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Aim. Physiological blood flow patterns are themselves poorly understood despite their impact on arterial disease. Stable spiral (helical) laminar flow (SLF) has been observed in normal subjects. The purpose of the present study is to develop a method of magnetic resonance (MR) flow pattern visualization and to analyze spiral and non-spiral flow patterns with and without luminal narrowing in vitro. The flow conditions were then modeled using computational fluid dynamics (Star-CD).
Methods. Laminar integrity was examined in a flow-rig using spin and gradient echo magnetic resonance imaging (MRI) in non-stenosed and stenosed conduits in the presence of non-spiral and spiral flow.
Results. No difference was observed in a non-stenosed conduit between non-spiral and spiral flow. In the presence of a stenosis spiral flow preserves flow velocity coherence whereas non-spiral flow increasingly lost coherence beginning proximal to the stenosis. Computational fluid dynamic modeling of the in vitro experiment showed marked differences between the 2 flow patterns. Non-spiral flow produced greater inwardly directed forces just beyond the stenosis and greater outward pressures at more distal sites. The near wall turbulent energy was up to 700% less with spiral flow over non-spiral flow beyond the stenosis.
Conclusion. Spiral flow appears to offer clear flow profile stabilizing advantages over non-spiral flow, by significantly reducing the turbulence caused by a stenosis. Spiral flow also produces lower forces acting on the vessel wall.
[Int Angiol 2004;23:276-83]
Key words: Spiral flow - Helical flow - Stenosis - Magnetic resonance imaging - Computational fluid dynamics.
Physiological blood flow patterns are poorly understood despite their potential impact on arterial disease. The complex phenomena of blood flow in the heart and vessels are worthy of study because they give an insight into the physiology and pathophysiology of the cardiovascular system. Flow profiles are known to be modified in some diseases.1, 2 However there have been few in vivo measurements of the 3-dimensional (3D) blood flow patterns.
The first report of stable spiral laminar flow within human vessels was following the angioscopic examination of the luminal surface of arteries which showed a series of spiral folds and spiral flow patterns.3 This was confirmed with the mapping of flow in vivo using duplex scanning. Simple velocity, speed, and vector maps were constructed by ensembling multiple...