Pitfalls During PCI in Acute Coronary Syndrome: Optical Coherence Tomography (OCT) Assessment Can Help Identify the Target

Case report

A 69-year-old man presented with a 30-minute history of chest pain due to an inferior ST-elevation myocardial infarction (STEMI). The intake of oral sublingual nitrates and oral antiplatelet therapy in the emergency department was associated with ST segment and pain resolution. He was taken to the cardiac catheterization laboratory for urgent coronary evaluation. Coronary angiography demonstrated a patent right coronary artery without significant stenosis and a TIMI flow grade 2. During the injection of the left coronary artery, the patient became symptomatic again, with typical pain and inferior ST-segment elevation (Figure 1). Right anterior oblique (RAO) projection showed the presence of a collateral circulation to the right coronary artery. A second set of images for the right coronary artery showed a filling defect, consistent with a possible thrombus, in the distal segment, with TIMI flow grade 2 (Figure 2). Unsuccessful manual thrombectomy was performed (Export, Medtronic). An abciximab bolus had no effect. Optical coherence tomography (OCT) imaging revealed the signal absence for a distance of about 12 mm, corresponding to the region of contrast attenuation on the angiogram. These images were interpreted as a consequence of an intra-plaque or subintimal position of the wire. A second guide wire was placed in the right coronary artery. The new introduction of a manual aspiration system at this point revealed the presence of a large, soft plaque determining a critical stenosis (Figure 3). The procedure was completed with the implantation of a 4.0 x 25 mm coronary stent (Avantgarde, CID), with resulting symptom and ST-segment elevation resolution. An OCT assessment confirmed adequate stent expansion and apposition. 

Discussion

New intracoronary diagnostic tools provide comprehensive, tomographic, high-resolution insights on vessel wall pathology, allowing for the precise evaluation of a culprit lesion.^1,2 OCT is a recently developed intravascular imaging modality using near-infrared light to create images. Compared with various other coronary imaging modalities, the greatest advantage of OCT is its high resolution, approximately 10 times higher than that of intravascular ultrasound (IVUS).³ Because OCT uses light to create the image, it has limited tissue penetration (2 to 3 mm) and is attenuated by blood, thus requiring the use of occlusive saline flushes to obtain good-quality images.^3,4 Second-generation OCT technology, called frequency-domain OCT (FD-OCT), eliminates this limitation by imaging at higher frame rates, with a deeper penetration depth and greater scan area. With a short, non-occlusive contrast medium flush and rapid spiral pullback, FD-OCT permits the operator to obtain longer coronary artery segment images. In addition, FD-OCT facilitates tissue characterization, identification of vulnerable plaque, and allows for a more precise and easier assessment of culprit lesion morphology.³ Currently, many patients with negative angiographic findings are readily diagnosed with these tools if the level of clinical suspicion is adequate. The present case clearly illustrates OCT’s potential complementary value in selected patients. FD-OCT provides uniquely high-resolution images of the intimomedial “flap” and is able to accurately identify the “entry door.”⁵ 

This article received double-blind peer review from members of the Cath Lab Digest editorial board.

The authors can be contacted via Dr. Marcello Ravani at ravani@ftgm.it.

References

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