1

Introduction

A third of patients undergoing percutaneous coronary intervention (PCI) are diagnosed with chronic total occlusions (CTO), however, only 8–15% of all attempted PCIs in USA are Coronary CTOs . CTO revascularization remains a challenging technique, high atherosclerotic plaque burden, heavily calcified fibrous cap, difficulty in crossing the lesion, complexity of the procedure and the potential for complications are the major reasons many CTOs have been regarded as generally unsuitable for PCI. Total occlusion was the most common (68%) angiographic exclusion criteria in the BARI study leading to bypass surgery . CTO plaque is composed of lipids, smooth muscle cells, extracellular matrix (collagens), and calcium . Proximal cap (PC) crossing is a difficult step during CTO revascularization, PC varies in morphology, composition (fatty, fibrous, calcified) and presence or absence of micro-channels (MC) . These variations can affect outcomes of CTO interventions; however, major barrier to success is the so called blunt stump. Intravascular ultrasound (IVUS) has been used for characterization of PC, however, OCT is not. In this case we used OCT to visualize PC and MC of a flush total occlusion. Since forward looking catheters are not yet available, IVUS and OCT are limited to lateral imaging. To overcome this limitation we identified a side branch lesion with an occlusion flush with the main vessel. We performed an OCT run in the main vessel, to capture an image of side branch’s ostial PC.

2

Case description

A 61 y/o male with diabetes mellitus-II, hypertension, hyperlipidemia and coronary artery disease status post myocardial infarction, with stents to left anterior descending (LAD), presented with unstable angina. 5Fr JR4 and JL4 catheters were used for diagnostic imaging. Angiography showed left dominance with normal left main (LM), patent stents in proximal and mid LAD, with lesions in left posterolateral-1, left posterior descending and luminal irregularities in left circumflex (Cx). Three vessels, right coronary (non-dominant), 2nd diagonal and ostial obtuse marginal-1 (OM-1) were occluded. Distal OM-1, filled via left to left collaterals and based on large size of the distal vessel, was our target. An 8 F EBU guiding catheter was used to intubate left coronary system. Hi-Torque Balance Middleweight Universal (BMW) guidewire was placed in Cx artery, both IVUS and OCT runs were performed from proximal-Cx to LM for visualizing the PC. OCT images showed three important details which helped us in this case; 1) PC was predominantly fibrous plaque. 2) A micro channel in PC which could be potential target for wire crossing. 3) Relative position of occluded OM to a small branch ostium ( Fig. 2 ), this branch was also identified on angiogram ( Fig. 1 ) and so was used as a landmark to guide the wire.

Panel 1.1 & 1.2 show baseline diagnostic angiography, with 2 views of proximal left circumflex artery (hollow arrow) and proximal cap of obtuse marginal 1(solid thick arrow). Panel 1.3 shows a magnified view of panel 1.2 where the small side branch is clearly visible (thin Arrow).

Baseline OCT Images. Panel 2.1 shows a longitudinal view of proximal left circumflex artery and proximal cap of obtuse marginal’s total occlusion. The details of proximal cap morphology are visible on cross-sectional views (panel 2.2 & 2.3). The relative position of the occlusion to the small side branch (thin arrow) can be clearly appreciated (panel 2.1 & 2.4). Occluded OM’s micro-channel (panel 2.5).

Post intervention images, show reinstated flow in Obtuse marginal 1 (bold arrow in 3.1 & 3.2), left circumflex has also maintained good blood flow. The small side branch is no longer visible at the origin of OM-1 probably because it was compressed during balloon and stent inflations. Fig. 3 .3 is post stent deployment OM1 IVUS image showing the final area and diameter of this vessel.

Based on this information Miracle 3 wire was selected for first attempt at crossing this lesion. Position of the small branch helped us guide the wire directly towards PC and into the micro channel. Miracle 3 successfully crossed the occlusion and then was exchanged with a universal BMW. Balloon angioplasty was performed, using a Trek 3.00 × 20 mm balloon with 2 inflations and maximum pressure of 16 atmospheres(atm). IVUS was performed in OM-1 to check for vessel condition after balloon angioplasty. A Resolute Rx 3.5 × 22 mm drug-eluting stent was placed across the lesion and deployed with one inflation at pressure of 16 atm. IVUS was performed again to check for optimal stent deployment. Guidewire was removed and post intervention angiographic images were taken right before removing the catheters and access sheath. Wire crossing time was less than 3 min and time from wire introduction to stent deployment was less than 14 min. Radiation dose, fluoroscopy time and contrast volume for wire crossing were approximately 68 mGy, 30 s, and 6.5 ml, and from the time of wire introduction to stent deployment at the occlusion site were approximately 270 mGy, 150 s, and 31 ml, respectively.