Sunday, October 7, 2012

The Standing Waves

Standing waves in the superficial femoral artery (ref 2).
Standing waves in a vessel are an artifact that has been noticed since the early days of angiography, and has been called by a number of different terms, including: "stationary arterial waves." "regular alternating changes in arterial width," "beading," "crenation," "bamboo pattern," and the confusing "string of pearls" which sounds very similar to fibromuscular dysplasia.

Standing waves are distinct from arterial spasm and fibromuscular dysplasia, although it somewhat resembles both of these entities. An important feature of standing waves are their transience... they are frequently gone before a second contrast injection.

Standing waves have a smooth sinusoidal appearance and can appear in multiple segments of a vessel.  The phenomenon is noted to occur primarily in medium and small arteries, and has been noted in the lower extremity arteries, renal arteries, mesenteric arteries, and (rarely) in the carotids... but the artifact is noted to occur most commonly in the renal and lower extremity arteries (~3%).

The mechanism of standing waves is not completely agreed upon, but some think it process probably more complex than simple transient spasm due to power injection of contrast.  One argument in favor of a more complex physiologic process are reports of standing waves in other modalities, such as MRA and ultrasound, where obviously no contrast injection has taken place.

40Y F with DSA of the lower extremities for evaluation of "fibromuscular dysplasia." a) Beaded appearance of the right superficial femoral artery, b) beaded appearance of the right pedal arteries.  This appearance was transient, compatible with standing waves. (ref 3)
1. Lehrer, H. "The Physiology of Angiographic Arterial Waves" Radiology. 89, 11-19 (1967)
2."Vascular and Interventional Radiology: The Requisites" Kaufman, et al. 1st ed (2004)
3. Sharma AM, Gornick HL. "Standing Arterial Waves Is NOT Fibromuscular Dysplasia" Circulation: Cardiovascular Interventions. 2012; 5 e9-e11
4. New PFJ. "Arterial Stationary Waves" AJR 97:2, 488-499 (June 1966).
5. Kroger K, Massalha K. "Sonographic Correlate of Stationary Waves." Journal of Clinical Ultrasound. Vol 32:3 pp 158-161. (Mar/Apr 2004).
6. Peynircioglu B, Cil BE, Karcaaltincaba M. Standing or Stationary Arterial Waves of the Superior Mesenteric Artery at MR Angiography and Subsequent Conventional Arteriography. vol 18:10  October 2007, Pages 1329–1330