6%-54%) of the LV. Using an EF < or = 35% or absolute WTh < or = 2 mm as criteria for infarcted myocardium, EBCT yielded 28% (+/- 17%) and 27% (+/- 16%), respectively (P = NS, paired Students t test, versus 99mTc sestamibi). Although, with use of the other criteria, EBCT tended to underestimate infarct size compared with 99mTc sestamibi, a close correlation across the entire range of infarct size determinations (range, 0.72-0.82) regardless of the underlying criteria suggested an internal consistency of the data. CONCLUSIONS Quantitative analysis of regional myocardial function by EBCT allows an estimate of anterior infarct size when compared with 99mTc sestamibi. This suggests that in addition to previously established applications after acute myocardial infarction such as examination of cardiac volumes and mass, EBCT also may provide for infarct size determination.

Feasibility of planar virtual pathology: a new paradigm in volume-rendered CT colonography.

Planar virtual pathology (PVP) is an isometric rendering method for examining the CT colonography dataset, which renders the colon in discrete colonic segments. Ten patients with 36 polyps were evaluated using traditional 2D axial, 2D multiplanar reformatted, and 3D endoluminal images as well as PVP. PVP displayed 13 of 17 (76%) polyps of >1 cm, whereas 11 of 17 (65%) were detected using traditional rendering methods. PVP may be a useful adjunct in detecting additional polyps at CT colonography.

Automatic detection of myocardial contours in cine-computed tomographic images

Quantitative evaluation of cardiac function from cardiac images requires the identification of the myocardial walls. This generally requires the clinician to view the image and interactively trace the contours. This method is susceptible to great variability that depends on the experience and knowledge of the particular operator tracing the contours. The particular imaging modality that is used may also add tracing difficulties. Cine-computed tomography (cine-CT) is an imaging modality capable of providing high quality cross-sectional images of the heart. CT images, however, are cluttered, i.e., objects that are not of interest, such as the chest wall, liver, stomach, are also visible in the image. To decrease this variability, investigators have developed computer-assisted or near-automatic techniques for tracing these contours. All of these techniques, however, require some operator intervention to confidently identify myocardial borders. The authors present a new algorithm that automatically finds the heart within the chest, and then proceeds to outline (detect) the myocardial contours. Information at each tomographic slice is used to estimate the contours at the next tomographic slice, thus allowing the algorithm to work in near-apical cross-sectional images where the myocardial borders are often difficult to identify. The algorithm does not require operator input and can be used in a batch mode to process large quantities of data. An evaluation and correction phase is included to allow an operator to view the results and selectively correct portions of contours. The authors tested the algorithm by automatically identifying the myocardial borders of 27 cardiac images obtained from three human subjects and quantitatively comparing these automatically determined borders with those traced by an experienced cardiologist.

System for quantitative analysis of coronary calcification via electron-beam computed tomography

Electron beam computed tomography (EBCT) has provided a new tool for identification and possible quantification of coronary arterial plaque calcium. EBCT is the only imaging modality currently available which generates images of the spatial, temporal, and contrast resolution required for the identification of small foci of calcium and the potential for accurate quantification of calcium. Meanwhile, interest in quantification of coronary arterial calcium via EBCT and its correlation with severity of coronary atherosclerosis is increasing. Data remain inconclusive, but it appears that the reproducibility of quantitative grading of the extent of calcification by EBCT may be limited, in part, by the arbitrary nature of the scoring algorithm employed within the analysis tools currently provided by the EBCT manufacturer. It has not been possible to objectively determine optimum values for minimum plaque area and brightness threshold or to quantitatively determine whether single optimal values even exist. Also, although the current system tabulates the score, area, and mean attenuation for each plaque, the locations of the plaques are not reported.

Right ventricular dilatation and remodeling the first year after an initial transmural wall left ventricular myocardial infarction

Left ventricular (LV) remodeling after LV myocardial infarction was described previously. Little is known regarding concomitant adaptation, if any, in right ventricular (RV) volumes after LV infarction. To examine this issue, cine-computed tomography was used to determine serial changes in absolute global LV and RV volumes in 27 patients without clinical heart failure during the first year after an initial Q-wave myocardial infarction (14 anterior and 13 inferior). The patient group with anterior wall LV infarction showed progressive increases in LV and RV volumes from hospital discharge to 1 year (end-diastolic volumes +25 and +13%, respectively; and end-systolic volumes +35 and +15%, respectively). In patients with inferior wall LV infarction, both LV end-diastolic and end-systolic volumes increased significantly during the study period (+13 and +15%, respectively). Despite a trend for RV end-diastolic volume to be increased at 1 year, neither end-diastolic nor end-systolic volume increased significantly after hospital discharge following inferior wall LV infarction. Absolute RV end-diastolic volume was not significantly different between the infarct groups at any time after infarction. In conclusion, global changes occur in both LV and RV volumes during the first year after an initial infarction regardless of infarct location. The magnitude of these changes was greater after anterior than inferior wall LV infarction.

Serial changes in left and right ventricular systolic and diastolic dynamics during the first year after an index left ventricular Q wave myocardial infarction

OBJECTIVES This study quantified serially biventricular emptying and filling after infarction and related these to changes in volume, muscle mass, wall stress and contractility. BACKGROUND There are limited data on serial changes in ventricular dynamics after infarction. METHODS Forty patients had serial electron beam computed tomographic examinations during the first year after index Q wave infarction (21 anterior, 19 inferior), and global biventricular volumes, peak rates of emptying and filling and left ventricular muscle masses were quantified. Mean mid-left ventricular end-systolic wall stresses, rate-corrected velocities of circumferential shortening and two indexes of left ventricular contractility--the end-systolic wall stress/volume ratio and the end-systolic wall stress/rate-corrected velocity of circumferential shortening relation--were estimated in each instance. RESULTS Patients with anterior infarction had an increase in biventricular chamber volume of 15% to 35% by 1 year. Global biventricular peak rates of emptying and filling were decreased by 20% to 30% from hospital discharge to 6 weeks but thereafter remained unchanged. Despite a significant increase in mean wall stresses, the end-systolic wall stress/volume ratio remained unchanged during the year. The rate-corrected velocities of circumferential shortening declined serially after anterior infarction but did so in proportion to the increase in mean wall stresses, consistent with no net change in left ventricular contractility. Patients with inferior infarction showed a trend toward similar changes, but the magnitudes did not reach significance. CONCLUSIONS Left (and right) ventricular global peak rates of emptying and filling during the first year after infarction can be altered in the absence of additional ischemic injury but are more consistent with responses to changes in left ventricular afterload than changes in intrinsic ventricular performance or contractility. Serial changes in left ventricular afterload after infarction are largely due to progressive chamber enlargement and limited development of compensatory hypertrophy during the first year. Intrinsic global left ventricular contractile performance was not altered by postinfarction cardiac remodeling in the patients examined.

Regional left ventricular wall thickness and systolic function during the first year after index anterior wall myocardial infarction: Serial effects of ventricular remodeling

There is controversy regarding changes in regional left ventricular systolic function and thickness during remodeling after infarction. To address this, electron beam computed tomography was done in 22 patients with an index anterior wall infarction at discharge, 6 weeks, 6 months and 1 year, and global ventricular chamber volumes and mass quantified. A mid-ventricular short-axis scan from each study was divided into 4, 90 degrees sectors (anterior, septal, lateral and posterior walls). Regional wall thickness, ejection fraction, and absolute and percent wall thickening were determined and compared with 10 normal adults. Global infarct size was estimated at 24.2%+/- 3.4% of the ventricle. In these subjects, the ventricular chamber enlarged steadily during the year, while global ventricular mass initially decreased during the first 6 weeks, but then increased by 1 year. Regional ejection fraction changed little during the year, apart from the lateral wall, which was less than normal. Absolute wall thickening was reduced in the anterior (infarct) and septal walls throughout the year, but was normal and unchanged in the posterior and lateral walls. Regional percent wall thickening was not different from normal individuals. The anterior wall was thinned at discharge and tended to thin further during the year. The lateral wall was thinner than normal 6 weeks after infarction, but remained unchanged thereafter. The posterior wall tended to thin for the first 6 months, but the values at any time were not above normal. There was little change in septal wall thickness throughout the year. It is concluded that, after a moderate size, uncomplicated index anterior infarction, regional systolic function remains generally unaffected by remodeling. However, regional walls tend to thin and/or remain at normal thickness. These data confirm differential regional patterns after anterior infarction for systolic function, muscle atrophy and/or minimal hypertrophy which accompany serial changes in global ventricular chamber volumes and mass.