The use of intraoperative Doppler ultrasound in endoscopic transsphenoidal surgery

INTRODUCTION

Doppler ultrasound (DUS) has been widely used in neurosurgical practice to diagnose various cerebrovascular diseases. This technique is used in transsphenoidal surgery to identify the localization of intracranial arteries when making an approach or during tumor resection.

MATERIAL AND METHODS

To identify the cavernous segment of the internal carotid artery (ICA) and/or basilar artery during endoscopic transsphenoidal surgery, we used a combined device on the basis of a click line curette («Karl Storz») and a 16 MHz Doppler probe (Lassamed). The technique was used in 51 patients during both standard transsphenoidal surgery (23 cases) and transsphenoidal tumor resection through an extended approach (28 cases).

RESULTS AND DISCUSSION

Doppler ultrasound was used in different situations: to determine a trajectory of the endonasal transsphenoidal approach in the absence of the normal anatomical landmarks (16 cases), to define the limits of safe resection of a tumor located in the laterosellar region (7), and to implement an extended transsphenoidal endoscopic approach (28). Intraoperative Doppler ultrasound enabled identification of the cavernous segment of the internal carotid artery in 45 cases and the basilar artery in 2 cases; a blood vessel was not found in 4 cases. Injury to the cavernous segment of the internal carotid artery was observed only in 1 case.

CONCLUSION

The use of the described combined device in transsphenoidal surgery turned Doppler ultrasound into an important and useful technique for visualization of the ICA within the tumor stroma as well as in the case of the changed skull base anatomy. Its use facilitates manipulations in a deep and narrow wound and enables inspection of the entire surface of the operative field in various planes, thereby surgery becomes safer due to the possibility of maximum investigation of the operative field.

Comparison of three-dimensional proximal isovelocity surface area to cardiac magnetic resonance imaging for quantifying mitral regurgitation

The aim of our study was to evaluate 3-dimensional (3D) color Doppler proximal isovelocity surface area (PISA) as a tool for quantitative assessment of mitral regurgitation (MR) against in vitro and in vivo reference methods. A customized 3D PISA software was validated in vitro against a flowmeter MR phantom. Sixty consecutive patients, with ≥mild MR of any cause, were recruited and the regurgitant volume (RVol) was measured by 2D PISA, 3D peak PISA, and 3D integrated PISA, using transthoracic (TTE) and transesophageal echocardiography (TEE). Cardiac magnetic resonance imaging (CMR) was used as reference method. Flowmeter RVol was associated with 3D integrated PISA as follows: y = 0.64x + 4.7, r(2) = 0.97, p <0.0001 for TEE and y = 0.88x + 4.07, r(2) = 0.96, p <0.0001 for TTE. The bias and limit of agreement in the Bland-Altman analysis were 6.8 ml [-3.5 to 17.1] for TEE and -0.059 ml [-6.2 to 6.1] for TTE. In vivo, TEE-derived 3D integrated PISA was the most accurate method for MR quantification compared to CMR: r(2) = 0.76, y = 0.95x - 3.95, p <0.0001; 5.1 ml (-14.7 to 26.5). It was superior to TEE 3D peak PISA (r(2) = 0.67, y = 1.00x + 6.20, p <0.0001; -6.3 ml [-33.4 to 21.0]), TEE 2D PISA (r(2) = 0.54, y = 0.76x + 0.18, p <0.0001; 8.4 ml [-20.4 to 37.2]), and TTE-derived measurements. It was also most accurate by receiver operating characteristic analysis (area under the curve 0.99) for the detection of severe MR, RVol cutoff = 48 ml, sensibility 100%, and specificity 96%. RVol and the cutoff to define severe MR were underestimated using the most accurate method. In conclusion, quantitative 3D color Doppler echocardiography of the PISA permits a more accurate MR assessment than conventional techniques and, consequently, should enable an optimized management of patients suffering from MR.

Single-ensemble-based eigen-processing methods for color flow imaging--Part I. The Hankel-SVD filter

Because of their adaptability to the slow-time signal contents, eigen-based filters have shown potential in improving the flow detection performance of color flow images. This paper proposes a new eigen-based filter called the Hankel-SVD filter that is intended to process each slowtime ensemble individually. The new filter is derived using the notion of principal Hankel component analysis, and it achieves clutter suppression by retaining only the principal components whose order is greater than the clutter eigen-space dimension estimated from a frequency based analysis algorithm. To assess its efficacy, the Hankel-SVD filter was first applied to synthetic slow-time data (ensemble size: 10) simulated from two different sets of flow parameters that model: 1) arterial imaging (blood velocity: 0 to 38.5 cm/s, tissue motion: up to 2 mm/s, transmit frequency: 5 MHz, pulse repetition period: 0.4 ms) and 2) deep vessel imaging (blood velocity: 0 to 19.2 cm/s, tissue motion: up to 2 cm/s, transmit frequency: 2 MHz, pulse repetition period: 2.0 ms). In the simulation analysis, the post-filter clutter-to- blood signal ratio (CBR) was computed as a function of blood velocity. Results show that for the same effective stopband size (50 Hz), the Hankel-SVD filter has a narrower transition region in the post-filter CBR curve than that of another type of adaptive filter called the clutter-downmixing filter. The practical efficacy of the proposed filter was tested by application to in vivo color flow data obtained from the human carotid arteries (transmit frequency: 4 MHz, pulse repetition period: 0.333 ms, ensemble size: 10). The resulting power images show that the Hankel-SVD filter can better distinguish between blood and moving-tissue regions (about 9 dB separation in power) than the clutter-downmixing filter and a fixed-rank multi ensemble-based eigen-filter (which showed a 2 to 3 dB separation).

Single-ensemble-based eigen-processing methods for color flow imaging--Part II. The matrix pencil estimator

Parametric spectral estimators can potentially be used to obtain flow estimates directly from raw slow-time ensembles whose clutter has not been suppressed. We present a new eigen-based parametric flow estimation method called the matrix pencil, whose principles are based on a matrix form under the same name. The presented method models the slow-time signal as a sum of dominant complex sinusoids in the slow-time ensemble, and it computes the principal Doppler frequencies by using a generalized eigen-value problem-formulation and matrix rank reduction principles. Both fixed rank (rank-one, rank-two) and adaptive-rank matrix pencil flow estimators are proposed, and their potential applicability to color flow signal processing is discussed. For the adaptive-rank estimator, the nominal rank was defined as the minimum eigen-structure rank that yields principal frequency estimates with a spread greater than a prescribed bandwidth. In our initial performance evaluation, the fixed-rank matrix pencil estimators were applied to raw color flow data (transmit frequency: 5 MHz; pulse repetition period: 0.175 ms; ensemble size: 14) acquired from a steady flow phantom (70 cm/s at centerline) that was surrounded by rigid-tissue-mimicking material. These fixed-rank estimators produced velocity maps that are well correlated with the theoretical flow profile (correlation coefficient: 0.964 to 0.975). To facilitate further evaluation, the matrix pencil estimators were applied to synthetic slow-time data (transmit frequency: 5 MHz; pulse repetition period: 1.0 ms; ensemble size: 10) modeling flow scenarios without and with tissue motion (up to 1 cm/s). The bias and root-mean-squared error of the estimators were computed as a function of blood-signal-to-noise ratio and blood velocity. The matrix pencil flow estimators showed that they are comparatively less biased than most of the existing frequency-based flow estimators like the lagone autocorrelator.

Vibrating interventional device detection using real-time 3-D color Doppler

Ultrasound image guidance of interventional devices during minimally invasive surgery provides the clinician with improved soft tissue contrast while reducing ionizing radiation exposure. One problem with ultrasound image guidance is poor visualization of the device tip during the clinical procedure. We have described previously guidance of several interventional devices using a real-time 3-D (RT3-D) ultrasound system with 3-D color Doppler combined with the ColorMark technology. We then developed an analytical model for a vibrating needle to maximize the tip vibrations and improve the reliability and sensitivity of our technique. In this paper, we use the analytical model and improved radiofrequency (RF) and color Doppler filters to detect two different vibrating devices in water tank experiments as well as in an in vivo canine experiment. We performed water tank experiments with four different 3- D transducers: a 5 MHz transesophageal (TEE) probe, a 5 MHz transthoracic (TTE) probe, a 5 MHz intracardiac catheter (ICE) transducer, and a 2.5 MHz commercial TTE probe. Each transducer was used to scan an aortic graft suspended in the water tank. An atrial septal puncture needle and an endomyocardial biopsy forceps, each vibrating at 1.3 kHz, were inserted into the vascular graft and were tracked using 3-D color Doppler. Improved RF and wall filters increased the detected color Doppler sensitivity by 14 dB. In three simultaneous planes from the in vivo 3-D scan, we identified both the septal puncture needle and the biopsy forceps within the right atrium using the 2.5 MHz probe. A new display filter was used to suppress the unwanted flash artifact associated with physiological motion.

Full motion and flow field recovery from echo Doppler data

We present a new computational method for reconstructing a vector velocity field from scattered, pulsed-wave ultrasound Doppler data. The main difficulty is that the Doppler measurements are incomplete, for they do only capture the velocity component along the beam direction. We thus propose to combine measurements from different beam directions. However, this is not yet sufficient to make the problem well posed because 1) the angle between the directions is typically small and 2) the data is noisy and nonuniformly sampled. We propose to solve this reconstruction problem in the continuous domain using regularization. The reconstruction is formulated as the minimizer of a cost that is a weighted sum of two terms: 1) the sum of squared difference between the Doppler data and the projected velocities 2) a quadratic regularization functional that imposes some smoothness on the velocity field. We express our solution for this minimization problem in a B-spline basis, obtaining a sparse system of equations that can be solved efficiently. Using synthetic phantom data, we demonstrate the significance of tuning the regularization according to the a priori knowledge about the physical property of the motion. Next, we validate our method using real phantom data for which the ground truth is known. We then present reconstruction results obtained from clinical data that originate from 1) blood flow in carotid bifurcation and 2) cardiac wall motion.

Doppler myocardial imaging in adult male rats: Reference values and reproducibility of velocity and deformation parameters

AIM

Limited data are available about the use of Doppler myocardial imaging (DMI) in small animals. We intend to provide reference values for velocity, strain and strain rate in a large group of healthy rats and studied the reproducibility and repeatability of these parameters.

METHODS AND RESULTS

A total of 33 male Wistar rats (503+/-41g) underwent baseline transthoracic echocardiography with DMI of the anterior and inferior wall in a short-axis view using a 13MHz linear probe. Adequate tissue Doppler measurements could be obtained in 30 rats. On average 10+/-4 consecutive cycles were studied in post-processing using dedicated software (SPEQLE). Mean radial peak systolic velocity, strain and strain rate were respectively -0.8+/-0.3cm/s, 38+/-8% and 9.1+/-2.0/s in the anterior wall and 3.1+/-0.6cm/s, 49+/-10% and 13.7+/-3.7/s in the inferior wall. The reproducibility and repeatability of the DMI measurements assessed in 10 rats was good.

CONCLUSION

DMI is feasible and reproducible in healthy rats. Establishing reference values opens new perspectives towards the use of strain and strain rate imaging in small rodents in the assessment of myocardial diseases.

Ultrasound Mini-Transducer with Malleable Handle for Coronary Artery Surgery

PURPOSE

A 13 MHz epicardial ultrasound mini-transducer (15 x 9 x 6 mm) with a custom made malleable handling tool was evaluated to assess the coronary artery and anastomosis on all sides of the heart.

DESCRIPTION

On indication, in 8 patients undergoing coronary artery bypass surgery on the arrested heart, 8 coronary arteries as well as 27 coronary anastomoses were scanned.

EVALUATION

The malleable handle was easily adjusted, and all sides of the heart were accessible for scanning with the mini-transducer. Based on intraoperative scanning, the anastomotic site was altered (n = 4), an additional coronary artery was grafted (n = 2), and the left anterior descending coronary artery was identified after incorrect conventional selection of the diagonal branch (n = 1). No anastomosis construction errors were detected. In one anastomosis, a calcified plaque was seen in the outflow corner.

CONCLUSIONS

The epicardial ultrasound mini-transducer with its malleable handle allowed successful visualization and assessment of the coronary arteries and anastomoses on all sides of the heart. Ultrasound information greatly aided in intraoperative decision making that resulted in anastomotic site changes and prevented grafting of the wrong vessel.

Agreement between community echocardiography and hospital echocardiography in patients suspected of having left ventricular systolic dysfunction

BACKGROUND

Smaller echocardiography machines, when used in hospitals, are accurate for detecting left ventricular dysfunction and valvular disease. This paper assessed the detection of left ventricular dysfunction and of valvular disease in the community setting by a smaller machine.

AIMS

To measure the agreement in patients with suspected heart failure between community echocardiography and traditional echocardiography in the hospital in detecting left ventricular dysfunction and significant valve disease.

METHODS

Suspected heart failure patients were referred to one of the authors (SJ) for community echocardiography using a Siemens Cypress machine. The patients had a second echocardiogram in the hospital by another sonographer who was blinded to the results of the first echocardiogram. The reports of the two sonographers were assessed for agreement using kappa statistics.

RESULTS

458 patients had a community echocardiogram and 136 agreed to a second echocardiogram in the hospital. There was excellent agreement, kappa = 0.87 (0.06 SE), for the detection of left ventricular dysfunction between community echocardiography and the hospital machine. The detection of significant valvular disease was good, kappa = 0.75 (0.06) between the community echocardiogram and hospital machines.

CONCLUSIONS

In suspected heart failure patients, community echocardiography gives comparable results to traditional hospital echocardiography for left ventricular dysfunction detection and for significant valvular disease detection.

A novel method for the assessment of the accuracy of computing laminar flow stroke volumes using a real-time 3D ultrasound system: In vitro studies

AIMS

Laminar flow stroke volume (SV) quantification in the ascending aorta or pulmonary artery can provide a measure for determining cardiac output (CO). Comparing flows across different valves can also compute shunt volumes and regurgitant fractions. Quantification methods for 3D color Doppler laminar flow volumes have been developed using reconstructive 3D, but these are cumbersome and time-consuming both in acquisition and measurement. Our study evaluated newly developed color Doppler mapping with real-time live 3D echo to test velocity, spatial and temporal resolution for computing SV.

METHODS AND RESULTS

Five rubber tubes (diameters=3.0, 2.25, 2.0, 1.9, 1.7 cm), a freshly dissected porcine aorta (Ao) and a pulmonary artery (PA) (both 2-3 cm diameter) were connected to a pulsatile pump in a water bath. Different SV, from 10 to 80 ml/beat, were studied at pump rates of 40-60 bpm in this phantom model with flow quantified by timed collection. The Nyquist limit was set between 43 and 100 cm/s and frame rate ranged from 14 to 23/s. ECG triggered 3D color Doppler volumes were acquired with a 2-4 MHz probe. The digital scan line data from the 3D volumes, with retained velocity assignments, was exported and analyzed offline by MatLab custom software. Close correlations were found between 3D calculated SV and reference data for all tubes (r=0.98, y=1.14x-1.69, SEE=2.82 ml/beat, p<0.0001). Both Ao and PA flows were also highly correlated with the reference measurements (PA: r=0.98, SEE=3.17 ml/beat; Ao: r=0.99, SEE=3.20 ml/beat).

CONCLUSIONS

Real-time 3D color Doppler method could provide an efficient, accurate and reliable method for clinical evaluation and quantification of flow volumes in patients.

Doppler Echocardiographic Assessment of Valvular Regurgitation Severity by Measurement of the Vena Contracta: An In Vitro Validation Study

BACKGROUND

Noninvasive quantitation of valvular regurgitation remains a difficult problem. Measurements of the vena contracta (VC) by color Doppler echocardiography have been proposed but limited data are available on the actual accuracy of this method.

METHODS

To evaluate how closely the color Doppler VC reflects the true fluid dynamic VC and the anatomic regurgitant orifice and whether this measurement is affected by flow changes, various models of valvular regurgitation were studied in an in vitro flow circuit. The VC diameter was measured with color Doppler using two different ultrasound systems (Agilent Sonos 5500; Agilent Technologies Inc, Palo Alto, Calif and Vingmed CFM 800; GE Healthcare, Chalfront St Giles, UK). Optical planimetry of the anatomic regurgitant orifice was performed, the true VC diameter was determined by laser particle flow visualization.

RESULTS

Because of flow contraction, the true VC diameter was consistently smaller than the anatomic regurgitant orifice diameter. Anatomic orifice and true VC only marginally changed with flow rate. The diameter of the color Doppler VC, however, not only overestimated the anatomic orifice diameter by 45% to 60% and the true VC diameter by 130% to 160%, but was also highly affected by the flow rate and the ultrasound system. Despite these limitations a color Doppler VC diameter of 0.77 cm or more (Agilent) and 0.89 cm or more (Vingmed) detected severe regurgitation with a sensitivity of 93% and 84% and a specificity of 96% and 79%, respectively.

CONCLUSIONS

Color Doppler estimates of the VC markedly overestimate regurgitant orifice and true VC. In contrast to the true VC, Doppler measurements are significantly affected by flow rate and by the ultrasound system used. Nevertheless, they allow semiquantitative assessment of valvular regurgitation separating severe from nonsevere regurgitation with acceptable accuracy.

The rate at which residents learn to use hand-held echocardiography at the bedside

PURPOSE

Because there is little information about the training that general internists require to perform hand-carried cardiac ultrasonography (HCU), we studied the rate of learning of a group of medical residents performing HCU after minimal formal training.

METHODS

Medical residents on the inpatient services at Johns Hopkins Bayview Medical Center received formal training in HCU consisting of 15-30 minutes of didactic instruction about the principles of echocardiography, followed by ongoing one-on-one instruction in performing HCU and subsequent ongoing one-on-one training from a certified echocardiography technician as they were doing scans. The residents were shown how to position the patient to obtain 2-dimensional echo images from the parasternal short and long axes and apical 4-chamber views, and how to obtain color-flow Doppler images across the mitral and aortic valves. Residents were asked to determine whether pericardial effusion was present and to assess left ventricular size, left ventricular function, and the mitral and aortic valves. The residents performed cardiac physical examination and HCU independently on patients who had a conventional transthoracic echocardiogram (CTTE) performed within 24 hours of the HCU. The residents' HCU results were compared with the CTTE results by a cardiologist specializing in echocardiography. The rates at which residents gained technical proficiency and skills in interpreting their studies were measured by linear regression to fit various outcome variables against their experience at scanning as gauged by the number of scans performed.

RESULTS

Thirty medical residents performed a total of 231 HCU studies. Linear regression models showed that the residents' overall technical proficiency skills improved at the rate of 0.79 (95% confidence interval [CI] 0.53-1.04) points on an overall assessment index (0-3 scale) per 10 scans completed. Interpretation accuracy improved at a rate of 1.01 (95% CI 0.69-1.39) points per 10 scans as measured by an interpretation accuracy index (0-3 scale). Because scanning efforts and instruction in HCU occurred during residents' usual rotation duties, some residents gathered experience in HCU slowly and sporadically.

CONCLUSION

This study, the first prospective, experimental effort of its kind, shows that residents as a group learned important aspects of HCU scanning and interpretation at a reasonably rapid rate.

A mechanism for immediate reduction in mitral regurgitation after cardiac resynchronization therapy: insights from mechanical activation strain mapping

OBJECTIVES

We tested the hypothesis that an immediate reduction in mitral regurgitation (MR) after cardiac resynchronization therapy (CRT) results from improved coordinated timing of the papillary muscle insertion sites, using the novel approach of mechanical activation strain mapping.

BACKGROUND

Heart failure patients with left bundle branch block often benefit acutely from CRT; however, the role and mechanism of reduction of MR are unclear.

METHODS

Twenty-six consecutive patients undergoing CRT with at least mild MR were studied (ejection fraction 24 +/- 6%; QRS duration 168 +/- 30 ms). Echocardiographic Doppler and strain imaging was performed immediately before and the day after CRT, as well as in 10 normal control subjects. Mechanical activation sequence maps were constructed using longitudinal strain from 12 basal and mid-LV sites, with color coding of time-to-peak strain.

RESULTS

Mitral regurgitation by the volumetric method consistently decreased after CRT: regurgitant volume from 40 +/- 20 ml to 24 +/- 17 ml and regurgitant fraction from 40 +/- 12% to 25 +/- 14% (both: p < 0.001 vs. baseline). Normal controls had uniform segmental time-to-peak strain, with a difference of only 12 +/- 8 ms between all segments. In contrast, CRT patients at baseline had a 106 +/- 74 ms time delay between papillary muscle insertion sites (p < 0.001 vs. normal). This interpapillary muscle time delay shortened after CRT to 39 +/- 43 ms (p < 0.001 vs. baseline) and was significantly correlated with reductions in mitral regurgitant fraction (r = 0.77, p < 0.001).

CONCLUSIONS

Cardiac resynchronization therapy significantly and immediately reduced MR. Improved coordinated timing of mechanical activation of papillary muscle insertion sites appears to be a mechanistic contributor to immediate MR reduction by CRT.

Real-time three-dimensional echocardiography: still a research tool or an imaging technique ready for daily routine practice? A pilot feasibility study in a tertiary cardiology centre

BACKGROUND

The majority of studies demonstrating the diagnostic potential of three-dimensional (3D) echocardiography have been conducted on selected series of patients in research laboratories.

AIM

To investigate the feasibility and usefulness of real-time 3D transthoracic echocardiography (RT 3D TTE) in daily routine practice.

METHODS

The study group consisted of 35 consecutive patients referred to our echocardiographic laboratory. All subjects underwent standard 2D TTE and RT 3D TTE with the use of a commercially available ultrasound system (Sonos 7500, Philips Medical Systems). The quality of 3D acquisitions and post-processed images was graded as: insufficient, satisfactory, good or demo.

RESULTS

3D TTE of the study group yielded 298 acquisitions. 87,2% of acquisitions required post-processing. The quality of 3D datasets was graded as insufficient in 8,0%, satisfactory in 31,4%, good in 37,2% and demo in 23,4% of all acquisitions and reconstructions. Mean time required for 3D TTE, including post-processing, was 12 minutes. 3D reconstructions were particularly helpful in patients with valvular disease or prostheses (n=13), enabling detailed qualitative analysis of leaflets morphology and mobility. In cases of mitral valve prolapse (n=4) 3D TTE allowed identification of the prolapsing scallops. 3D color Doppler flow mapping enabled complete visualization of the regurgitant jets. "En face" reconstructions of atrial septal defects (n=2) facilitated assessment of the morphology of the defects and the tissue rims. In patients with cardiac pacemaker (n=4) 3D TTE allowed excellent visualization of the ventricular lead along with its tip. In patients with ischemic heart disease (n=14) 3D TTE failed to provide additional, clinically relevant information.

CONCLUSIONS

RT 3D TTE may be used in clinical settings with high feasibility rate and provides additional, clinically relevant qualitative information. The lack of on-board quantitative analysis tools is the main limitation of the currently available system.

Rapid screening of cardiac patients with a miniaturized hand-held ultrasound imager--comparisons with physical examination and conventional two-dimensional echocardiography

BACKGROUND

Rapid screening of cardiac patients with a hand-held ultrasound imager (SonoHeart [SH]) could provide valuable clinical information.

HYPOTHESIS

Whether the use of this device yields additional information to a carefully conducted physical examination and comparable findings to those of conventional two-dimensional echocardiography (2-D) during inpatient rounds is not well established and is the subject of this study.

METHODS

In all, 100 consecutive telemetry patients underwent rapid screening with 2-D and color Doppler SH during inpatient rounds. SonoHeart findings were compared with results from conventional 2-D and physical examination conducted by an attending cardiologist.

RESULTS

All patients had interpretable images. Mean scanning time with SH was 5.0 +/- 1.2 min; 2-D and SH findings were comparable. The parameters studied included chamber sizes, left ventricular (LV) systolic function, presence of LV hypertrophy (LVH), wall motion abnormalities (WMA), pericardial effusion (PE), and valvular regurgitations. Mild to moderate valvular regurgitation and LV systolic dysfunction were reliably diagnosed by SH in a number of patients whose symptoms were unrelated to the abnormalities detected.

CONCLUSIONS

Rapid screening with SH provides accurate and valuable information that would otherwise be undetected during physical examination. Its introduction into clinical practice may redefine the initial approach to patients with cardiovascular disease.

Hand-Carried Ultrasound Improves the Bedside Cardiovascular Examination

OBJECTIVES

We assessed the clinical utility of hand-carried cardiac ultrasound (HCU) devices to assist physicians in the diagnosis of cardiovascular disease.

MATERIALS AND METHODS

We reviewed 42 articles published from 1978 to 2004.

RESULTS

The capability and simplicity of the HCU device assist physicians in the diagnosis of cardiovascular disease at the initial patients contact. HCU is particularly useful in the setting of emergency or critical care, community screening, or in remote areas with limited access to health care.

CONCLUSION

The inherent limitations of the physical examination as well as the reduced focus and training in physical diagnosis of current and recent medical school graduates has set the stage for the HCU device to modify traditional medical practices by complementing the physical examination with real-time cardiovascular imaging.

Directional synthetic aperture flow imaging

A method for flow estimation using synthetic aperture imaging and focusing along the flow direction is presented. The method can find the correct velocity magnitude for any flow angle, and full color flow images can be measured using only 32 to 128 pulse emissions. The approach uses spherical wave emissions with a number of defocused elements and a linear frequency-modulated pulse (chirp) to improve the signal-to-noise ratio. The received signals are dynamically focused along the flow direction and these signals are used in a cross-correlation estimator for finding the velocity magnitude. The flow angle is manually determined from the B-mode image. The approach can be used for both tissue and blood velocity determination. The approach was investigated using both simulations and a flow system with a laminar flow. The flow profile was measured with a commercial 7.5 MHz linear array transducer. A plastic tube with an internal diameter of 17 mm was used with an EcoWatt 1 pump generating a laminar, stationary flow. The velocity profile was measured for flow angles of 90 and 60 degrees. The RASMUS research scanner was used for acquiring radio frequency (RF) data from 128 elements of the array, using 8 emissions with 11 elements in each emission. A 20-micros chirp was used during emission. The RF data were subsequently beamformed off-line and stationary echo canceling was performed. The 60-degree flow with a peak velocity of 0.15 m/s was determined using 16 groups of 8 emissions, and the relative standard deviation was 0.36% (0.65 mm/s). Using the same setup for purely transverse flow gave a standard deviation of 1.2% (2.1 mm/s). Variation of the different parameters revealed the sensitivity to number of lines, angle deviations, length of correlation interval, and sampling interval. An in vivo image of the carotid artery and jugular vein of a healthy 29-year-old volunteer was acquired. A full color flow image using only 128 emissions could be made with a high-velocity precision.

Hand-carried cardiac ultrasound enhances healthcare delivery in developing countries

The availability of cardiac ultrasound is limited in developing countries. We evaluated the feasibility and diagnostic capability of a hand-carried cardiac ultrasound device in 126 patients (age 44 +/- 24 years) referred for consultation to a cardiology clinic in rural Mexico. The hand-carried cardiac ultrasound device identified 86 cardiac findings and obviated the need for further comprehensive echocardiographic evaluation in 90% of patients (113 of 126).

Second-generation real-time three-dimensional echocardiography. Finally on its way into clinical cardiology?

Three-dimensional (3D) echocardiographic imaging has been introduced as a tool to improve the assessment of both morphologic and functional parameters of the cardiovascular system. In the past, data acquisition was limited due to time-consuming sequential acquisition of multiple triggered 2D image planes from 10-60 heart cycles using transesophageal rotational, transthoracic rotational or transthoracic freehand approaches. Recent improvements in the size of matrix array probes and in computing power of modern ultrasound equipment have significantly increased both spatial and temporal resolution of "second-generation" real-time 3D scanners. Although the superiority of 3D echocardiography in the determination of ventricular volume, ventricular mass or valvular orifice area had already been demonstrated in the late 1990s, widespread use in clinical cardiology was limited on account of difficulties in acquisition and post-processing. Clinical use of modern 3D echocardiography is boosted by the marked reduction in acquisition time and the unique possibility of on-line rendering on the ultrasound system. The ability to visualize a virtual 3D surface in real time-although limited to a sector size of about 30 degrees-offers new insights into cardiac pathomorpholgy even in patients with arrhythmias and may in realtime 3D-contrast flow analysis. Analysis of wide-angle 3D datasets (90 by 90 degree pyramidal shape) is possible by combining the 3D information of several [4-7] consecutive heart cycles. 3D datasets including the complete left ventricle provide comprehensive information on ventricular and mitral valve morphology and function. Qualitative and quantitative analyses of regional wall motion at rest and during stress become possible. Combination with 3D color Doppler data allows additional assessment of valvular function as well as determination of flow in the left ventricular outflow tract and across septal defects. The integration and future quantification of these new parameters together with on-line review allows new insights into cardiac function, morphology and synchrony that offer great potentials in the evaluation of right and left ventricular global and regional function, diagnosis of small areas of ischemia, congenital and valvular heart disease and effects of biventricular pacing in dilated heart asynchrony.

Colour-duplex echography in atherosclerotic carotid artery disease

The first and larger part of this article is devoted to a brief review of colour duplex echography of atherosclerotic lesions of the carotid artery: history, basic principles, technique, and diagnostic value. The authors, a vascular surgical team, witness from their own experience, with due attention to surgical practice. In the last part concerning duplex-based surgical decision, the results of a small scale trial conducted in 1996 in their department are presented: in 36 consecutive operated cases, the operative data and excised plaque were compared to the preoperative colour-duplex data regarding degree of stenosis, geometry of the lesion, and plaque composition. Results were expressed as perfect, fair, poor: stenosis (33, 2, 1), geometry (27, 5, 4), plaque (20, 10, 6). The surgical decision appeared perfectly justified in 35 cases (97%). It is concluded that colour-duplex echography is invaluable in the management of carotid artery atherosclerotic disease and that carotid artery surgery may generally be performed after a "duplex only" investigation. Every laboratory should make continuous efforts in monitoring and improving its own quality.

Echoscintigraphy: a new imaging modality for the reduction of color blooming and acoustic shadowing in contrast sonography

The purpose of this study was to develop and evaluate a new imaging modality (echoscintigraphy) to reduce color blooming and acoustic shadowing in contrast sonography. After injection of various amounts (700 to 40,000 bubbles/mL) of the echo contrast agent SH-U 563A into a flow phantom, artificial vessels were insonated in the intermittent harmonic-power Doppler imaging (H-PDI) mode. The receive gain was varied from 50% to 75%. The cross-sectional area (CSA) of the tube was assessed using a new summation algorithm (echoscintigraphy) and a conventional single-frame analysis (S-FA) of the H-PDI-signals. Echoscintigraphy is based on the recording and summation of low-intensity signals that are emitted during the ultrasound (US)-induced destruction of microbubbles. Application of the summation algorithm at low-contrast concentration allowed a gain-independent automatic calculation of the CSA at medium and high gain settings. Using the S-FA method, the assessment of the vessel diameter and the CSA was gain-dependent and allowed correct measurements only from 60% to 65% gain. At a high receive-gain and high contrast concentration, S-FA resulted in an overestimation of the CSA up to 35.5%. Echoscintigraphy allows correct display of contrast-filled vessels over a wide range of gain settings at low contrast concentrations, where S-FA does not adequately display echo contrast. Thus, echoscintigraphy minimizes artefacts resulting from color blooming and acoustic shadowing.

Role of intracardiac echocardiographic guidance in transcatheter closure of atrial septal defects and patent foramen ovale using the Amplatzer device

Transesophageal echocardiography (TEE) has been successfully used for guiding transcatheter device closure of secundum atrial septal defect (ASD) and patent foramen ovale (PFO). However, the use of TEE for device closure requires general anesthesia. Experience with intracardiac echocardiographic (ICE) guidance to close ASD and PFO is limited. One hundred eleven patients (76 female/35 male) with secundum ASD (82 patients) and PFO (29 patients) associated with a stroke underwent an attempt of transcatheter closure of their defects under ICE guidance using the new AcuNav catheter. The median age of patients was 40 years (range 2.5-80.7) and the median weight was 66 kg (range 12.7-128 kg). The median two-dimensional size of secundum defects as measured by ICE was 17 mm (range 3-32 mm). The median balloon stretched diameter of the ASDs was 22 mm (range 4-36 mm). Five patients had more than one defect that required placement of two devices to close the defects. The median Qp/QS ratio for patients with secundum ASD was 2.1 (range 1-18). ICE provided adequate views of the defects and surrounding structures and the various stages of device deployment. All patients had successful device placement, including the patients who received simultaneous two devices with immediate complete closure of the defects in 100 patients, whereas four and seven patients had trivial and small residual shunt, respectively. The median fluoroscopy time was 10.2 minutes (range 3.7-38.4 minutes) and the median total procedure time was 60 minutes (range 28-180 minutes). There were no complications related to the use of the AcuNav catheter. We conclude that ICE provided unique images of the atrial communications and facilitated device closure of secundum ASD and PFO in children and adults. We believe ICE should replace TEE as a guiding imaging tool for ASD and PFO device closure, thus eliminating the need for general anesthesia.

[Assessment of the clinical feasibility of OptiGo for hand-held echocardiography]

OBJECTIVES

Hand-held ultrasound devices are becoming available for clinical examination, but the accuracy and precision of such devices are unclear. This study compared the accuracy of a hand-held echo device to a standard echo system.

METHODS

Twenty-two patients were examined with the OptiGo (Phillips Medial Systems) hand-held ultrasound system with a 2.5 MHz transducer and SONOS 5500 (Phillips Medial Systems) standard ultrasound system with a 2 to 4 MHz wideband transducer. Patients with cardiac arrhythmia and tachycardia were excluded. Image quality, chamber size (left ventricle, left atrium), global and regional left ventricular function, valve morphology and severity of valve regurgitation were assessed.

RESULTS

There was good agreement between the two imaging devices for image quality (77.3%), left ventricular ejection fraction (90.5%), regional wall motion score (> 90%), valve morphology (> 90%), severity of valve regurgitation (> 81.0%) and there was good correlation and agreement for left ventricular and left atrial size.

CONCLUSIONS

Although the OptiGo has limitations, the hand-held examination appropriately estimates global and regional left ventricular function, valve morphology, valve regurgitation and chamber size.

Noninvasive phenotypic analysis of cardiovascular structure and function in fetal mice using ultrasound

METHODS

We established methods for noninvasive mouse fetal heart imaging using an Acuson/Siemens Sequoia ultrasound scanner equipped with a single-pulse CHIRP Coded Excitation program, and a highfrequency linear array transducer. Mouse fetuses spanning gestation day 12.5 to 18.5 (E12.5-E18.5) were studied.

RESULTS

Controlled anesthetic and constant body temperature were found to be essential for hemodynamic stability of the mother and fetuses. Fetal heart rates increased from 160 to 220 beats/min as development progressed. These heart rates were lower than those of newborn mice, so that frame rates above 100 Hz adequately resolved structural details in 2D without misregistration. Analysis of 2D images showed a doubling in crown-torump length (8-19 mm), and rapid growth of the heart from 1 to 3 mm in diameter as fetuses developed from E12.5 to E18.5. A cumulative increase in scanning modalities was achieved with increasing developmental age, with the optimal stage for scanning being E16.5. At E16.5 right and left could be distinguished, and it was possible to obtain diagnostic 2D color flow Doppler in the four-chamber, apical long axis 3/5-chamber and short axis views. In addition, M-mode images of high quality were obtainable from E15.5 to E18.5, whereas spectral Doppler signals could be obtained readily from E12.5 onwards.

CONCLUSIONS

These studies show that ultrasound imaging can be used for structural and functional analysis of the developing mammalian heart, even at early stages of development. Such noninvasive cardiovascular ultrasonic evaluation should be ideally suited for high throughput screening of mutagenized mice.

Ecocardiograma portátil: ¿qué añade a la valoración cardiovascular inicial?

INTRODUCTION AND OBJECTIVES

Hand-held echocardiographic devices have recently become available. Our objective was to determine, on the basis of clinical data and basic diagnostic techniques, whether hand-held devices offer additional information useful not provided by the initial cardiovascular diagnosis.

PATIENTS AND METHOD

We prospectively studied the presence and severity (absent, mild, significative) of 7 frequent heart diseases (aortic or mitral stenosis-regurgitation, tricuspid regurgitation, and left ventricular systolic dysfunction-hypertrophy) in 36 consecutive patients (50% men; mean age 68 12 years) with 3 different methods: clinical examination and basic complementary exams, hand-held echocardiography with 2D and color Doppler imaging (OptiGo, Philips Medical Systems, The Netherlands) and a standard, last-generation transthoracic echocardiogram (Sonos 550, Philips Medical Systems, The Netherlands). We compared the results obtained with the first two methods, and combined the results of both to compare these findings against the results obtained with standard electrocardiography. Percentage agreement and Somer's D, a measure of association between ordinal variables, were calculated.

RESULTS

The hand-held device obtained better results than clinical examination (agreement 87 vs. 65%; D = 0.79 0.04 vs. 0.19 0.53) and identified severe lesions that were classified incorrectly by clinical examination in 39% (14/36) patients. However, in 8 patients (10 evaluations) it misclassified severe lesions.

CONCLUSIONS

In experienced hands, a hand-held echocardiographic device offers additional information not obtained from an initial cardiovascular diagnosis for common cardiovascular disorders, but it is no substitute for complete echocardiographic examination.

Epicardial 10-MHz ultrasound in off-pump coronary bypass surgery: a clinical feasibility study using a minitransducer

OBJECTIVE

In off-pump coronary artery bypass surgery, both plaque and calcifications and torrential back flow from side branches in the isolated coronary segment may hamper coronary anastomosis suturing. The epicardial application of an ultrasonographic minitransducer with color Doppler scanning modality was studied in off-pump coronary surgery to detect septal perforating side branches; to assess the location, size, and quality of the coronary vessel; and to visualize the anastomotic orifice before chest closure.

METHODS

Thirteen patients were selected for multivessel off-pump bypass. The investigation was limited to the left anterior descending coronary artery. The anastomotic target site was chosen on preoperative and intraoperative findings. The conventionally designated site was scanned with a novel 10-MHz ultrasonographic miniprobe (15 x 6 x 9 mm) that fitted in between the cardiac stabilizer pods.

RESULTS

In 11 of the 13 cases, the course of the left anterior descending coronary artery could be properly identified. In 3 cases detection of perforating side branches caused a change in anastomotic site. A sufficiently dry field was obtained in all 13 cases. In 11 cases the anastomotic orifice was adequately visualized.

CONCLUSION

During off-pump coronary surgery, 10-MHz ultrasonographic images from a minitransducer aided in the intraoperative choice of anastomotic site.

A new dynamic three-dimensional digital color doppler method for quantification of pulmonary regurgitation: validation study in an animal model

OBJECTIVES

The purpose of the present study was to validate a newly developed three-dimensional (3D) digital color Doppler method for quantifying pulmonary regurgitation (PR), using an animal model of chronic PR.

BACKGROUND

Spectral Doppler methods cannot reliably be used to assess pulmonary regurgitation.

METHODS

In eight sheep with surgically created PR, 27 different hemodynamic states were studied. Pulmonary and aortic electromagnetic (EM) probes and meters were used to provide reference right ventricular (RV) forward and pulmonary regurgitant stroke volumes. A multiplane transesophageal probe was placed directly on the RV and aimed at the RV outflow tract. Electrocardiogram-gated and rotational 3D scans were performed for acquiring dynamic 3D digital velocity data. After 3D digital Doppler data were transferred to a computer workstation, the RV forward and pulmonary regurgitant flow volumes were obtained by a program that computes the velocity vectors over a spherical surface perpendicular to the direction of scanning.

RESULTS

Pulmonary regurgitant volumes and RV forward stroke volumes computed by the 3D method correlated well with those by the EM method (r = 0.95, mean difference = 0.51 +/- 1.89 ml/beat for the pulmonary regurgitant volume; and r = 0.91, mean difference = -0.22 +/- 3.44 ml/beat for the RV stroke volume). As a result of these measurements, the regurgitant fractions derived by the 3D method agreed well with the reference data (r = 0.94, mean difference = 2.06 +/- 6.11%).

CONCLUSIONS

The 3D digital color Doppler technique is a promising method for determining pulmonary regurgitant volumes and regurgitant fractions. It should have an important application in clinical settings.

Epicardial echocardiography for correct placement of the intracardial biventricular assist device (Impella)

BACKGROUND

Correct placement of the intracardial biventricular assist device (Impella) as a supporting system for off-pump coronary surgery is routinely checked by transesophageal echocardiography and invasive pressure measurements. However, it remains difficult to verify the accurate position of the right heart system when the posterior wall is exposed.

METHODS

In 23 patients undergoing augmented beating heart CABG surgery, the correct placement of the lmpella-system was controlled by TEE as well as by a new 15-6 L epicardial echotransducer (EE) (Agilent, Andover, MA).

RESULTS

TEE assisted well in inserting the system in all patients. The correct placement of the distal end of the right heart system 1.5 cm behind the pulmonary valve was verified in 18/23 cases by TEE vs. 23/23 cases by EE. Dislocation of the devices during tilting of the heart could only be verified by EE.

CONCLUSIONS

Epicardial echocardiography is a useful, innovative method for monitoring the correct placement of the new intracardial biventricular assist device during beating-heart surgery.

Epicardial colour-Doppler scanning of coronary artery stenoses and graft anastomoses

OBJECTIVE

Epicardial ultrasound scanning was applied during coronary surgery to assess coronary artery stenoses and quality of distal graft anastomoses, with special emphasis to the left anterior descending artery (LAD).

DESIGN

Twenty-three patients with coronary artery disease (M:F 19:4, mean age 65.0 +/- 9.5 years) had coronary artery bypass grafting (CABG) on cardiopulmonary bypass. Intraoperative scanning of coronary artery stenoses and graft anastomoses was performed with a new 10 MHz linear array Vingmed transducer connected to a GE Vingmed System FiVe echocardiography unit. Coronary stenoses detected by ultrasound were compared with preoperative angiograms. Intraoperatively, coronary graft flow was assessed with a Medi-Stim transit-time flowmeter.

RESULTS

Twenty LADs were investigated. In 17 LADs (85%) stenoses were clearly identified. In three LADs (15%) stenoses were not identified because LADs were deeply intramyocardial or the stenosis was very proximal. There was a significant correlation between LAD stenoses detected by ultrasound and angiogram (R = 0.7; p < 0.01). Mean number of grafts was 3.8 +/- 0.9. Of 26 LAD anastomoses assessed, good images were obtained in 22 cases (84.4%); the mean LAD diameter measured 1 cm below the anastomosis was 1.6 +/- 0.2 mm. In two LADs images were rated fair and in two LADs images were poor because of intramyocardial LAD. No technical error of the anastomoses was detected. All grafts had good flows as ascertained by flow measurements.

CONCLUSION

Epicardial ultrasound scanning with the new 10 MHz transducer allowed satisfactory imaging of coronary stenoses and graft anastomoses. Factors limiting the quality of imaging are proximal lesions, intramyocardial vessel, vessel tortuosity, and extensive calcifications. Epicardial ultrasound scanning with updated technology should become a further advancement to graft assessment during off-pump coronary surgery.

Evaluation of ventricular myocardial velocities and heart motion of the fetal heart by tissue Doppler image

Fetal echocardiogram has developed into a reliable tool for prenatal diagnosis of congenital heart disease. It is also used to evaluate ventricular function. Recently, Tissue Doppler Imaging (TDI) has been introduced to evaluate ventricular functions especially in ischaemic heart disease. The objective of this study was to evaluate myocardial velocities and heart motions of the normal fetal heart by using TDI. The TDI was preformed in 28 fetal hearts with a gestational age of 20-35 wks (Mean 29 +/- 3.7 wks) to evaluate myocardial velocities and heart motion. The Toshiba, Power Vision, machine with 3.75 and 5 MHz transducers was used with an appropriate setting of colour-coded tissue velocities. The apical four chamber and apical or parasternal long axis views were the standard planes for measuring myocardial velocities and evaluating the heart motions. The results showed the myocardial velocities of the posterior wall of the left ventricle during the early, mid, and late systolic phases were 1.5 +/- 0.2, 2.1 +/- 0.9, and 1.0+0.5 cm/sec and early, mid, and late diastolic phases were 1.3 +/- 0.7, 1.9 +/- 0.8, and 1.1 +/- 0.7 cm/sec respectively. The myocardial velocity of the anterior wall of the right ventricle during the early, mid, and late systolic phases were 1.7 +/- 0.9, 1.7 +/- 0.6, and 1.0 +/- 0.6 cm/sec and early, mid, and late diastolic phases were 1.1 +/- 0.6, 1.8 +/- 0.7, and 1.5 +/- 1.0 cm/sec respectively. The myocardial velocity of the interventricular septum could not be measured due to the abnormal septal motion and the total fetal heart movement during the cardiac cycle. The fetal heart had anterior displacement during systole and posterior translation during diastole and also had counter-clockwise rotation during the systolic phase.

CONCLUSION

Using the TDI to evaluate myocardial velocities of the fetal heart is limited by the angle of ultrasound beam and the total fetal heart motion. The fetal heart movement is similar to the newborn or young adult heart.

Full performance of modern echocardiography within the heart: in-vivo feasibility study with a new intracardiac, phased-array ultrasound-tipped catheter

BACKGROUND

Intracardiac echocardiography with full performance of high-resolution two-dimensional-, M-mode-, colour, pulsed and continuous wave Doppler and Doppler tissue imaging has not been previously demonstrated.

AIMS

This first European in-vivo study was designed to determine the utility and feasibility of a new ultrasound-tipped catheter for intravascular and intracardiac echocardiography.

METHODS

The miniaturized, multi-modal, multiple-frequency (5-10MHz) transducer tipped 10Fr (3.3mm) catheter was tested in five anaesthetized mongrel dogs linked to a standard echocardiographic platform. The catheter was introduced through an 11 Fr femoral venous sheath into the inferior vena cava and right heart chambers and the pulmonary artery under limited fluoroscopic and catheter ultrasound guidance.

RESULTS

Abdominal and thoracic aorta as well as their branches, both ventricles and atrias with their appendices, all valves, pulmonary arteries and all veins could be visualized with excellent quality. All Doppler signals and the determined haemodynamics, global and regional wall motion and Doppler tissue imaging were of high diagnostic quality. Coronary flow reserve could also be determined.

CONCLUSIONS

Intracardiac echocardiography is feasible and potentially useful for assessing functional and morphological disorders, and probably for the guidance of interventional procedures as well as monitoring of cardiac function. A new window to the heart has been opened.

Novel method for assessing myocardial perfusion: visualization and measurement of intramyocardial coronary blood flow in the entire left ventricular wall using contrast enhanced, high frequency Doppler echocardiography

Using a high frequency ultrasonic transducer, intramyocardial coronary blood flow (IM-CBF) can be visualized and evaluated during hemodynamic changes in the anterior wall and septum of the left ventricle (LV). We tested the hypothesis that detection and quantitative measurement of IM-CBF of entire LV segments are feasible using a high frequency ultrasonic transducer in conjunction with intravenous contrast injection in vivo. A 3 - 8 MHz transducer was used to image and measure IM-CBF in 10 anesthetized dogs. We obtained a color Doppler image of IM-CBF in the LV short-axis view after intravenous Levovist injection (25 mg/ml). The IM-CBF velocity was recorded using spectral Doppler in the antero-septal and infero-posterior wall of closed chest dogs and in the entire LV after opening the chest. A significant increase in IM-CBF velocity was observed in all LV regions after adenosine 5'- triphosphate (ATP) administration. After Levovist(TM) injection, the visualization of IM-CBF was improved and the spectral Doppler pattern of coronary flow velocity was clarified compared to baseline. IM-CBF was assessed in the antero-septal region of the LV before and after left anterior descending coronary artery occlusion. A high frequency ultrasonic transducer in conjunction with intravenous contrast injection improved IM-CBF visualization, enabling quantitative evaluation of the intramyocardial coronary circulation in the entire LV after coronary occlusion and hyperemia. This study may represent a step towards noninvasive assessment of myocardial perfusion before and after coronary reperfusion.

Automated cardiac output measurements by ultrasound are inaccurate at high cardiac outputs

OBJECTIVE

The sonographic technique of automated cardiac output measurement (ACM) is a promising new method to measure cardiac output and could be of use in a high-risk obstetric unit in the treatment of pre-eclamptic patients. The aim was to determine the accuracy of the ACM method.

DESIGN

Comparative study of the sonographic technique of ACM versus cardiac output measured by thermodilution (TD).

METHODS

The study included 39 intensive care patients, 21 men, 13 non-pregnant women and five severely pre-eclamptic pregnant patients, with a wide range of cardiac outputs, in whom TD catheters had been inserted for clinical reasons. Two separate experienced observers, blinded to the results obtained with the other method, performed four successive measurements in each patient with either the ACM or TD technique. The averaged cardiac output value per patient and method was used for comparison.

RESULTS

Cardiac output was successfully measured with ACM and TD in 85 and 100% of patients, respectively. Mean cardiac output measured by ACM (6.77 +/- 1.90 L/min) was significantly lower than that measured by TD (9.12 +/- 3.06 L/min). Although cardiac output values obtained with ACM were significantly correlated with those measured by TD, the ACM values were consistently lower than TD values in the higher cardiac output range; the relationship was represented by ACM = 0.35 TD + 3.55 L/min (r = 0.57, P < 0.001). The (ACM - TD) difference increased significantly with cardiac output, through a difference in stroke volume, not in heart rate.

CONCLUSION

The ACM is not an accurate tool to measure cardiac output in patients with a high cardiac output, including treated pre-eclamptic women.

[Patency study of internal mammary artery grafts: the usefulness of echo-enhancers for identifying the flow signal by color Doppler echocardiography]

OBJECTIVES

a) To study the capacity of the technique of high-frequency color Doppler to detect flow signal of left internal mammary artery grafts; b) to assess the usefulness of an echo-enhancer agent to facilitate the detection of the signal, and c) to evaluate the patency of the graft according to its pulsed Doppler velocity profile pattern.

METHODS

39 consecutive patients were studied. A Hewlett-Packard 5500 echocardiograph was used, with a high-frequency probe (S12) applied at the high left parasternal border. When a graft signal was not elicited after a predetermined 5-minute check period, an intravenous dose of 4 g of Levovist (Schering España) at 400 mg/ml was administrated. According to previous studies, a pulsed Doppler flow profile with a predominantly diastolic pattern was considered a normal graft patency, while a systolic one was deemed as abnormal.

RESULTS

Graft flow was identified by color Doppler in 33/39 patients (85%). The additional use of an echo-enhancer in 6 patients with no detected signal increased this proportion to 38/39 (97%). Normal flow patterns were seen in 34/38 (89%). Among the four patients with abnormal pattern, 1 case of early myocardial infarction was observed, while angiographic studies showed distal occlusion of the graft in 1 or the presence of competitive flow in 2 patients.

CONCLUSIONS

The high-frequency color Doppler technique allows the detection of a flow signal from internal mammary artery grafts in most patients. The administration of an echo-enhancer agent is useful in those with non detectable signals. An abnormal pulsed Doppler velocity pattern indicates graft malfunction.

Color Doppler velocity accuracy proximal to regurgitant orifices: influence of orifice aspect ratio

Many noninvasive methodologies used for the accurate evaluation of valvular regurgitation require precise velocity measurements from ultrasound instruments. Previous studies have indicated that velocity measurements from color Doppler (CD) instruments are susceptible to errors due to the interaction of the ultrasound beam and the proximal orifice flow field. This study examined the influence of high aspect ratio (AR) orifices on the CD velocity error. Center line velocity error distributions for orifices ranging from 7.07 to 78.5 mm2, varying in shape from circular to an AR = 8 ellipse, were evaluated using a numerical model of the ultrasound beam and the simulated regurgitant flow field. An in vitro study was also performed and confirmed the findings of the numerical model. The study showed that increasing AR does not significantly change the error characteristics. The study confirmed that orifice size is the dominant factor in the error distribution, and that corrections speculated for circular orifices can be extended to elliptical orifices without significant errors.

Assessment of transmural coronary blood flow with intraoperative transesophageal color Doppler echocardiography during coronary revascularization

Intraoperative color Doppler transesophageal echocardiography with a 4- to 7-MHz transducer was performed on 28 consecutive patients who underwent coronary artery bypass grafting to image and evaluate the transmural coronary blood flow before and after cardiopulmonary bypass. The transmural coronary flow was visualized in 26 (92.8%) of 28 patients in the inferior wall and in 13 (46.4%) of 28 patients in the lateral wall. The peak diastolic flow velocity of the transmural coronary artery in the inferior and lateral wall was significantly increased after coronary revascularization in patients with a successful bypass graft to the right coronary artery (from 34.0 +/- 19.7 to 64.9 +/- 30.9 cm/s, P <.001, n = 10) and to the left circumflex coronary artery (from 35.1 +/- 18.6 to 62.1 +/- 21.1 cm/s, P <.001, n = 10). No significant changes were observed in patients with no bypass graft to the right or left circumflex coronary artery. Coronary blood flow can be mapped and the velocity measured with Doppler transesophageal echocardiography with a high-frequency (4- to 7-MHz) transducer. Assessment of the transmural coronary flow may provide valuable information and aid in decision making during surgical revascularization.

Improved high-frequency transthoracic flow velocity measurement in the left anterior descending coronary artery after intravenous peripheral injection of levovist

New ultrasonic technology allows noninvasive measurement of the flow in the distal left anterior descending coronary artery. The goal of this study was to validate transthoracic determination of coronary flow velocity with the intracoronary Doppler flow wire technique. In 20 patients with normal coronary arteries, 2 intracoronary and 2 comparative transthoracic Doppler measurements (TTDMs) of the average peak velocity (APV) and the mean systolic and diastolic velocities were performed. The diastolic/systolic ratio was calculated. Blood flow velocity was determined in the distal left anterior descending coronary artery with a Doppler guide wire. Color Doppler and subsequent pulsed wave Doppler readings in an optimal left lateral position were available within 1 hour after completion of the invasive examinations. TTDM were performed during continuous administration of 2.0 g of contrast agent. A modified apical view was obtained from the fourth or fifth intercostal space, and a high-frequency transducer was used (7 MHz for 2-dimensional and 6 MHz for color Doppler imaging; 3.5 MHz for pulsed wave Doppler readings). The Doppler flow signal quality was graded from I to III (I = no flow mapping obtainable, II = poor quality, III = Doppler signals with a well-defined outline). In 13 (65%) patients, 26 TTDMs revealed signal quality of grade III. APV was calculated to be within normal limits (APVecho = 19.96 +/- 7.62 cm/s vs APVinvasive = 20.77 +/- 7.87 cm/s). APVecho correlated well with APVinvasive (r = 0.85, y = 0.82x + 2.85, P <.001). The mean difference between APVecho and APVinvasive (Bias) was -0.81 +/- 4.23 cm/s. No correlation was found between invasive and noninvasive measurements of diastolic/systolic velocity ratios (P >.05). High-frequency TTDM provides reliable data on APV in the majority of patients. It has the potential to be introduced as a relevant screening test for follow-up of patients after interventional treatment.

[The Doppler color detection of internal mammary artery anastomoses and a functional assessment of their patency]

BACKGROUND

Left internal mammary artery coronary graft patency is usually evaluated invasively by cardiac catheterization. The objective of this study was to assess the ability of a high-frequency transthoracic Doppler echocardiographic system in the evaluation of patency and flow velocities changes in left internal mammary artery.

METHODS

Twenty-two patients (63 +/- 9 years, 17 male) who had previously undergone left internal mammary artery to left anterior descending artery were evaluated by transthoracic echocardiography, with an Acuson Sequoia C256 equipment (Acuson, Mountain view, USA), placing the transducer (5 MHz) in the second-third left intercostal space. Left internal mammary artery flow was considered to be found in the presence of one systolic/diastolic biphasic blood flow. Dipiridamol 0.5 mg/kg was administered in absence of contraindications in order to evaluate the flow reserve.

RESULTS

In 16 patients (73%), a biphasic systolic-diastolic flow was visualized. Peak velocity of systolic and diastolic waves was 38 +/- 13 and 37 +/- 15 cm/s, respectively. Eleven patients received i.v. dipiridamol 0.5 mg/kg. After dipiridamol, systolic and diastolic velocities rose from 32 +/- 8 to 43 +/- 14 cm/s (p = 0.0429) and from 25 +/- 8 to 50 +/- 17 cm/s (p = 0.0002), respectively (an increasing of 33 +/- 22% and 103 +/- 46% over the baseline, respectively).

CONCLUSION

This descriptive study shows that a non-invasive functional evaluation of left internal mammary artery grafts by a transthoracic approach with a high-frequency echocardiographic equipment is possible.

Transeptal approach to ablation of left-sided arrhythmias does not lead to persisting interatrial shunt: a transesophageal echocardiographic study

In experienced hands, antegrade left heart catheterization via a transeptal puncture is a safe and effective method of performing radiofrequency ablation on the left side of the heart. Persistence of atrial septal defect following transeptal puncture for mitral valvuloplasty has been widely reported although hemodynamically significant shunts are rare. To investigate the persistence of interatrial shunt following transeptal puncture in patients undergoing left-sided electrophysiological procedures using TEE. Fifty-one adult patients, 20 men, aged 19-82 (mean 42.4) years underwent 55 transeptal punctures. Either an 8 Fr Mullins or 8 Fr Swartz transeptal sheath was deployed in all cases. Of these, 28 consecutive patients were approached and 26 consented to undergo TEE. TEE was performed at least 3 weeks post transeptal puncture using a single-plane transducer for the first 18 patients, superseded by a multiplane transducer for the later cases. Both color flow Doppler and microcavitation contrast imaging of the interatrial septum were performed. One patient in the single-plane transducer group was excluded as the failed to swallow the TEE probe. In the remaining 25 patients studied, 9 men aged 21-82 (mean 44.1) years, TEE was performed at a mean of 12.2 (range 3-52) weeks post procedure. No evidence of interatrial shunt was detected by either color flow or contrast studies. Transeptal puncture used in electrophysiological procedures does not result in interatrial shunts persisting > 3 weeks post procedure.

Right heart flow dynamics after tricuspid valve annuloplasty. Characteristics and time course

To evaluate the effect of tricuspid annuloplasty (TAP) on right heart flow dynamics, we analyzed tricuspid inflow velocity pattern, jugular venous pulse and color Doppler flow signal of tricuspid regurgitation (TR) before and after surgery in 16 patients who underwent TAP (TAP group). Cardiac rhythm was atrial fibrillation in all patients. Twelve patients with lone atrial fibrillation served as controls (AF group). Patients in the TAP group were studied before and serially after surgery with a mean follow-up period of 2.7 years. TAP was performed according to the modified De Vega technique in all patients. In a comparison of the most recent data in the TAP group and the data in the AF group, the maximum tricuspid inflow velocity was significantly increased, and both the deceleration time of the tricuspid inflow velocity wave and the y-h interval of the jugular venous pulse were significantly prolonged in the TAP group compared to the AF group. Immediately after surgery, in the TAP group, the area of the TR jet was markedly decreased, and the deceleration time of the tricuspid inflow velocity wave was significantly prolonged compared to those before surgery. The area of the TR jet was dramatically decreased and remained small during the follow-up period. Thus, TAP may produce mild tricuspid stenosis but may also confer sustained preventive effects against TR.

Color Doppler imaging of the myocardium: current status and potential clinical applications

Doppler myocardial imaging (DMI) is a new technique with potential clinical and research applications. It applies traditional pulsed and color Doppler techniques to the analysis of myocardial contractile velocity. A major area of focus is in the quantitation of regional and global myocardial function and evaluation of myocardial perfusion in conjunction with myocardial contrast studies. DMI may also provide a direct, relatively load-independent assessment of diastolic function. Further work is required to identify its role in clinical and research studies.

Internal mammary artery: 100% visualization with new ultrasound technology

We report our experience in visualizing the internal mammary artery (IMA) with new enhanced Doppler technology. Twenty-three patients without previous coronary artery bypass grafting formed the study group. Bilateral transthoracic two-dimensional and color flow Doppler IMA images were acquired from multiple intercostal spaces with a prototype ultrasound machine equipped with coherent beam formation technology. In all patients, the IMA was followed from its origin for an average of 15 cm. To our knowledge, a high rate of direct visualization (100%) of the IMA has not been reported previously. Noninvasive ultrasound assessment of the IMA may reduce the need for invasive preoperative testing for patency and length and allow postoperative assessment of coronary artery flow reserve.

The agreement between colour Doppler systems in measuring internal carotid artery peak systolic velocities

The study was undertaken to determine if the internal carotid artery peak systolic velocities (ICA PSVs) measured by two colour Doppler imaging systems (Acuson 128 and Siemens Quantum) agree sufficiently for the two systems to be interchangeable in evaluating carotid artery disease. One operator obtained blinded measurements of ICA PSV in 63 prospective nonrandomized patients at risk of stroke. The operator examined 20 patients in the first cohort to assess the intraobserver variation, and 43 patients in the second cohort to assess the limits of agreement between the systems. In vitro comparisons of the systems were also undertaken, using both string and flow phantoms. Excluding one outlier, the intraobserver reproducibility coefficient for both machines was 0.48 m s-1. The limits of agreement (within which 95% of differences lie) between systems were -0.47 to 0.45 m s-1. This reduced to -0.39 to 0.33 m s-1 when the one outlier was excluded. This is within the intraobserver reproducibility range. In vitro data show little intersystem variation with phantom velocity. Intratransducer differences increase when the Doppler angle is increased using the string phantom; maximum differences: Acuson 0.30 m s-1 (42%) and Siemens 0.32 m s-1 (32%). These are within the in vivo reproducibility range. Intratransducer difference decreases when the Doppler angle is increased using the flow phantom, maximum differences: Acuson 0.05 m s-1 and Siemens 0.07 m s-1. The results show the systems agree sufficiently to be interchangeable in evaluating carotid artery disease; however, errors in maximum PSVs, caused by operator or system variation, may lead to errors in percent stenosis grading of the carotid arteries.

Calculation of aortic regurgitant volume by a new digital Doppler color flow mapping method: an animal study with quantified chronic aortic regurgitation

OBJECTIVES

The aim of the present study was to quantitate aortic regurgitant volume and regurgitant fraction in a chronic animal model with surgically created aortic regurgitation using a new semiautomated color Doppler flow calculation method.

BACKGROUND

The conventional noninvasive methods for evaluating the severity of aortic regurgitation have not been accepted widely nor compared with truly quantitative reference standards.

METHODS

Eight to 20 weeks after aortic regurgitation was surgically induced in six sheep, a total of 22 hemodynamic states were studied. Electromagnetic flow probes and meters provided reference flow data. Epicardial color Doppler echocardiographic studies were performed to image left ventricular outflow tract forward and aortic regurgitant blood flows. The new method digitally integrated spatial and temporal color flow velocity data for left ventricular outflow tract forward flow and ascending aortic regurgitant flow. The pulsed Doppler method using the velocity-time integral was also used to obtain regurgitant volumes and regurgitant fractions.

RESULTS

Regurgitant volumes and regurgitant fractions by the new method agreed well with those obtained electromagnetically, whereas the pulsed Doppler method overestimated these reference data (mean [+/-SD] difference 0.23 +/- 2.9 ml vs. 11 +/- 5.8 ml, p < 0.0001 for regurgitant volume; mean difference 1.2 +/- 7.6% vs. 19 +/- 13%, p < 0.0001 for regurgitant fraction).

CONCLUSIONS

This animal study, using strictly quantified aortic regurgitant volumes, demonstrated that the digital color Doppler method provides accurate aortic regurgitant volumes and regurgitant fractions without cumbersome measurements.

Stress echocardiography: new techniques

Stress echocardiography is frequently used to evaluate coronary artery disease, and also in quantitative assessment of right and left ventricular function or cardiac valve integrity in patients with cardiomyopathy or during chemotherapy. Various new ultrasound techniques in stress echocardiography are now playing a significant role in this important area of cardiological diagnostics. New methods of echocardiographic signal processing have been developed to provide more quantitative and reproducible information on cardiac function during stress. The most important are: (1) raw data analysis techniques for endocardial border detection (acoustic quantification, CK = colour kinesis), (2) tissue Doppler imaging for myocardial velocity analysis and (3) transpulmonary contrast agents (Albunex, Laevovist, BY 963) for improving endocardial border delineation and for future analysis of myocardial perfusion. Like all new techniques, they must first be subjected to comprehensive scientific assessment, and appropriate training should be given, taking into account physical and physiological limits. These limits will constantly be redefined as echocardiographic techniques continue to change presenting new challenges for the further development of ultrasound technology. In this review, the improved new techniques will be discussed in detail.