Biomedical subjects
Publications and source records attributed to David J Sahn.
Ventricular septal defects are the most common congenital heart defect. They vary greatly in location, clinical presentation, associated lesions, and natural history. The present article describes the clinical aspects of ventricular septal defects and current management strategies.
Over the past 3 decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into the human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technology. One of the most significant developments of the last decades was the introduction of 3-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging. While continuing its meteoric rise instigated by constant technological refinements and continuing increase in computing power, this tool is guaranteed to be integrated in routine clinical practice. The major proven advantage of this technique is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic and unique comprehensive views of cardiac valves and congenital abnormalities. In addition, 3D imaging is extremely useful in the intraoperative and postoperative settings because it allows immediate feedback on the effectiveness of surgical interventions. In this article, we review the published reports that have provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart and discuss its potential future applications.
Heart disease remains a leading cause of death worldwide. Previous research has indicated that the dynamics of the cardiac left ventricle (LV) during diastolic filling may play a critical role in dictating overall cardiac health. Hence, numerous studies have aimed to predict and evaluate global cardiac health based on quantitative parameters describing LV function. However, the inherent complexity of LV diastole, in its electrical, muscular, and hemodynamic processes, has prevented the development of tools to accurately predict and diagnose heart failure at early stages, when corrective measures are most effective. In this work, it is demonstrated that major aspects of cardiac function are reflected uniquely and sensitively in the optimization of vortex formation in the blood flow during early diastole, as measured by a dimensionless numerical index. This index of optimal vortex formation correlates well with existing measures of cardiac health such as the LV ejection fraction. However, unlike existing measures, this previously undescribed index does not require patient-specific information to determine numerical index values corresponding to normal function. A study of normal and pathological cardiac health in human subjects demonstrates the ability of this global index to distinguish disease states by a straightforward analysis of noninvasive LV measurements.
The Working Group on research in adult congenital heart disease (ACHD) was convened in September 2004 under the sponsorship of National Heart, Lung, and Blood Institute (NHLBI) and the Office of Rare Diseases, National Institutes of Health, Department of Health and Human Services, to make recommendations on research needs. The purpose of the Working Group was to advise the NHLBI on the current state of the science in ACHD and barriers to optimal clinical care, and to make specific recommendations for overcoming those barriers. The members of the Working Group were chosen to provide expert input on a broad range of research issues from both scientific and lay perspectives. The Working Group reviewed data on the epidemiology of ACHD, long-term outcomes of complex cardiovascular malformations, issues in assessing morphology and function with current imaging techniques, surgical and catheter-based interventions, management of related conditions including pregnancy and arrhythmias, quality of life, and informatics. After research and training barriers were discussed, the Working Group recommended outreach and educational programs for adults with congenital heart disease, a network of specialized adult congenital heart disease regional centers, technology development to support advances in imaging and modeling of abnormal structure and function, and a consensus on appropriate training for physicians to provide care for adults with congenital heart disease.
Real-time 3-dimensional echocardiography is increasingly used in clinical cardiology. Studies have been shown that this technique can be accurately used to assess both cardiac mass and chamber volumes. We review the work showing that real-time 3-dimensional Doppler echocardiography can be used to accurately calculate intracardiac flow volumes that can potentially be used to assess cardiac function, intracardiac shunt, and valve regurgitation.
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OBJECTIVE: Normal left ventricular contraction involves a twisting component that helps augment stroke volume, the unwinding of which also very usefully contributes to early diastolic filling. Abnormalities of cardiac twist have been related to abnormal cardiac function. We sought to quantify the twisting action using a new sonographically based angle-independent motion-detecting echo method. METHODS: A twist model was developed with a variable-speed motor to rotate a wheel in water bath. A freshly harvested pig heart was mounted on it as a twist phantom. Short axis views were acquired with a GE/VingMed Vivid 7 system (GE Healthcare, Milwaukee, WI) at 3.5 MHz and more than 100 frames/s. Eight different speeds (30-100 cycles/min of winding and unwinding) were studied at 5 degrees of rotation (10 degrees , 20 degrees , 30 degrees , 40 degrees , and 50 degrees ). Data were analyzed off-line for twist analysis with a new 2-dimensional speckle-tracking-based program (2-dimensional strain rate method [2DSR]) embedded in EchoPac software (GE Healthcare). Ten freshly harvested pig hearts were studied in this model. RESULTS: The 2DSR program tracked the twist well (mean determination at 10 degrees = 16.88 degrees +/- 1.81 degrees [SD]; at 20 degrees = 26.5 degrees +/- 1.05 degrees ; at 30 degrees = 36.47 degrees +/- 1.31 degrees ; at 40 degrees = 44.03 degrees +/- 1.39 degrees ; and at 50 degrees = 54.1 degrees +/- 1.96 degrees ). CONCLUSIONS: The 2DSR program can be used to study twisting action of the heart.
OBJECTIVES: We sought to evaluate the effects of biventricular (BDOO) pacing compared with conventional (CDOO) atrioventricular (AV) sequential and atrial (AOO) pacing in children and infants in the early postoperative period after open heart surgery for congenital heart disease (CHD). BACKGROUND: Biventricular pacing using right ventricular (RV) and left ventricular (LV) leads can improve hemodynamics in patients with CHD, but it is unclear whether this occurs in early postoperative children with CHD. METHODS: Nineteen children (age, 5 days to 5.4 years; median, 5.5 months) with a definitive biventricular repair for CHD underwent AOO, CDOO, and BDOO pacing with temporary epicardial leads for 10 min each. The AV delay was 80% of the PR interval for the CDOO and BDOO modes. Lead placement was two right atrial, two RV, and one LV. Blood samples for cardiac index (arterial and venous) and tissue Doppler (TDI) traces were obtained in each pacing mode with a Vivid 7 BT04 digital ultrasound system (GE/VingMed, Horten, Norway) from an apical four-chamber view and analyzed with EchoPac software. RESULTS: The QRS duration was significantly shorter for BDOO compared with CDOO, and the cardiac index was higher with BDOO compared with CDOO. Systemic blood pressure was not different between the three modes of pacing (AOO, CDOO, BDOO). The TDI-derived strain rate showed minimal dyssynchrony in AOO as seen by isovolumic tensing (IVT) and peak systolic contraction (PSC) timing differences between RV and LV. The CDOO worsened dyssynchrony with prolonged DeltaIVT and PSC. The BDOO showed improved synchrony as seen by DeltaIVT and PSC. CONCLUSIONS: The TDI-derived strain rate showed worsened ventricular dyssynchrony with CDOO and improvement with BDOO. Cardiac index and QRS duration were improved by BDOO compared with CDOO. This suggests that short-term pacing with BDOO may benefit children with CHD needing pacing in the postoperative period.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
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.
OBJECTIVES: The purpose of this study was to investigate whether cardiac output (CO) could be accurately computed from live three-dimensional (3-D) Doppler echocardiographic data in an acute open-chested animal preparation. BACKGROUND: The accurate measurement of CO is important in both patient management and research. Current methods use invasive pulmonary artery catheters or two-dimensional (2-D) echocardiography or esophageal aortic Doppler measures, with the inherent risks and inaccuracies of these techniques. METHODS: Seventeen juvenile, open-chested pigs were studied before undergoing a separate cardiopulmonary bypass procedure. Live 3-D Doppler echocardiography images of the left ventricular outflow tract and aortic valve were obtained by epicardial scanning, using a Philips Medical Systems (Andover, Massachusetts) Sonos 7500 Live 3-D Echo system with a 2.5-MHz probe. Simultaneous CO measurements were obtained from an ultrasonic flow probe placed around the aortic root. Subsequent offline processing using custom software computed the CO from the digital 3-D Doppler DICOM data, and this was compared to the gold standard of the aortic flow probe measurements. RESULTS: One hundred forty-three individual CO measurements were taken from 16 pigs, one being excluded because of severe aortic regurgitation. There was good correlation between the 3-D Doppler and flow probe methods of CO measurement (y = 1.1x - 9.82, R(2) = 0.93). CONCLUSIONS: In this acute animal preparation, live 3-D Doppler echocardiographic data allowed for accurate assessment of CO as compared to the ultrasonic flow probe measurement.
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Visualization of myocardial perfusion is possible in both 2-dimensional and from reconstructive 3-dimensional echocardiography. We present the findings of our experimental pilot study of myocardial perfusion detection using live real-time 3-dimensional echocardiography in an animal model.
BACKGROUND: Invasive monitors and noninvasive 2-dimensional echocardiography are the standard clinical methods for stroke volume (SV) and cardiac output computation. We studied the use of real-time color Doppler 3-dimensional (3D) echocardiography (3DE) for the assessment of SV in human beings. METHODS: In all, 55 pediatric and adult patients with good transthoracic windows and a normal aortic valve were studied. Real-time 3DE color Doppler volumes incorporating the left ventricular outflow tract and aortic valve were taken. SV was calculated from the color Doppler data in the 3DE DICOM dataset. This was compared with 2-dimensional echocardiography SV calculation from the pulsed wave velocity through the aortic valve along with the left ventricular outflow tract diameter. RESULTS: Five patients were excluded because of mismatching of the 3D color Doppler segments in the 3D volume. The 3D Doppler volumes from the remaining 50 patients were analyzed. There was good correlation between the patients' averaged 3DE SV calculations and the 2-dimensional echocardiography pulsed wave SV estimation (y = 0.84x + 7.8, r2 = 0.90). CONCLUSION: Real-time 3D Doppler echocardiography can be used to accurately calculate SV and cardiac output, compared with conventional pulsed Doppler measurement, in pediatric and adult patients from transthoracic imaging.
OBJECTIVES: We and others have reported on the use of digital color Doppler sonography from real-time 3-dimensional (3D) echocardiography and its use in accurately calculating cardiac flow volumes, namely stroke volume (SV) and, hence, cardiac output. However, in some patients, image depth is higher than average, and this may affect the accuracy of volume calculation. We sought to investigate the impact of image depth and the accompanying change in signal strength, spatial resolution, and pulse repetition frequency on the accuracy of SV calculation from 3D color Doppler data in an in vitro model. METHODS: A tube model of the left ventricular outflow tract was constructed from plastic tubing and connected to a pulsatile pump. The volume flowing through the tube was imaged using a 3D echocardiography system. Stroke volumes from the pump were computed from the DICOM data using commercially available software and compared with a reference standard of timed volumes with the use of a graduated measuring cylinder over a range of depth settings and SVs. RESULTS: There was good correlation between the 3D-derived SVs and the reference cylinder measures over all depths from 4 to 16 cm at 1-cm increments with a tube diameter of 17 mm, a pump rate of 60 beats/min, and SVs ranging from 20 to 70 mL. The average r(2) value for the 13 different depths was 0.976. However, the accuracy of the 3D method of volume calculation appeared to fall at depths greater than 13 cm, especially at higher SVs. CONCLUSIONS: Stroke volume calculation from real-time 3D color Doppler data in this in vitro study shows that at depths greater than approximately 13 cm, accuracy decreases, especially at higher SVs. This may be due to decreased resolution and the reduced frame rate at these depths. At shallower depths, volume calculation form the 3D Doppler data appears very accurate.
OBJECTIVES: Our purpose was to evaluate a tissue Doppler-based index-peak myocardial acceleration (pACC)-during isovolumic relaxation and in evaluating left ventricular (LV) diastolic function. BACKGROUND: Simple, practical indexes for diastolic function evaluation are lacking, but are much desired for clinical evaluation. METHODS: We examined eight sheep by using tissue Doppler ultrasound images obtained in the apical four-chamber views to evaluate mitral valve annular velocity at the septum and LV wall. The pACC thus derived was analyzed during isovolumic relaxation (IVRT) and during the LV filling period (LVFP). We then changed the hemodynamic status of each animal by blood administration, dobutamine, and metoprolol infusion. We compared the pACC values during IVRT and LVFP over the four different hemodynamic conditions with a peak rate of drop in LV pressure (-dP/dt(min)) and the time constant of LV isovolumic pressure decay (tau), as measured with a high-frequency manometer-tipped catheter. RESULTS: The pACC of the septal side of the mitral valve annulus during IVRT showed a good correlation with -dP/dt(min) (r = -0.80, p < 0.0001) and tau (r = -0.87, p < 0.0001). The mean left atrial pressure (LAP) correlated well with the septal side pACC during LVFP (r = 0.81, p < 0.0001). There was a weak correlation between the mitral valve annulus pACC at the LV lateral wall and mean LAP. CONCLUSIONS: The pACC during IVRT is a sensitive, preload-independent marker for evaluation of LV diastolic function. In addition, pACC during LVFP correlated well with mean LAP.