IVUS: Cracking the “Code” in the wall

Percutaneous balloon angioplasty (PTA) and endovascular stenting techniques have rapidly evolved during the past decade. The advances in technology, including guidewires with the ability to traverse long total occlusions safely, balloon catheters, and refinements in stent design has afforded the interventionalist a broad array of tools in his arsenal to optimize technical and clinical results in their patients. As a result, the vascular community as a whole has embraced these techniques and adopted their formidable role in their respective practices, including our vascular surgical colleagues. Acknowledging there has been historically a dearth of evidence-based literature supporting the results of these endovascular procedures involving different vascular beds, angioplasty, and stenting in the aorto-iliac axis has enjoyed excellent technical, clinical success along with durable long-term patency outcomes. These procedures are not only well-tolerated and safe, but rival the results of bypass surgery in this vascular bed that are associated with much higher morbidity, complications, and mortality [1]. In the interventionalist’s search for the holy grail, the ‘‘perfect’’ angiographic result, he has explored numerous therapeutic strategies to facilitate achieving this elusive prize. Intravascular ultrasound (IVUS) has been a tremendous tool when appropriately utilized by the skilled and experienced interventionalist in uncovering many of the secrets of balloon angioplasty such as to show the way it works, its mechanisms and an invaluable resource to overcome the methodological limitations of contrast angiography [2]. Furthermore, it has been demonstrated to optimize the final results following PTA and stenting in both the coronary and peripheral vasculature [3,4]. In this issue of CCI, Hara and Nishino report two cases of infrarenal aortic stenosis that were successfully stented with the use of IVUS guidance to achieve technical success in both patients [5]. They utilized IVUS technology to overcome the inherent limitations imposed by contrast angiography, notably, the propensity to underestimate the degree of stenosis. In each respective case, equivocal findings were apparent to the operators as to the severity of the lesion, described as ‘‘shaggy and fuzzy moderately stenotic’’, and in the second case, it was difficult to discern as to the etiology of the pathophysiology demonstrated on angiography representing an aortic dissection with a ‘‘flaplike’’ structure in the distal aorta. In both cases, employment of IVUS confirmed that the lesions were composed of very heavily calcified plaque, consistent with advanced atherosclerosis. In addition to clarifying the morphology of the lesions, they were able to quantitatively assess the minimum lumen diameter, reference diameter of the proximal and distal aspects of the vessels, in concert with acquiring the total length of the diseased segment involved. They acknowledged the difficulty imposed by the equivocal findings on angiography as the solo diagnostic modality and subsequently relied on the accrued data acquisition from IVUS to ensure a successful result. They were able to select the appropriate sized balloon-stent combination that was matched to the reference diameter of the adjacent disease-free segment as well as judging the length of stent needed to cover the lesion in its entirety. Complementing the preprocedural selection of equipment they also optimized their final result with IVUS, in the context of an underexpanded stent not readily apparent on angiography that warranted a larger balloon catheter and dilatation to ensure the struts of the stent were fully embedded into the arterial wall, with uniform expansion of the stent. The excellent technical success in these two cases were further reinforced with hemodynamic success reflected by normalization of the ABI’s in both legs in each respective case, as well as abolishment of trans-lesion hemodynamically significant gradients at conclusion of the procedures.