Key Points

• Although rare, SCAD can occur in men and can present in the setting of arteriopathies and emotional triggers.

• Early diagnosis, conservative management, and avoidance of percutaneous intervention lead to meaningful recovery and favorable outcomes in patients presenting with SCAD.

• Patients who present with SCAD, regardless of their sex, should undergo further workup to evaluate for underlying arteriopathies.

Abbreviations and Acronyms

ACS

acute coronary syndrome

FMD

fibromuscular dysplasia

MI

myocardial infarction

SCAD

spontaneous coronary artery dissection

Case Report

Technique

The patient's laboratory findings were clinically significant for high-sensitivity troponin: 12 ng/L at presentation and 55 ng/L at 1 hour (>51 ng/L signifies a high risk for myocardial injury). Complete blood cell count and kidney function panel results were within normal limits. Chest radiographic findings were clinically significant for low lung volumes and for patchy opacities suggestive of atelectasis in the setting of an elevated hemidiaphragm. Point-of-care cardiac ultrasound imaging showed anterior apical wall motion abnormalities. The interpretation of an electrocardiogram in the emergency department showed ST-segment elevations in the anterior leads consistent with an anterolateral MI. The patient's initial presentation was to a facility that did not perform percutaneous coronary interventions, so thrombolysis was administered along with a loading dose of clopidogrel 300 mg. He was transferred to a facility capable of percutaneous coronary intervention, where he underwent urgent angiography. This procedure demonstrated several radiolucent lumens in the mid–left anterior descending coronary artery, with moderate stenosis likely from intramural hematoma (Fig. 1). Given that the vessel had grade 3 thrombolysis in MI flow, the intervention was deferred, and the patient was treated conservatively. He was started on aspirin 81 mg/d, atorvastatin 80 mg/d, clopidogrel 75 mg/d, and metoprolol 50 mg/d. Initiation of an angiotensin-converting enzyme inhibitor and an angiotensin II receptor blocker was deferred given his borderline low blood pressure readings on presentation.

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Outcome

The patient was discharged on his third hospital day, and his left ventricular function was normal at the time of discharge. Given his index SCAD event, the patient underwent brain-to-pelvis imaging to identify possible underlying arteriopathies. A computed tomographic angiogram of the head and neck was clinically significant for fibromuscular dysplasia (FMD) involving the mid–cervical right internal carotid artery (Fig. 2) as well as for focal involvement of the left vertebral artery's V3 segment at the C2 level (Fig. 3). Computed tomograms of the abdomen and pelvis revealed FMD of the bilateral renal arteries (Fig. 4). The patient was evaluated by a neurologist, who recommended avoiding activities that would result in neck manipulation or prolonged hyperextension or flexion.

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Discussion

Spontaneous coronary artery dissection has previously been thought to be a rare diagnosis, but with advances in intracoronary imaging, SCAD has been increasingly identified as the cause for ACS in a small number of patients overall, though it may account for up to 30%¹ of ACS cases in women younger than 60 years of age.² Of note, 43% of all pregnancy-related MIs are secondary to SCAD.³

Spontaneous coronary artery dissection in men continues to be a rare finding. Historically it has been reported that as many as 81% to 92% of all SCAD cases occur in female patients.⁴ Spontaneous coronary artery dissection can affect all coronary arteries; however, the left anterior descending coronary artery appears to be affected most, and multivessel SCAD occurs in only 9% to 23% of cases.⁵ It is hypothesized that in SCAD, an intramural hematoma spontaneously forms in the outer one-third of the tunica media.^6,7 Though the condition's pathophysiology is currently not fully understood, 2 leading theories describe possible mechanisms of SCAD development. One theory suggests that a disruption in the vessel wall, an intimal tear, is the primary mechanism that allows an intramural hematoma to form. The second theory proposes that the initiating event leading to an intramural hematoma is a hemorrhage from the vasa vasorum within the vessel wall.^5,8 Although further research is required to identify the true cause of these spontaneous events, it is evident that the formation of an intramural hematoma at any level may lead to decreased blood flow, ischemia, and clinical symptoms.

Several conditions have been associated with SCAD and are thought to contribute to the disease process in select cases. Systemic arteriopathies—in particular, FMD—have most commonly been associated with the formation of SCAD. Fibromuscular dysplasia affects medium-sized arteries and causes fibrous tissue to build up, leading to luminal narrowing. In addition to narrowing, patients may develop small arterial aneurysms, tortuosities, or dissections. Arterial “buildup” in FMD can be distinguished from atherosclerotic plaque by its more distal development along the vessel.⁹ Several case reports have discussed the likely correlation between SCAD and FMD. The phosphatase and actin regulator 1 (PHACTR1) gene, a pleiotropic locus found in several vasculopathies, has been closely associated with FMD. This locus codes for a phosphatase and actin–binding protein that allows for cellular mobility and organization, and its disruption may lead to disorganized vascular formation. Of note, this same pleiotropism has been associated with SCAD, coronary artery disease, and MI.¹⁰

Angiographically, 3 variations of SCAD have been identified. Type 1 SCAD is seen in approximately 25% of patients and is defined by typical contrast dye staining of the arterial wall along with multiple visible radiolucent lumens. As many as 70% of patients have been found to have type 2 SCAD, in which diffuse stenosis causes coronary arterial narrowing. Because of its wide range of presentations, type 2 SCAD is further differentiated into type 2A and type 2B. The difference between the 2 subtypes is that a patient with type 2A SCAD continues to have normal coronary arterial segments distal to the occlusion, while a patient with type 2B typically does not. Finally, type 3 SCAD is most similar to atherosclerotic lesions and is therefore difficult to recognize. This variation of the condition often requires intracoronary imaging to reconcile its symptoms with its diagnosis. The absence of atherosclerotic disease in unaffected coronary arteries can be a hint at type 3 SCAD.^11,12

Any patient presenting with signs and symptoms of ACS should be treated according to evidence-based guidelines. Once SCAD is diagnosed in a patient, however, treatment management slightly differs from that of atherosclerotic coronary artery disease. Though the mainstay therapy of atherosclerotic disease involves revascularization through percutaneous intervention, SCAD is primarily managed medically.¹³ Findings suggest that a majority of dissected vessels heal completely over time. Revascularization has also been associated with higher risks of failure and poor outcomes because of arterial instability and friability secondary to the dissection. Mechanically speaking, an arterial dissection poses several risks when trying to place or maintain a stent: The guidewire can be placed in a false lumen, causing worsening of the dissection. In cases of proximal left anterior descending coronary artery or left main SCAD, this error can be catastrophic. Balloon dilatation may dislodge or extend the intramural hematoma and cause obstruction proximally or distally to the dilated segment. Eventual healing of the intramural hematoma may lead to late-acquired malposition of a stent^3,14; however, high-risk features, including left main coronary artery dissections, ongoing ischemia, hemodynamic instability, low-grade (0-1) thrombolysis in MI flow, and refractory arrhythmias, are treated with revascularization procedures because of their high mortality rates without intervention.¹³

Medical therapy begins with the use of antiplatelet therapies, per ACS guidelines.¹⁵ Anticoagulation is generally avoided because it poses a theoretical risk of worsening intramural hematoma.¹⁶ β-Blockers represent a major component of medical therapy because they help control heart rate, decrease sheer stress, reduce blood pressure, and clinically are associated with a reduced risk of recurrent SCAD.

The current case highlights the importance of maintaining a high index of suspicion for SCAD in patients presenting with signs and symptoms of ACS, even in the absence of classic risk factors, as well as awareness that the presentation may happen in men. The likely trigger in the current patient was emotional stress brought on by his mother's enrollment in hospice care. This case supports the idea that early diagnosis and conservative management have positive outcomes in SCAD. This patient's diagnosis of FMD also suggests that SCAD can be a first presenting sign in this patient population. All individuals found to have SCAD should undergo further testing to identify comorbidities that may contribute to or predispose them to the development of vascular injury. Further studies are required to better understand the pathophysiology of SCAD and to propose more targeted therapies.