To the Editor,
Although spontaneous coronary artery dissection (SCAD) is well known clinically, the
diagnosis of SCAD is occasionally difficult using only conventional coronary angiography
(CAG) without additional imaging tools such as intravascular ultrasound (IVUS) or
cardiac computed tomography (CCT).
A 55-year-old woman presented to the emergency department with resting anterior chest
pain after emotional stress. She had a 7-year history of hypertension. Electrocardiography
and transthoracic echocardiography results were unremarkable, and CCT was performed
to evaluate the cause of the chest pain. This revealed severe luminal narrowing in
the middle part of the left anterior descending coronary artery (LAD) (Fig. 1A). CAG
showed 60% stenosis of the middle to distal LAD (Fig. 1B). IVUS to evaluate the lesion
revealed coronary artery dissection and a hematoma in the middle LAD, from the 2nd
diagonal to the 4th septal branch (Fig. 1C and 1D). As there was no coronary flow
limitation and the symptoms stabilized, the patient was managed medically without
additional procedures. The 3-month follow-up CCT showed resolution of the compressed
luminal narrowing (Fig. 1E).
A 70-year-old man presented to the emergency department with sudden-onset severe resting
chest pain for 30 minutes. Electrocardiography showed ST segment elevation in leads
I and aVL. Emergency CAG revealed mild stenosis in the proximal LAD and left circumflex
coronary artery (LCX) (Fig. 2A). The ST-segment elevation resolved spontaneously.
IVUS revealed coronary artery dissection and a hematoma from the left main (LM) to
the proximal LAD and proximal LCX (Fig. 2B and 2C). The patient was treated medically
due to stabilized symptom. One week later, CCT revealed a minimal residual hematoma
in the left main bifurcation area (Fig. 2D).
SCAD is a rare cause of acute coronary syndrome. The clinical presentation can range
from angina to ST segment elevation myocardial infarction, ventricular fibrillation,
and sudden death [1]. SCAD is a hematoma or thrombus in a false lumen, usually in
the outer third layer of the coronary artery wall; this compresses the true lumen
and leads to coronary ischemia [2]. SCAD should be considered in patients, especially
women in the peripartum period and those using oral contraceptives, who complain of
chest pain and have atherosclerosis or cardiovascular risk factors, or vascular disease.
Other risk factors are connective tissue disorders, cocaine use, exercise, and medications
such as 5-fluorouracil, cyclosporine, and fenfluramine.
The etiology and pathophysiology of SCAD are poorly understood [3]. The optimal treatment
strategy for SCAD remains undetermined, and treatment varies according to the type
and severity of presentation [4]. Treatment options include percutaneous coronary
intervention, coronary artery bypass grafting, and conservative medical management
such as a β-blocker to reduce the vascular shear forces and antiplatelet therapy to
reduce thrombus formation. The choice is based on the patient's hemodynamic status,
coronary artery flow, dissection location, number of involved vessels, and other clinical
situations.
The diagnosis of SCAD is made principally based on the appearance of a radiolucent
intimal flap or slow clearance of contrast from the false lumen on CAG. When an intimal
tear is absent, the medial hematoma can appear as a narrowed or occluded vessel on
CAG. The true incidence of SCAD can be underestimated when diagnosed using CAG alone
[5]. Imaging tools such as CCT and IVUS can support the diagnosis of SCAD. IVUS can
distinguish atherosclerotic stenosis and spasm from hematoma or dissection, and can
identify the length of the hematoma or location of the dissection. In addition, IVUS
can be used during percutaneous coronary intervention for SCAD. IVUS can facilitate
the placement of the angioplasty guidewire within the true lumen; assist in determining
stent size, length, and optimal deployment; and ensure obliteration of the false lumen
and flow within it, or adequate compression of the intramural hematoma [5]. CCT is
an ideal noninvasive imaging technique for delineating intramural hematomas and assessing
luminal narrowing. Furthermore, follow-up of SCAD without invasive diagnostic CAG
is an important benefit of CCT, as in our cases. To make the diagnosis, a clinical
suspicion of SCAD is important when it is difficult to explain the pathogenesis of
a stenotic lesion, especially in young patients with no conventional risk factors.
In conclusion, SCAD is an unusual cause of acute coronary syndrome and is difficult
to diagnose. Therefore, a clinical suspicion of SCAD and the use of additional imaging
tools such as IVUS and CCT are vital. In the presented cases, SCAD was diagnosed successfully
using IVUS and followed up using CCT.