Shock Buddy Technique for Intravascular Lithotripsy of Severe Eccentric Arterial Calcification (2024)

Advanced age and increasing frequency of diabetes mellitus, systemic hypertension, and chronic kidney disease contribute to the increasing prevalence and severity of vascular calcification. Calcified plaques negatively impact clinical and angiographic outcomes following percutaneous interventions (percutaneous transluminal angioplasty [PTA]) by impeding stent delivery; disrupting polymers; and causing stent malapposition, asymmetry, and underexpansion.1 Multiple technologies—including high-pressure, noncompliant, cutting or scoring balloons; atheroablative technologies (laser, rotational, or orbital atherectomy); and, recently, intravascular lithotripsy (IVL)—have been used to modify calcified plaques, facilitate procedural success, and optimize stent implantation.

Eccentric or nodular calcific plaques present unique challenges for PTA. Wire biases, in effect, may direct atheroablative technologies away from nodular calcific plaques when the nodules are on the “inner” or “lesser” curvature of tortuosity. Additionally, balloons may preferentially expand away from eccentric calcified lesions because the noncalcified radius of the vessel is more compliant. Finally, the optimal sizing of IVL balloons requires the ratio of the diameter of the balloon to that of the artery to be 1:1,2 and only recently have 8-mm IVL PTA balloons become available. Many iliofemoral vessels exceed this diameter, potentially impeding the transmission of sonic pressure waves to the target lesion. In this context, the “shock buddy” technique was developed to facilitate the preparation of eccentric calcified lesions.

Intravascular lithotripsy allows safe and effective calcium modification in coronary or peripheral arteries.3^,4 Acoustic pressure waves are generated from lithotripsy emitters incorporated onto the shaft of a balloon angioplasty catheter and transmitted through a fluid-filled balloon to the vessel wall, where they have an effect on multiplanar calcium fractures; this enhances transmural vessel compliance, mitigates fibroelastic recoil, and optimizes lumen area without requiring high-pressure balloon inflation with potential barotrauma.2 Although IVL effectively modifies concentric and eccentric calcified lesions,5 its effectiveness in modifying nodular calcium is poorly understood. Furthermore, the efficacy of IVL in arteries with diameters exceeding those of available IVL balloons is diminished. We present the first description of the shock buddy technique to facilitate the treatment of severe, eccentric, nodular calcium involving a large vessel.

Case description

An 80-year-old man with a history of coronary disease, coronary bypass grafting, abdominal aortic aneurysm with endovascular repair, dyslipidemia, and hypertension presented with Fontaine class IIb claudication symptoms.

Based on his clinical presentation and abnormal noninvasive vascular study results, peripheral angiography was performed via right radial access.

The left external iliac artery had nonobstructive disease, and the left common femoral artery (CFA) had eccentric, heavily calcified 80% stenosis (Figure1A). Long, 75% calcified stenosis was observed in the midleft superficial femoral artery (SFA), the left popliteal artery was patent, and there was 3-vessel runoff.

The radial sheath was exchanged for a 119-cm radial-to-peripheral sheath. A 6F pedal sheath was placed in the left posterior tibial (PT) using ultrasound guidance. A 0.014-inch guide wire was advanced through the tibial sheath and across the areas of stenosis.

Intravascular ultrasound demonstrated the reference diameters of the left CFA (Figure1B) and left SFA to be 8.98 and 7.04 mm, respectively. Intravascular ultrasound confirmed the presence of dense, eccentric calcification; a heavy burden of plaques; and severe stenoses in both the left CFA (Figure1C) and left SFA.

Intravascular lithotripsy was performed in the left SFA using the 8 × 60 mm Shockwave M5+ balloon (Shockwave Medical), which was delivered through the left PT sheath. After 150 pulses were delivered to the left SFA, the balloon was advanced into the left CFA. A 0.014-inch wire was advanced through the radial-to-peripheral sheath, and a 5 × 60 mm balloon was placed across the stenosis in the left CFA. The 5 × 60 mm balloon was inflated first (Figure1D), followed by inflation of the Shockwave M5+ balloon to 4 atm (Figure1E), and 150 pulses were delivered using the shock buddy technique.

Balloon angioplasties were then performed in the left CFA using a 9 × 40 mm balloon via right radial access and in the left SFA using a 7 × 150 mm Ranger drug-coated balloon (Boston Scientific) via left PT access. Final images of the left CFA and left SFA were obtained (Figure1F). All equipment was removed, and transradial bands were placed. The patient was discharged for home on the same day in a stable condition.

Summary

In the shock buddy technique, the IVL balloon catheter is paired with a “buddy balloon” catheter of similar or longer length having a combined balloon diameter (buddy balloon + IVL balloon) that slightly exceeds the ratio of the combined balloon diameter to artery diameter of 1:1. The balloons are centered with the objective to place the IVL balloon middle sonic pressure wave emitter over the site of heaviest calcification to maximize the impact of pressure waves.5 The buddy balloon is inflated first, forcing the IVL balloon closer to the eccentric lesion. Next, the IVL balloon is inflated, and acoustic pressure waves are delivered. Because the balloon wall and IVL emitters are positioned closer to the eccentric calcium by the inflation of the buddy balloon, the transmission of sonic pressure waves should be facilitated and effectiveness enhanced compared with the use of IVL balloon inflation alone. Enhanced effectiveness of IVL was suggested by an excellent angiographic result achieved in the present case despite the size of the target vessel and eccentricity of nodular calcium.

Peer review statement

References