Original Research ArticleA novel application of CT angiography to detect extracoronary vascular abnormalities in patients with spontaneous coronary artery dissection
Introduction
Spontaneous coronary artery dissection, often referred to as SCAD, is a relatively uncommon but increasingly recognized cause of myocardial infarction (MI), which predominantly afflicts young women without conventional risk factors for coronary heart disease. The etiology of SCAD is unclear, although an underlying systemic vasculopathy may be present in some patients.1, 2, 3 The pathology involves intramural hematoma and/or dissection, both of which may occlude blood flow and lead to ischemia. Clinical presentation is variable, with most patients experiencing signs and symptoms of MI, including chest pain, dyspnea, and/or arrhythmia.1 ST-elevation MI is the presenting diagnosis in 49% of patients.1 Although typically discovered during coronary angiography for evaluation of MI, postmortem autopsy studies have implicated SCAD as the underlying cause of sudden cardiac death in some instances, particularly in young women.4 Techniques such as intravascular ultrasound and optical coherence tomography are helpful in making the diagnosis when angiography is inconclusive.5, 6
Earlier publications have described SCAD associated with extracoronary vascular abnormalities, and a strong association between SCAD and fibromuscular dysplasia (FMD) has been proposed.1, 2, 3 Imaging plays an important role in diagnosis and management of extracoronary vascular abnormalities in patients with SCAD, and multiple modalities may be used, including CT angiography (CTA), magnetic resonance angiography (MRA), duplex Doppler ultrasound, and invasive angiography. Saw et al3 found FMD in the renal, iliac, and cerebrovascular territories on index angiography and subsequent CTA or MRA imaging in 86% of 50 patients with SCAD. In another series of 87 patients with SCAD who did not undergo routine imaging for extracoronary vascular abnormalities, Tweet et al1 described iliac artery FMD in half of patients (8/16), who underwent limited femoral angiography incidental to coronary angiography, and in 2 patients with carotid FMD and dissection by CTA. Toggweiler et al7 performed screening whole-body MRA in 12 patients and found renal artery abnormalities (FMD and spontaneous renal artery dissection) in 25% of patients with SCAD.7
As a referral center for patients with SCAD, we have observed that the number of patients who warrant imaging of extracoronary vessels to confirm suspected abnormalities identified during coronary angiography, evaluate signs or symptoms, evaluate risk, or identify conditions associated with SCAD has increased substantially. The impetus for development of a more comprehensive, convenient, safe, and standardized approach to care and imaging came out of our early experience of performing extracoronary imaging on a selective basis, followed by additional imaging as indicated. Before developing the SCAD CTA imaging protocol described herein, extracoronary vascular imaging was performed as clinically indicated for specific indications such as findings detected on physical examination (bruits, reduced volume pulses, aneurysmal dilation), symptoms (claudication or transient ischemic attacks), or personal or family history of potential high-risk conditions (aneurysm, sudden death, and genetic mutations). A significant proportion of these limited territory-imaging studies were abnormal, requiring additional imaging as recommended by either the interpreting radiologist or the clinician caring for the patient. This resulted in additional radiation and contrast exposure, and also patient inconvenience.
Given the known common distribution of extracoronary vascular abnormalities in the carotid, visceral, and iliac arteries in patients with SCAD, along with the lack of agreement of a single imaging evaluation for determination of the extent of extracoronary vascular abnormalities, we developed a dedicated CTA protocol of the neck, chest, abdomen, and pelvis using a single acquisition and injection of contrast material combined with radiation dose modulation techniques to use on patients with SCAD. We report our evaluation of the effectiveness of the protocol and initial radiographic findings.
Section snippets
Methods
We performed this retrospective study to determine the prevalence of extracoronary vascular abnormalities as detected by a dedicated CTA protocol in patients with previous SCAD. Approval to conduct this study was granted by the Mayo Foundation Institutional Review Board. All patients provided authorization for use of their records for research purposes, per Minnesota state statute. Baseline characteristics were abstracted from patient electronic medical records by a trained physician.
Technical success of the SCAD CTA protocol
Complete SCAD CTA protocol was successful performed in 37 (95%) of 39 patients. Two patients (5%) had incomplete imaging, with a nondiagnostic neck CTA because of technical errors during the CTA acquisitions. Both of these nondiagnostic studies occurred early in the study period and were due to size and placement of the region of interest for CTA scan triggering. Additional CT technologist training was provided which mitigated subsequent errors.
Patient baseline characteristics
Thirty-eight (97.4%) of the patients undergoing
Optimal method for detection of extracoronary vascular abnormalities in patients with SCAD
The high prevalence of extracoronary vascular abnormalities in more than two-thirds of our SCAD cohort (69%) and in prior reports (25%–86%)1, 3, 7 suggests that SCAD patients may benefit from additional arterial imaging to provide additional diagnostic and prognostic information. Our study demonstrated the effectiveness of a specific CTA imaging protocol to detect extracoronary vascular abnormalities in patients with SCAD. The criterion standard for detection of vascular abnormalities
Summary
Our application of CTA for a novel imaging protocol assesses vascular beds from the neck to the pelvis and is an effective imaging modality to detect extracoronary vascular abnormalities in patients with SCAD. A dedicated CTA protocol is convenient and avoids the invasiveness of catheter angiography. The extent of extracoronary vascular abnormalities detected in our cohort of patients imaged using our CTA protocol is higher and more extensive than prior series using whole-body MRA, possibly due
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Conflict of interest: The authors have no conflicts of interest or financial disclosures.