Svein Arne Aase

Segmental and global longitudinal strain and strain rate based on echocardiography of 1266 healthy individuals: the HUNT study in Norway

AIMS To study the distribution of longitudinal systolic strain and strain rate (SR) as indicators of myocardial deformation according to age and sex in a healthy population. METHODS AND RESULTS Longitudinal strain and SR were determined in 1266 healthy individuals from three standard apical views, using a combination of speckle tracking (ST) and tissue Doppler imaging (TDI) to track regions of interest (ROIs). To test applicability of the reference values, we used a subset of the population to compare four methods of assessing myocardial deformation: (1) a combination of TDI and ST; (2) TDI with fixed ROIs; (3) TDI with tracking of ROIs; and (4) ST. Mean (SD) overall global longitudinal strain and SR were -17.4% (2.3) and -1.05 s(-1) (0.13) in women, and -15.9% (2.3) and -1.01 s(-1) (0.13) in men. Deformation indices decreased with increasing age. The combined and ST methods showed identical SR, but values were significantly lower than those obtained by TDI. Strain was overestimated by the ST method (18.4%) compared with the combined method (17.4%). CONCLUSION The reference values for global and segmental longitudinal strain and SR obtained from this population study are applicable for use in a wide clinical setting.

Reference Values and Distribution of Conventional Echocardiographic Doppler Measures and Longitudinal Tissue Doppler Velocities in a Population Free From Cardiovascular Disease

Background—This study aimed to investigate the distribution of conventional Doppler measurements, pulsed wave tissue Doppler imaging (pwTDI)- and color tissue Doppler imaging-derived velocities, by age and sex in a healthy population. Methods and Results—Longitudinal tissue Doppler velocities were determined in 1266 healthy individuals from standard apical 4- and 2-chamber views. By the pwTDI method, mean±SD systolic mitral annular velocities were 8.2±1.3 cm/s in women and 8.6±1.4 cm/s in men, and by color tissue Doppler, they were 6.6±1.1 cm/s in women and 6.9±1.3 cm/s in men. With pwTDI, diastolic early mitral annular velocities were 11.8±3.2 cm/s in women and 10.8±3.0 cm/s in men, with corresponding ratios between mitral early flow velocity and early diastolic tissue velocity of 6.7±0.8 in women and 6.4±0.8 in men. By pwTDI, tricuspid annular systolic and early diastolic velocities were 12.5±1.9 and 13.3±3.0, respectively, in women and 12.8±2.2 and 12.5±3.3, respectively, in men. There was a significant decrease in left and right ventricular function with increasing age. Conclusions—The longitudinal mitral and tricuspid annular velocities from this population study are widely applicable as reference values. Reference values for annular velocities should be specified by sex and age. The average of inferoseptal and anterolateral wall velocities may be the preferred index of left ventricular performance.

Reproducibility in echocardiographic assessment of the left ventricular global and regional function, the HUNT study

AIMS The study aimed to compare the inter-observer reproducibility of new and traditional measurements of the left ventricular (LV) global and regional function. METHODS AND RESULTS Two experienced echocardiographers performed 20 complete echo/Doppler examinations and 50 analyses on ten healthy subjects. All recordings were analysed for systolic and diastolic conventional and deformation measurements by both echocardiographers. Inter-observer mean error (absolute difference divided by the mean) was 4% and lowest (P = 0.001) for systolic M-mode annulus excursion. Mean error for the regional deformation indices was significantly higher than for all the global measurements (all P < 0.001). Mean error for analyses of the same recording was 34% (P = 0.002) lower for global systolic indices and 44% (P < 0.001) lower for global diastolic indices than inter-observer mean error for analyses made in separate recordings. CONCLUSION Systolic M-mode annulus excursion showed better inter-observer reproducibility than other traditional and newer measurements of LV systolic and diastolic function. Repeated analyses of the same recordings underestimate the more clinically relevant inter-observer reproducibility by approximately 40% for most measurements of LV function.

Cardiovascular Risk Factors and Systolic and Diastolic Cardiac Function: A Tissue Doppler and Speckle Tracking Echocardiographic Study

BACKGROUND The aim of this study was to determine whether blood pressure, body mass index (BMI), serum lipids, glucose, and renal function are associated with left ventricular (LV) and right ventricular function in a low-risk population. METHODS The associations of common risk factors with cardiac function were assessed, using multiple linear regression, in a random sample of 1,266 individuals free from hypertension, diabetes, and cardiovascular disease. A combination of conventional echocardiographic, speckle-tracking, and tissue Doppler methods was used to assess cardiac function. RESULTS Older age and higher BMI, systolic and diastolic blood pressure, and non-high-density lipoprotein (HDL) cholesterol were associated with lower LV function. Thus, LV strain was reduced by approximately 5% per 5 kg/m(2) increase in BMI and by 4% per 10 mm Hg increase in diastolic blood pressure. Corresponding reductions in peak early diastolic mitral annular velocity were 7% for both BMI and diastolic blood pressure. Higher HDL cholesterol was associated with better LV function. In women, smoking was also associated with reduced LV function. LV function was lower also at low levels of diastolic pressure and BMI. Reduced right ventricular function was related to older age, smoking, higher diastolic blood pressure and non-HDL cholesterol, and lower HDL cholesterol. CONCLUSIONS These findings suggest that conventional risk factors may predict cardiac function many years before clinical disease. The J-shaped associations related to diastolic blood pressure and BMI may suggest that in some individuals, low levels of these factors may indicate underlying but unknown disease.

Aortic valve closure: relation to tissue velocities by Doppler and speckle tracking in normal subjects

AIMS The aim of this study is to resolve what event in velocity/time curves represents aortic valve closure (AVC) by comparing the timing of AVC visually seen in high frame rate B-mode images with simultaneously recorded apical tissue Doppler imaging (TDI) and speckle-tracking-based velocity/time curves from normal subjects. METHODS AND RESULTS A total of 73 recordings from 11 normal subjects were analysed. The acquisition frame rate was equal for both TDI and B-mode (mean 147.5 FPS). The study shows conclusively that the initial negative velocity spike at end-systole occurs before AVC, 26.7 +/- 6.2 ms before reference (P < 0.001). The event closest to the reference was the time point of zero velocity after the negative spike, 2.6 +/- 8.2 ms before reference. These events are related to the reference in the same way for velocity/time curves by speckle tracking, colour M-mode, and pulsed wave tissue Doppler. CONCLUSIONS AVC in velocity/time curves should be positioned at the end of the negative spike after ejection. Establishing AVC from the correct event in velocity/time curves will ensure more consistent displacement, velocity, strain, and strain rate parameters.

The impact of aberration on high frame rate cardiac B-mode imaging

In echocardiography, especially in 3D echocardiography, achieving high frame rates is a major challenge. A suggested solution is parallel receive beamforming. With out any compensation, this approach is known to produce block-like artifacts, where each block corresponds to one parallel receive group. In this work, in vitro imaging, in vivo imaging, and simulations were used to investigate the artifacts. In vitro, imaging a tissue phantom, the artifacts were successfully compensated for. However, in vivo, imaging the heart, the compensation techniques no longer sufficed and the artifacts persisted. With in vivo imaging, aberrating tissue layers are present between the heart and the probe. To investigate the effects of aberration on a parallel receive sys tem, an in vitro experiment was performed with and without a silicon phase aberrator in front of the probe. The aberrator caused the artifacts to appear even when co techniques were applied. Simulations confirmed the measured results and indicated that distorted beam profiles and decorrelation between parallel receive groups caused the artifacts. To quantify the magnitude of the artifacts, a correlation-based indicator was developed. The indicator separated images with and without artifacts and confirmed that the artifacts appeared from the combination of parallel receive beams and aberration.

Strain rate imaging combined with wall motion analysis gives incremental value in direct quantification of myocardial infarct size

BACKGROUND The study aimed to evaluate the diagnostic accuracy of a new method for direct echocardiographic quantification of the myocardial infarct size, using late enhancement magnetic resonance imaging (LE-MRI) as a reference method. METHODS AND RESULTS Echocardiography and LE-MRI were performed on average 31 days after first-time myocardial infarction in 58 patients. Echocardiography was also performed on 35 healthy controls. Direct echocardiographic quantification of the infarct size was based on automated selection and quantification of areas with hypokinesia and akinesia from colour-coded strain rate data, with manual correction based on visual wall motion analysis. The left ventricular (LV) ejection fraction, speckle-tracking-based longitudinal global strain, wall motion score index (WMSI), longitudinal systolic motion and velocity, and the ratio of early mitral inflow velocity to mitral annular early diastolic velocity were also measured by echocardiography. The area under the receiver-operating characteristic curves for the identification of the infarct size >12% by LE-MRI was 0.84, using the new method for direct echocardiographic quantification of the infarct size. The new method showed significantly a higher correlation with the infarct size by LE-MRI both at the global (r = 0.81) and segmental (r = 0.59) level compared with other indices of LV function. CONCLUSION Direct quantification of the percentage infarct size by strain rate imaging combined with wall motion analysis yields high diagnostic accuracy and better correlation to LE-MRI compared with other echocardiographic indices of global LV function. Echocardiography performed ~1 month after myocardial infarction showed ability to identify the patients with the infarct size >12%.

Echocardiography without electrocardiogram.

AIMS automatic detection of the QRS complex on electrocardiogram (ECG) is used on cardiac ultrasound scanners to separate ultrasound image series into cardiac cycles for playback and storage. On small hand-held scanners it is unpractical to connect ECG cables. We therefore aim to do automatic cardiac cycle separation using apical B-mode ultrasound images. METHODS AND RESULTS cardiac cycle length is estimated by cyclicity analysis of B-mode intensities. To determine a cycle start estimate near QRS, a deformable model is fitted to the left ventricle in real-time. The model is used to initialize and constrain a speckle tracker positioned near the mitral annulus. In the displacement curve generated by the speckle tracker, a time point near maximum distance from the probe is detected as a cardiac cycle start estimate. Validation against ECG was done on 233 recordings from normal subjects and 46 recordings from subjects with coronary pathology. Several test cases were run for each recording to emulate B-mode series starting at all time points in the cardiac cycle. Totally, 11 886 test cases were run. Cycle length estimation was feasible in 98% of normal subject cases and 91% of pathology cases. Median difference in cycle length by ECG was 0 and -3 ms, respectively. Cycle start estimation was feasible in 90% of normal subject cases and 77% of pathology cases. Median difference to cycle start by ECG was 62 and 76 ms, respectively. CONCLUSION apical B-mode series can automatically be separated into cardiac cycles without using ECG.

Automatic real-time view detection

This work presents an algorithm capable of classifying an echocardiographic view as either an apical two chamber view, four chamber view or long axis view. It also provides a score on the overall image quality. The algorithm is based on a deformable non uniform rational B-spline (NURBS) model updated in an extended Kalman filter framework. Models are constructed for each of the three standard views. Each model is updated using a combination of edge and speckle-tracking measurements, where weak edges and edges strongly deviating from their neighbor edges are discarded. The most probable standard view is found using feature detection and general successfulness in detecting edges. This is also used as a measure of overall view quality. The algorithm was trained and validated using 68 recordings from the Norwegian HUNT database. An echocardiographer classified each recording as one of three standard views. 33 randomly chosen recordings, with approximately 10 of each view, were used for training. The other 35 recordings were used for validation. The algorithm successfully classified the view in 32 of 37 cases (86.5%). Each classification is accompanied by a score, which can be used to assess image quality.

Aortic valve closure: relation to tissue velocities by Doppler and speckle tracking in patients with infarction and at high heart rates.

Aim: To resolve the event in tissue Doppler (TDI)‐ and speckle tracking‐based velocity/time curves that most accurately represent aortic valve closure (AVC) in infarcted ventricles and at high heart rates. Methods: We studied the timing of AVC in 13 patients with myocardial infarction and in 8 patients at peak dobutamine stress echo. An acquisition setup for recording alternating B‐mode and TDI image frames was used to achieve the same frame rate in both cases (mean 136.7 frames per second [FPS] for infarcted ventricles, mean 136.9 FPS for high heart rates). The reference method was visual assessment of AVC in the high frame rate narrow sector B‐mode images of the aortic valve. Results: The initial negative velocities after ejection in the velocity/time curves occurred before AVC, 44.9 ± 21.0 msec before the reference in the high heart rate material, and 25.2 ± 15.2 msec before the reference in the infarction material. Using this time point as a marker for AVC may cause inaccuracies when estimating end‐systolic strain. A more accurate but still a practical marker for AVC was the time point of zero crossing after the initial negative velocities after ejection, 5.4 ± 15.3 msec before the reference in high heart rates and 8.2 ± 12.9 msec after the reference in the infarction material. Conclusion: The suggested marker of AVC at high heart rate and in infarcted ventricles was the time point of zero crossing after the initial negative velocities after ejection in velocity/time curves. (Echocardiography 2010;27:363‐369)