Accurate estimation of large vessel length in growing children and adolescents for the purpose of pulse wave velocity calculation.

Witbooi, Lee-Roy Cecil (2018-12)

Thesis (MMed)--Stellenbosch University, 2018.

Thesis

Background Cardiovascular disease is a major cause of death in adults worldwide. Early detection allows for early intervention to prevent vascular events such as strokes, heart attacks, etc. Although these vascular events typically occur in late adulthood, the underlying atherosclerosis often begins during childhood. Early subclinical atherosclerosis can be detected by measuring the elasticity of the large arteries, particularly when performed serially over time. Normally, the elasticity of a healthy aorta helps to slow down the speed of the pressure wave created by contraction of the heart muscle. This is an important way of maintaining smooth laminar blood flow. Atherosclerosis causes the vessel wall to harden and lose elasticity. As the vessel wall hardens, the speed of the pressure wave increases. Pulse wave velocity (PWV) is a sophisticated method of detecting early elasticity changes, and is a preferred non-invasive technique to measure arterial wall stiffness. The velocity calculation requires accurate measurement of both distance travelled and time taken for the pulse wave to travel between two points. The distance used for pulse wave velocity calculation is an approximation of the intraluminal distance travelled by the pulse wave and is estimated by measuring the distance between various surface anatomy landmarks. The expert consensus document on arterial wall stiffness described carotid–femoral PWV as the “gold standard” measurement of arterial wall stiffness, yet there is no consensus on the arterial path length estimation method. A variety of arterial path length estimation methods exist, and this makes inter-study comparison of PWV very difficult. The purpose of the current study was to investigate the most accurate method of estimating the true distance travelled by the aorto-femoral pressure wave. We compared distances between a range of commonly used surface anatomy landmarks, and compared these to the true intraluminal distance measured on multi-planar reformations of archived computerized tomography imaging in children of varying ages. Our findings will allow standardization of PWV calculation in children and allow for inter-study comparisons. Methods Vessel lengths in children (aged 0-18 years) were measured with multi-planar reformation (MPR) imaging software. These measurements were then compared with the surface anatomy measurements also obtained using the MPR imaging software. The comparisons between vessel lengths and surface anatomy distances were performed in segments, since there were no whole body CT scans available on the Picture Archiving and Communication System (PACS) at the research site. Results The surface anatomy measurements from the suprasternal notch to the angle of the mandible (on the right) correlated well with the intraluminal vessel length from the origin of the brachiocephalic trunk to the external carotid at the angle of the mandible (r2=0.92; p<0.0001). The surface anatomy measurements from the suprasternal notch to the midpoint of the right inguinal crease, correlated well with the intraluminal vessel length from the origin of the brachiocephalic trunk to the right femoral artery at the right inguinal ligament (r2=0.98; p<0.0001). The surface anatomy measurements from the suprasternal notch to the xiphisternum, plus the surface distance between xiphisternum and the umbilicus, plus the surface distance between the umbilicus and the midpoint of the right inguinal crease, correlated well with the intraluminal vessel length from the origin of the brachiocephalic trunk to the right femoral artery at the right inguinal ligament (r2=0.97; p<0.0001). The surface anatomy measurement from the suprasternal notch to the xiphisternum, plus the surface distance between the xiphisternum and the midpoint of right inguinal crease, correlated well with the intraluminal vessel length from the origin of the brachiocephalic trunk to the right femoral artery at the right inguinal ligament (r2=0.97; p<0.0001). A regression equation is provided for each set of surface anatomy measurements, allowing further adjustment of measurements to more accurately represent the true intraluminal distance travelled by the pulse wave. Conclusions The surface anatomy distance between the suprasternal notch and the angle of the mandible, subtracted from the distance between the suprasternal notch and mid-inguinal crease, provides the closest approximation of true intraluminal distance travelled and would be the best method to standardize pulse wave velocity calculation in children and adolescents. However, surface anatomy estimations using the xiphisternum and umbilicus as landmarks produced very similar correlations.

Agtergrond Kardiovaskulêre siekte is een van die voorste oorsake van dood in volwassenes wêreldwyd. Vroeë opsporing maak voorsiening vir vroeë intervensie om vaskulêre gebeure soos beroertes, hartaanvalle, ens. te voorkom. Alhoewel hierdie vaskulêre gebeure tipies in die laat volwassenheid voorkom, begin die onderliggende aterosklerose dikwels gedurende die kinderjare. Vroeë subkliniese aterosklerose kan opgespoor word deur die elastisiteit van arteries te meet, met jaarlikse opvolg ondersoeke. Die elastisiteit van 'n gesonde aorta help om die spoed van die pols wat deur die samespanning van die hartspier geskep word, te vertraag. Dit is 'n belangrike manier om egalige laminêre bloedvloei te handhaaf. Aterosklerose veroorsaak dat bloedvate verhard en elastisiteit verloor. Soos die bloedvate verhard, verhoog die pols spoed. Pols spoed/snelheid berekenings ondersoeke is 'n gesofistikeerde metode om vroeë bloedvaat elastisiteits veranderings op te spoor, en is vir baie die ondersoek van keuse om vir arteriële bloedvaat styfheid te meet. Die snelheidsberekening vereis akkurate meting van beide afstand agelê en tyd wat dit neem vir die pols om tussen twee punte te beweeg. Die afstand wat gebruik word vir hierdie ondersoek is 'n skatting en word gemeet met behulp van 'n maatband oor die liggaamsoppervlak. Die deskundige konsensus dokument oor arteriële bloedvat styfheid beskryf karotis-femorale pols snelheids berekenings ondersoek as die "gouestandaard" meting vir arteriële wandstyfheid, maar daar is geen konsensus oor die arteriële padlengte skattingsmetode nie. 'n Verskeidenheid van arteriële padlengte skattings metodes bestaan, en dit maak inter-studie vergelyking in verband met pols snelheid berekenings baie moeilik. Die doel van hierdie studie was om die akkuraatste skattings metode van afstand wat deur die aorto-femorale pols afgelê word te ondersoek, deur oppervlakanatomiese afstande, wat verkry is met behulp van 3D rekenaar tomografie (RT) beelde, te vergelyk met bloedvaat lengtes wat verkry was met behulp van multi-planêre rekonstruksie rekenaar tomografie beelde in kinders van verskillende ouderdomme. Om sodoende pols snelheid berekenings ondersoeke in kinders te standaardiseer en inter-studie vergelykings in verband met pols snelheid berekenings te vergemaklik. Metodes Bloedvaat lengtes is gemeet met behulp van multi-planêre rekonstruksie (MPR) beeldings sagteware (IntelliSpace Portal, Koninklike Philips elektroniese NV, Nederland) by kinders (tussen die ouderdomme 0 tot 18 jaar). Hierdie metings is dan vergelyk met die oppervlakanatomie metings wat ook verkry is met behulp van die MPR beeldings sagteware. Hierdie vergelykings is in segmente uitgevoer, aangesien daar geen RT-skanderings beskikbaar was, wat vanaf die basis van die skedel tot by die pelvis strek nie, by die hospitaal waar die studie uitgevoer was nie. Resultate Die oppervlakanatomiese meting vanaf die suprasternale kerf tot by die hoek van die mandibel (regs) het positief gekorreleer met die bloedvaat metings vanaf die oorsprong van die brachiokefaliese stam tot by die eksterne karotis by die hoek van die mandibel (r2 = 0.92; p <0,0001). Die oppervlaksanatomiese meting vanaf die suprasternale kerf tot by die middelpunt van die lies vou, het positief gekorreleer met die bloedvaat metings vanaf die oorsprong van die brachiokefaliese stam tot by die regter femorale arterie by die inguinale ligament (r2 = 0.98; p <0,0001). Die oppervlakanatomiese meting vanaf die suprasternale kerf tot by die xifisternum, plus die oppervlakafstand vanaf die xifisternum tot by die umbilikus, plus die oppervlakafstand vanaf die umbilikus tot by die middelpunt van die regter lies vou, positief gekorreleer met die bloedvaatmetings vanaf die oorsprong van die brakiokefaliese stam tot by die regter femorale arterie by die inguinale ligament (r2 = 0.97; p <0.0001). Die oppervlaksanatomiese meting vanaf die suprasternale kerf tot by die xifisternum, plus die oppervlakafstand vanaf die xifisternum tot by die middelpunt van die lies vou het positief gekorreleer met die bloedvaat metings vanaf die oorsprong van die brachiokefaliese stam tot die regter femorale arterie by die inguinale ligament (r2 = 0,97; p <0,0001). 'n Formule word verskaf vir elke stel oppervlakanatomie metings, wat die aanpassing van metings moontlik maak om die ware intraluminale afstand wat deur die pols aglê word, meer akkuraat voor te stel. Gevolgtrekkings Die oppervlak anatomie afstand tussen die suprasternale kerf en die hoek van die mandibel moet afgetrek word van die afstand tussen die suprasternale kerf en die regter lies vou, aangesien dit die naaste benadering bied van ware intraluminale afstand agelê en sal die beste metode wees om pols snelheid ondersoeke in kinders and adolessente te standaardiseer.

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