Fetal ventricular mass determination on three-dimensional echocardiography: studies in normal fetuses and validation experiments.

BACKGROUND: Estimation of ventricular volume and mass is important for baseline and serial evaluation of fetuses with normal or abnormal hearts. Direct measurement of chamber wall volumes and mass can be made without geometric assumptions by 3D fetal echocardiography. Our goals were to determine the feasibility of using fast nongated 3D echocardiography for fetal volumetric and mass assessments, to validate the accuracy of the ultrasound system and the measurement technique, and if satisfactory, to develop normal values for fetal ventricular mass during the second and third trimesters. METHODS AND RESULTS: This was a prospective outpatient study of 90 consecutive normal pregnancies during routine obstetric services at Oregon Health & Science University (Portland). Optimized 3D volumes of the fetal thorax and cardiac chambers were rapidly acquired and later analyzed for right and left ventricular mass by radial summation technique from manual epicardial and endocardial traces. Experiments to validate the ultrasound system and measurement technique were performed with modified small balloon models and in vivo and ex vivo small animal experiments. Our study established the feasibility of fetal ventricular mass measurements with 3D ultrasound technology and developed normal values for right and left ventricular mass from 15 weeks' gestation to term. CONCLUSIONS: Nongated fast 3D fetal echocardiography is an acceptable modality for determination of cardiac chamber wall volume and mass with good accuracy and acceptable interobserver variability. The method should be especially valuable as an objective serial measurement in clinical fetal studies with structurally or functionally abnormal hearts.

Tissue Doppler-derived myocardial acceleration for evaluation of left ventricular diastolic function.

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.

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.

Latest advances and topics in fetal echocardiography.

PURPOSE OF REVIEW: Fetal diagnosis and the supporting specialties of perinatology, neonatology, and surgery have made rapid strides in the last decade. Numerous centers are focusing on this multifaceted niche area as the medical field realizes its vast promise and potential. The authors review some of the major advancements in thought and practice in the field of fetal echocardiography while attempting to give a less detailed overview for the less involved perinatologist. RECENT FINDINGS: First trimester fetal echocardiography has been an area of recent interest as transducer technology improves. As a result, optimum timing of first and subsequent scans and the population profile they are to be applied to have become an issue that begs consensus. Three-dimensional and four-dimensional fetal echocardiography have also received a boost for the same reasons, and both are being studied for feasibility and accuracy. Fetal tissue Doppler and spectral Doppler imaging are potential areas for exploration; the early steps have been taken. Awareness of associated ultrasound markers, such as exaggerated nuchal translucency, as clues to the presence of congenital heart disease is important, even if controversial. SUMMARY: The issue of missed prenatal diagnosis is disturbing, especially when it arises against a background of tremendous skill and technologic support. Strategies to minimize mistakes in this critical aspect need to be agreed on by the involved teams and put in place in a multidisciplinary manner if they are to have an important impact.

Congenital heart disease never goes away, even when it has been 'treated': the adult with congenital heart disease.

PURPOSE OF REVIEW: As the specialties of pediatrics and pediatric cardiology continue to forge ahead with better diagnoses, medical care, and surgical results, an expanding population of patients with congenital heart disease (CHD) outgrows the pediatric age group, yet does not quite graduate to routine adult cardiology or general medicine. The adult with congenital heart disease (ACHD) faces medical, surgical, and psychosocial issues that are unique to this population and must be addressed as such. This review attempts to discuss and highlight some of the important advances and controversies brought up in the past year, in the care and management of these patients. RECENT FINDINGS: The past five to 10 years have seen dynamic interest in understanding sequelae of corrected, uncorrected, or palliated congenital heart disease. The search for the ideal surgery, optimal prosthesis, and a smooth transition to adult care continues and is reflected in the vast amount of academic work and publications in this field. Of particular interest, conduit reoperations and single ventricle pathway modifications are still an art and a science in evolution. SUMMARY: While all are agreed that there is a pressing need to focus on the delivery of care to the adult with congenital heart disease, this essentially requires a clearer understanding of late sequelae of CHD. The sheer heterogeneity of anatomy, age, surgery, and institutional management protocols can make it difficult to develop clear guidelines. This review attempts to give an up-to-date perspective on some of the new findings related to the more common lesions and problems faced in this group.

Validation of volume and mass assessments for human fetal heart imaging by 4-dimensional spatiotemporal image correlation echocardiography: in vitro balloon model experiments.

OBJECTIVE: This study was designed to validate a slow-sweep real-time 4-dimensional (4D) spatiotemporal image correlation method for producing quantitatively accurate dynamic fetal heart images using an in vitro pulsatile balloon model and apparatus. METHODS: To model fetal heart chambers, asymmetric double-walled finger stalls (tips of surgical latex gloves) were used and attached to a laboratory-designed circuit that allowed calibrated changes in the inner balloon volume as well as an intermediate gel mass interposed between the 2 layers. The water-submerged model was attached to a small-volume pulsatile pump to produce phasic changes in volume within the inner balloon at a fixed rate. A sonography system with 4D spatiotemporal image correlation (STIC) capabilities was used for 3-dimensional (3D) and 4D data acquisition. Volume data were analyzed by customized radial summation techniques with 4D data analysis software and compared with known volumes and masses. RESULTS: Fifty-six individual volumes ranging from 2.5 to 10 mL were analyzed. Volume and mass measurements with 4D STIC were highly correlated (R2 > 0.90). The mean percentage error was better (<6%) for volumes exceeding 4 mL and was as low as 0.3% for 6-mL estimations. Measurements in the diastolic phase were the most accurate, followed by mass estimations equivalent to chamber walls. There was a wider range of percentage error in the lowest volumes tested (2.5 mL), which might have arisen from difficulties in spatial resolution or distortions from within the model apparatus itself. Resolution limitations of 4D technology in combination with extremely small volume targets may explain higher error rates at these small volumes. CONCLUSIONS: Four-dimensional STIC is an acceptably accurate method for volume and mass estimations in the ranges comparable with mid- and late-gestation fetal hearts. It is particularly accurate for diastolic estimations, for chamber wall mass measurements, and at volumes of greater than 2.5 mL. This study validates use of 4D STIC technology to overcome the limitations of nongated 3D technology for phasic and quantitative assessments in fetal echocardiography.