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F H Sheehan

Publications and source records attributed to F H Sheehan.

At least 37 records · Page 2Linked to original sources
PubMed1997

A general technique for automatic left ventricle boundary validation: relation between gray scale cardioangiograms and observed boundary errors.

This article presents an automatic left ventricle boundary validation technique using the gray scale cardioangiograms, the observed boundary errors, and the left ventricle boundaries from any source that needs to be validated. This validation technique is based on the gray scale information near the boundary of the left ventricle in the cardioangiograms. Using a mutually exclusive window of fixed size, which is centered on the left ventricle boundary vertex and along the left ventricle contour, we compute a difference in contrast value for areas of the window both inside and outside the left ventricle region. These contrast values then are regressed against the observed boundary errors. The observed boundary errors are computed using the polyline distance measure, by comparing two sets of boundaries: boundaries estimated from any boundary estimation algorithm, and the original ground truth boundaries as traced by the cardiologist. We performed our experiments on a database of 245 patient studies, each having two frames: end-diastole (ED) and end-systole (ES). The mean boundary error before running the validation system was 4.4 mm. Using our boundary validation system, by rejecting 5% to 10% of the patient studies, the validation system results in an error of 4.0 mm for the cross-validation case and 3.85 mm for the ideal case. We show the reliability curves of our validation system by computing the probability of false alarm, probability of mis-detection, and mean predicted errors when a total of n patients are rejected from the database of 245 studies.

Algorithms↗
PubMed1997

Quantitative three-dimensional echocardiography by rapid imaging from multiple transthoracic windows: in vitro validation and initial in vivo studies.

Three-dimensional echocardiography has demonstrated superiority over two-dimensional techniques in the determination of left ventricular mass and volumes. We describe a technique based on a magnetic tracking system which provides rapid three-dimensional image acquisition from multiple acoustic windows. Interactive three-dimensional border tracking and reconstruction with a piecewise smooth subdivision model accurately reproduced phantom volume (calculated volume = 1.00 true volume - 0.6 ml, r = 1.000, standard error of the estimate = 1.3 ml), in vitro heart volume (calculated volume = 1.02 true volume - 1.3 ml, r = 1.000, standard error of the estimate = 0.4 ml), in vitro heart mass (calculated mass = 0.98 true mass + 1.4 gm, r = 0.998, standard error of the estimate = 2.5 gm), and in vivo stroke volume (calculated stroke volume = 1.18 Doppler stroke volume - 17.9 ml, r = 0.990, standard error of the estimate = 2.8 ml). The three-dimensional in vivo data sets, which include views from three acoustic windows, were acquired in less than 90 seconds. We conclude that this method of three-dimensional echocardiographic data acquisition and analysis overcomes limitations inherent in currently available systems.

Animals↗
PubMed1997

The effect of normalization in reducing variability in regional wall thickening.

This study was performed to evaluate a new method for measuring regional left ventricular wall thickening in terms of its variability, normal range, and diagnostic sensitivity. Two-dimensional echocardiographic images in the parasternal short-axis view of 44 normal patients and 17 patients with recent myocardial infarction were analyzed. Regional wall thickness was measured according to the centerline method at 100 chords. Wall thickening at each chord i was calculated as the change in wall thickness between end diastole and end systole at chord i, normalized by the average end-diastolic thickness of the wall segment extending from chord (i - n) to chord (i + n). Five widths of the normalization segment, defined as (2n + 1), were tested: 1 (baseline method), 5, 11, 15, and 21 chords. Widening the normalization segment significantly reduced point-to-point variability by up to 20% (p = 0.0001) evenly over the entire left ventricular contour. The magnitude of reduction approached a plateau at a normalization segment width of 11 chords. The normal mean and standard deviation for regional wall thickening were also reduced slightly but significantly in a progressive and uniform manner. The apparent severity of hypokinesis worsened by up to 0.1 +/- 0.1 SD (p = 0.006) as the normalization segment was widened. The circumferential extent of hypokinesis was not lengthened significantly until the normalization segment was 21 chords wide. The magnitude of hyperkinesis was unchanged. Normalizing over a wider segment of the myocardium reduces variability in the measurement of wall thickening, widens the separation between normal patients and those with disease, and enhances the diagnostic accuracy of quantitative two-dimensional echocardiography. The optimal normalization segment width is 11 chords.

Echocardiography↗
PubMed1997

Variability in frame by frame analysis of left ventricular wall motion from contrast angiograms.

BACKGROUND: Measurement of the timing of left ventricular (LV) wall motion, of asynchrony, and of diastolic function from contrast angiograms requires delineation of the endocardial border frame by frame through the cardiac cycle. This study was performed to determine the magnitude of intraobserver and interobserver variability in manual border tracing, and to measure the impact of this variability on the derived functional parameters. METHODS: The contrast ventriculograms of 25 patients with coronary artery disease (CAD) or with normal coronary arteries were analyzed frame by frame, by two observers or twice by the same observer. Motion was measured using the centerline method at each twelfth of systole and of diastole. Variability was calculated as the absolute difference between repeated measurements of: wall motion, asynchrony, and the time at which each region of the LV reached 10%, 50%, and 100% of peak contraction, and 50% of filling. RESULTS: Intraobserver and interobserver variability in wall motion were similar, and varied with time in the cycle, and with location on the LV contour. Variability was highest at end systole, when it averaged 8% of the normal mean for wall motion. Variability in timing was highest at peak contraction; however, the variability in measuring asynchrony averaged only 18 msec. CONCLUSION: Analysis of the magnitude and synchrony of regional LV wall motion through the cardiac cycle from contrast ventriculograms can be performed with reproducibility comparable to that at end systole.

Aged↗
PubMed1997

Effect of myocardial viability assessed by technetium-99m-sestamibi SPECT and fluorine-18-FDG PET on clinical outcome in coronary artery disease.

UNLABELLED: PET imaging of myocardial perfusion and metabolism identifies regional viability as well as patients at high risk for future cardiac events. This study evaluated a combined "hybrid" imaging approach using 99mTc-sestamibi SPECT and [18F]fluoro-2-deoxy-D-glucose (FDG) PET with regard to reversibility of regional dysfunction and to patient clinical outcome during a 2-yr follow-up. METHODS: In this study, 161 consecutive patients underwent baseline viability imaging. All had regional wall motion (RWM) abnormalities and 88% had a history of previous myocardial infarction. Regions were classified by semiquantitative analysis of sestamibi and FDG uptake as normal, mild match, mismatch or scar. For clinical outcome, patients were divided into three groups: predominantly scar tissue (Group A, n = 90), mild match (Group B, n = 26) and mismatch (Group C, n = 45). Treatment was performed with the knowledge of nuclear results. Cardiac events during follow-up were defined as death, myocardial infarction, unstable angina requiring revascularization, heart transplantation and survived resuscitation. RESULTS: Patients were followed for 29 +/- 6 mo. Revascularization rate was 30% in Group A, 81% in Group B and 80% in Group C, whereas the other patients were treated by medication. Only Group C demonstrated a significant reduction of cardiac events after revascularization, whereas, particularly in Group A, revascularization did not influence the frequency of events. Subjective assessment of angina pectoris and heart failure revealed more patients with improvement after revascularization as compared with conservative treatment. Of the 84 revascularized patients, 61 underwent follow-up angiography at 5 +/- 2 mo with RWM analysis using the centerline method. RWM improved only in mismatch regions from -2.2 +/- 1.0 s.d. to -1.0 +/- 1.4 s.d. (p < 0.01), whereas regions with a mild match or scar did not change. CONCLUSION: Nuclear imaging using 99mTc-sestamibi SPECT and [18F]FDG PET allows diagnosis of viability in regions with reduced perfusion and function with prognostic implications for functional outcome as well as for identification of patients who benefit most from revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1996

Myocyte degeneration and cell death in hibernating human myocardium.

OBJECTIVES: The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques. BACKGROUND: Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium. METHODS: In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall. RESULTS: The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups. CONCLUSIONS: Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.

Adult↗
PubMed1996

Recovery of regional left ventricular dysfunction after coronary revascularization. Impact of myocardial viability assessed by nuclear imaging and vessel patency at follow-up angiography.

OBJECTIVES: This study sought to evaluate an imaging approach using technetium-99m sestamibi scintigraphy and positron emission tomography with fluorine-18 fluorodeoxyglucose for assessment of myocardial viability proved by serial quantitative left ventricular angiography. Furthermore, the influence of successful long-term revascularization on functional recovery was studied. BACKGROUND: Previous studies using positron emission tomography of myocardial perfusion and metabolism have demonstrated accurate identification of myocardial viability. However, most of these studies used a qualitative or semiquantitative wall motion analysis approach. METHODS: Nuclear imaging with semiquantitative analysis of tracer uptake was performed in 193 patients with regional wall motion abnormalities. Regions were categorized as normal, viable with perfusion/metabolism mismatch, viable without mismatch (intermediate) and scar. Seventy-two of 103 patients with subsequent revascularization underwent follow-up angiography. In 52 of 72 patients, changes in regional wall motion were measured by the centerline method from serial angiography. RESULTS: Wall motion improved in mismatch regions from -2.2 +/- 1.0 to -1.1 +/- 1.4 SD (p < 0.001). In contrast, regions with an intermediate pattern and those with scar did not improve. Restenosis or graft occlusion influenced functional outcome because regions with preoperative mismatch and successful long-term revascularization improved at follow-up (from -2.3 +/- 1.0 to -0.8 +/- 1.4 SD, p < 0.001), whereas wall motion did not change with recurrent hypoperfusion. Metabolic imaging added diagnostic information, particularly in regions with mild and moderate perfusion defects. CONCLUSIONS: This imaging approach allows detection of viability in regions with myocardial dysfunction. Wall motion benefits most in myocardium with perfusion/metabolism mismatch and successful long-term revascularization.

Aged↗
PubMed1996

[Effect of myocardial viability and coronary revascularization on clinical outcome and prognosis: a follow-up study of 161 patients with coronary heart disease].

One hundred and sixty-one consecutive patients (144 male, 57 +/- 9 years) with stable coronary artery disease underwent nuclear imaging for assessment of myocardial viability using Tc-99m sestamibi single-photon emission computed tomography (SPECT) and F-18 fluoro-deoxy-glucose (FDG) positron emission tomography (PET). 88% had a history of chronic myocardial infarction and all had angiographically proven regional wall motion (RWM) abnormalities in the distribution territory of a stenosed or occluded coronary artery. Patients were followed for 29 +/- 6 (22-44) months with 84/161 patients (52%) receiving elective revascularization by either bypass surgery or angioplasty. 61/84 patients underwent follow-up angiography after 5 +/- 2 months for quantitative assessment of RWM changes using serial analysis with the centerline method in 45 pts with technically suitable paired angiograms. Myocardial regions were classified according to semiquantitative analysis of regional sestamibi and FDG uptake as either normal, regions with evidence for maintained viability but no mismatch ("mild match"), regions with a perfusion/metabolism "mismatch," or scar. RWM improved in "mismatch" regions from -2.2 +/- 1.0 SD to -1.0 +/- 1.4 SD (p < 0.01) compared to the mean of a normal reference population. In contrast, in regions with a "mild match" or those classified as scar, RWM analysis revealed no functional changes at follow-up. For the assessment of clinical outcome, patients were divided into three groups depending on the result of viability imaging. Those with predominantly scar tissue in the target region for viability assessment (group A, n = 90), those with a "mild match" (B, n = 26), and group C (n = 45) consisting of patients with a "mismatch" pattern. Subsequent treatment was not blinded to nuclear imaging results and revascularization was performed in 30% of group A (group A2), 81% of group B, and 80% of group C, while the other patients were treated medically only. Cardiac events during follow-up were defined as cardiac death, myocardial infarction, unstable angina with subsequent revascularization, cardiac transplantation, and survived resuscitation without evidence for myocardial infarction. Group C demonstrated a significant reduction of cardiac events from 22% to 0% following revascularization, whereas in group A coronary revascularization did not influence the frequency of events. Subjective assessment of angina pectoris and heart failure symptoms revealed more patients with improvement following revascularization as compared to those treated medically. Thus, combined nuclear imaging using sestamibi SPECT and FDG PET with quantitative tracer uptake analysis allows detection of absent or preserved myocardial viability in regions with reduced perfusion and function with prognostic implication for regional myocardial functional outcome as well as for identification of patients who benefit most from coronary revascularization.

Adult↗
PubMed1993

A difference between front-loaded streptokinase and standard-dose recombinant tissue-type plasminogen activator in preserving left ventricular function after acute myocardial infarction (the Central Illinois Thrombolytic Therapy Study).

A blinded, randomized trial compared the effects of front-loaded streptokinase with those of the conventional dose of intravenous recombinant tissue-type plasminogen activator (rt-PA) on left ventricular (LV) function after acute myocardial infarction (AMI). Thrombolytic therapy was administered in the emergency departments of 30 community hospitals in central Illinois, and subsequent studies were performed at 1 tertiary referral center. Patients aged < or = 75 years with a first AMI who could be treated within 4 hours of the onset of chest pain were randomly assigned to receive either streptokinase (375,000 IU bolus, followed by 1,125,000 IU over 1 hour) or rt-PA (10 mg bolus, followed by 50 mg in the first hour, and 20 mg/hour for the next 2 hours). All patients were treated with aspirin (325 mg) and intravenous heparin. Patients were transferred for angiography within 24 hours. During the 30-month study, 253 patients were treated with intravenous thrombolytic therapy 2.4 +/- 1.0 hour after the onset of AMI. In patients with anterior wall AMI (n = 90), global LV ejection fraction measured by angiography within 24 hours was 45 +/- 12% with rt-PA, and 39 +/- 13% with streptokinase (p < 0.03). Convalescent radionuclide angiography documented a persistent beneficial effect of rt-PA on LV regional wall contractility, but not global ejection fraction. There were no differences between rt-PA and streptokinase in preserving global or regional LV function in patients with inferior wall AMI.

Aged↗
PubMed1993

Three-dimensional transesophageal echocardiography for depiction of regional left-ventricular performance: initial results and future directions.

To assess the potential of a prototype transesophageal echocardiography probe for evaluating left-ventricular wall motion in three dimensions, we acquired images under anesthesia in 15 patients who had akinesia or dyskinesia and 8 patients who had normal function demonstrated on preoperative ventriculography. Short-axis, oblique transgastric scans were obtained in 16 of the patients and four-chamber, long-axis oblique scans were obtained in 12 patients, with five patients (22%) yielding good-quality scans of both types. Off-line, we outlined the endocardial borders manually and used the outlines to make computer-generated three-dimensional models of the endocardial surfaces, color-tiled according to regional ejection fraction. Compared with contrast ventriculograms, the regional ejection fraction histograms derived from these models showed 86% concordance for detecting dyssynergy. However, the concordance between the ventriculograms and the color-tiled models in localizing the dyssynergy was only 67% overall. Uncertainty in rotational alignment between the reconstructions and the ventriculograms appeared to contribute to misreading the location of dyssynergy. In addition, the apical region appeared to have been missed in 8 (50%) of the short-axis scans, whereas it was visualized in all long-axis scans. We conclude that three-dimensional analysis of the location, extent, and degree of left-ventricular dyssynergy is feasible from transesophageal echocardiograms and could have wide application in the study of regional ventricular function. However, improvements are necessary to enable the transducer to scan the cardiac apex more reliably from the short-axis viewpoint and to have a means for spatially orienting the images with respect to an external frame of reference.

Computer Graphics↗
PubMed1993

Methodology for three-dimensional reconstruction of the left ventricle from transesophageal echocardiograms.

A technique is presented for three-dimensional (3-D) reconstruction of the left-ventricular endocardial surface from multiplanar transesophageal echocardiograms, using both commercial software and investigator written Fortran programs for Intel 80286 and 80386 microcomputers. The approach provides quantitative global and regional cardiac performance measures and allows viewing the endocardial surface, at end-diastole and end-systole, from chosen perspectives. Anatomical landmarks are incorporated to aid in orientation. For regional calculation, the surface is divided into equal angular elements with each conceptually connected to the left-ventricular end-diastole centroid, forming a pyramidal volume element. This angular division automatically normalizes for heart size. The fractional change of these elements over the cardiac cycle provides a regional ejection fraction measure which is color-coded on the reconstructed endocardial surface. Composite perspective views, regional ejection fraction histograms and calculations of global end-diastolic, end-systolic, and stroke volumes, are all performed by the method.

Algorithms↗
PubMed1993

Effect of thrombolysis on acute mitral regurgitation during evolving myocardial infarction. Experience from the Thrombolysis in Myocardial Infarction (TIMI) Trial.

OBJECTIVES: This study was undertaken to determine whether early successful thrombolysis can reverse infarct-associated mitral valve dysfunction. BACKGROUND: Mitral regurgitation is a common complication of acute myocardial infarction and has been shown to adversely affect both short- and long-term prognosis. Although anecdotal reports have suggested that reperfusion of the infarct-related artery may restore normal function to the mitral valve, this theory has not been subjected to formal investigation. METHODS: Patients with total or partial obstruction of the infarct-related artery received intravenous thrombolytic therapy with either streptokinase or recombinant tissue-type plasminogen activator within 7 h of symptom onset (mean 4.8 h) as part of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial. Repeat coronary angiography assessed arterial patency at 90 min and 10 days after attempted reperfusion. The presence and severity of mitral regurgitation were determined by contrast ventriculography both before thrombolysis and before hospital discharge. RESULTS: Overall, 21 (16%) of the 132 study patients exhibited mitral regurgitation on either their initial or their predischarge ventriculogram. The proportion of infarct-related arteries found to be patent (TIMI flow grade 2 or 3) was statistically similar in patients with and without mitral regurgitation during each angiographic evaluation period (initial, 90 min and 10 days). Although coronary artery perfusion increased overall during sequential measurement (mean TIMI grade was 0.4 +/- 0.6 initially, 1.5 +/- 1.3 at 90 min and 2.2 +/- 1.0 at 10 days), the pattern of reperfusion observed could not predict an increase or decrease in regurgitant severity (p = NS). Early mitral regurgitation resolved in 57% of patients by 10 days, but this resolution appeared independent of the presence or absence of improved coronary perfusion (60% vs. 50%). The development of new regurgitation during the recovery period (6%) was also unrelated to improved perfusion (7% vs. 4%). CONCLUSIONS: Acute mitral regurgitation developing during myocardial infarction shows frequent changes in its presence or severity during the 1st 10 days, appears independent of coronary artery patency both early and late after thrombolysis and cannot be reliably treated by improving arterial perfusion with thrombolytic agents.

Acute Disease↗
PubMed1993

Extension of hypokinesia into angiographically perfused myocardium in patients with acute infarction.

OBJECTIVE: This study was performed to determine whether left ventricular hypokinesia due to acute myocardial infarction lies between the site of coronary artery occlusion and the end of the infarct-related artery in patients. BACKGROUND: Normalizing for the size of the risk region reduces variability in measuring infarct size in experimental studies. The ability to gauge the size of the region at risk of becoming dysfunctional may help reduce variability in measuring regional hypokinesia due to acute myocardial infarction. METHODS: Angiograms of 84 patients with acute infarction due to isolated stenosis of the right coronary artery (n = 40) or the left anterior descending coronary artery (n = 44) were analyzed. The location and length of the segment with hypokinesia more severe than -1 or -2 SD below the normal mean were determined by the centerline method. The risk region was defined as the left ventricular contour between the site of the occlusion and the end of the infarct-related artery on the angiogram. RESULTS: The segment with hypokinesia below -1 SD was longer than the risk region in 52% of patients with occlusion of the left anterior descending coronary artery, more frequently (p < 0.01) than in right coronary artery occlusion (22%), owing to extension of hypokinesia beyond the distal end of the artery. Extension of severe hypokinesia (below -2 SD) beyond the risk region occurred in 33% of patients with an anterior infarct and in 9% of patients with an inferior infarct. CONCLUSIONS: The size of the risk region cannot be assessed accurately from coronary angiography.

Bias↗
PubMed1993

Time course of left ventricular function and coronary patency after saruplase vs streptokinase in acute myocardial infarction. The PRIMI Trial Study Group.

As part of a prospective randomized double-blind trial (PRIMI) to study the early patency rate of the infarct-related artery after saruplase (INN for recombinant unglycosylated full-length human single-chain urokinase-type plasminogen activator) vs streptokinase in a subgroup of patients, left ventricular function was compared between both treatment groups at 90 min and 24 h after thrombolysis and at discharge, and ventricular function was related to the coronary perfusion grade. Despite a higher patency rate in the saruplase group 60 min after initiating thrombolysis, neither global ejection fraction nor hypokinesia at the infarct site were significantly different between the treatment groups at any of the three time points when function was measured. Hypokinesia at the infarct site remained almost equally severe throughout the study in patients with perfusion grade O, I, and II, and was consistently significantly milder in patients with perfusion grade III. In contrast, in patients with perfusion grade II there was a significant drop in hyperkinesia at the opposite wall at 24 h after thrombolysis and before discharge despite unchanged wall motion at the infarct site. Although patients treated with saruplase had a higher patency rate in the infarct related vessel shortly after the start of thrombolysis, no difference was found in left ventricular function compared to patients treated with streptokinase. Complete reperfusion (TIMI grade III) seems to be a prerequisite for left ventricular function recovery after thrombolysis, whereas only an occluded vessel (TIMI grade O and I) seems to be related to a longer lasting hyperkinesia at the opposite wall.

Double-Blind Method↗
PubMed1992

Radionuclide cardiac volumes: effects of region of interest selection and correction for Compton scatter using a buildup factor.

The effects of region of interest (ROI) selection and correction for Compton-scattered photons using a buildup factor on radionuclide left ventricular volumes calculated by the Links method were compared in 19 humans with contrast ventriculography and in phantoms. Three different methods of ROI selection were compared: a manual ROI, a second derivative ROI and a 50% count-threshold ROI. In phantoms without Compton scatter correction, volumes were overestimated by 30% (manual ROI), 20% (derivative ROI) and 1% (count threshold ROI). In subjects, results without Compton scatter correction were similar with overestimates of 50% (manual ROI) and 20% (derivative ROI) and an underestimate by 3% (count threshold method). Correction for Compton-scattered photons with the use of a phantom-derived buildup factor resulted in improved accuracy for the manual ROI (+15%) and the derivative ROI (0%). A 50% count threshold ROI following interpolative background subtraction allows the accurate calculation of cardiac volumes without the need for scatter correction, while a second derivative ROI method requires a correction for Compton scatter with the use of a buildup factor.

Cardiac Volume↗
PubMed1992

Four radionuclide methods for left ventricular volume determination: comparison of a manual and an automated technique.

This study compared the accuracy and reproducibility of three previously described and one new radionuclide method of measuring left ventricular volumes in 19 subjects using contrast ventriculographic volumes (n = 38, mean volume = 126.6 ml) as the gold standard. The four methods were compared using both manual and automated ROIs. For manual ROIs, the Links (189.7 ml, r = 0.85), Starling (183.2 ml, r = 0.77) and the new count ratio method (141.4 ml, r = 0.90) overestimated contrast volumes, while the Massardo method (122.5 ml, r = 0.91) provided accurate volumes. For the automated ROIs, we performed an interpolative background subtraction and used a 50% threshold of the highest count pixel to define the ventricular regions. The automated Massardo method severely underestimated the contrast volume (59.5 ml, r = 0.90), while the other automated methods yielded accurate volumes: Links (122.4 ml, r = 0.89), Starling (118.1 ml, r = 0.81) and the new count ratio method (125.0 ml, r = 0.90). The interobserver reproducibility of the automated methods was excellent (mean difference = 1%-4%) compared to the manual methods (2%-8%). Because no additional images, blood counting, attenuation, or decay correction were necessary, the manual Massardo method and the automated count ratio method are the simplest to perform. We conclude that automated determination of left ventricular volumes using the new count ratio method is rapid, accurate, reproducible and could readily be incorporated into routine clinical use.

Algorithms↗
PubMed1992

Quantitative analysis of regional wall thickening by transesophageal echocardiography.

To develop a method for quantitative analysis of regional left ventricular function from transesophageal two-dimensional echocardiograms, we conducted studies 10 and 20 minutes after induction of anesthesia in 16 patients with normal hearts who were undergoing minor orthopedic operations. Wall thickening was measured with the centerwall method along 100 chords drawn perpendicular to a line constructed around the center of the ventricular wall, midway between the endocardial and epicardial contours. Thickening, either normalized by the length of the end-diastolic perimeter or expressed as a percentage of the end-diastolic wall thickness at each chord, was compared with measurements of endocardial motion. Wall motion was relatively diminished in the anteroseptal region and enhanced on the contralateral wall, but wall thickening was homogeneous throughout the contour. Normalized wall thickening was significantly less variable (standard deviation/mean, 0.47 +/- 0.13) in the normal population than were either percent wall thickening (0.53 +/- 0.012) or wall motion (0.51 +/- 0.09) (p less than 0.005 for both comparisons). There was no significant change in regional or global function between 10 minutes and 20 minutes after the induction of anesthesia. In summary, normalized wall thickening as a parameter of regional left ventricular function is more homogeneous and less variable in subjects with normal hearts than is endocardial motion because wall thickening measurements are not subject to cardiac translocation artifacts. This low variability suggests that normalized wall thickening measured by the centerwall method may prove particularly useful for intraoperative and postoperative monitoring of regional left ventricular function by transesophageal echocardiography in patients undergoing both cardiac and noncardiac surgical procedures.

Adult↗