Optical Coherence Tomography in the Diagnosis and Treatment of Spontaneous Coronary Artery Dissection

ABSTRACT: The diagnosis of spontaneous coronary artery dissection (SCAD) is not always readily apparent on coronary angiography. Even if the diagnosis is suspected, angiography often conveys limited information about the underlying pathology, much of which is crucial for successful percutaneous coronary intervention (PCI). Due to the dissection flap and the resultant double lumen, SCAD poses unique challenges for PCI, specifically in securing wire access to the true lumen without propagation of the dissection. Optical coherence tomography (OCT) is a wire-based intravascular imaging modality with a high resolution of 10–20 µm. We present a case demonstrating the use of OCT in emergency PCI of SCAD, where OCT was integral not only to the diagnosis of SCAD, but also to successful PCI of the condition. It is a valuable aid to PCI in cases where there is uncertainty regarding the precise guidewire location, proving its use in the cardiac catheterization laboratory beyond that of merely a diagnostic tool. J INVASIVE CARDIOL 2010;22:559–560 ———————————————————— Spontaneous coronary artery dissection (SCAD) is an uncommon but important cause of acute myocardial infarction, typically presenting in females without classic coronary risk factors. The diagnosis and treatment of SCAD is often challenging. It can be difficult to diagnose on coronary angiography alone, and crucial information to aid successful percutaneous treatment is often lacking, such as the extent of the dissection, the location of the intimal flap, and most importantly, the distinction between the true and false lumens. The main challenge in emergent PCI is wire access and securing a position within the true lumen, while avoiding further propagation of the dissection or flow compromise. Optical coherence tomography (OCT) — a wire-based intravascular imaging modality with a high resolution of 10–20 µm — allows detailed visualization of the lumen and vessel wall pathology, and in this case of SCAD, was instrumental in the definitive diagnosis of the condition and the success of the PCI procedure.
Case Description. A 51-year-old female with a history of hypertension and smoking presented with sudden-onset dull chest pain at rest. Her blood pressure was 160/90, her heart rate was 90, but examination was otherwise unremarkable. The electrocardiogram showed deep T-wave inversion in precordial leads V2–V5 without ST elevation. Her cardiac troponin I was elevated. Coronary angiography revealed TIMI (thrombolysis in myocardial infarction) grade 1 flow in the mid-to-distal left anterior descending artery (LAD), with a subtle step-down in lumen caliber compared to a more proximal segment, leading to suspicion of a spontaneous coronary dissection (Figure A). Other vessels were without significant obstructive disease. Wire passage in the LAD was difficult due to uncertainty of the true intraluminal position of the guidewire. OCT imaging (Lightlab Imaging, Inc.) confirmed the presence of a dissection flap and a large intramural hematoma compressing the true lumen (Figure B). Furthermore, it guided coronary guidewire placement by demonstrating its correct intraluminal position (Figure C). OCT also enabled identification of the proximal extent of the dissection. Having established true luminal position of the guidewire and the extent of the dissection, the vessel was successfully stented in a proximal-to-distal fashion to avoid proximal propagation of the dissection flap. TIMI 3 flow was established (Figure D). After intervention, OCT demonstrated complete sealing along the length of the flap, compression of the intramural hematoma, good stent expansion and good apposition of stent struts (Figure E).

Discussion

OCT imaging of SCAD has only recently been described.^1–2 However, there are few reports detailing its use in guiding PCI of this condition. This case demonstrates not only the diagnostic utility of OCT in identifying the underlying pathology, but also its therapeutic utility in assisting PCI and in demonstrating an optimum final stented result. Traditional intraluminal techniques such as intravascular ultrasound (IVUS) have similar potential, however the lower resolution of IVUS makes it more difficult to identify thin intimal flaps, and the diameter of current ultrasound probe catheters compared to the OCT wire may pose access difficulties, potentially aggravate the dissection and may necessitate larger guide-catheter sizes for adequate simultaneous intraluminal and angiographic imaging. OCT should be considered as an adjunctive imaging modality to ensure true luminal placement of a coronary guidewire in cases of coronary dissection where there is uncertainty as to the precise location of the guidewire. It is a valuable addition to the armamentarium of the cardiac catheterization laboratory, where its use extends beyond that of merely a diagnostic tool.

References

1. Alfonso F, Canales E, Aleong G. Spontaneous coronary artery dissection: Diagnosis by optical coherence tomography. Eur Heart J 2009;30:385. 2. Ishibashi K, Kitabata H, Akasaka T. Intracoronary optical coherence tomography assessment of spontaneous coronary artery dissection. Heart 2009;95:818.

———————————————————— From John Radcliffe Hospital, Oxford, United Kingdom. The authors report no financial relationships or conflicts of interest regarding the content herein. Manuscript submitted June 16, 2010, provisional acceptance given July 13, 2010, final version accepted August 18, 2010. Address for correspondence: Chris C. Lim, MBBS, John Radcliffe Hospital, Department of Cardiology Level 2, Headley Way, Headington, Oxford, OX3 9DU, United Kingdom. E-mail: chingsung@yahoo.com