Catheter-Tipped Ultrasonic Intravascular Imaging

Abstract

New methods for vascular recanalization such as balloon angioplasty, 1,2 transluminal atherectomy,3,4 and laser ablation5~6 have emerged over the past 10 years as alternatives to bypass surgery. These methods are designed to deal with specific morphologic characteristics of atheromatous lesions that are generally not apparent on angiogram. Despite several new advances in the area of contrast imaging such as improved signal-to-noise levels, postprocessing techniques, and real-time digital subtraction angiography,' angiography is limited as a guidance modality for interventional therapy in complex lesions. For example, the success of angioplasty depends on the composition and relative compliance of the lesion and the normal vessel wall. Angiograms provide information about the location of the critical narrowing and relative degree of stenosis but add little information concerning the likelihood of successful dilation vs. significant dissection. Several studies8,9 have documented the fairly limited sensitivity and specificity of angiographic data compared with surgical or pathologic data. Epicardial ultrasound has shown that the atherosclerotic process is diffuse rather than localized as depicted by angiograms. 10 Postmortem studiesll show that nearly 75% of all atherosclerotic lesions are eccentric. Asymmetric lesions may account in part for the difficulty in accurately predicting the degree and extent of stenosis based on angiography.The shape of the lesion is especially important when considering interventional therapy that depends on the spatial orientation of the stenotic region. Transluminal atherectomy devices are now emerging in the clinical arena. 12 The Simpson Atherocath makes use of a fine cutting edge mounted within a housing element at the tip of a catheter to &dquo;shave&dquo; off the atheromatous lesion. Perforation is a potentially critical complication of these devices 13; therefore precise orientation of the cutting blade and knowledge about the characteristics of the lesion are desired. Angiograms help in the positioning of the atherectomy at UNIV TORONTO on June 5, 2016 pvs.sagepub.com Downloaded from