How many planes are necessary for accurate cardiac output measurement using surface integration of velocity vectors (SIVV) in the left ventricular outflow tract? Pediatric application
(English)Manuscript (preprint) (Other academic)
Flow measurements with surface integration of velocity vectors, (SIVV) is a three dimensional approach where velocities measured by colour Doppler from several two-dimensional imaging planes are gathered and flow is automatically calculated. With SIVV no assumptions regarding the Doppler insonation angle, area changes and flow profile are necessary, thus avoiding such errors. Numerical simulations have shown that an elliptic area less than 1:2 in major minor axis relation needs at least two equidistant (preferably four) planes for accurate measurements. The purpose of this study was to evaluate this finding in a controlled in vitro environment and in high quality in vivo observations. A Plexiglass® pulsatile flow model was used where the outflow tract allows for insertion of an artificial valve. A total of 12 images were acquired with an increment of 15o at three flow rates (0.9- 3.0 1/min). A series of piglets (13.5-17 kg) were stemotomized, and a 5MHz phased array transthoracic probe placed at the apex with the beam directed towards the left ventricular outflow tract, (LVOT) simulating the transoesophageal transgastric or transthoracic apical view. Epicardial images were acquired in 4 planes (45o increments). Ten high quality sequences at different cardiac output levels (0.9 - 2.1 1/min) were selected and compared to ultrasound transit time (TT) cardiac output measurement. The results show that for the in-vitro case, at least two planes were necessary for measurements with an error of <10%. In-vivo, four planes were required for errors of <20%. Our study confirms the theoretical assumption that at least two planes are preferable to obtain accurate flow measurements from colour Doppler data.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-89306OAI: oai:DiVA.org:liu-89306DiVA: diva2:607674