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Biomedical subjects

Roberto M Lang

Publications and source records attributed to Roberto M Lang.

At least 55 records · Page 3Linked to original sources
PubMed2005

Interrupted infusion of echocardiographic contrast as a basis for accurate measurement of myocardial perfusion: ex vivo validation and analysis procedures.

BACKGROUND: Echocardiographic quantification of myocardial perfusion is based on analysis of contrast replenishment after destructive high-energy ultrasound impulses (flash-echo). This technique is limited by nonuniform microbubble destruction and the dependency on exponential fitting of a small number of noisy time points. We hypothesized that brief interruptions of contrast infusion (ICI) would result in uniform contrast clearance followed by slow replenishment and, thus, would allow analysis from multiple data points without exponential fitting. METHODS: Electrocardiographic-triggered images were acquired in 14 isolated rabbit hearts (Langendorff) at 3 levels of coronary flow (baseline, 50%, and 15%) during contrast infusion (Definity) with flash-echo and with a 20-second infusion interruption. Myocardial videointensity was measured over time from flash-echo sequences, from which characteristic constant beta was calculated using an exponential fit. Peak contrast inflow rate was calculated from ICI data using analysis of local time derivatives. Computer simulations were used to investigate the effects of noise on the accuracy of peak contrast inflow rate and beta calculations. RESULTS: ICI resulted in uniform contrast clearance and baseline replenishment times of 15 to 25 cardiac cycles. Calculated peak contrast inflow rate followed the changes in coronary flow in all hearts at both levels of reduced flow (P < .05) and had a low intermeasurement variability of 7 +/- 6%. With flash-echo, contrast clearance was less uniform and baseline replenishment times were only 4 to 6 cardiac cycles. beta Decreased significantly only at 15% flow, and had intermeasurement variability of 42 +/- 33%. Computer simulations showed that measurement errors in both perfusion indices increased with noise, but beta had larger errors at higher rates of contrast inflow. CONCLUSION: ICI provides the basis for accurate and reproducible quantification of myocardial perfusion using fast and robust numeric analysis, and may constitute an alternative to the currently used techniques.

Animals↗
PubMed2005

Dual triggering improves the accuracy of left ventricular volume measurements by contrast-enhanced real-time 3-dimensional echocardiography.

Real-time 3-dimensional echocardiographic continuous imaging (CIM) with contrast underestimates left ventricular (LV) volumes. We studied the effects of dual-triggered (DT) acquisition on the accuracy of LV volume measurements for patients with poor acoustic windows. Real-time 3-dimensional echocardiographic imaging was performed in 20 patients during LV opacification (Definity) on the same day as cardiac magnetic resonance imaging. Both CIM and DT data were analyzed using custom software to calculate end-systolic volume (ESV) and end-diastolic volume (EDV), which were compared with the cardiac magnetic resonance reference. CIM correlated well with the cardiac magnetic resonance reference (EDV: r = 0.89; ESV: r = 0.93), but underestimated EDV and ESV by 17% and 19%, respectively. In contrast, DT resulted in higher correlation (EDV: r = 0.95; ESV: r = 0.96) and smaller biases (9% and 6%, respectively). In conclusion, because the accuracy of LV volume measurements depends on the acquisition strategy of contrast-enhanced real-time 3-dimensional echocardiographic images, the use of DT instead of the conventional CIM acquisition is recommended.

Computer Systems↗
PubMed2005

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.

Adult↗
PubMed2005

Improved quantification of left ventricular volumes and mass based on endocardial and epicardial surface detection from cardiac MR images using level set models.

PURPOSE: The reproducibility of left ventricular (LV) volume and mass measurements based on subjective slice-by-slice tracing of LV borders is affected by image quality, and volume estimates are biased by geometric modeling. The authors developed a technique for volumetric surface detection (VoSD) and quantification of LV volumes and mass without tracing and geometric approximations. The authors hypothesized that this technique is accurate and more reproducible than the conventional methodology. METHODS: Images were obtained in 24 patients in 6 to 10 slices from LV base to apex (GE 1.5 T, FIESTA). Volumetric data were reconstructed, and endocardial and epicardial surfaces were detected using the level set approach. LV volumes were obtained from voxel counts and used to compute ejection fraction (EF) and mass. Conventional measurements (MASS Analysis) were used as a reference to test the accuracy of VoSD technique (linear regression, Bland-Altman). For both techniques, measurements were repeated to compute inter- and intra-observer variability. RESULTS: VoSD values resulted in high correlation with the reference values (EDV: r = 0.98; ESV: r = 0.99; EF: r = 0.91; mass: r = 0.98), with no significant biases (8 ml, 5 ml, 0.2% and -9 g) and narrow limits of agreement (SD: 13 ml, 10 ml, 6% and 9 g). Inter-observer variability of the VoSD technique was lower (range 3 to 5%) than that of the reference technique (5 to 11%; p < 0.05). Intra-observer variability was also lower (1 to 3% vs. 7 to 10%; p < 0.05). CONCLUSION: VoSD technique allows accurate measurements of LV volumes, EF, and mass, which are more reproducible than the conventional methodology.

Cardiac Volume↗
PubMed2005

Prognostic value of echocardiography in peripartum cardiomyopathy.

OBJECTIVE: To estimate whether echocardiography findings at the time of diagnosis of peripartum cardiomyopathy are predictive of persistent cardiac dysfunction. METHODS: Chart review of patients with peripartum cardiomyopathy between 1988 and 2001 was performed. Data from echocardiography, including fractional shortening and left ventricular end diastolic dimension, were recorded both at the time of diagnosis and at follow-up. Left ventricular dysfunction was defined by echocardiography as fractional shortening less than 30% and left ventricular end diastolic dimension of 4.8 cm or more. RESULTS: Of 32 patients meeting our definition for peripartum cardiomyopathy and for whom follow-up data were available, 13 (41%) had recovery of ventricular function, while 19 (59%) continued to have persistent left ventricular dysfunction. Those who did not recover cardiac function had a higher left ventricular end diastolic dimension and a lower fractional shortening at diagnosis than those who recovered. A fractional shortening value less than 20% and a left ventricular end diastolic dimension 6 cm or greater at the time of diagnosis was associated with a more than 3-fold higher risk for persistent left ventricular dysfunction. CONCLUSION: Along with being an important diagnostic tool in peripartum cardiomyopathy, echocardiography may provide significant prognostic information with regards to recovery of cardiac function.

Adolescent↗
PubMed2005

Feasibility of measuring coronary flow velocity and reserve in the left anterior descending coronary artery by transthoracic Doppler echocardiography in a relatively obese American population.

BACKGROUND: Transthoracic Doppler echocardiography (TTDE) assessment of coronary flow velocity reserve (CFVR) has been validated in Asian and European centers. This methodology has not gained acceptability in the United States due to the bias that coronary flow velocity (CFV) by TTDE might be difficult in an obese population with relatively poor acoustic windows. METHODS: Baseline CFV in the left anterior descending coronary artery (LAD) by TTDE was obtained in 67 nonselected American patients. A subset of 38/67 received adenosine infusion for measuring CFVR of the LAD. PURPOSE: The aim of this study was twofold: (1) to determine the feasibility of measuring CFV and CFVR in the LAD by TTDE in a relatively obese American population, and (2) to compare CFV and CFVR values in this population with those previously obtained in a group of Japanese patients. RESULTS: The mean body mass index (BMI) of the American population (28 +/- 6 kg/m2, range: 18-46 kg/m2) was significantly higher than that of the Japanese group (23 +/- 4 kg/m2, range: 15-37 kg/m2). Twenty-five American patients were classified as obese (BMI >30 kg/m2). Baseline CFV was obtained in 60/67 patients (feasibility: 90%) with a 10% need for intravenous contrast agent to enhance the delineation of the CFV envelope. The success rate in recording CFVR in American patients (92%) was nearly identical to that of a Japanese group (99%). The time-averaged peak diastolic coronary flow velocity increased from 15.6 +/- 5.5 cm/sec at baseline to 47.1 +/- 17.9 cm/sec during adenosine infusion, and CFVR was calculated to be 3.22 +/- 1.15 (range: 0.94-5.69). Intraobserver and interobserver variability for the CFV recording was 4.7 and 6.2%, respectively. CONCLUSIONS: These results suggest that the noninvasive measurement of CFV and CFVR of the LAD is feasible even in a relatively obese American population. Furthermore, the success rates for recording CFV and CFVR are similar to those measured in a Japanese population. This methodology has the potential to provide useful physiological information on the coronary circulation in American patients.

Adenosine↗
PubMed2005

The arterial system in pre-eclampsia and chronic hypertension with superimposed pre-eclampsia.

OBJECTIVES: To determine if the normal gestational changes in mechanical properties of the arterial system are altered in pre-eclampsia. DESIGN: Prospective controlled observational study. SETTING: University urban tertiary medical centre. POPULATION: Eleven pre-eclamptics and 10 chronic hypertensives with superimposed pre-eclampsia were compared with 14 normotensive gravidas experiencing preterm labour, all receiving MgSO(4). Two additional control groups were studied as well: (A) nine normal pregnant women receiving neither magnesium nor epidural, for baseline comparisons; and (B) eight normotensive gravidas receiving epidural anaesthesia. METHODS: Two-dimensional targeted M-mode echocardiograms and continuous wave Doppler velocity were used to obtain instantaneous pressure and flow data. Total vascular resistance (TVR) quantified the steady component of systemic arterial load; pulsatile arterial load was characterised by global arterial compliance (AC), aortic input impedance spectrum (Z(1)) and characteristic impedance (Z(0)). MAIN OUTCOME MEASURES: TVR, AC, Z(1), Z(0). RESULTS: Controls, pre-eclamptics and chronic hypertensives with superimposed pre-eclampsia, respectively: TVR index 1328 [299], 1973 [609]*, 2428 [562]*(,#) dyn second cm(-5) m(2); AC area index 1.69 [0.46], 1.19 [0.46]*, 0.93 [0.38]* mL mmHg(-1) m(-2); Z(0) index 253.2 [61.3], 327.0 [135.1], 307.5 [130.9] dyn second cm(-5) m(2); and Z(1) index 184.2 [56.5], 283.6 [81.6]*, 357.1 [119.5]* dyn second cm(-5) m(2) (*P < 0.05 vs control;(#)P < 0.05 vs pre-eclampsia). Normal gravidas (in secondary controls group A) had decreased mean systolic and diastolic blood pressures, and increased AC and cardiac indices, compared with women receiving magnesium tocolysis, verifying the need for these primary controls. No differences were noted between normotensive gravidas receiving epidural anaesthesia (secondary controls group B) and the non-anesthetised controls (group A), eliminating epidural as a confounder. CONCLUSIONS: The normal gestational changes in systemic arterial mechanical properties are significantly altered in pre-eclampsia and these alterations are more marked with superimposed hypertensive disease.

Adult↗
PubMed2004

Meeting highlights of the 15th annual Scientific Sessions of the American Society of Echocardiography: June 26 to 30, 2004.

"Echocardiography is the heart of clinical cardiology" was an appropriate theme for the 15th Scientific Sessions of the American Society of Echocardiography. Care of the cardiovascular patient is constantly changing, and this meeting showcased how echocardiographic and Doppler methods continue to be critically important to detect and quantify disease, determine response to therapy, and guide clinical decision making in contemporary medicine. This highly successful five-day educational event attracted a record number of attendees and focused on disease-based clinical applications of the latest technological advances in cardiac ultrasound, including advances in diagnosis and treatment of heart failure, valvular disease, coronary disease, and congenital disease.

Coronary Disease↗
PubMed2004

Racial differences in aortic atheroma in patients undergoing transesophageal echocardiography for unexplained stroke or transient ischemic attack.

Racial differences in the prevalence of complex thoracic aortic atheroma were evaluated in 318 patients referred for transesophageal echocardiography after unexplained stroke or transient ischemic attack. African-Americans were found to have fewer complex thoracic aortic atheroma and fewer combined cardiac sources of embolus than Caucasian patients. This finding persists after adjusting for racial differences in atherosclerotic risk factors.

Adult↗
PubMed2004

Fast measurement of left ventricular mass with real-time three-dimensional echocardiography: comparison with magnetic resonance imaging.

BACKGROUND: Left ventricular (LV) mass is an important predictor of morbidity and mortality, especially in patients with systemic hypertension. However, the accuracy of 2D echocardiographic LV mass measurements is limited because acquiring anatomically correct apical views is often difficult. We tested the hypothesis that LV mass could be measured more accurately from real-time 3D (RT3D) data sets, which allow offline selection of nonforeshortened apical views, by comparing 2D and RT3D measurements against cardiac MR (CMR) measurements. METHODS AND RESULTS: Echocardiographic imaging was performed (Philips 7500) in 21 patients referred for CMR imaging (1.5 T, GE). Apical 2- and 4-chamber views and RT3D data sets were acquired and analyzed by 2 independent observers. The RT3D data sets were used to select nonforeshortened apical 2- and 4-chamber views (3DQ-QLAB, Philips). In both 2D and RT3D images, LV long axis was measured; endocardial and epicardial boundaries were traced, and mass was calculated by use of the biplane method of disks. CMR LV mass values were obtained through standard techniques (MASS Analysis, GE). The RT3D data resulted in significantly larger LV long-axis dimensions and measurements of LV mass that correlated with CMR better (r=0.90) than 2D (r=0.79). The 2D technique underestimated LV mass (bias, 39%), whereas RT3D measurements showed only minimal bias (3%). The 95% limits of agreement were significantly wider for 2D (52%) than RT3D (28%). Additionally, the RT3D technique reduced the interobserver variability (37% to 7%) and intraobserver variability (19% to 8%). CONCLUSIONS: RT3D imaging provides the basis for accurate and reliable measurement of LV mass.

Adult↗
PubMed2004

Real-time three-dimensional echocardiography for rheumatic mitral valve stenosis evaluation: an accurate and novel approach.

OBJECTIVES: Our aim was to assess which echo-Doppler method has the best agreement with the mitral valve area (MVA) invasively evaluated by the Gorlin's formula. We also evaluated the feasibility and reproducibility of real-time three-dimensional echocardiography (RT3D) for the estimation of MVA and the Wilkins score in patients with rheumatic mitral stenosis (RMVS). BACKGROUND: Real-time three-dimensional echocardiography is a novel technique that allows us to visualize the mitral valvular anatomy in any desired plane orientation. The usefulness and accuracy of this technique for evaluating RMVS has not been established. METHODS: We studied a series of consecutive patients with RMVS from two tertiary care hospitals. Mitral valvular area was determined by conventional echo-Doppler methods and by RT3D, and their results were compared with those obtained invasively. Real-time three-dimensional echocardiography planimetry and mitral score were measured by two independent observers and then repeated by one of them. RESULTS: Eighty patients with RMVS comprised our study group (76 women; 50.6 +/- 13.9 years). Compared with all other echo-Doppler methods, RT3D had the best agreement with the invasively determined MVA (average difference between both methods and limits of agreement: 0.08 cm(2) [-0.48 to 0.6]). Interobserver variability was as good for RT3D (intraclass correlation coefficient [ICC] = 0.90) as for pressure half-time (PHT) (ICC = 0.95). For PHT and RT3D, the intraobserver variability was similar (ICC 0.92 and 0.96, respectively). Real-time three-dimensional echocardiography valvular score evaluation showed a better interobserver agreement with RT3D than with 2D echocardiography. CONCLUSIONS: Real-time three-dimensional echocardiography is a feasible, accurate, and highly reproducible technique for assessing MVA in patients with RMVS. Real-time three-dimensional echocardiography has the best agreement with invasive methods.

Echocardiography, Three-Dimensional↗
PubMed2004

Differential diagnosis of cardiac masses using contrast echocardiographic perfusion imaging.

OBJECTIVES: We investigated the usefulness of echocardiographic contrast perfusion imaging in differentiating cardiac masses. BACKGROUND: Two-dimensional echocardiography is the primary diagnostic modality for cardiac masses. However, differentiation between the different types of cardiac masses may be difficult at times. We hypothesized that echocardiographic contrast perfusion imaging would differentiate the neo-vascularization of malignancies from the avascularity of thrombi and the sparse vascularity of stromal tumors. METHODS: Sixteen patients with cardiac masses underwent power-modulation imaging after echocardiographic intravenous contrast administration. Pixel intensities in the mass and an adjacent section of myocardium were analyzed visually and by dedicated software. All masses had a pathologic diagnosis or resolved after anticoagulation. In a subset of patients, video-intensity curves of contrast replenishment in the mass and myocardium over time were generated. The post-impulse steady-state pixel intensity (A) and initial rate of contrast replenishment after impulse (beta) were compared with an index of blood vessel area on pathology. RESULTS: In seven of 16 patients, contrast enhancement resulted in greater pixel intensity in the mass than in the adjacent myocardium. All of these masses were classified pathologically as malignant (n = 6) or benign and vascular (n = 1). Nine masses demonstrated decreased pixel intensity, compared with the myocardium, and were diagnosed pathologically as myxomas (n = 2) or thrombi (n = 5), or they resolved with anticoagulation (n = 2). For the subset of patients, beta correlated with the vessel area index (r = 0.60). CONCLUSIONS: Echocardiographic contrast perfusion imaging aids in the differentiation of cardiac masses. Compared with the adjacent myocardium, malignant and vascular tumors hyper-enhanced, whereas stromal tumors and thrombi hypo-enhanced.

Adult↗
PubMed2004

Ventricular resynchronization by multisite pacing improves myocardial performance in the postoperative single-ventricle patient.

BACKGROUND: Ventricular resynchronization with multisite pacing in heart failure patients results in acute improvement of myocardial performance, but the mechanism is unknown. Our goals were to determine whether multisite pacing results in acute improvement of myocardial performance in postoperative single-ventricle patients, and to elucidate the mechanism by assessing the synchronization of regional ventricular contraction during multisite pacing using real-time three-dimensional echocardiographic imaging. METHODS: Multisite pacing studies were performed in 26 single-ventricle patients (mean age, 28 months; range, 7 days to 11 years) undergoing some form of single-ventricle palliation (stage I Norwood, 4; aortopulmonary shunt, 1; cavopulmonary shunt, 9; Fontan, 8; Fontan revision, 3; valve replacement, 1). Electrocardiogram, blood pressure, mixed-venous oxygen saturation, and three-dimensional echocardiograms (n = 10) were recorded at baseline and during multisite pacing. Data were analyzed to obtain regional volume-time curves for 16 three-dimensional segments of the systemic ventricle. An index of asynchrony was calculated at baseline and during pacing as the standard deviation of all segmental volume-time curves from onset to end of ejection. RESULTS: With multisite pacing performed at a median postoperative day 2 (range, 0 to 9), QRS duration decreased in 24 of 26 patients (93.9 +/- 17.5 versus 71.7 +/- 10.8 ms; p < 0.001); systolic blood pressure increased in 25 of 26 patients (86.3 +/- 20.0 versus 93.8 +/- 20.2 mm Hg; p < 0.001); cardiac index increased in 21 of 22 patients (3.2 +/- 0.8 versus 3.7 +/- 1.0 L x min(-1) x m(-2); p < 0.001); and the index of asynchrony improved in 8 of 10 patients (10.3 +/- 4.8 versus 6.0 +/- 1.4; p < 0.04). CONCLUSIONS: Multisite pacing improves cardiac performance after single-ventricle palliation. Real-time three-dimensional echocardiography demonstrated that multisite pacing improved the synchrony of ventricular contraction.

Cardiac Pacing, Artificial↗
PubMed2004

Assessment of left ventricular function with contrast echocardiography.

Echocardiography continues to be the primary noninvasive imaging modality for the assessment of cardiac structure and function because of significant advances in ultrasound imaging technology over the last two decades, yet quantification of the LV function has remained an elusive goal. The introduction of contrast agents has represented a major advance in clinicians' ability to visualize the endocardium and to assess LV function accurately, particularly in patients who have poor acoustic windows. Ongoing and future refinements in imaging technology used with contrast enhancement have placed automated quantification of LV function on the brink of widespread clinical use.

Contrast Media↗