Effect of fitness on cardiac structure and function in overweight and obesity (the FATCOR study).

BACKGROUND AND AIMS: Obesity is associated with reduced left ventricular (LV) systolic myocardial function. We aimed to explore by means of a cross-sectional study whether this effect is offset in the presence of good fitness. METHODS AND RESULTS: We studied clinical and echocardiographic data from 469 overweight (body mass index [BMI] >27 kg/m2) and obese (BMI ≥30 kg/m2) women and men without known cardiovascular (CV) disease in the FAT associated CardiOvasculaR dysfunction (FATCOR) study. The participants were grouped according to obesity and sex- and age adjusted peak oxygen uptake, obtained by ergospirometry. LV systolic myocardial function was assessed by peak systolic global longitudinal strain (GLS) measured by speckle tracking echocardiography. The association of fitness with GLS was tested in logistic regression analyses and reported as odds ratio (OR) with 95% confidence interval (CI). In the total study population, participants were 47 years old, 60% were women, and mean BMI was 32.0 kg/m2. GLS did not differ between fit and unfit subjects within the overweight and obese groups (both p > 0.05), but the overweight fit group had higher GLS (more negative value) compared to the obese unfit group (-20.1 ± 2.6 vs. -19.0 ± 3.0, p < 0.05). In obese subjects, fitness was associated with higher GLS (OR 0.88 [95% CI 0.79-0.99, p < 0.05) in multivariable logistic regression analysis, independent of significant associations with higher arterial stiffness and lower fat percentage (all p < 0.05). In the overweight group, fitness was not significantly associated with GLS. CONCLUSION: In obesity, fitness was independently associated with higher GLS, while no association was found in overweight. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.govNCT02805478.

Measured acoustic intensities for clinical diagnostic ultrasound transducers and correlation with thermal index.

OBJECTIVES: To investigate if the thermal index for bone (TIB) displayed on screen is an adequate predictor for the derated spatial-peak temporal-average (ISPTA.3 ) and spatial-peak pulse-average (ISPPA.3 ) acoustic intensities in a selection of clinical diagnostic ultrasound machines and transducers. METHODS: We calibrated five clinical diagnostic ultrasound scanners and 10 transducers, using two-dimensional grayscale, color Doppler and pulsed-wave Doppler, both close to and far from the transducer, with a TIB between 0.1 and 4.0, recording 103 unique measurements. Acoustic measurements were performed in a bespoke three-axis computer-controlled scanning tank, using a 200-µm-diameter calibrated needle hydrophone. RESULTS: There was significant but poor correlation between the acoustic intensities and the on-screen TIB. At a TIB of 0.1, the ISPTA.3 range was 0.51-50.49 mW/cm2 and the ISPPA.3 range was 0.01-207.29 W/cm2 . At a TIB of 1.1, the ISPTA.3 range was 19.02-309.44 mW/cm2 and the ISPPA.3 range was 3.87-51.89 W/cm2 . CONCLUSIONS: TIB is a poor predictor for ISPTA.3 and ISPPA.3 and for the potential bioeffects of clinical diagnostic ultrasound scanners. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Authors' reply Cobb correspondence re: J-E. Gjertsen, S. A. Lie, T. Vinje, et al. More re-operations after uncemented than cemented hemiarthroplasty used in the treatment of displaced fractures of the femoral neck: An observational study of 11 116 hemiarthroplasties from a national register. J Bone Joint Surg [Br] 2012;94-B:1113-1119.

We welcome letters to the Editor concerning articles that have recently been published. Such letters will be subject to the usual stages of selection and editing; where appropriate the authors of the original article will be offered the opportunity to reply.

Rome III subgroups of functional dyspepsia exhibit different characteristics of antral contractions measured by strain rate imaging - a pilot study.

PURPOSE: Rome III defines two distinct entities of functional dyspepsia (FD), namely epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS). We aimed at studying these subgroups of FD by simultaneously assessing antral strain, gastric accommodation and emptying and visceral hypersensitivity. MATERIALS AND METHODS: Strain during antral contractions was assessed by ultrasound strain rate imaging in 15 controls and 19 FD patients (8 EPS patients and 11 PDS patients). Gastric accommodation and emptying were assessed using B-mode ultrasonography. Symptoms were assessed by visual analogue scale (VAS). RESULTS: During fasting, antral strain in EPS patients (mean±SEM) was 61.4 ±â€Š6.4 %, significantly higher than in controls (47.5 ±â€Š3.3 %; p = 0.042) and in PDS patients (28.6 ±â€Š1.7 %; p = 0.001). PDS patients had lower strain than controls (p < 0.001). Postprandially, EPS patients had higher strain than both controls and PDS patients (p < 0.01) but no difference was found between controls and PDS patients. Compared with controls, PDS patients had significantly larger fasting proximal area than controls (14.9 ±â€Š1.6 cm2 vs. 7.8 ±â€Š0.2 cm2; p < 0.001), whereas EPS patients did not differ (12.1 ±â€Š1.9 cm2; p = 0.057). Gastric emptying fraction (1 - proximal area at 40 min postprandially/area at 1 min postprandial × 100) at 40 min postprandially in EPS patients 46.4 ±â€Š6.6 % was lower than in controls (62.9 ±â€Š1.3 %; p = 0.032), but higher than PDS patients (27.4 ±â€Š5.3 %; p = 0.018). CONCLUSION: Anterior radial strain measured by ultrasound strain rate imaging may discriminate between subgroups of FD and healthy controls. This study supports the Rome III classification of FD into EPS and PDS groups.

More re-operations after uncemented than cemented hemiarthroplasty used in the treatment of displaced fractures of the femoral neck: an observational study of 11,116 hemiarthroplasties from a national register.

Using data from the Norwegian Hip Fracture Register, 8639 cemented and 2477 uncemented primary hemiarthroplasties for displaced fractures of the femoral neck in patients aged > 70 years were included in a prospective observational study. A total of 218 re-operations were performed after cemented and 128 after uncemented procedures. Survival of the hemiarthroplasties was calculated using the Kaplan-Meier method and hazard rate ratios (HRR) for revision were calculated using Cox regression analyses. At five years the implant survival was 97% (95% confidence interval (CI) 97 to 97) for cemented and 91% (95% CI 87 to 94) for uncemented hemiarthroplasties. Uncemented hemiarthroplasties had a 2.1 times increased risk of revision compared with cemented prostheses (95% confidence interval 1.7 to 2.6, p < 0.001). The increased risk was mainly caused by revisions for peri-prosthetic fracture (HRR = 17), aseptic loosening (HRR = 17), haematoma formation (HRR = 5.3), superficial infection (HRR = 4.6) and dislocation (HRR = 1.8). More intra-operative complications, including intra-operative death, were reported for the cemented hemiarthroplasties. However, in a time-dependent analysis, the HRR for re-operation in both groups increased as follow-up increased. This study showed that the risk for revision was higher for uncemented than for cemented hemiarthroplasties.

Ultrasound safety in early pregnancy: reduced energy setting does not compromise obstetric Doppler measurements.

OBJECTIVES: We hypothesized that first-trimester Doppler ultrasonography can be carried out at lower output energies than the currently advocated limits without compromising clinically important information. METHODS: We recruited 42 pregnant women for an ultrasound examination at 12 weeks' gestation. Twenty-one women were examined with a transvaginal transducer, the rest with a transabdominal transducer. We used pulsed Doppler to measure pulsatility index (PI) and peak systolic velocity (PSV) in five clinically relevant fetal and maternal blood vessels. The energy indicator thermal index for bone (TIb) was set at 1.0, 0.5 and 0.1. Each measurement was repeated three times. A mixed linear regression model accounting for correlation between measurements was used to assess the effect of different TIb levels and transducers. RESULTS: We were able to visualize the vessels by color Doppler and measure PI and PSV in all vessels at all energy levels in all the participants with the exception of the ductus venosus in two participants, yielding 1872 recordings for statistical analysis. A reduction in TIb from 1.0 to 0.5 and 0.1 had no effect on the PI or PSV values, nor was there any trend towards higher parameter variance with decreasing TIb. There was no difference between measured values of PI and PSV between the transducers, but the transabdominal technique was associated with a greater parameter variance. CONCLUSION: Reliable first-trimester Doppler data can be obtained with output energy reduced to a TIb of 0.5 or 0.1.

Strain measurement during antral contractions by ultrasound strain rate imaging: influence of erythromycin.

Strain rate imaging (SRI) is a non-invasive ultrasound (US) modality that enables the study of mechanical deformation (strain) with high spatial and temporal resolution. A total of 244 contractions in seven healthy volunteers were studied by SRI on two separate days to characterize radial strain of antral contractions in the fasting and fed states and to assess the influence of intravenous erythromycin. Gastric accommodation and emptying were assessed by 2D ultrasonography. The perception of hunger was registered by the participants. The strain increased from early to late phase II and phase III activity by (median) 18%, 58% and 82%, respectively, P < 0.05. Erythromycin infusion in phase I induced contractions with median strain of 35%, but did not increase postprandial strain. Both fasting and postprandially, lumen-occlusive contractions with erythromycin were more frequent than in naturally occurring contractions, 69%vs 48%, P = 0.036 and 40%vs 5%, P < 0.001 respectively. All subjects had rumbling in their abdomens when intraluminal air was detected sonographically (85% of all phase III contractions) and that rumbling was perceived by the participant as maximal awareness of hunger. SRI enabled detailed strain measurement of individual antral contractions. Erythromycin initiated fasting antral contractions and increased the number of lumen-occlusive contractions.

A multimodal laser Doppler and endosonographic distension device for studying mechanosensation and mucosal blood flow in the oesophagus.

We describe the development of a multimodal device combining bag distension, manometry, high frequency intraluminal ultrasound, laser Doppler flowmetry and symptom registration. Bench tests showed that the different modalities did not influence each other. During bag distension we obtained high quality images of the oesophageal wall for computing biomechanical parameters, and laser Doppler signals showing variation in mucosal perfusion. We conclude that the principle of measurement is sound and that the device can provide a basis for further studies.

An anaesthetic protocol in the young domestic pig allowing neuromuscular blockade for studies of cardiac function following cardioplegic arrest and cardiopulmonary bypass.

BACKGROUND: Neuromuscular blockade should, for ethical reasons, not be allowed in animal experiments unless the use is strongly motivated. Beforehand, the anaesthetic protocol must be documented without muscle relaxation in the species studied. Documentation is difficult to obtain from the scientific literature. When focusing on cardiac function over time, in particular, the ideal anaesthetic protocol should cause no or minor alterations in cardiac variables. METHODS: We intended to document an anaesthetic protocol involving ventilation with N(2)O combined with loading doses and continuous infusions of pentobarbital, fentanyl and midazolam in seven pigs by applying potentially painful stimuli every 15 min for 7 h. Subsequently, left ventricular global and regional function was studied with conductance catheter and strain rate imaging by echocardiography in eight pigs with pancuronium included. RESULTS: Pigs without pancuronium were completely immobilized and unresponsive to potentially painful stimuli and sternotomy, with no accumulation or degradation of anaesthetic agents. With pancuronium included, left ventricular preload gradually decreased together with reduction of cardiac index from 3.52 +/- 0.14 at 2 h to 2.84 +/- 0.11 L min(-1). m(-2) (+/-SEM) after 7 h of observation. Preload recruitable stroke work decreased after 7 h, whereas peak systolic strain in the anterior left ventricular wall and load-independent indices of diastolic function were not significantly altered. CONCLUSION: In specific experimental protocols, the anaesthetic protocol described could allow the use of muscular paralysis in young domestic pigs, for instance when involving hypothermic cardiopulmonary bypass, cardioplegic arrest and reperfusion.

The effect of body weight on the degree of blood velocity profile skewness in the aortic annulus in domestic pigs.

We investigated the blood velocity profile in the aortic annulus (AA) in two groups of domestic pigs using epicardial Doppler echocardiography. The velocity profile skewness in terms of max/mean TVI (the ratio of maximal to cross-sectional mean time-velocity integral along the diameter) was 1.107 +/- 0.01 in the small pigs (n = 10; body weight: 24.6 +/- 0.8 kg) and 1.216 +/- 0.026 in the large pigs (n = 8; body weight: 50.6 +/- 2.5 kg) (P = 0.002). The velocity profile in the AA is more skewed in large animals than in small animals and the skewness in the larger animals is similar to that in normal adult humans. This study shows the importance of choosing animals of sufficient size if flow method investigations are to be performed. This is particularly important for ultrasound Doppler investigations based on a limited sample of velocities across the flow channel.

Determination of plasma volume in anaesthetized piglets using the carbon monoxide (CO) method.

Based on measurements of the circulating red blood cell volume (V(RBC)) in seven anaesthetized piglets using carbon monoxide (CO) as a label, plasma volume (PV) was calculated for each animal. The increase in carboxyhaemoglobin (COHb) concentration following administration of a known amount of CO into a closed circuit re-breathing system was determined by diode-array spectrophotometry. Simultaneously measured haematocrit (HCT) and haemoglobin (Hb) values were used for PV calculation. The PV values were compared with simultaneously measured PVs determined using the Evans blue technique. Mean values (SD) for PV were 1708.6 (287.3)ml and 1738.7 (412.4)ml with the CO method and the Evans blue technique, respectively. Comparison of PVs determined with the two techniques demonstrated good correlation (r = 0.995). The mean difference between PV measurements was -29.9 ml and the limits of agreement (mean difference +/-2SD) were -289.1 ml and 229.3 ml. In conclusion, the CO method can be applied easily under general anaesthesia and controlled ventilation with a simple administration system. The agreement between the compared methods was satisfactory. Plasma volume determined with the CO method is safe, accurate and has no signs of major side effects.

Mechanical properties in the human gastric antrum using B-mode ultrasonography and antral distension.

The aims of this study were to investigate gastric antral geometry and stress-strain properties by using transabdominal ultrasound scanning during volume-controlled distensions in the human gastric antrum. Seven healthy volunteers underwent stepwise inflation of a bag located in the antrum with volumes up to 60 ml. The stretch ratio and Cauchy stress and strain were calculated from measurements of pressure, diameter, and wall thickness. A second distension series was conducted in three volunteers during administration of the anticholinergic drug butylscopolamine. Analysis of stretch ratios demonstrated positive strain in the circumferential direction, negative strain in the radial direction, and no strain in the longitudinal direction. The stress-strain relation was exponential and did not differ without or with the administration of butylscopolamine. The wall stress was decomposed into its active and passive components. The well-known length-tension diagram from in vitro studies of smooth muscle strips was reproduced. The maximum active tension appeared at a volume of 50 ml, corresponding to a stretch ratio of 1.5. We conclude that the method provides measures of antral biomechanical wall properties and can be used to reproduce the muscle length-tension diagram in humans.

Velocity distribution in the ascending aorta in pigs during chronotropic and inotropic stimulation.

The influence of heart rate, stroke volume and myocardial contractility on temporal and spatial velocity distribution in the ascending aorta was investigated in 10 pigs. A pulsed Doppler ultrasound technique with intraluminal probe and a single crystal connected to a position-sensitive device was used to measure blood velocity. After baseline registration, the heart rate was increased in two discrete steps of 20 beats/min by right atrial pacing. Isoproterenol infusion was given to increase contractility. Finally, without isoproterenol, the heart rate was again raised to the values found during inotropic stimulation. The first three measuring situations did not differ haemodynamically, apart from increased heart rate and reduced stroke volume. Increased heart rates were not associated with significant change in the parameters for skewness of velocity distribution (peak systolic slope and ratio, maximum skewness slope and ratio). During inotropic stimulation the peak left ventricular dP/dt, aortic systolic pressure, cardiac output and stroke volume were greater than at comparable paced heart rate, and the peak systolic slope of velocity distribution was significantly increased. Velocity distribution in the ascending aorta thus was not altered by increased heart rate alone, whereas skewness of distribution was enhanced by increased inotropic drive of the myocardium and the concomitant central and peripheral vascular changes.

In vitro volume estimation of kidneys using three-dimensional ultrasonography and a position sensor.

OBJECTIVE: A new 3D ultrasound system using a position sensor based on magnetic scanhead tracking and new software utilising automatic contour tracing between manually traced contours was tested for volume estimation of kidneys in vitro. METHODS: Kidneys from piglets and pigs were fixed in formaldehyde. A reservoir with 0.9% saline kept at 37 degrees C was used. The kidneys were scanned either by a linear translational movement along the organ or by a tilting movement. The outer contour of the kidneys was traced manually, by two independent investigators. The volume of each kidney was also measured using the Archimedes principle (true volumes). RESULTS: Good agreement between 3D ultrasound volume estimates and true volumes was found for both probe movements. For translational movement of the transducer, the mean errors between the methods were 4.17 and 4.31 ml for the two independent investigators, and the volume range was 96-203 ml. The corresponding error values for tilting movement were 1.10 and 0.19 ml. The interobserver variation was also small, there was no difference in the volumes obtained by the two investigators, or by the two scanning movements. CONCLUSION: Volume estimates using this 3D ultrasound method showed very good agreement with true volumes, both mean errors and interobserver variation were low.

In vitro evaluation of three-dimensional ultrasonography based on magnetic scanhead tracking.

The objective of this study was to evaluate the accuracy and precision of a magnetic position sensor system for acquisition of three-dimensional (3D) ultrasound images in volume estimation of phantoms in vitro. Installation of either 0.9% solution of saline at 37 degrees C or distilled water at 20 degrees C to a condom was performed. Scanning was performed either by a continuous or stepwise acquisition. This 3D ultrasound system demonstrated good correlation (r = 0.99-1.0, n = 8) between estimated (EV) and true volumes (TV). The errors were in the range 1.3%+/-0.3% (SEM) to 1.9%+/-0.6%, independent of sound velocity. Scanning through a porcine abdominal wall positioned at the fluid surface yielded a systematic underestimation of the volume: mean (EV - TV) = -7.2+/-0.8 ml. Eight repeated scans of the same volume yielded a coefficient of variation of 1.1%. Interobserver error of the tracing procedure was 2.6%+/-0.9%. This 3D ultrasound system gave high accuracy and precision in volume estimation in vitro, and yielded low interobserver error. A change in ultrasound velocity of approximately 60 m/s did not influence the accuracy significantly. Scanning through an abdominal wall underestimated volumes slightly.

Resetting of renal blood autoregulation during acute blood pressure reduction in hypertensive rats.

Decrease in systemic blood pressure, duration of pressure decrease, and change in the activity of the renin or the sympathetic nervous system may represent mechanisms involved in resetting the renal blood flow (RBF) autoregulation found in hypertensive rats. Autoregulation of RBF, plasma renin concentration (PRC), and the time needed for resetting to take place were studied in the nonclipped kidney before and after removal of the clipped kidney of two- kidney, one-clip (2K1C) hypertensive rats and before and after mechanical reduction of the renal arterial pressure (RAP) for 10 min in the spontaneously hypertensive rat (SHR) and in the nonclipped kidney of 2K1C hypertensive rats with and without renal denervation. Mean arterial pressure (MAP) fell from 147 to 107 mmHg 30 min after removal of the clipped kidney, and the lower pressure limit of RBF autoregulation decreased from 113 to 90 mmHg (P < 0.01); PRC fell. Mechanical reductions of RAP from 161 to 120 mmHg in the nonclipped kidney for 10 min did not change RBF, but at 120 mmHg, the lower pressure limit of RBF autoregulation was reduced from 115 mmHg before pressure reduction to 96 mmHg afterwards (P < 0.02). In SHR, similar pressure reduction for 10 min decreased the lower pressure limit of RBF autoregulation from 106 to 86 mmHg (P < 0.01). PRC was unchanged in both models, and denervation did not change RBF autoregulation. When RAP was reduced below the lower pressure limit of RBF autoregulation, RBF decreased approximately 20%; the lower pressure limit of RBF autoregulation remained unchanged. In normotensive Wistar-Kyoto rats, pressure reduction did not change the range of RBF autoregulation. These results indicate that acute normalization of the pressure range of RBF autoregulation in hypertensive rats is dependent on the degree of pressure reduction of RAP, whereas renal innervation and PRC do not play a major role. We propose that the mechanism of resetting is due to afterstretch of noncontractile elements of the vessel wall or is caused by pure myogenic mechanisms. An effect of intrarenal angiotensin cannot be excluded.

Dieulafoy's vascular malformation: role of endoscopic ultrasonography in therapeutic decision-making.

BACKGROUND: Dieulafoy's vascular malformation may cause severe, potentially life-threatening gastrointestinal bleeding. Endoscopic diagnosis may be difficult because of minute mucosal lesions, and additional intramural abnormalities are usually not encountered. Endoluminal high-frequency ultrasonography is a new modality for imaging intramural and perivisceral structures. METHODS: We report two cases of recurrent severe gastric bleeding in which different endosonographic modalities were used in the diagnosis of Dieulafoy's malformation, and the impact of endosonography on therapeutic strategy is discussed. In the first case a radial-scanning 7.5/12-MHz echoendoscope and a linear 20-MHz miniature probe were applied for B-mode imaging in a stable-state patient who had undergone previous endoscopic sclerotherapy, and arterial flow signals from the small intramural lesion were recorded using a 10-MHz transendoscopic pulsed Doppler probe. In the other case urgent endosonography was performed shortly after a bleeding episode, disclosing an aberrant large-calibre artery entering the gastric wall with a long submucosal branch. RESULTS: Both patients were successfully operated on with a transabdominal approach. CONCLUSION: Endosonography is a quick and safe diagnostic method and should be considered when vascular malformations are suspected as the cause of gastric bleeding.

Effects of velocity distribution, diameter measurement and velocity tracing on the accuracy of cardiac output measurement by pulsed Doppler echocardiography in the aortic annulus of pigs.

UNLABELLED: The accuracy of cardiac output measurement by pulsed Doppler echocardiography can be affected by several factors, such as the velocity distribution, the measurement of diameter and the method of tracing the pulsed Doppler flow spectrum. This experimental study was designed to find the most accurate way of measuring cardiac output in consideration of all these factors. In 10 open-chest normal piglets (24 +/- 1 kg), the velocity distribution in the aortic annulus was evaluated using Doppler colour flow mapping. Cardiac output was measured by pulsed Doppler echocardiography in the aortic annulus by a number of different ways and compared to the simultaneous result of the thermodilution method. All measurements were made at baseline, after intravenous injection of esmolol and during infusion of dobutamine. RESULTS: (1) the velocity distribution in the aortic annulus in the piglets was just slightly skewed during all three haemodynamic situations; (2) The in vivo measurements of the diameter of the aortic annulus varied throughout the ejection period, but the average of the three largest diameter measurements was almost identical with the diameter measured in vitro (18.5 +/- 0.3 mm vs. 18.6 +/- 0.2 mm; p = NS); (3) Tracing the maximal velocity of the pulsed Doppler flow spectrum produced a cardiac output that was 18%-21% higher than that measured by the thermodilution method, while tracing the brightest part (modal velocity) of the pulsed Doppler flow spectrum yielded a cardiac output very close to the thermodilution measurement. CONCLUSION: The velocity distribution in the aortic annulus in the piglet has little effect on cardiac output measurement by pulsed Doppler. Using the maximal measurable diameter of the aortic annulus and tracing the brightest part of the pulsed Doppler flow spectrum yielded the cardiac output closest to that measured by the thermodilution method.

Three-dimensional cross-sectional velocity distribution in the ascending aorta in cardiac patients.

Knowledge of the distribution of velocities across the ascending aorta is important for measurements of cardiac output; for understanding the function of normal and diseased valves and for the evaluation of prosthetic valves. The aim of this study was to investigate, in detail, the spatial distribution of axial velocities in the human ascending aorta, covering a nearly complete cross-section of the lumen in a time continuous modus. During open-heart surgery, blood velocities in the ascending aorta were mapped in 10 patients. All patients had aortic valves with no significant clinical evidence of disease. Pulsed Doppler ultrasound technique was used to measure blood velocity using an intraluminal probe with a 1 mm, 10 MHz crystal connected to a position-sensitive device. The distribution of blood velocity in the aorta 6-8 cm above the valve was characterized by a skewed and irregular peak systolic flow, with maximum velocity posteriorly. There was a positive correlation (r=0.854, P<0.002) between the maximum skewness slope and the stroke volume. Significant retrograde flow was recorded in all patients in the left posterior part of aorta in late systole and early diastole. The rotation of the point of maximal velocity was anticlockwise in six patients, clockwise in three and alternating in one. The present study shows that there is a considerable individual variation in the velocity distribution in the ascending aorta, with no plane symmetric features, and that large sampling volumes are required for reliable estimates of mean velocity.

The velocity distribution in the aortic annulus at different times during systole is mainly determined by the pattern of flow convergence in the left ventricular outflow tract--an experimental study using Doppler colour flow mapping.

An experimental study in 10 open chest normal pigs (body weight: 24 +/- 1 kg) was carried out to explore the relationship between the velocity distribution in the aortic annulus and the pattern of flow convergence in the left ventricular outflow tract. The cross-sectional velocity profiles in the aortic annulus were constructed by using Doppler colour flow mapping with a previously validated time-interpolation method. The pattern of flow convergence in the left ventricular outflow tract was quantified by measuring the colour flow areas on the anterior and posterior sides of the central axis of the aortic annulus, and calculating their difference. The dynamic changes of the velocity distribution, the pattern of flow convergence and the septal angle throughout systole were observed. The velocity distribution in the aortic annulus changed according to the pattern of flow convergence in the left ventricular outflow tract. During early systole, the pattern of flow convergence was most asymmetrical. With the central longitudinal axis of the aortic annulus as a reference, the main part of the converging flow was along the anterior wall of the left ventricular outflow tract. Consequently, the velocity profile in the aortic annulus was most skewed during the early systole, with the highest velocity along the anterior wall. Towards late systole, the pattern of flow convergence became more and more symmetrical, and the velocity distribution in the aortic annulus gradually became flat. A significant correlation was found between the extent of asymmetry of the pattern of flow convergence in the left ventricular outflow tract and the extent of skewness of the velocity distribution in the aortic annulus (r = 0.69, P < 0.001). Throughout systole, septal angle increased very slightly (from 35 +/- 3 to 38 +/- 3 degrees, P < 0.01). The pattern of flow convergence in the left ventricular outflow tract is a major determinant of the velocity distribution in the aortic annulus in pigs.