Side Branch Occlusion After Intravascular Lithotripsy: A Case Report

Intravascular lithotripsy (IVL) delivers acoustic shockwaves to fracture coronary calcifications and optimize stent expansion, yet side branch (SB) occlusion after IVL is rarely documented. We report the case of an 80-year-old man with prior stents in the distal right coronary and proximal left circumflex arteries who underwent elective percutaneous coronary intervention for 75% proximal left anterior descending artery (LAD) stenosis supplying four diagonal branches: the first (D1), second (D2), third (D3), and fourth (D4) diagonal branches. The instantaneous wave-free ratio was 0.82 and the fractional flow reserve was 0.77, both indicating ischemia. Optical coherence tomography (OCT) demonstrated severe, long calcification (calcification score 4; maximum arc 330°; thickness 12.1 mm; length 38.2 mm; minimum lumen area 1.46 mm²), and IVL was selected over rotational atherectomy or scoring balloon angioplasty due to high calcification score and wire bias considerations. Eight cycles of IVL with a 2.5/12 mm balloon were applied from the D4 bifurcation to proximal LAD, followed by eight cycles with a 3.0/12 mm balloon, increasing the minimum lumen area to 3.31 mm². After pre-dilation with a 2.5/13 mm scoring balloon distally and a 3.0/15 mm non-compliant balloon proximally, a 2.5/38 mm everolimus-eluting stent was implanted, and the proximal segment was post-dilated with a 3.0/15 mm non-compliant balloon. Immediately after post-dilation, the patient developed chest pain and ST-segment elevation; angiography showed new occlusion of the third diagonal branch (D3, thrombolysis in myocardial infarction (TIMI) 0) and flow reduction in the first diagonal branch (D1) from TIMI 3 to TIMI 1, while all other branches maintained TIMI 3 flow. Wire recrossing and kissing balloon inflation (1.5/10 mm semi-compliant in D3, 3.0/15 mm non-compliant in the main vessel) restored TIMI 3 flow in D3 and relieved symptoms, whereas D1 remained TIMI 1 but asymptomatic. No protective wiring had been performed initially as the affected SB was <1.5 mm, but the subsequent ischemic event indicated it should be considered a significant branch. Angiography before and after IVL showed no change suggestive of SB risk, whereas OCT performed immediately after IVL revealed new protrusion of fractured calcifications into the D1 and D3 ostia, which was considered the cause of the subsequent side branch occlusion. IVL-related SB occlusion is an extremely rare complication in the literature, but meticulous pre-procedural OCT assessment and consideration of protective wiring in high-risk bifurcation lesions may help predict and prevent this event.