Assessment of coronary compensatory enlargement by three-dimensional intravascular ultrasound Jon D. Klingensmith 1 , D. Georey Vince 1; *, Barry D. Kuban 1 , Raj Shekhar 1 , E. Murat Tuzcu 2 , Steven E. Nissen 2 & J. Fredrick Cornhill 1 1 Department of Biomedical Engineering, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA; 2 Department of Cardiology, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA (* Corresponding author) Key words:atherosclerosis, coronary vessels, intravascular ultrasonography Abstract Severaltechniques have been used to demonstrate that human arteries respond to atherosclerosis by increasing their total arterial area to prevent a decrease in blood ¯ow. Three-dimensional reconstructions coronary arteries can document this compensatory response accurately and speci®cally. Seven human coronary arteries were reconstructed using intravascular ultrasound and biplane angiography, and vesse geometries were quanti®ed. In all seven vessels, as plaque area increased, overallvesselarea increased (R  0:986, 0.933,0.984,0.678,0.763,0.963,and 0.830), but luminalcross-sectional area did not signi®- cantly decrease. Focal compensatory enlargement was identi®ed in each vessel, and in some cases this response appeared to occur until the vessel was 65% occluded. Luminalenlargement near the proximal ends was attributed to the natural taper of the vessel. The semi-automated, three-dimensional segmenta technique used in this study allows reproducible quanti®cation, as there is no subjective manual tracing involved.Following the intravascular ultrasound transducer in time and space with biplane angiography allows for accurate reconstruction with or without automated pullback devices. Information on the rate of change of vessel measurements is also presented, which, when combined with visualization of accurate 3 geometry, providesa unique assessment of coronary compensatory enlargement. This reconstruction technique can be applied in a clinical environment with no major modi®cation. Introduction It has been shown thatas atherosclerosis pro- gresses, arteries undergo a compensatory response in which the overall vesselsize increases to pre- vent signi®cant luminal narrowing[1±5].The exactmechanismscontrollingthis positivere- modeling continue to be investigated. However, it is known thatthe ability ofendothelial cells to sense and respond to changes in blood ¯ow is centralto the modulation ofcompensatory en- largement [6]. In addition to investigation of the molecularcontrolmechanisms, the disease pro- cess and remodeling response in various human arteries,includingthe carotid [4], the femoral [2,7],and the coronary arteries [1, 5, 8±11], have been studied. Many techniques have been used to assess this response including microscopy [1, 3], intravascularultrasound (IVUS) [2, 7±10],and B-mode scanning ultrasound [4]. The impetus for these numerous investigations is the clinical rele- vance of compensatory enlargement. Studies have shown thatthe processof outward remodeling may causea predisposition to plaquerupture, resulting from a structural weakening of the pla- que [12]. International Journal of Cardiac Imaging 16: 87±98, 2000. Ó 2000 Kluwer Academic Publishers. Printed in the Netherlands. 87