Estimation of left ventricular cavity area with an on-line, semiautomated echocardiographic edge detection system

Image-based clustering and connected component labeling for rapid automated left and right ventricular endocardial volume extraction and segmentation in full cardiac cycle multi-frame MRI images of cardiac patients

A rapid method for left and right ventricular endocardial volume segmentation and clinical cardiac parameter calculation from MRI images of cardiac patients is presented. The clinical motivation is providing cardiologists a tool for assessing the cardiac function in a patient through the left ventricular endocardial volume's ejection fraction. A new method combining adapted fuzzy membership-based c-means pixel clustering and connected regions component labeling is used for automatic segmentation of the left and right ventricular endocardial volumes. This proposed pixel clustering with labeling approach avoids manual initialization or user intervention and does not require specifying the region of interest. This method fully automatically extracts the left and right ventricular endocardial volumes and avoids manual tracing on all MRI image frames in the complete cardiac cycle from systole to diastole. The average computational processing time per frame is 0.6 s, making it much more efficient than deformable methods, which need several iterations for the evolution of the snake or contour. Accuracy of the automated method presented herein was validated against manual tracing-based extraction, performed with the guidance of cardiac experts, on several MRI frames. Dice coefficients between the proposed automatic versus manual traced ventricular endocardial volume segmentations were observed to be 0.9781 ± 0.0070 (for left ventricular endocardial volume) and 0.9819 ± 0.0058 (for right ventricular endocardial volume), and the Pearson correlation coefficients were observed to be 0.9655 ± 0.0206 (for left ventricular endocardial volume) and 0.9870 ± 0.0131 (for right ventricular endocardial volume). Graphical abstract The left ventricular endocardial volume segmentation methodology illustrated as a series of algorithms.

Decision Support Tools, Systems, and Artificial Intelligence in Cardiac Imaging

Noninvasive cardiac imaging is widely used for the diagnosis and management of cardiac patients. The increasing demand for cardiac imaging begins to exceed the number of available interpreting physicians, leaving less time to interpret studies. In addition, the busy clinician is facing the increasingly daunting task of keeping abreast of current medical advancements and the ongoing changes in disease diagnosis and therapy. Committing to memory and recalling such large volumes of information is challenging and is responsible for difficulties in adopting the rapid changes in imaging practice, and is likely partially responsible for errors in patient diagnosis and management. Diagnostic errors rank high in the cause of death in the United States, and are more common than any other medical error and are responsible for most malpractice claims. Most of these errors are related to cognitive errors. The use of artificial intelligence systems that can serve as complementary methods to assist humans with decision making can potentially prevent these errors. The past decades witnessed the development and integration of these tools, which can assist physicians with image interpretation. These tools work to optimize image quality for better visualization and accompany all imaging modalities, starting from patient selection for the appropriate test, patient preparation, image acquisition, processing, and finally interpretation. Current and future directions for technologies that support cardiac imaging physicians are discussed in this review.

Association of CHADS2, CHA2DS2-VASc, and R2CHADS2 scores with left atrial dysfunction in patients with coronary heart disease (from the Heart and Soul study)

The predictive ability of the CHADS2 index to stratify stroke risk may be mechanistically linked to severity of left atrial (LA) dysfunction. This study investigated the association between the CHADS2 score and LA function. We performed resting transthoracic echocardiography in 970 patients with stable coronary heart disease and normal ejection fraction and calculated baseline LA functional index (LAFI) using a validated formula: (LA emptying fraction×left ventricular outflow tract velocity time integral)/LA end-systolic volume indexed to body surface area. We performed regression analyses to evaluate the association between risk scores and LAFI. Among 970 subjects, mean CHADS2 was 1.7±1.2. Mean LAFI decreased across tertiles of CHADS2 (42.8±18.1, 37.8±19.1, 36.7±19.4, p<0.001). After adjustment for age, sex, race, systolic blood pressure, hyperlipidemia, myocardial infarction, revascularization, body mass index, smoking, and alcohol use, high CHADS2 remained associated with the lowest quartile of LAFI (odds ratio 2.34, p=0.001). In multivariable analysis of component co-morbidities, heart failure, age, and creatinine clearance<60 ml/min were strongly associated with LA dysfunction. For every point increase in CHADS2, the LAFI decreased by 4.0%. Secondary analyses using CHA2DS2-VASc and R2CHADS2 scores replicated these results. Findings were consistent when excluding patients with baseline atrial fibrillation. In conclusion, CHADS2, CHA2DS2-VASc, and R2CHADS2 scores are associated with LA dysfunction, even in patients without baseline atrial fibrillation. These findings merit further study to determine the role of LA dysfunction in cardioembolic stroke and the value of LAFI for risk stratification.

Short-lag spatial coherence imaging of cardiac ultrasound data: initial clinical results

Short-lag spatial coherence (SLSC) imaging is a novel beamforming technique that reduces acoustic clutter in ultrasound images. A clinical study was conducted to investigate clutter reduction and endocardial border detection in cardiac SLSC images. Individual channel echo data were acquired from the left ventricle of 14 volunteers, after informed consent and institutional review board approval. Paired B-mode and SLSC images were created from these data. Contrast, contrast-to-noise, and signal-to-noise ratios were measured in paired images, and these metrics were improved with SLSC imaging in most cases. Three cardiology fellows rated the visibility of endocardial segments in randomly ordered B-mode and SLSC cine loops. SLSC imaging offered 22%-33% improvement (p < 0.05) in endocardial border visibility when B-mode image quality was poor (i.e., 80% or more of the endocardial segments could not be visualized by the three reviewers). The percentage of volunteers with poor-quality images was decreased from 21% to 7% with the SLSC beamformer. Results suggest that SLSC imaging has the potential to improve clinical cardiac assessments that are challenged by clutter.

Left atrial function predicts heart failure hospitalization in subjects with preserved ejection fraction and coronary heart disease: longitudinal data from the Heart and Soul Study

OBJECTIVES

This study sought to determine whether left atrial (LA) dysfunction predicts heart failure (HF) hospitalization in subjects with preserved baseline ejection fraction (EF).

BACKGROUND

Among patients with preserved EF, factors leading to HF are not fully understood. Cross-sectional studies have demonstrated LA dysfunction at the time of HF, but longitudinal data on antecedent atrial function are lacking.

METHODS

We performed resting transthoracic echocardiography in 855 subjects with coronary heart disease and EF ≥50%. Left atrial functional index (LAFI) was calculated as ([LA emptying fraction × left ventricular outflow tract-velocity time integral] / [indexed LA end-systolic volume]), where LA emptying fraction was defined as (LA end-systolic volume--LA end-diastolic volume) / LA end-systolic volume. We used Cox models to evaluate the association between LAFI and HF hospitalization.

RESULTS

Over a median follow-up of 7.9 years, 106 participants (12.4%) were hospitalized for HF. Rates of HF hospitalization were inversely proportional to quartile (Q) of LAFI: Q1, 47 per 1,000 person-years; Q2, 18.3; Q3, 9.6; and Q4, 5.3 (p < 0.001). Each standard deviation decrease in LAFI was associated with a 2.6-fold increased hazard of adverse cardiovascular outcomes (unadjusted hazard ratio: 2.6, 95% confidence interval: 2.1 to 3.3, p < 0.001), and the association persisted even after adjustment for clinical risk factors, N-terminal pro-B-type natriuretic peptide, and a wide range of echocardiographic parameters (adjusted hazard ratio: 1.5, 95% confidence interval: 1.0 to 2.1, p = 0.05).

CONCLUSIONS

Left atrial dysfunction independently predicts HF hospitalization in subjects with coronary heart disease and preserved baseline EF. The LAFI may be useful for HF risk stratification, and LA dysfunction may be a potential therapeutic target.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Left ventricular geometry, global function, and dyssynchrony in infants and children with pompe cardiomyopathy undergoing enzyme replacement therapy

BACKGROUND

Enzyme replacement therapy (ERT) for infantile-onset Pompe disease effectively reduces the left ventricular (LV) mass. This study sought to explore detailed process of LV reverse remodeling after ERT with the use of tissue Doppler and stain rate imaging.

METHODS AND RESULTS

Nine infants and children with Pompe cardiomyopathy undergoing ERT for ≥1 year, as well as 36 healthy control subjects, were studied. Global systolic and diastolic function was evaluated by peak systolic and early-diastolic velocity at mitral annulus. Temporal systolic and diastolic dyssynchrony was evaluated by the coefficient of variation of the time from the QRS complex to peak systolic and early-diastolic strain rate among 12 LV segments. All pre-ERT patients had impaired global systolic and diastolic function as well as increased regional dyssynchrony (P < .001 for each of all). During the regression of LV hypertrophy, all of these functional indices improved (P for trend <.001), with temporal diastolic dyssynchrony being a significant factor linking to LV mass index in multivariate analysis (P < .001).

CONCLUSIONS

ERT improved global LV function and dyssynchrony in Pompe patients. The relationship between LV mass and temporal diastolic dyssynchrony during reverse remodeling suggested a pathophysiologic role of dyssynchrony in Pompe cardiomyopathy.

Sensitivity and specificity of left ventricular ejection fraction by echocardiographic automated border detection: comparison with radionuclide ventriculography

BACKGROUND

Echocardiographic automated border detection (ABD) provides on-line, beat-to-beat estimation of left ventricular (LV) ejection fraction (EF). Sensitivity and specificity of using ABD-EF for diagnosing LV dysfunction in routine clinical situations have not been previously studied.

HYPOTHESIS

Analysis of ABD-EF data based on receiver operating characteristic (ROC) should provide useful information about sensitivity and specificity for clinical diagnosis of LV function based on ABD-EF.

METHODS

The study group included 50 consecutive patients with EF measured by both ABD and radionuclide ventriculography (RVG). ABD-EF was recorded for 25 consecutive heart beats in the apical four-chamber view. Data were analyzed statistically by linear regression, Bland-Altman plot, and ROC. In ROC analysis, abnormal LV function was defined RVG-EF < or = 40%.

RESULTS

ABD and RVG showed a moderate correlation in the EF measurements: slope = 0.93, intercept = 17%, r = 0.79 (n = 50). Interbeat variability in ABD was diminished by averaging consecutive beats; standard error of estimate (SEE) decreased from 15.6% without averaging to 12.5% with 25-beat averaging. Bland-Altman analysis indicated that ABD-EF compared unfavorably with RVG-EF, with limits of agreement from -11% to 39%. ABD-EF showed a systematic overestimation (p < 0.005), which was compensated by increasing the threshold for abnormal ABD-EF to 56%. With the optimized threshold, ABD-EF provided 89% sensitivity and 89% specificity (85% overall diagnostic accuracy) for diagnosing abnormal LV function.

CONCLUSION

This study explored the limitations of on-line echocardiographic measurement of EF in a clinical setting and provided useful data for assessing interbeat variability, sensitivity, and specificity.

Milrinone increases flow in coronary artery bypass grafts after cardiopulmonary bypass: a prospective, randomized, double-blind, placebo-controlled study

OBJECTIVE

To compare the effects of a bolus of milrinone, 50 microg/kg, versus placebo on flow in coronary artery bypass grafts after cardiopulmonary bypass (CPB).

DESIGN

A prospective, randomized, double-blind study.

SETTING

A university hospital.

PARTICIPANTS

Forty-four patients with stable angina and left ventricular ejection fraction >30% scheduled for elective coronary artery bypass graft (CABG) surgery were included.

INTERVENTION

Patients were randomized to receive 50 microg/kg of milrinone (n = 22) or placebo (n = 22) after aortic declamping.

MEASUREMENTS AND MAIN RESULTS

The flow in coronary artery bypass grafts was measured with a transit time flow meter at 10 minutes and 30 minutes after termination of CPB. The hemodynamic evaluation included transesophageal echocardiography, mean arterial pressure (MAP), heart rate, and intracavitary measurement of left ventricular end-diastolic pressure (LVEDP). The flow in the saphenous vein grafts was significantly higher in the milrinone group when compared with the placebo group both at 10 and 30 minutes after termination of CPB (p < 0.001). At 10 minutes, the flow was 64.5 +/- 37.4 mL/min (mean +/- standard deviation) and 43.6 +/- 25.7 mL/min in nonsequential vein grafts for milrinone and placebo, respectively. Corresponding values at 30 minutes were 54.8 +/- 29.9 mL/min and 35.3 +/- 22.4 mL/min. The left internal thoracic artery (LITA) flow was higher in the milrinone group but did not reach statistical significance. The fractional area change was higher, and the MAP and calculated pressure gradient (MAP-LVEDP) were lower at 10 minutes in the milrinone group.

CONCLUSION

Milrinone significantly increases the flow in anastomosed saphenous vein grafts after CPB, and has beneficial effects on left ventricular function.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Association of African American race with elevated pulmonary artery diastolic pressure: data from the Heart and Soul Study

BACKGROUND

Whether increased severity of heart failure in African Americans is a result of differences in cardiac physiology is uncertain. The end-diastolic pulmonary regurgitation (EDPR) gradient is associated with abnormal cardiac physiology. We hypothesized that African American race is associated with an elevated EDPR gradient that may partially predispose African Americans to heart failure.

METHODS

The Heart and Soul Study prospectively assessed the EDPR gradient in 480 patients with coronary disease. We used multivariable linear regression to investigate the independent association of African American race with EDPR gradient.

RESULTS

Compared with 393 non-African Americans, the 87 African Americans had similar indices of left ventricular systolic and diastolic function, left ventricular mass index, mitral regurgitation, peak tricuspid regurgitation gradient, and pulmonary velocity time integral. However, the EDPR gradient was significantly higher in African Americans (4.2 +/- 3.3 mm Hg) than in Caucasians (3.1 +/- 2.5 mm Hg) or other racial groups (3.5 +/- 2.7 mm Hg) (P = .008). In a multivariable model, African American race was a significant predictor of elevated EDPR gradient (beta coefficient 0.75, P = .03).

CONCLUSION

African American race is independently associated with an elevated EDPR gradient in patients with coronary artery disease.

Role of Echocardiography in the Diagnostic Assessment and Etiology of Heart Failure in the Elderly—Opacify, Quantify, and Rectify

Echocardiography offers comprehensive, noninvasive, and relatively inexpensive tools for diagnosing cardiac pathology in the elderly. With an organized approach using two-dimensional echocardiography and Doppler echocardiography, clinicians can determine the systolic and diastolic left ventricular performance; estimate the cardiac output, pulmonary artery, and ventricular filling pressures; and identify surgically correctable valve disease. Meanwhile, real-time three-dimensional echocardiography provides unprecedented volume data to quantify the left ventricular status. Tissue Doppler-derived myocardial velocity and strain imaging data provide extremely fine details about the regional variations in myocardial synchrony and predict responders to cardiac resynchronization therapy. Thus, echocardiographic tools provide the basis for determining when to attempt to rectify the left ventricular dysfunction with strategically placed, biventricular pacemaker leads.

Diastolic Heart Failure in the Elderly

Most elderly patients, particularly women, who have heart failure have a normal ejection fraction. Patients who have this syndrome have severe symptoms of exercise intolerance, frequent hospitalizations, and increased mortality. The pathophysiology and treatment are not well defined. Control of systemic hypertension may be a key to prevention and treatment. Several large trials of specific agents are currently underway.

Prediction of fluid responsiveness using respiratory variations in left ventricular stroke area by transoesophageal echocardiographic automated border detection in mechanically ventilated patients

Background

Left ventricular stroke area by transoesophageal echocardiographic automated border detection has been shown to be strongly correlated to left ventricular stroke volume. Respiratory variations in left ventricular stroke volume or its surrogates are good predictors of fluid responsiveness in mechanically ventilated patients. We hypothesised that respiratory variations in left ventricular stroke area (ΔSA) can predict fluid responsiveness.

Methods

Eighteen mechanically ventilated patients undergoing coronary artery bypass grafting were studied immediately after induction of anaesthesia. Stroke area was measured on a beat-to-beat basis using transoesophageal echocardiographic automated border detection. Haemodynamic and echocardiographic data were measured at baseline and after volume expansion induced by a passive leg raising manoeuvre. Responders to passive leg raising manoeuvre were defined as patients presenting a more than 15% increase in cardiac output.

Results

Cardiac output increased significantly in response to volume expansion induced by passive leg raising (from 2.16 ± 0.79 litres per minute to 2.78 ± 1.08 litres per minute; p < 0.01). ΔSA decreased significantly in response to volume expansion (from 17% ± 7% to 8% ± 6%; p < 0.01). ΔSA was higher in responders than in non-responders (20% ± 5% versus 10% ± 5%; p < 0.01). A cutoff ΔSA value of 16% allowed fluid responsiveness prediction with a sensitivity of 92% and a specificity of 83%. ΔSA at baseline was related to the percentage increase in cardiac output in response to volume expansion (r = 0.53, p < 0.01).

Conclusion

ΔSA by transoesophageal echocardiographic automated border detection is sensitive to changes in preload, can predict fluid responsiveness, and can quantify the effects of volume expansion on cardiac output. It has potential clinical applications.

Diastolic heart failure in the elderly

Most elderly patients, particularly women, who have heart failure have a normal ejection fraction. Patients who have this syndrome have severe symptoms of exercise intolerance, frequent hospitalizations, and increased mortality. The pathophysiology and treatment are not well defined. Control of systemic hypertension may be a key to prevention and treatment. Several large trials of specific agents are currently underway.

A Novel Two-Dimensional Echocardiographic Image Analysis System Using Artificial Intelligence-Learned Pattern Recognition for Rapid Automated Ejection Fraction

OBJECTIVES

We sought to test the hypothesis that a novel 2-dimensional echocardiographic image analysis system using artificial intelligence-learned pattern recognition can rapidly and reproducibly calculate ejection fraction (EF).

BACKGROUND

Echocardiographic EF by manual tracing is time consuming, and visual assessment is inherently subjective.

METHODS

We studied 218 patients (72 female), including 165 with abnormal left ventricular (LV) function. Auto EF incorporated a database trained on >10,000 human EF tracings to automatically locate and track the LV endocardium from routine grayscale digital cineloops and calculate EF in 15 s. Auto EF results were independently compared with manually traced biplane Simpson's rule, visual EF, and magnetic resonance imaging (MRI) in a subset.

RESULTS

Auto EF was possible in 200 (92%) of consecutive patients, of which 77% were completely automated and 23% required manual editing. Auto EF correlated well with manual EF (r = 0.98; 6% limits of agreement) and required less time per patient (48 +/- 26 s vs. 102 +/- 21 s; p < 0.01). Auto EF correlated well with visual EF by expert readers (r = 0.96; p < 0.001), but interobserver variability was greater (3.4 +/- 2.9% vs. 9.8 +/- 5.7%, respectively; p < 0.001). Visual EF was less accurate by novice readers (r = 0.82; 19% limits of agreement) and improved with trainee-operated Auto EF (r = 0.96; 7% limits of agreement). Auto EF also correlated with MRI EF (n = 21) (r = 0.95; 12% limits of agreement), but underestimated absolute volumes (r = 0.95; bias of -36 +/- 27 ml overall).

CONCLUSIONS

Auto EF can automatically calculate EF similarly to results by manual biplane Simpson's rule and MRI, with less variability than visual EF, and has clinical potential.

Role of echocardiography in the diagnostic assessment and etiology of heart failure in the elderly--opacify, quantify, and rectify

Echocardiography offers comprehensive, noninvasive, and relatively inexpensive tools for diagnosing cardiac pathology in the elderly. With an organized approach using two-dimensional echocardiography and Doppler echocardiography, clinicians can determine the systolic and diastolic left ventricular performance;estimate the cardiac output, pulmonary artery, and ventricular fill-ing pressures; and identify surgically correctable valve disease.Meanwhile, real-time three-dimensional echocardiography provides unprecedented volume data to quantify the left ventricular status. Tissue Doppler-derived myocardial velocity and strain imaging data provide extremely fine details about the regional variations in myocardial synchrony and predict responders to cardiac resynchronization therapy. Thus, echocardiographic tools provide the basis for determining when to attempt to rectify the left ventricular dysfunction with strategically placed, biventricular pace-maker leads.

Automatic Endocardial-Boundary Detection in Low Mechanical-Index Contrast Echocardiography

This paper presents a novel algorithm, aimed at automatic endocardial boundary (inner boundary) detection in myocardial opacification scenarios. The data acquisition protocol uses (on purpose) low mechanical index imaging (i.e., weak ultrasound signal), so that the acquired images are characterized by low signal-to-noise ratios. The proposed algorithm is based on converting the frames, given in Cartesian coordinates, into polar coordinates, and applying a set of filters in order to compute the initial estimation of the endocardial boundary. The final estimation of the endocardial boundary is produced by an error correction process, which uses both spatial and temporal filtering. The estimated boundaries are converted into Cartesian coordinates, for display. Our algorithm has been tested on nine cine-loops. The resulting myocardial outlines have been separately assessed by two clinicians, scoring each segment in each cine-loop on a scale between 5 (excellent) and 1 (completely unacceptable). The mean overall score is 3.8 +/- 0.8, which seems adequate. The same clinicians have also manually drawn the contours of the endocardial boundary for the end-systolic and the end-diastolic frames of each cine-loop. The results show, that the mismatch between the automatically determined outlines and the manually drawn outlines is of the same order of magnitude as the interobserver variability. These results further support the validity of our method.

Time-varying elastance concept applied to the relation of carotid arterial flow velocity and ventricular area

OBJECTIVE

In this study, the relationship V(f)AR, which was obtained from carotid blood-flow velocity (V(f)) and the cross-sectional area (A) of the left ventricle, was used to assess changes in left ventricular (LV) systolic performance as indicated by the LV pressure-volume relationship (PVR) and end-systolic LV elastance (E(es)).

BACKGROUND

The relationship of maximum systolic V(f) as a surrogate for LV pressure and end-systolic LV area as a surrogate for end-systolic LV volume may allow for the estimation of LV elastance and ejection properties.

METHODS

In 25 pigs, internal carotid V(f) was recorded by using continuous-wave Doppler mode. Echocardiographic measurements of A were continuously performed with an automated border detection system and combined with data for V(f) to display V(f)AR as a series of loop diagrams. These were shifted during acute preload reduction, and an index E'(es) was calculated by applying the time varying elastance concept to end-systolic V(f)AR. Simultaneously, E(es) was acquired by conductance catheter and micromanometer techniques. Comparisons of E'(es) and E(es) were made at various contractility levels obtained by the administration of dobutamine, 5 microg/kg/min, and esmolol, 40 to 60 mg, and at various cardiac load levels, obtained by a fluid bolus infusion or administration of a vasoconstrictor.

RESULTS

Highly linear elastance curves (r >or= 0.85, p < 0.0001) were derived from both end-systolic V(f)AR and PVR. Correlation of E'(es) and E(es) revealed an almost linear function: E'(es) = 0.052 + 0.11 E(es) (r = 0.98, p < 0.0001). Administration of dobutamine increased E(es) from 5.8 +/- 3.04 mmHg/mL to 10.1 +/- 4.19 mmHg/mL (p < 0.05), and E('es) from 0.68 +/- 0.288 cm(2)/min/mL to 1.24 +/- 0.458 cm(2)/min/mL (p < 0.05). After administration of esmolol, E(es) and E'(es) both dropped significantly by 3.7 +/- 2.4 mmHg/mL and 0.44 +/- 0.15 cm(2)/min/mL, respectively. No load dependency of E'(es) was seen. Bland-Altman analysis revealed that the change in E'(es), which is required to predict a significant change in E(es), should exceed +16.9% or -13.1% of the preceding value.

CONCLUSION

Application of the time-varying elastance concept on the relation of V(f) and LV area allows for the determination of an index E'(es) that may be used to estimate E(es).

Evaluation of Left Ventricular Systolic Function Using Automated Angle-Independent Motion Tracking of Mitral Annular Displacement

Determination of ejection fraction (EF) in clinical practice typically involves manual tracing of endocardial borders. This method is time-intensive and highly dependent on image quality. Mitral annular displacement (MAD) has been shown to correlate well with EF. Previously, this method involved tedious analysis of M-mode tracings. We developed and studied a new technique that is ultrasound beam angle-independent for automated detection of MAD, based on a tissue tracking algorithm. A regression formula was derived in a study group to predict EF from MAD measurements and tested prospectively in a separate group of patients. We found that our technique provides accurate, ultra-fast estimation of EF with lower inter- and intraobserver variability when compared with manually traced biplane EF.

Performance of User Independent Echocardiographic Border Detection Algorithm: Comparison with Human Observer Variability

INTRODUCTION

We evaluated a method for autonomous, user-independent automated border delineation (ABD) developed by Geiser and Wilson, by comparing the accuracy of ABD relative to manual border tracing.

METHODS

Short axis echocardiographic images of 84 patients from 3 clinical sites were analyzed using ABD and by manual tracing performed by two observers at each site and two observers at a core laboratory. The centerline method was used to measure the distance between each pair of computer-generated and hand-traced borders. Cardiac parameters were also measured from all sets of borders: LV area, fractional area change, antero-posterior diameter, wall motion, and wall thickening.

RESULTS

The distance between computer-generated and hand-traced borders was slightly but significantly greater than human interobserver variability between the clinical sites and the core laboratory (0.34+/-0.25 (N = 328) vs. 0.26+/-0.16 (N = 320) cm for the endocardium at end diastole, p = 0.0001). Measurements of LV area and fractional area change were similar by ABD and manual tracing. Other cardiac parameters showed greater deviation between ABD and manually traced borders than between human observers.

CONCLUSION

Autonomous ABD provides accurate measurements of LV area and area-derived indices. However measurements dependent on border point location deviate more by ABD.

Determination of preload-recruitable stroke work and elastance by the relationship of arterial blood flow velocity to left ventricular area

OBJECTIVE

The authors investigated the feasibility of an online sampling and display of LV flow-area loops for the determination of LV elastance and preload-recruitable stroke work (PRSW). Automated LV area measurements by echocardiography may be combined with flow velocity measurements in the internal carotid artery to construct LV flow-area loops as estimates of the systolic pressure-volume relationship.

SETTING

University hospital.

DESIGN

Open chest model.

PARTICIPANTS

Eight anesthetized minipigs.

INTERVENTIONS

Inferior vena cava occlusion was performed to simultaneously obtain parameters of the LV flow-area relationship and the LV pressure-area relationship.

MEASUREMENTS AND MAIN RESULTS

Parameters were obtained at baseline and during sequential administration of dobutamine (5 microg/kg/min) and halothane (0.8 vol%). Linear regression analysis and analysis of variance were performed to investigate an underlying linear relationship between the corresponding variables. Highly linear elastance and PRSW curves were derived from the flow-area and pressure-area loops (n = 24, R >/= 0.85). Changes of the curve slopes indicated inotropic changes as well as model independent dP/dt(max). Elastance from the pressure-area relationship was expressed by elastance from the flow-area relationship by the term y = 0.52 + 0.04. x (R(2) = 0.84; p < 0.0001). Linear regression of PRSW as derived from the flow-area relationship with PRSW as derived from the pressure-area relationship was expressed by y = 0.43 + 0.02. x (R(2) = 0.77; p < 0.0001).

CONCLUSION

Indices of the LV pressure-area relationship can be derived from real-time loops constructed from arterial flow velocity and LV area.

Three-dimensional ultrasonography for volume measurement of thyroid nodules in children

OBJECTIVE

The aim of this study was to compare the accuracy of thyroid nodule volume measurements performed by 2- and 3-dimensional ultrasonography and to evaluate the dependence of volume measurement results on nodule size and echographic characteristics.

METHODS

Results of multiple 2- and 3-dimensional ultrasonographic volume measurements of thyroid nodules in 102 children with different variants of thyroid nodular disease were reviewed retrospectively. The standardized difference, within-observer variability, and repeatability were estimated for both 2- and 3-dimensional ultrasonography. The mean age of the patients +/- SD in the examined group was 14.9 +/- 2.8 years; the mean volume of thyroid nodules was 0.78 +/- 0.13 mL.

RESULTS

The SD of the normalized difference for 3-dimensional ultrasonography (2.8%) showed the clear superiority of its accuracy over 2-dimensional ultrasonography (15.9%; F test, P < .01). Intraobserver variability and repeatability for both examined methods had significant dependence on the nodule outline. For 2-dimensional ultrasonography, the intraobserver variability increased from 14.0% in nodules with a regular outline to 24.5% in those with an irregular outline (P < .001), and for 3-dimensional ultrasonography, it increased from 5.1% to 9.3% (P < .001). Intraobserver repeatability dropped from 85.4% in regular nodules to 74.6% in irregular nodules (P < .001) for 2-dimensional ultrasonography and from 94.7% to 90.4% (P < .001) for 3-dimensional ultrasonography.

CONCLUSIONS

Volume measurements by 3-dimensional ultrasonography are more accurate, showing lower intraobserver variability and higher repeatability, than those made by 2-dimensional ultrasonography with less dependence on nodule size and echographic characteristics.

Accuracy of three-dimensional ultrasound for thyroid volume measurement in children and adolescents

The aim of this study was to estimate accuracy, intraobserver variability, and repeatability of thyroid volume measurement by ultrasound using conventional two-dimensional ellipsoid model (2D US) and manual planimetry of three-dimensional images (3D US). The sonographic images of 47 children with thyroid nodular pathology who were referred for thyroid surgery in Belarus were evaluated prospectively. Two-dimensional images were acquired using the ultrasound scanner with 7.5-MHz linear probe. Three-dimensional data sets were created using three-dimensional system, FreeScan. For each patient thyroid volume was measured three times using both two- and three-dimensional methods. Results of volume estimation were then compared to the volume of thyroid gland determined after surgery. Standardized difference between thyroid volume estimated by ultrasound and surgery (mean +/- standard deviation (SD), %) for 3D and 2D US methods was 1.8 +/- 5.2% and 3.2 +/- 15.3%, respectively. The 3D US has lower intraobserver variability (3.4%) and higher repeatability (96.5%) than 2D US with 14.4% variability and 84.8% repeatability (p < 0.001). In conclusion, three-dimensional sonography allows accurate measurement of thyroid volume with low intraobserver variability and high repeatability.

Quantitative analysis of left ventricular regional wall motion with color kinesis during abdominal aortic cross-clamping

OBJECTIVES

The authors aimed to establish a technique for quantitative analysis of regional wall motion abnormality (RWMA) using color kinesis (CK) of transesophageal echocardiography (TEE) in surgical patients. This technique was used to determine whether RWMAs develop de novo after infrarenal aortic cross-clamping in patients undergoing vascular surgery with a preoperative dipyridamole thallium stress test (DTST).

DESIGN

An observational study.

SETTING

University hospital.

PARTICIPANTS

Thirty-eight patients undergoing infrarenal abdominal aortic aneurysm resection or aortofemoral bypass.

MEASUREMENTS AND MAIN RESULTS

CK images of the left ventricle (LV) were obtained from the midventricular transgastric short-axis view before and after infrarenal aortic cross-clamping using TEE and analyzed off-line using custom software. The predictive value of the category "reversible perfusion defect" (RD) was also estimated from DTST for predicting new RWMAs with CK. CK analysis is suitable for clinical use based on the comparison with conventional two-dimensional echocardiogram measurements and interobserver variability. CK analysis showed all 7 patients with persistent perfusion defects on DTST had RWMAs. New RWMAs occurred in 2 of 9 patients with RD and in 2 of 15 patients with normal DTST, indicating that there was no significant difference between RD and normal DTST in the incidence of new RWMAs.

CONCLUSIONS

A new method is available for clinical use, which is capable of visualizing RWMAs. These results suggest that new RWMAs introduced by aortic cross-clamping occur irrespective of the risk as assessed by preoperative DTST. CK with the new analysis method might be a useful tool to quantitatively evaluate RWMAs during surgery.

Rapid and accurate noninvasive assessment of global left ventricular systolic function using biplane advanced automated contour tracking method

BACKGROUND

The advanced automated contour tracking (AACT) method has been newly developed for automated detection of the left ventricular endocardial boundary. Left ventricular ejection fraction (LVEF) may be estimated by applying the AACT method to 2 orthogonal planes of patients even when regional wall-motion abnormalities exist. The purpose of this study was to examine the reliability of the biplane AACT method in the measurement of LVEF in patients with suggested ischemic heart disease with use of quantitative gated single photon emission computed tomography (QGS) as a reference standard.

METHODS

The study population consisted of 47 consecutive patients with suggested ischemic heart disease. All patients underwent 2-dimensional echocardiography and QGS. Biplane LVEF from apical 4- and 2-chamber views was measured offline by the AACT method using disk summation method. The accuracy of the AACT method for LVEF measurement was determined in comparison with QGS.

RESULTS

In 41 (29 with and 12 without regional wall-motion abnormalities) of 47 patients (87%), automated tracing of the endocardial border was adequately achieved with the AACT method. LVEF measured by the AACT method correlated well with that measured by QGS (y = 0.97x +2.4, r = 0.91). The mean difference between AACT and QGS was 0.6 +/- 5.5% (mean +/- SD). The mean time required for analysis of 1 set of images during 1 cardiac cycle by the AACT method was much shorter than that required by manual tracing method (7 +/- 1 vs 37 +/- 4 seconds, P <.0001).

CONCLUSION

The biplane AACT method provides accurate and quick measurement of LVEF in patients even with regional wall-motion abnormalities.

Automated quantification of left ventricular function by the automated contour tracking method

The automated contour tracking (ACT) method has been developed for the automated measurement of area volume using the energy minimization method without tracing a region of interest. The purpose of this study was to compare the ACT method and left ventriculography (LVG) for the measurement of left ventricular (LV) function in the clinical setting. An apical four-chamber view was visualized by two-dimensional echocardiography and recorded for off-line analysis in 14 patients with high-quality images who underwent LVG. The ACT method automatically traces the endocardial border from the recorded images and calculates LV volumes (end-diastole and end-systole) and ejection fraction (EF). Both ACT and LVG were compared by linear regression analysis for the measurement of EF. EF determined by the ACT method agreed well with that by LVG (r = 0.96, y = 0.94x + 4.6, standard error of the estimate = 3.9%). The mean difference between the ACT and LVG was -1.4%+/- 7.3%. In conclusion, the ACT method is reliable for noninvasive estimation of EF in high-quality images. This suggests that this new technique may be useful in the automated quantification of LV function.

Quantitative assessment of pericardial effusion volume by two-dimensional echocardiography

The clinical applicability of a method for quantifying pericardial effusion (PE) was studied. The pericardial and cardiac volumes were determined from border tracings of 2-dimensional echocardiograms fitted with 3-dimensional disk models. The PE volume was the difference between pericardial and cardiac volumes. A phantom study included 54 cases with different volumes and viewing geometry showed a correlation coefficient r = 0.98 and an accuracy of +/- 6%. A clinical study included 20 cases showing that the estimated PE volume correlated well with that drained surgically (between 100 mL and 1200 mL): y = 0.81 x + 120 mL; r = 0.91, P <.0001. The percent error, determined by the standard error of the estimate (114 mL) over mean (548 mL), was 20%. Intraobserver variability was 4% and interobserver variability 6%. The 3-dimensional disk method provides a quick and convenient way to quantify PE from 2-dimensional echocardiograms with acceptable accuracy and reproducibility.

Automated endocardial border detection and evaluation of left ventricular function from contrast-enhanced images using modified acoustic quantification

Automated border detection (ABD) techniques have been used for the quantitative assessment of left ventricular (LV) performance but require adequate visualization of the endocardial border to accurately track the blood-tissue interface. We sought to evaluate whether ABD could be used in conjunction with an infusion of echocardiographic contrast to objectively quantify LV systolic performance. Twenty-one subjects had LV volume and ejection fraction (EF) assessed by hand-tracing and prototype ABD software during contrast infusion. The mean hand-traced EF was 45% +/- 16%. Automatic tracking of contrast-enhanced endocardial borders with prototype ABD software was possible in all subjects. This allowed generation of signal averaged LV volume waveforms, from which quantitative LV ejection fraction was obtained. There were no significant differences in LV volumes or EF between contrast-enhanced acoustic quantification and manually traced borders. This technique has the potential of providing objective quantitation of LV volume and function in patients with technically limited echocardiograms.

Quantification of left ventricular diastolic pressure-volume relations during routine cardiac catheterization by two-dimensional digital echo quantification and left ventricular micromanometer

BACKGROUND

Currently there is no simple clinical method for quantifying the left ventricular (LV) diastolic pressure-volume relation. Echocardiographic-automated endocardial border detection, however, may be combined with LV micromanometer to construct LV pressure-volume loops. We investigated the feasibility of on-line display and sampling of LV pressure-volume loops by such an approach. For this purpose we used a new echocardiographic digital echo quantification (DEQ) method in combination with LV pressures on-line and in real-time.

METHODS

Eighteen patients were screened by conventional echocardiography and DEQ. Ten of the patients with high quality images were included in the study. Left ventricular pressures and volumes were recorded simultaneously and were displayed on-line as pressure-volume loops. Changes in LV volume were induced by intravenous saline. Left ventricular chamber compliance was estimated as change in volume divided by change in pressure from minimum diastolic pressure to end-diastolic pressure (average LV chamber compliance).

RESULTS

Left ventricular pressure-volume loops were displayed on-line during the examination. When compared with the Simpson's method, DEQ underestimated end-diastolic volume (EDV) by 35% and overestimated end-systolic volume (ESV) by 14%. Beat-to-beat variability for ESV and EDV were 7.4% +/- 0.8% and 7.2% +/- 0.7 %, respectively. Volume loading increased LV end-diastolic pressure (LVEDP) from 14.0 +/- 1.6 to 24.7 +/- 2.0 mm Hg (P <.05) and EDV from 79 +/- 10 to 85 +/- 11 mL (NS), and decreased LV chamber compliance from 4.0 +/- 0.7 to 2.0 +/- 0.3 mL/mm Hg (P <.05).

CONCLUSION

The current study demonstrates that LV pressure-volume loops can be displayed and evaluated in real-time during routine cardiac catheterization. This may represent a clinically useful method for identifying patients with reduced chamber compliance. The underestimation of the volumes by DEQ compared with the Simpson's method suggests that further refinements should be performed to improve the endocardial border detection algorithm.

Subjective assessment of left ventricular preload using transesophageal echocardiography: corresponding pulmonary artery occlusion pressures

OBJECTIVE

To record pulmonary artery occlusion pressures (PAOPs) in patients whose left ventricular preload reserve was subjectively determined using transesophageal echocardiography (TEE).

DESIGN

Prospective, blinded, nonrandomized.

SETTING

University hospital.

PARTICIPANTS

Twenty-three patients with well-preserved left ventricular function during nonemergent cardiac surgery.

INTERVENTIONS

After separation from cardiopulmonary bypass, patients received repeated boluses of fluid volume through the aortic inflow cannula while being monitored with TEE. The endpoint for this fluid administration was a plateau in left ventricular fractional area change and end-diastolic area. This point at which additional fluid failed to cause noticeable increases in left ventricular end-diastolic area and fractional area change was defined as the preload reserve volume. After reaching the preload reserve volume, the PAOP was measured, as were the systolic blood pressure, left ventricular fractional area change, and end-diastolic area.

MEASUREMENTS AND MAIN RESULTS

The mean PAOP for all patients at the time of achieving preload reserve volume was 18.6 +/- 2.9 mmHg. In 8 patients, the PAOP corresponding to preload reserve volume was elevated (20 to 25 mmHg). The remaining 15 patients had PAOPs ranging from 13 to 19 mmHg. When these 2 groups were compared with respect to left ventricular end-diastolic area, fractional area change, and systolic blood pressure, there were no significant differences between groups. The left ventricular wall thickness was significantly greater, however, in the group with elevated PAOP (1.37 +/- 0.04 cm) when compared with the group with normal ventricular filling pressures (1.05 +/- 0.15 cm) (p = 0.001).

CONCLUSIONS

In patients with well-preserved left ventricular function and normal wall thickness, preload reserve volumes subjectively determined by TEE corresponded to a range of filling pressures historically targeted to maximize cardiac performance (13 to 19 mmHg). In a subset of patients with increased wall thickness, however, subjective determination of preload reserve was associated with filling pressures that were higher than traditionally considered optimal (20 to 25 mmHg). Similarities in left ventricular fractional area change and end-diastolic area between these 2 groups suggest that patients with elevated filling pressures had decreased ventricular compliance and were managed correctly with higher than usual PAOPs.

New method of on-line quantification of regional wall motion with automated segmental motion analysis

We have recently developed an automated segmental motion analysis (A-SMA) system, based on an automatic "blood-tissue interface" detection technique, to provide real-time and on-line objective echocardiographic segmental wall motion analysis. To assess the feasibility of A-SMA in detecting regional left ventricular (LV) wall motion abnormalities, we performed 2-dimensional echocardiography with A-SMA in 13 healthy subjects, 22 patients with prior myocardial infarction (MI), and 9 with dilated cardiomyopathy (DCM). Midpapillary parasternal short-axis and apical 2- and 4-chamber views were obtained to clearly trace the blood-tissue interface. The LV cavity was then divided into 6 wedge-shaped segments by A-SMA. The area of each segment was calculated automatically throughout a cardiac cycle, and the area changes of each segment were displayed as bar graphs or time-area curves. The systolic fractional area change (FAC), peak ejection rate (PER), and filling rate (PFR) were also calculated with the use of A-SMA. In the control group, a uniform FAC was observed in real time among 6 segments in the short-axis view (60% +/- 10% to 78% +/- 9%), or among 5 segments in either the 2-chamber (59% +/- 12% to 75% +/- 16%) or 4-chamber view (58% +/- 13% to 72% +/- 12%). The variations of FAC, PER, and PFR were obviously decreased in infarct-related regions in the MI group and were globally decreased in the DCM group. We conclude that A-SMA is an objective and time-saving method for assessing regional wall motion abnormalities in real time. This method is a reliable new tool that provides on-line quantification of regional wall motion.

Inferior vena cava occlusion catheter for pediatric patients with heart disease: for more detailed cardiovascular assessments

Traditional evaluation of cardiac function is too often limited by reliance on measurements with complex interdependence between cardiac properties and loading factors. Analysis by ventricular pressure-volume (P-V), -area (P-A), or -dimension (P-D) relations during inferior vena caval (IVC) occlusion independently quantifies ventricular properties and loading conditions, providing detailed information about cardiovascular dynamics. However, there has been no appropriate size of balloon catheter that can effectively occlude IVC of pediatric patients, hindering the application of P-V (P-A, or P-D) analysis to children with heart disease despite its potential benefit. To address this problem, we have developed a new balloon catheter for IVC occlusion in children. The catheter effectively occluded IVC in 92 pediatric patients with varying forms of heart disease who underwent cardiac catheterization, yielding end-systolic pressure-area relations. Thus a newly developed balloon catheter would contribute to establishing more accurate and detailed cardiovascular assessments in children with heart disease. Cathet Cardiovasc Intervent 2001;53:392-396.

Diastolic dysfunction in the elderly. Genesis and diagnostic and therapeutic implications

Diastolic left ventricular function is altered substantially with advancing age in healthy persons, and diastolic dysfunction impacts most cardiovascular disorders in the elderly. Older, healthy persons have a delayed relaxation Doppler filling pattern and their early deceleration time is similar to, or modestly lengthened, compared with younger, healthy persons. Two abnormal Doppler filling patterns, the pseudo-normal and the restricted, are discerned more easily, and are more specific in the elderly than the young, because they are the opposite (reverse) of the normal elderly pattern. Most heart failure in the elderly occurs in the presence of preserved systolic function (presumed diastolic heart failure). Elderly patients with diastolic heart failure tend to be women with hypertrophied, hyperdynamic left ventricles, and chronic hypertension. Prognosis may be somewhat better than in systolic heart failure, but the difference diminishes when adjusted for gender and in the very elderly. The pathophysiology of this disorder is not well characterized, diagnostic criteria have not been standardized, and there are no large, multicenter, randomized trials to guide therapy. Further research in this area should be a high priority.

Heart failure with normal systolic function

Contrary to popular belief, population studies indicate that most elderly patients with heart failure have preserved left ventricular systolic function (i.e., presumed diastolic heart failure). Several normal aging changes may predispose older individuals to diastolic heart failure, including increased hypertrophy and stiffness of the left ventricle, increased vascular stiffness, and decreased cardiovascular reserve. Progress in diastolic heart failure has been hindered by a lack of standard case definition; absence of a readily available, reliable test to quantitate diastolic function; poor understanding of the pathophysiology of heart failure; and lack of data from randomized, controlled, multicenter trials. Typical patients are older women with chronic hypertension, left ventricular hypertrophy, chronic exercise intolerance, and occasional acute exacerbations (pulmonary edema). Although heart failure is a clinical, bedside diagnosis, echocardiography is helpful in differentiating diastolic from systolic heart failure and in ruling out other disorders. Although optimal pharmacologic therapy has not been clarified, control of blood pressure; exercise conditioning; and a multidisciplinary, case management approach seem beneficial.

Role of echocardiography in the diagnosis and management of heart failure in the elderly

Heart failure is the most common cause of cardiovascular hospitalization in older adults in the United States. This disease is common, disabling, and commonly fatal, especially in the elderly population. Hypertension and coronary artery disease are the leading causes of heart failure. A precise diagnosis of the cardiac abnormality is paramount for adequate treatment, and echocardiography offers the most comprehensive, noninvasive evaluation. With an organized approach using two-dimensional and Doppler echocardiography, the systolic and diastolic left ventricular performance can be determined; the cardiac output, pulmonary artery, and ventricular filling pressures can be estimated; and surgically correctable valve disease can be identified. The response and success of treatment also may be monitored by the judicious use of echocardiography.

Validity and reproducibility of echocardiographic measurement of left ventricular ejection fraction by acoustic quantification with tissue harmonic imaging technique

The tissue harmonic imaging technique can enhance detection of the cardiac endocardial border. When combined with an acoustic quantification (AQ) method, an improvement of accuracy and reproducibility of real-time measurement of left ventricular (LV) function might be expected. However, few data exist regarding the measurement of LV function by AQ with the harmonic imaging technique. Therefore, we evaluated the validity and reproducibility of AQ measurement of LV ejection fraction with or without harmonic imaging technique. A total of 50 patients (mean age 58 +/- 10 years) who underwent left ventriculography were included in our study. The LV end-diastolic and end-systolic volumes by ventriculography were 131 +/- 52 mL and 72 +/- 43 mL, respectively, and were underestimated by both conventional (70 +/- 32 mL and 36 +/- 25 mL) and harmonic (67 +/- 30 mL and 34 +/- 22 mL) AQ obtained in the apical 4-chamber view. The calculated ejection fraction by ventriculography was 0.49 +/- 0. 11 and correlated with that by conventional AQ (0.51 +/- 0.11; y = 0. 72x + 0.152; r = 0.73). This was a marked improvement when compared with the ejection fraction by harmonic AQ (0.50 +/- 0.11; y = 0.89x + 0.065; r = 0.91). Interestingly, interobserver and intraobserver variabilities of conventional AQ, which were 15.6% and 8.6%, respectively, were much improved by harmonic AQ (8.9% and 4.5%, respectively). These results indicate the feasibility of real-time measurement of LV ejection fraction by harmonic imaging, although absolute LV volume can be underestimated even by this technique.

A multiresolution image segmentation technique based on pyramidal segmentation and fuzzy clustering

In this paper, an unsupervised image segmentation technique is presented, which combines pyramidal image segmentation with the fuzzy c-means clustering algorithm. Each layer of the pyramid is split into a number of regions by a root labeling technique, and then fuzzy c-means is used to merge the regions of the layer with the highest image resolution. A cluster validity functional is used to find the optimal number of objects automatically. Segmentation of a number of synthetic as well as clinical images is illustrated and two fully automatic segmentation approaches are evaluated, which determine the left ventricular volume (LV) in 140 cardiovascular magnetic resonance (MR) images. First fuzzy c-means is applied without pyramids. In the second approach the regions generated by pyramidal segmentation are merged by fuzzy c-means. The correlation coefficients of manually and automatically defined LV lumen of all 140 and 20 end-diastolic images were equal to 0.86 and 0.79, respectively, when images were segmented with fuzzy c-means alone. These coefficients increased to 0.90 and 0.93 when the pyramidal segmentation was combined with fuzzy c-means. This method can be applied to any dimensional representation and at any resolution level of an image series. The evaluation study shows good performance in detecting LV lumen in MR images.

Means for load variation during echocardiographic assessment of the Frank-Starling relationship

Because minimally invasive methods of preload variation are not validated for load-insensitive indexes of cardiac performance, intravenous nitroglycerin (NTG), phenylephrine, and saline solution (VOL) boluses were used in blocked and intact autonomic states to alter load and were compared with vena caval occlusion in the assessment of preload recruitable stroke work relationships between stroke work and left ventricular end-diastolic volume in dogs. In both autonomic states NTG and VOL produced comparable linear relationships. NTG and saline solution were combined with noninvasive measurements of left ventricular pressure and volume to construct echocardiographic relationships between stroke work and left ventricular end-diastolic cross-sectional area; NTG produced linear relationships similar to vena caval occlusion. Therefore NTG and VOL reliably alter load in constructing preload recruitable stroke work relationships, and NTG may be used with noninvasive measurements to provide load-insensitive estimates of cardiac function in a minimally invasive manner.

Artificial neural networks and spatial temporal contour linking for automated endocardial contour detection on echocardiograms: a novel approach to determine left ventricular contractile function

This study investigated the use of artificial neural networks (ANN) for image segmentation and spatial temporal contour linking for the detection of endocardial contours on echocardiographic images. Using a backpropagation network, the system was trained with 279 sample regions obtained from eight training images to segment images into either tissue or blood pool region. The ANN system was then applied to parasternal short axis images of 38 patients. Spatial temporal contour linking was performed on the segmented images to extract endocardial boarders. Left ventricular areas (end-systolic and end-diastolic) determined with the automated system were calculated and compared to results obtained by manual contour tracing performed by two independent investigators. In addition, ejection fractions (EF) were derived using the area-length method and compared with radionuclide ventriculography. Image quality was classified as good in 12 (32%), moderate in 13 (34%) and poor in 13 (34%) patients. The ANN system provided estimates of end-diastolic and end-systolic areas in 36 (89%) of echocardiograms, which correlated well with those obtained by manual tracing (R = 0.99, SEE = 1.44). A good agreement was also found for the comparison of EF between the ANN system and Tc-radionuclide ventriculography (RNV, R = 0.93, SEE = 6.36). The ANN system also performed well in the subset of patients with poor image quality. Endocardial contour detection using artificial neural networks and spatial temporal contour linking allows accurate calculations of ventricular areas from transthoracic echocardiograms and performs well even in images with poor quality. This system could greatly enhance the feasibility, accuracy and reproducibility of calculating cardiac areas to derive left ventricular volumes and ejection fractions.

Determinants of aortic pressure variation during positive-pressure ventilation in man

STUDY OBJECTIVES

To define the relation between systolic arterial pressure (SAP) changes during ventilation and left ventricular (LV) performance in humans.

DESIGN

Prospective repeat-measures series.

SETTING

University of Pittsburgh Medical Center Operating Room.

PATIENTS

Fifteen anesthetized cardiac surgery patients before and after cardiopulmonary bypass when the mediastinum was either closed or open.

INTERVENTIONS

Positive-pressure ventilation.

MEASUREMENTS AND RESULTS

SAP and LV midaxis cross-sectional areas were measured during apnea and then were measured for three consecutive breaths. SAP increased during inspiration, this being the greatest during closed chest conditions (p < 0.05). Changes in SAP could not be correlated with changes in either LV end-diastolic areas (EDAs), end-systolic areas, or stroke areas (SAs). If SAP decreased relative to apnea, the decrease occurred during expiration and was often associated with increasing LV EDAs and SAs. SAP often decreased after a positive-pressure breath, but the decrease was unrelated to SA deficits during the breath. Increases in SAP were in phase with increases in airway pressure, whereas decreases in SAP, if present, followed inspiration. No consistent relation between SAP variation and LV area could be identified.

CONCLUSIONS

In this patient group, changes in SAP reflect changes in airway pressure and (by inference) intrathoracic pressure (as in a Valsalva maneuver) better than they reflect concomitant changes in LV hemodynamics.

Impact of on-line endocardial border detection on determination of left ventricular volume and ejection fraction by transthoracic 3-dimensional echocardiography

This study was performed to determine whether use of on-line automated border detection (ABD) could reduce data analysis time for 3-dimensional echocardiography (3DE) while maintaining accuracy of 3DE in measures of left ventricular (LV) volumes and ejection fraction (EF). The study proceeded in 2 phases. In the validation phase, 20 subjects were examined with the use of 3DE and of monoplane 2-dimensional (2D) ABD. Results were compared with the reference standard of magnetic resonance imaging (MRI). In the test phase, 20 subjects underwent two 3DE studies (once with images optimized for visual border definition and once with images optimized for ABD border tracking) and a conventionally used 2D ABD study. For 3DE, volumes and EF were determined with the use of manually traced borders and ABD. Analysis times were recorded with a digital stopwatch. In the validation phase, 3DE and MRI results correlated very well (r = 0.99) without systematic differences. Comparison of 2D ABD with MRI showed good correlation for LV volumes (r >/= 0.90) and EF (r = 0.85) despite significant underestimation. For the test phase, Acoustic Quantification-optimized 3-dimensional datasets underestimated end-diastolic volume and EF relative to visually optimized 3-dimensional datasets regardless of whether borders were hand-traced or ABD was used. However, correlations ranged from r = 0.96 to r = 0.98 for LV volumes and 0.88 to 0.91 for LV EF and were superior to those for 2D ABD. Data analysis times decreased moderately with the use of ABD, but scan times increased; total study times were unchanged. Use of on-line ABD with 3DE reduces data analysis time and is more accurate than conventional monoplane 2D ABD but results in underestimation of LV volumes and EF. Additional automated postprocessing techniques may be required to obtain accurate measures, consistently using 3DE in conjunction with on-line ABD.

Evaluation and management of pulmonary atresia with intact ventricular septum

Pulmonary atresia with intact ventricular septum (PA/IVS) is a spectrum of diseases with varying severity of right ventricle hypoplasia and potential for biventricular, univentricular, or hybrid repairs. Pessimistic outcome measures for PA/IVS may give way to optimism with the refinement of early diagnosis and early intervention to encourage right ventricle flow and optimize growth. To this end, PA/IVS has become a focus of innovative interventions (e.g., fetal surgery) and new catheter-based and surgical techniques.

Online Quantification of Left Ventricular Function: Correlation with Various Imaging Modalities

The need for more objectively quantifiable evaluation of the left ventricular function, obtainable on line with echocardiography, was fulfilled through modifications of integrated backscatter imaging to permit real-time differentiation of the endocardium and the blood pool area in every image frame. Operator-guided study of individual cardiac chambers permitted instantaneous measurement of chamber areas in either the systole or diastole, with resulting physiologically meaningful recordings that relate to cardiac function. Validation studies by various approaches suggest that the methodology is clinically relevant, and further improvements in design will sharpen its applicability in the future.

Load-Independent Indices of Left Ventricular Function Using Automated Border Detection

Echocardiographic automated border detection is the ability to assess left ventricular (LV) cross-sectional cavity areas and volumes on line. This capability has enabled the use of LV pressure-volume relationships as a means to determine LV function in a manner relatively independent of loading conditions. This discussion reviews previous validation studies in animal models and humans using LV cross-sectional area as a surrogate for LV volume and the clinical applications of LV pressure-area relations. Applications of arterial pressure as a substitute for LV ejection pressure to assess pressure-area relations are also reviewed, along with the use of pressure-area relations to assess right ventricular performance. Last, preload-adjusted maximal power as an alternative load-insensitive means to determine LV performance is discussed.

Comparison of echocardiographic acoustic quantification with off-line manual tracing for determining left ventricular volume and ejection fraction in pediatric patients

Echocardiographic measurement of left ventricular systolic and diastolic volume and ejection fraction in pediatric patients by acoustic quantification using automated border methods compares well with measurements done by manual trace. The time necessary for completion of measurements was similar for the two methods.