Diet and Selection of Major Prey Species by Lake Michigan Salmonines, 1973–1982

To elucidate prey preferences, we quantified stomach contents of 1,231 salmonines collected from inshore (21 m or shallower) southeastern Lake Michigan during 1973–1982. Predators ate 12 species of fish. Alewife Alosa pseudoharengus made up 48–79% by weight of the diet of brown trout Salmo trutta, chinook salmon Oncorhynchus tshawytscha, coho salmon Oncorhynchus kisutch, lake trout Salvelinus namaycush, and rainbow trout Salmo gairdneri. Alewives eaten ranged from 23 to 245 mm total length; 46% were 150–200 mm. Rainbow smelt Osmerus mordax eaten were 21–245 mm long and made up 4–11% of the salmoninesˈ prey. There were significant direct linear relationships between lengths of alewives and rainbow smelt eaten and lengths of the five predators. Alewives are currently declining in Lake Michigan. If their population collapses, there should be a shift to alternative prey species. We have seen no such shift through 1982, although more recent data of other investigators show a decline in the importance of alewife in salmonine diets. Diets of the midwater‐feeding chinook and coho salmon were heavily dominated by the pelagic alewife, whereas brown and lake trout diets were more diverse. This suggests that trout should have better survival and growth than salmon, because trout would be able to utilize the more benthic yellow perch, Perca flavescens, rainbow smelt, and, to some degree, bloater Coregonus hoyi. The latter species are becoming more abundant with the decline in alewife. Under the current salmonine stocking regime, alewives will continue to supply a lower and variable portion of the salmonine diet, and predatory pressure on alewife should lead to increases in endemic prey speciesˈ populations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141728/1/tafs0677.pd

The effects of acute ischemia on the isovolumic index

The isovolumic index is the ratio of the duration of isovolumic contraction (IVC) and relaxation (IVR) divided by ejection time (ET), and has been proposed as a more sensitive descriptor of ventricular performance than the systolic time index, which ignores the period of isovolumic relaxation. To determine the effects of acute ischemia on these indices, IVC, IVR, and ET were measured in seven open-chest dogs instrumented with high-fidelity micromanometers and ultrasonic crystals and subjected to a 10-second period of coronary occlusion. Fractional shortening was significantly impaired (18.4 +/- 6.9% vs 1.9 +/- 7.3%, p p p p p < 0.05 cs control), though ET and the systolic time index were unchanged. Through incorporation of IVR, the isovolumic index was more sensitive to acute brief ischemia than the systolic time index.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27601/1/0000645.pd

Effect of coronary stenosis severity on variability of quantitative arteriography, and implications for interventional trials

Quantitative coronary arteriography is now routinely used in studies assessing arterial remodelling in response to interventions such as lipid lowering and percutaneous transluminal coronary angioplasty. Although this methodology provides both relative and absolute measurements that can be evaluated statistically as continuous variables, it is, however, often desirable or necessary to establish categorical responses to the interventions based on the variability inherent in the quantitative methods (i.e., it is often necessary to state whether individual patients, as opposed to entire groups, have "restenosed," "progressed," "regressed," and so forth, and these categorical designations are based on critical limits of variability). 1,2 These limits are generally based on an analysis of a rather diverse range of lesion severity, and the question arises as to whether the variability of measuring changes in lesion or segment morphology is affected by the initial severity of the lesion being studied. It is conceivable that variability may be greater at 1 end than at the other end of the spectrum of lesion severity. If this is true, then the use of 1 critical value to designate whether a subject has responded in a certain way would be inappropriate, and this designation would be better achieved by using criteria that more directly reflect the measurement variability of lesions of a specified, initial severity. This report examines whether the variability of measuring morphologic parameters of stenoses is affected by the baseline severity of the lesion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30152/1/0000529.pd

The hemodynamic determinants of the isovolumic index

The isovolumic index is a recently described echocardiographic parameter of left ventricular function that is calculated as the ratio between the sum of the time of isovolumic contraction and relaxation divided by the ejection time. Although the individual components of this index may be altered by heart rate and loading conditions, an analysis of the net effect of such alterations on the isovolumic index has not been undertaken. Thus, dogs were instrumented with high-fidelity micromanometers in the left ventricle, ascending aorta, and left atrium to allow determination of the individual comoonents of the isovolumic index and calculation of the index itself. Four sets of experiments were undertaken in random order. Left atrial pacing was used to increase heart rate by approximately 10 bpm in five steps. Preload was elevated in five stages by saline infusions which caused successive increases of 1 to 2 mm Hg in the left ventricular end-diastolic pressure. Systolic blood pressure was lowered or raised by approximately 10 mm Hg per stage by three progressive, steady-state infusions of nitroprusside and phenylephrine, respectively. These experiments demonstrated little change in the isovolumic index over a broad range of heart rate. Increased left ventricular end-diastolic pressure and decreased systemic pressure caused shortening of the index. Multiple regression analysis of all experiments yielded the following: isovolumic INDEX = 0.41 - 0.015 (left ventricular end-diastolic pressure) + 0.004 (systolic blood pressure); r = 0.57, standard ERROR = 0.13, p < 0.0001. Therefore, this investigation establishes the hemodynamic determinants of the isovolumic index and provides the basis for interpretation of directional changes in response to cardiac diseases and cardioactive drugs that can alter loading conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26036/1/0000109.pd

Quantitative regional curvature analysis: A prospective evaluation of ventricular shape and wall motion measurements

To overcome the assumptions and approximations mandated by the use of traditional wall motion methodologies, a method was recently developed for measuring ventricular shape based on quantitative curvature analysis of ventricular outlines. This study was designed to assess prospectively the performance of this algorithm, to compare it to traditional wall motion measurements (centerline method), and to determine the comparative degree to which each method mimicked the interpretation of wall motion by clinical observers. Semiquantitative visual grading of regional function in 52 patients was performed by four independent observers on two occasions. Anterior, apical, or inferior segments were judged to be normal (0 points) or abnormal (1 point) based on viewing nonrealigned, end-diastolic and end-systolic ventricular silhouettes from cineventriculograms obtained in the 30-degree right anterior oblique projection. Each segment was assigned a collated score ranging from 0 (all observers felt the region was normal on both readings) to 8 (all observers felt the region was abnormal on both readings). Quantitative regional curvature analysis and wall motion analysis (centerline method) were performed. Quantitative shape and wall motion scores correlated equally well with the semiquantitative visual scores. When a visual score of >=4 was used to designate an abnormal segment, both quantitative approaches demonstrated comparable sensitivity, specificity, and concordance rates. Both methods achieved optimal performance when maximum and minimum deviations from normal were recorded. Under these circumstances, the shape analysis demonstrated a greater concordance with the clinical diagnosis than did wall motion analysis (99% vs 93%, p < 0.04). Thus new information is provided by the shape analysis program that reflects clinical evaluations more closely and does not require assumptions mandated by traditional wall motion methods. This confirms the value of quantitative regional curvature analysis in a prospectively studied patient population with subtle wall motion abnormalities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27056/1/0000046.pd

A comparison of traditional wall motion assessment and quantitative shape analysis: A new method for characterizing left ventricular function in humans

To forego the need to arbitrarily choose coordinate, reference, and indexing systems and to make other assumptions mandated by traditional methods of measuring walf motion, a technique of regional function analysis based on shape characteristics and pattern recognition was developed. The method is based on curvature analysis, a fundamental shape parameter, and is adaptive to the complex geometry of cineangiographic ventricular images. Quantitative shape parameters were compared to a standard method of regional function analysis (center-line method) in 130 patients. Quantitative shape and wall motion indexes showed a positive correlation over a broad range of normal and abnormal function (r = 0.748, p < 0.001). Overall sensitivity and specificity for categorization of regional function were not statistically different for either technique. Within regions, however, shape criteria were more specific in categorizing inferior zones than anterior zones and were more often abnormal in the presence of mild regional abnormalities that were not located in the apical region. In conclusion, shape analysis and pattern recognition techniques can be used to forego dependence on the numerous assumptions and approximations required by traditional wall motion techniques, while providing performance characteristics that are similar to, and in some instances better than, traditional approaches. Incorporation of shape information in assessments of regional function provides a more comprehensive evaluation that includes the important visual cues used by experienced observers or "experts."Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26530/1/0000069.pd

Cardiac care unit admission criteria for suspected acute myocardial infarction in new-onset atrial fibrillation

Management of new-onset atrial fibrillation (AF) varies between institutions and individual physicians. Because AF often occurs in elderly patients and is associated with coronary artery disease, patients presenting for the first time are often selected for admission to the coronary care unit to exclude the possibility of acute myocardial infarction (AMI). A review of 245 patients with AF admitted to an intensive care unit revealed 45 cases that were of new onset. AMI was diagnosed in 5 (11 % ) on the basis of elevated serum creatine kinase-MB levels. Evaluation of 56 clinical variables available during initial assessment indicated that infarction patients could be distinguished from others by the presence of left ventricular hypertrophy (p <0.01), electrocardiographic evidence of old myocardial infarction (p <0.01), typical cardiac chest pain (p <0.01), and duration of cardiac symptoms less than 4 hours (p <0.05). The presence of 2 or more of these features identified all AMI patients and 7 others at high risk for serious cardiac complications. The findings indicate that new-onset AF in the absence of clinical predictors suggesting myocardial ischemia or AMI does not warrant routine admission to the coronary care unit.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26764/1/0000316.pd

Effects of video frame averaging, smoothing and edge enhancement on the accuracy and precision of quantitative coronary arteriography

Digital analysis of cine film provides numerous options for altering images by frame averaging or filtering algorithms that either smooth or enhance edges. While these may subjectively enhance image quality, there is no uniformity in their use among laboratories and effects on quantitative coronary analysis may not be ideal. To determine which processing algorithms might help or hinder quantitative coronary arteriography, cine film images of precision drilled stenotic cylinders (0.83 to 1.83 mm diameter) implanted in dog coronary arteries were analyzed with and without such algorithms. Video frame averaging of 1 to 49 frames had no effect on measures of accuracy (mean differences) but precision (standard deviation of mean differences) was improved from 0.23 to 0.17 mm (p<0.05) with video averaging of ≥25 frames. Edge enhancement filtering algorithms resulted in slight deterioration of accuracy and precision and smoothing filtering algorithms caused modest improvements in these parameters; however, these changes were not significantly different from unprocessed images. Using edge enhancement filtering algorithms, accuracy was significantly worse (−0.27 mm) compared to a smoothing filter enhancement algorithm (−0.08 mm, p<0.001). The combination of video averaging and smoothing algorithms had no additional beneficial effects. Thus, precision of quantitative coronary analysis of cine film can be optimized by appropriate video averaging. Edge enhancement filtering algorithms should be avoided whereas smoothing filter enhancement algorithms may improve accuracy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42544/1/10554_2005_Article_BF01797840.pd

Comparison of automated quantitative coronary angiography with caliper measurements of percent diameter stenosis

Measurement of coronary artery stenosis is an invaluable tool in the study of coronary artery disease. Clinical trials and even day-to-day decision making should ideally be based on accurate and reproducible quantitative methods. Quantitative coronary angiography (QCA) using digital angiographic techniques has been shown to fulfill these requirements. Yet many laboratories have abandoned visual analysis in favor of the intermediate quantitative approach involving hand-held calipers. Thus, the purpose of this study was to determine the relation between QCA and the commonly used caliper measurements. Percent stenosis was assessed in 155 lesions using 3 techniques: QCA, caliper measures from a 35-mm cine viewer (cine) and caliper measures from a video display (CRT). Good overall correlation was noted among the 3 different techniques (r &gt;-0.72). Both of the caliper methods underestimated QCA for stenosis &gt;=75% (p &lt;=0.001) and overestimated stenosis &lt;75% (p &lt; 0.05). Reproducibility assessed in 52 lesions by independent observers showed QCA to be superior (r = 0.95) to either of the caliper measurements (cine: R = 0.63; CRT: R = 0.73). Therefore, the commonly used caliper method is not an adequate substitute for QCA because overestimation of noncritical stenoses and underestimation of severe stenoses may occur and the measurements have poor reproducibility. These factors definitely preclude its use in rigorous clinical trials. Moreover, since they do not appear to overcome known deficiencies of visual analysis, caliper measurements for day-to-day clinical use must also be seriously questioned.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28572/1/0000375.pd

Establishing comprehensive, quantitative criteria for detection of restenosis and remodeling after percutaneous transluminal coronary angioplasty

To establish comprehensive criteria for detecting restenosis and remodeling, inter- and intraobserver reproducibiltty of quantitative arteriography in the analysis of 20 lesions immediately after and 6 months after percutaneous transluminal coronary angioplasty (PTCA) were assessed. Geometric single-plane (minimum, maximum, mean diameter and percent diameter stenosis), biplane (absolute and relative cross-sectional area stenosis), relative densitometric area stenosis and the average of densitometric area stenosis in orthogonal views were compared. A high intra- and interobserver reproducibility of all absolute measurements was found, with the highest correlations for minimum diameter and cross-sectional area (interobserver, R = 0.85 and 0.85; intraobserver, R = 0.93, and 0.95 for minimum diameter and cross-sectional area, respectively). Of the relative measurements, biplane geometric percent crosssectional area stenosis was the most reliable and percent densitometric area stenosis was the most variable (Interobserver, R = 0.67; intraobserver, R = 0.71). Only small differences were demonstrated for the absolute measurements between the analysis of lesions immediately after PTCA and after follow-up, whereas a greater variability was found for relative measurements, especially videodensitometry. In both circumstances, a poor correlation between relative densitometric crosssectional area from orthogonal views was found, whereas geometric elliptical cross-sectional area correlated quite well with the average of densitometric percent cross-sectional area in orthogonal views (interobserver, R = 0.86; intraobserver, R = 0.84). Thus, data in this study support the suitability of geometric quantitative analysis for the assessment of PTCA results. Densitometry was the least reliable quantitative parameter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30287/1/0000689.pd