Figure 2: (a) We failed to engage the coronary trunk by using a 6-Fr AL-1 guiding catheter. We then engaged the coronary trunk by using a 5-Fr diagnostic catheter, and a 0.014-inch guide wire was advanced across the LAD lesion. (b) Removing the 5-Fr diagnostic catheter, leaving only the guide wire. (c) A 1.5 mm semicompliance balloon in the lead, along with a mother-child system, including a 6-Fr AL-1 guide catheter and a GuideLiner catheter, was advanced close to the orifice of the coronary trunk. (d) After anchoring it with a 1.5 mm balloon, the GuideLiner catheter was selectively introduced into the left coronary artery. In order to avoid coronary dissection, the contrast medium was gently introduced via manual injection. (e) Angiogram after dilatation with a 2.5 mm semicompliance balloon. Intravascular ultrasound (IVUS) images at the culprit lesion (i) and at the coronary ostium (ii). (f) Deploying a bioresorbable polymer sirolimus-eluting stent (Ultimaster® ). (g) Additional dilatation with a noncompliance balloon . (h) Final angiogram showing adequate dilatation of the culprit lesion.