Limits of reproducibility of mitral pulsed Doppler spectra.

The total intrinsic variability of pulsed Doppler spectra of mitral blood flow was evaluated in this study. Doppler examinations were performed in 10 normal volunteers (7 men, 3 women), ages 29 to 57 years (mean 41) with an interval period of 3 months. The recordings were made in the apical 4-chamber view, using a 2.25-MHz transducer. The sample was placed approximately 1 cm proximal (left atrium) and 1 cm distal (left ventricle) from the middle of the anulus of the mitral valve at the onset of diastole. Processing of the raw Doppler spectra was done in a way that avoided subjective manipulation by the investigators. Mitral peak velocities, accelerations and spectral widths were measured in early diastole and late diastole. From the parameters under investigation, maximal velocities showed the best reproducibility with a range of coefficients of variation of 9 to 13%. Peak acceleration in early diastole and spectral widths showed rather large coefficients of variation, ranging from 19 to 30 and 14 to 24%, respectively. Mitral pulsed Doppler spectra in the left atrium were more reproducible than in the left ventricle.

Reference values for pulsed Doppler signals from the blood flow velocity on both sides of the pulmonary valve.

Pulsed Doppler signals were recorded from the pulmonary artery and the right ventricular outflow tract in 215 healthy subjects (120 males, 95 females; 1-65 years). Amplitude spectra from these Doppler signals were stored in digital form together with adjustment data for the instrument and the simultaneously recorded ECG. From these Doppler spectra the median of the maximal velocity (Vmax), the maximal acceleration (Amax) and the dispersion of the velocity distribution around Vmax (width) were calculated. These three median values were used to characterize the Doppler spectra and to define normal values for bloodflow velocities. Thus, calculations were made without observer interacting using a well-defined computer program. The effect of age, gender, body surface area and heart rate were studied. Reference ranges were calculated. There is a slight decrease of the median value of Vmax and Amax in the pulmonary artery during lifetime from 80 to 70 cm s-1 and from 1,200 to 800 cm s-2, respectively. On the other hand, there is no correlation between age and Vmax and Amax in the right ventricular outflow tract. The width of the spectra increases with age at both sites. No significant changes with age were seen with the other variables.

Normal diastolic filling patterns of the left ventricle.

Pulsed Doppler measurements on both sides of the mitral valve and M-mode left ventricular echocardiograms were performed in 215 healthy subjects, 120 males and 95 females, between one and 65 years old, in order to evaluate normal diastolic filling patterns of the left ventricle. The relation between the maximum blood velocity during early passive filling (E wave) and during atrial contraction (A wave) was computed from the Doppler spectra obtained proximal and distal to the mitral valve, resulting in the EA ratio. The influence on the EA ratio of age, gender, body surface area, blood pressure, heart rate, PR interval, respiration, wall thickness and basal wall mass of the left ventricle was investigated. The study showed that the EA ratio measured proximal to the mitral valve (in the left atrium) was significantly smaller than the EA ratio measured distal (in the left ventricle) and that the only prominent relations with the EA ratio were those with age and heart rate. The EA ratio declines with age: proximal to the mitral valve from approximately (medians) 2.5 to 1 and distal to it from 3.5 to 1.5. All other physiological variables are weakly related or unrelated to the EA ratio in this group of healthy subjects.

Automated calculation of stenosis diameters from the width of the velocity jet with the use of a multi-gate pulsed Doppler system.

The aim of this study was to evaluate an algorithm for automated estimation of the width of a jet stream originating from a stenosis. The evaluation was performed in a pulsatile flow model. The width of the jetstream was assessed by measuring the diameter of the region with relatively high velocities (the jet) in the velocity profiles, as recorded with a multi-gate pulsed Doppler system. Measurements were performed at 3, 6, and 9 mm downstream of three different stenoses (stenosis diameter: 3, 5, or 8 mm) at different Reynolds numbers (200-1600) based on time averaged flow velocity for a tube of diameter 15 mm. The developed algorithm was used successfully for automated detection and quantification of jet flow diameters downstream to a stenosis. The algorithm can be used for calculating the stenosis diameter notwithstanding a theoretically predictable overestimation of about 1 mm, depending on the Reynolds number and the distance from the stenosis.

Reference values for pulsed Doppler signals from the blood flow on both sides of the aortic valve.

Pulsed Doppler signals were recorded in 215 healthy subjects, 120 males and 95 females, between 1 and 65 years of age. The measurements were performed in the left ventricular outflow tract (LVOT) and in the ascending aorta (AAO). Amplitude spectra from the Doppler signals were stored in digital form together with adjustment data for the instrument, the simultaneously registered ECG and respiration signal. The maximum velocity (Vmax), the maximum acceleration (Amax) and the width of the velocity distribution around Vmax (width) were derived from these spectra and used for the characterization of the signals. These parameters were computed without observer interaction using a computer program. Effects of age, sex, body surface area, heart rate and respiration were studied. Reference ranges were calculated. The following conclusions can be drawn: Vmax and Amax in the AAO decrease clearly with increasing age from approximately 100 to 60 cm s-1 and from 2000 to 1000 cm s-2 (medians), respectively. The variation of the width in the AAO is greater for people over 45 years. Vmax, Amax and width in the LVOT increase slightly with advancing age from approximately 60 to 80 cm s-1, 800 to 1000 cm s-2 and 12 to 15 cm s-1 (medians), respectively. These parameters of flow were either unrelated or only weakly related to other physiological variables in this study group.

The vibratory innocent heart murmur studied by echo-Doppler.

So-called innocent heart murmurs are thought to be originated by a possible physiologic narrowing of the left ventricular outflow tract, accentuated by a higher contractibility of the myocardium in some children. The aim of our studies was to evaluate this theory with pulsed Doppler echocardiography in order to detect possible local bloodstream disturbances. In a study of 20 children, with or without a vibratory innocent heart murmur no statistical difference was found in either peak-velocity, acceleration or width of the Doppler spectra, read out in an objective computed digital way. The hypothetic location of the origin of the vibratory innocent heart murmur in the left ventricular outflow tract has not yet been confirmed with Doppler echocardiography.