Application of Optical Coherence Tomography in the Treatment of Coronary Bifurcation Lesions

ABSTRACT: Optical coherence tomography (OCT) is a novel intravascular imaging modality with excellent resolution. We report the application of OCT in 3 coronary bifurcation interventions, in which OCT allowed optimization of the final procedural result, by detecting a dissection, intracoronary thrombus and by confirming complete ostial coverage by a stent.

J INVASIVE CARDIOL 2012;24(2):E39-E42

Key words: coronary bifurcation, optical coherence tomography, percutaneous coronary intervention

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Percutaneous coronary interventions (PCI) of coronary bifurcation lesions can be challenging, especially in cases with large side branches and in cases in which complex stenting techniques are utilized. Optical coherence tomography (OCT) is a novel intravascular imaging technique with excellent resolution (15-20 µm compared to 150-200 µm for intravascular ultrasonography).¹ We describe 3 bifurcation PCI cases in which OCT was used to optimize the procedural result.

Case Report 1. A 59-year-old man with no prior cardiac history presented with rest angina. Diagnostic coronary angiography revealed 2-vessel coronary artery disease (CAD) with a complex bifurcation lesion of the middle left anterior descending artery (LAD) at the origin of a large diagonal branch (Figure 1A) with diffuse disease in the circumflex artery. The patient elected to proceed with LAD PCI.

The left main coronary artery was engaged with an 8 Fr XB 3.5 guide catheter and anticoagulation was achieved with unfractionated heparin. Guidewires were placed in the LAD and the first diagonal branch, followed by kissing balloon inflation (Figure 1B). The distal LAD lesion was subsequently stented with a 2.5 x 23 mm everolimus eluting stent (Figure 1C). Post-stent angiography revealed a filling defect within the first diagonal artery ostium (arrow, Figure 1D) that persisted in spite of aspiration using a 6 Fr Export catheter (Medtronic Vascular) (Figure 1E). Activated clotting time was 276 seconds. A 3.0 x 23 mm stent was deployed from the mid LAD into the diagonal branch (arrows, Figure 1F). The LAD was rewired through the stent struts and repeat kissing balloon inflation was performed with two 2.75 x 15 mm balloons (Figure 1G). A hazy area appeared in the LAD distal to the stent (Figure 1H) that was shown to represent a large dissection by OCT (Figure 1I and 1J). After implantation of an additional stent in the LAD and repeat kissing balloon inflation an excellent angiographic result was obtained (Figure 1K). OCT demonstrated near complete obliteration of the dissection plane (Figure 1L). The patient had an uneventful recovery.

Case Report 2. A 74-year-old man with a history of hypertension and hyperlipidemia presented with anterior ST-segment elevation acute myocardial infarction (STEMI). Emergency diagnostic angiography revealed thrombotic ostial LAD occlusion (Figure 2A).

The left main coronary artery was engaged with a 7 Fr XB 3.5 guide catheter and anticoagulation was achieved with unfractionated heparin and tirofiban. Due to hypotension, an intra-aortic balloon pump was placed and dopamine infusion was initiated. The distal LAD was wired with a Runthrough wire (Terumo) and the lesion was predilated with a 2.0 x 20 mm balloon. Aspiration thrombectomy retrieved a large amount of thrombus restoring TIMI 3 distal flow. The proximal and ostial LAD were stented using everolimus-eluting stents, that were postdilated at 24 atm, but a filling defect persisted in the LAD ostium protruding into the left main coronary artery (Figure 2B). OCT imaging revealed that the LAD ostium was covered by a stent, and that a thrombus was present in the proximal LAD protruding into the left main coronary artery (Figure 2C). Activated clotting time was 261 seconds. Multiple attempts for aspiration thrombectomy were performed resulting in red thrombus removal. Repeat OCT imaging showed reduction of the ostial LAD thrombus (Figure 2D). The proximal portion of the ostial LAD stent was further postdilated with a 3.25 x 12 mm non-compliant balloon with an excellent final angiographic result. The patient’s post procedural course was complicated by a hospital-acquired pneumonia but he had complete recovery and no recurrent chest pain.

Case Report 3. A 77-year-old man with a history of peripheral vascular disease, diabetes, hypertension, and hyperlipidemia, presented with a 5-month history of exertional angina. A nuclear stress test revealed a large reversible defect in the territory of the circumflex artery. Diagnostic coronary angiography revealed a chronic total occlusion of the ramus (Figure 3A) without obstructive coronary disease in the other vessels.

The left main coronary artery was engaged with an 8 Fr XB 3.5 guide catheter and anticoagulation was achieved with unfractionated heparin. The chronic total occlusion was crossed easily with a Fielder XT wire (Abbott Vascular). Predilation was performed with 1.5 mm and 2.0 mm balloons, followed by implantation of two 2.25 x 23 mm and one 2.25 x 18 mm sirolimus-eluting stents, with an excellent angiographic result (Figure 3B). Post-PCI OCT demonstrated adequate coverage of the ramus ostium by stents (Figure 3C). There were no procedural complications and the patient has remained angina-free since the procedure.

Discussion. We describe 3 coronary bifurcation PCI cases, in which OCT helped guide the procedure by detecting a dissection (case 1), thrombus (case 2), and by confirming ostial vessel coverage (case 3).

Coronary bifurcation lesions represent about 15% to 20% of all PCIs² and are challenging to treat, in part because the optimal management strategy has yet to be ascertained. Stenting of the main branch with provisional stenting of the side branch is currently the preferred strategy,³ although loss of a large side branch may have grave clinical sequelae.

Coronary artery dissections can occur spontaneously or, more commonly, as complications of PCI. Although conventional angiography can provide information about lumen compromise, it only allows indirect visualization of the dissection flap and intravascular ultrasonography may not have high-enough resolution to delineate the dissection. OCT allows easy identification of the presence and extent of a coronary dissection, the total length of an affected coronary segment, and the origin of side branches. Large dissections, as in case 1, are best treated with additional stent implantation. OCT post-stenting can confirm sealing of the entry point, full apposition of the stent struts, and enable the visualization of the residual non-communicating hematoma.⁴ Although using a provisional stenting approach is appropriate for most bifurcation lesions, a significant dissection is usually treated with additional stent implantation, as in case 1. The choice of first stenting the side branch (diagonal) instead of the main branch (LAD) was based on the large caliber of the diagonal branch and the presence of thrombus within the diagonal ostium, which would place the patient at high risk of diagonal occlusion if LAD stenting was performed first.

OCT can identify an intracoronary thrombus with high accuracy as a mass protruding into the vessel lumen, discontinuous from the surface of the vessel wall (Figure 2C).¹ Both white and red thrombi are visualized as signal-rich structures without back-scattering.⁵ In ACS patients, OCT detection of a thrombus can help identify the culprit lesion and the site of plaque rupture. OCT has also been used to study the acute effects of manual or rheolytic thrombus aspiration.⁶ In our second case OCT confirmed that the intracoronary filling defect was due to a thrombus and not dissection or stent underexpansion. OCT imaging also confirmed that the thrombus was reduced after additional thrombectomy was performed.

Ostial lesions are commonly defined as stenoses within 5 mm of a vessel’s origin. PCI of ostial lesions are associated with high rates of repeat target vessel revascularization and adverse cardiac events despite the use of DES.⁷ Adequate ostial coverage with a stent (by allowing the stent to prolapse approximately 1 mm into the aorta) may decrease restenosis rates. OCT is not only able to confirm adequate ostial coverage (as shown in case 3) but also to ensure that the stent struts are well expanded and apposed, which is sometimes challenging in calcified and fibrotic ostial lesions.

Few studies have examined the utility of OCT in coronary bifurcation PCI. Tyczynski et al used OCT to assess stent strut apposition in 31 patients undergoing bifurcation PCI with either main branch stenting (n=17) or with the culotte technique (n=14).¹⁰ There was no difference in the overall incidence of stent strut malapposition in the 2 groups, but as expected, malapposition was significantly more frequent at the lumen half located on the same side as the side branch.¹⁰ Kyono et al reported high rates of uncovered stent struts at the side branch ostium when paclitaxel-eluting stents were used compared to the sirolimus- and zotarolimus-eluting stents at 6 months post-implantation.¹¹ OCT can also assist with assessment of the side branch lesion severity and plaque composition (calcific, lipid-laden, fibrotic, or thrombus-containing as in case 3), in order to predict the risk of side branch closure and the need for an upfront 2-stent bifurcation technique.¹² Another study reported incomplete stent strut apposition in 60% of lesions, mostly in the main vessel proximal to the carina, which might explain the higher prevalence of restenosis in this area.¹³

Using OCT to guide bifurcation PCI (or any complex PCI) has limitations. It requires administration of contrast to completely displace blood allowing stent and vessel wall visualization. It also has limited penetration, although this may be of lesser importance in guiding bifurcation PCI, in which lumen optimization is the major goal.

In summary, our cases demonstrate specific examples of how OCT imaging can assist optimization of coronary bifurcation PCI.

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From the VA North Texas Healthcare System and University of Texas Southwestern Medical Center at Dallas, Dallas, Texas.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Banerjee receives speaker honoraria from St. Jude Medical, Medtronic, Sanofi Aventis, Cordis, and Boehringer Ingelheim and research support from Boston Scientific and The Medicines Company. Dr. Brilakis receives a speaker honoraria from St Jude Medical and Terumo; research support from Abbott Vascular; salary support from Medtronic (spouse).
Manuscript submitted July 29, 2011, provisional acceptance given August 15, 2011, final manuscript accepted August 29, 2011.
Address for correspondence: Emmanouil S. Brilakis, MD, PhD, VA North Texas Health Care System, The University of Texas Southwestern Medical Center at Dallas, Division of Cardiology (111A), 4500 S. Lancaster Rd, Dallas, TX, 75216, USA. Email: esbrilakis@yahoo.com