Strategies for Successful Treatment of a Calcified Lesion

Hello, and welcome to the June issue of Vascular Disease Management. I have chosen to comment on the case report by Konstantinos Stavroulakis, MD, and colleagues. In this report, a patient presenting with gangrenous digits of the left foot and stage 4 chronic kidney disease (CKD) was noted to have a highly calcified critically stenotic popliteal artery by duplex ultrasound.

The patient was treated with lithoplasty utilizing the Shockwave medical device, followed by a drug-coated balloon (DCB). The procedure was guided by CO2 angiography. I have chosen to comment on this case as it incorporates so many of the complex issues faced in critical limb ischemia (CLI) intervention. These elements include dense calcium (which may be intravascular or more commonly medial), renal dysfunction, gangrenous digits, and a difficult lesion location such as the popliteal artery that is subject to significant mechanical stresses and is often a critical origin or touchdown site for bypass grafts. I will focus my comments on calcified lesions and the use of CO2 rather than iodinated contrast to guide interventional procedures in patients presenting with renal dysfunction.

Multiple reports have noted that severely calcified lesions represent a challenge to interventional and surgical therapy of peripheral arterial disease. Although several atherectomy tools can effectively treat areas of calcium involving the vascular lumen, medial calcification has historically been difficult to treat with intervention. Calcific lesions have been associated with higher reported rates of dissection, perforation, inadequate stent expansion, and restenosis. Most interventionists consider dense dystrophic calcium to have strongly negative prognostic significance.

The authors of this report utilized acoustic energy via a Shockwave lithoplasty balloon (5 mm × 60 mm) to successfully dilate a severely calcified popliteal artery without significant dissection or embolization. This was followed by treatment with an Admiral Impact DCB. The treatment resulted in an excellent initial angiographic result. Reports from the DISRUPT PAD I trial utilizing the Shockwave lithoplasty balloon have clearly demonstrated that calcified lesions can be dilated with less pressure and have less resultant dissections than standard balloon angioplasty. No significantly increased rates of embolization were reported.

The results of the ongoing DISRUPT PAD III trial utilizing the lithoplasty balloon followed by DCB to determine if this course of combination therapy will result in better long-term patency are highly anticipated. Will pretreatment with sonic waves result in adequate penetration and migration of the antiproliferative drugs delivered by DCBs to the arterial adventitia through densely calcified arterial media via possible “micro-channels” created by the sonic energy? The interventional community is closely watching the results of this study, as the results have the potential to change how we approach calcified lesions in claudicants as well as patients presenting with CLI. Densely calcified lesions will become an even greater problem in the future with the population having increased life expectancy, increased incidence of diabetes, and more CKD.

The use of CO₂ as the primary contrast agent is also worthy of comment. CO₂ enhances transmission of X-ray rather than blocking transmission like iodinated contrast. The net result is a negative image. New, dedicated CO₂ angiographic CO₂-delivery systems, including the one utilized in this report, facilitate delivery of medical grade CO₂ without significant contaminants. Avoiding the administration of iodinated contrast is crucial in patients with advanced CKD, but it is also reasonable in patients who are at higher risk of contrast-induced nephropathy, even with normal blood urea nitrogen and creatinine levels.

In this case, CO₂ was followed with a single injection of 10 ccs of iodinated contrast to obtain a final image. CO₂ has additional attributes. It is useful in patients with severe iodinated contrast allergy and it may demonstrate patent vessels or grafts that appear totally occluded by iodinated contrast (as CO₂ is 300 times less viscous). This case report by Stavroulakis highlights the utility of CO₂ angiography. It also demonstrates the use of acoustic energy to achieve better initial angiographic outcomes. This report brings hope that we might solve the problems that have been associated with the interventional treatment of severely calcified arterial obstructive lesions. We anxiously await the results of the DISRUPT III trial.