Spontaneous Coronary Artery Dissection: A Case Series Highlighting Diagnostic Challenges and the Potential for Underestimating the Incidence of This Presumed Rare Disorder

ABSTRACT: Spontaneous coronary artery dissection (SCAD) is an uncommon condition with a variety of clinical presentations. Our knowledge base for SCAD is limited and derives from case reports and retrospective reviews. Several aspects of this disorder, including its rarity, heterogeneity of its presentation, and lack of identification during initial assessment, propose obstacles to reliably secure an accurate diagnosis and consequently we believe that the incidence of this disorder is likely underestimated in the literature. We present a case series of 5 patients with SCAD who exhibit features of this disorder that pose diagnostic challenges and outline the aspects of their history, presentation, and work-up. We propose that this condition is more than rare and may be underestimated; improved awareness of this disorder and associated trends might improve a clinician’s index of suspicion and lead to a better diagnostic approach. Case reports and reviews remain vital to our understanding of this disorder and its true prevalence.

J INVASIVE CARDIOL 2013;25(7):E159-E162

Key words: spontaneous coronary artery dissection, idiopathic, misdiagnosis

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Spontaneous coronary artery dissection (SCAD) is considered a very rare disorder in the spectrum of cardiovascular disease, with a variety of clinical presentations.^1-7 Its underlying etiology and most appropriate clinical treatment are not well established. Due to its rarity, the majority of the information on this disorder is based on case reports and retrospective reviews.^3-17 Although physicians prefer to base treatment recommendations on more robust data, such data are lacking in SCAD. We present 5 cases of underdiagnosed SCAD that were managed at our center. The purpose of this study was to illustrate the potential for misdiagnosis and underestimation, and the importance of continued case reporting across the spectrum of this disease.

Case Report

Case 1. A 42-year-old male with no cardiovascular (CV) history or risk factors developed chest pain (CP) while swimming. The CP was exertional with mild dyspnea and recurred for 2 days, prompting him to seek medical attention. Admission electrocardiogram (ECG) showed anterior early repolarization. Troponin-I (TnI) values over 12 hours were elevated, but non-diagnostic for myocardial infarction (MI). Treatment was started for unstable angina. Initial catheterization revealed a 50% stenosis in his circumflex (CX) vessel, with diffuse narrowing of the distal vessel and normal flow. The other coronary arteries appeared normal. The patient continued to experience intermittent CP and 36 hours after initial angiography had a notable increase in his cardiac enzymes.  Repeat angiography revealed a spiral dissection of the CX, extending to the most distal portion of the vessel with antegrade flow in both lumens. Given its location and extension, no angioplasty was performed. There were no abnormalities on echocardiogram and low-level stress testing during the initial hospitalization. The patient was discharged in a stable condition on dual-antiplatelet therapy, a beta-blocker (BB), and a statin.

Case 2. A 45-year-old female with no CV history or risk factors was admitted to an external hospital with an acute episode of CP. ECG showed inferior ST elevations with an elevated TnI value.  She received appropriate acute coronary syndrome (ACS) protocol treatment and was transferred to our institution for urgent cardiac catheterization. Angiography revealed non-occlusive stenosis in the proximal RCA with an aneurysmal ostium and associated small ulcerative plaque.  There was Thrombolysis in Myocardial Infarction (TIMI) 3 flow in this vessel and no other coronary abnormalities. No intervention was performed.  Echocardiogram revealed an inferior wall motion abnormality with preserved LV function. She remained stable and was discharged home on dual-antiplatelet therapy, a BB, and a statin. Within 24 hours, the patient experienced another episode of acute CP.  ECG at the external hospital was again concerning for inferior ST elevations. She was transferred to our center for urgent angiography, which demonstrated right coronary artery (RCA) dissection. Four drug-eluting stents were placed to compress the false lumen and restore normal blood flow. Following this treatment, the patient remained asymptomatic and was discharged home on the previously noted regimen.

Case 3. A 36-year-old male with no CV history and a single risk factor of tobacco abuse presented to an external hospital with substernal CP on exertion. Admission ECG showed inferior ST elevation with reciprocal ST depression. Thrombolytic therapy was initiated. The patient’s CP resolved. Repeat ECG showed resolution of ST elevations. He developed ventricular tachycardia upon reperfusion, which resolved. He was transferred to our center the following day for cardiac catheterization in stable condition with no symptoms. Angiography revealed a large RCA with a long and tortuous filling defect consistent with dissection. He underwent placement of 3 bare-metal stents with no residual postintervention stenosis. The rest of the coronary arteries appeared normal. Therapy with dual-antiplatelet agents, a BB, and a statin was initiated.  The patient remained free of symptoms and was discharged home in stable condition.

Case 4. A 42-year-old female with no CV history or personal risk factors (possible early family history) presented to an external hospital with complaints of palpitations, dyspnea, chest discomfort, and bilateral upper-extremity paresthesia. Admission ECG showed sinus tachycardia and inferior ST elevations. Initial therapy followed ACS guidelines. Emergent catheterization was performed and the report described a small-caliber distal left anterior descending (LAD) coronary artery with diffuse disease up to 60% that did not change with intracoronary nitroglycerin. The rest of the coronary arteries were normal. The patient came to our center for a second opinion. A review of the catheterization films revealed that the proximal part of the LAD (and all other vessels) looked normal. There was an abrupt change in caliber of the LAD in its distal segment that did not have the appearance of atherosclerotic disease. This was felt to be consistent with dissection instead of diffuse distal disease. She was continued on medical therapy and enrolled in a rehabilitation program. Repeat angiography several months after the initial event showed no significant disease of the native coronary arteries with complete resolution of the distal LAD dissection. 

Case 5. A 46-year-old female with history of previous MI presented to an external facility with intermittent CP radiating to her left arm. She underwent cardiac catheterization that showed a CX dissection extending up into the left main and was transferred to our center for further management. An initial conservative approach was taken, including dual-antiplatelet agents, heparin, BB, and an angiotensin-converting enzyme inhibitor (ACEI). She had been stable for several days when she developed severe CP with ECG changes consistent with acute ischemia. She progressed to ventricular fibrillation requiring external cardiac massage and defibrillation therapy. The patient underwent emergent 2-vessel coronary artery bypass grafting (CABG). Her postoperative course was complicated by hypotension and ECG changes, prompting angiography. This revealed luminal irregularities, which had progressed proximally past the touchdown of her bypass grafts in both the LAD and CX systems. Dissections were confirmed by intravascular ultrasound (IVUS). Multiple stents were used to stabilize the lesions. The patient recovered well without further complications. 

Discussion. In our series, we have presented 5 cases from a single academic center and its affiliated referral hospitals in which the final diagnosis of SCAD has been considered definitive. The basic details of these cases are summarized in Table 1. Our data from these cases support many of the accepted or proposed ideas regarding the clinical presentation, associated patient population, and therapeutic approach to SCAD found in existing literature. These cases also outline several areas of diagnostic difficulty that suggest the potential for significant underestimation of this disease process.

SCAD is considered to be a very rare condition. The incidence in patients presenting with ACS or cardiac arrest who undergo angiography has been estimated between 0.1%-0.28%.^1-3 A recent review found fewer than 450 reported cases in the world literature.⁴ The rarity of SCAD in academic literature has led to little definite information regarding this disorder. Many theorized or reported aspects of this disease point toward areas of challenge in establishing SCAD as a definitive diagnosis.  

The initial clinical presentation of SCAD is impossible to differentiate from other causes of atherosclerotic-induced heart disease or non-cardiac pain. CP is the most common reported complaint with SCAD, but wide variations in presentation have been reported, ranging from atypical symptoms to sudden cardiac death.^1,2,5-7 Electrocardiograms and cardiac enzymes may be benign or indicate active myocardial injury.⁴ In our case series, all 5 patients presented with CP that was concerning for ACS and underwent angiography as part of their early work-up. Patients with less pronounced symptoms, however, may be managed differently and dismissed as atypical or non-cardiac pain after indeterminate biomarkers or non-invasive studies. There were no data found at the time of this research to indicate whether or not SCAD can be detected by non-invasive perfusion studies. Furthermore, cases of sudden death do not routinely undergo autopsy. Prior reviews have estimated that between 20%-50% of SCAD cases present as sudden cardiac death.^4,8,9 It is not the intent of this paper to suggest that angiography on all “low-risk” patients or autopsies on all sudden cardiac death cases is appropriate, but without these one must conclude that cases of SCAD go undiagnosed.

The pursuit of angiography alone does not ensure diagnosis. The pathognomonic finding of dissection is the appearance of a radiolucent intimal flap or slow clearance of contrast from the false lumen. Three of our 5 cases (1, 2, and 4) failed to definitively identify the spontaneous dissection on initial catheterization. In each of these instances, an angiographic abnormality was described and considered to be coronary disease that was non-occlusive or not amenable to intervention. Our cases suggest that one of the most significant limitations in the accurate diagnosis of SCAD stems from a lack of opacification of the false lumen. Opacification of only the true lumen results in an angiographic presentation consistent with a narrowed or occluded vessel. Figure 1 displays films from the initial angiography and subsequent studies for our patient presented in case 1. This may be due to several issues related to underlying pathophysiology of spontaneous dissection. The pathophysiology of SCAD is likely multifactorial. Several hypotheses have been based on information from autopsy studies, histopathology specimens, and review of confirmed clinical cases. 

Investigated dissections have been found to involve various layers of the vascular wall and an intimal tear is not routinely discovered on pathologic specimens.^10,11 Furthermore, it is not clear whether the intimal tears that are discovered result from an ingress of blood from the vessel lumen or an egress of blood from an original site of intramural injury.12 Tears may be precipitated by multiple inciting pathologies. Underlying atherosclerotic disease, altered connective tissue structure, hormonal changes in females,^4,13 or acute changes in intrathoracic pressure caused by heavy exertion^14,15 have all been proposed. Rupture of the vasa vasora or eosinophilic infiltrates causing cystic medical necrosis have been implicated as the primary injury in cases where no intimal tear can be identified.^5,12 Failure to opacify the false lumen may stem from lack of communication between the true and false lumens or be due to closure of an existing intimal tear.  

The anatomic location of dissection does not aid in definitive diagnosis. Dissection involving a single vessel is most common, representing approximately 75% of reported cases.⁴ Four of our 5 cases involved a single lesion. Single-vessel lesions involving the LAD are thought to be the most common, but all vascular territories can be involved.^4,5 As our fifth case demonstrates, multivessel involvement is also known to occur and may progress over time. Some multivessel cases include distal propagation from a more proximal lesion, while others have demonstrated separate involvement of multiple vessels. At least 5 cases have previously been reported that include sequential diagnosis of multivessel involvement on separate cardiac catheterizations.⁴ This may further limit our assessment of SCAD severity unless serial studies are performed.

These overlapping challenges surrounding the confirmation of a SCAD diagnosis strongly suggest that the actual incidence of the disorder is higher than reported estimates in the literature. The heterogeneity of SCAD presentation makes a single unifying pathophysiology unlikely and defining the features of its natural course difficult. While we cannot yet establish an evidence-based way of improving this deficiency, we believe some trends observed with SCAD may help provide insight into when an increased clinical index of suspicion is warranted.

No definite risk factors have been established, but some important associations are widely accepted. Patients with SCAD are more likely to be female, with women comprising up to 70% of reported cases.^1,3,4,16 Within this female population, up to one-third of cases occur peripartum, mainly during the third trimester and early postpartum period.4 The mean age at presentation is younger than average for atherosclerotic heart disease (41-45 ± 10-14 years).^4,16 Patients tend to have limited or no identifiable risk factors for heart disease.17 Except for the absence of pregnancy in our case series, our data lend further support to these trends. All of our patients were below the age of 50; all but 1 patient was below the age of 45 years. Three of our 5 patients were female. Three out of 5 patients had no identifiable risk factors for coronary disease and 1 patient had a single risk factor of tobacco use. 

At this time, we remain unable to provide any clinical or diagnostic findings that accurately predict SCAD. Some predisposing conditions, such as connective tissue disorders and pregnancy, are reasonably well known. Trends in case reports should be used to increase the clinical index of suspicion in appropriate cases and prompt more intensive review of data and consideration of repeat studies or additional diagnostic work-up.

Definitive diagnosis may be assisted by intravascular ultrasound (IVUS), which can distinguish atherosclerotic stenosis from intimal hematoma.¹⁸ IVUS may also be useful in identifying a dissection in which dye does not penetrate a false lumen within the coronary artery. The combination of angiography and IVUS has been noted to be superior to isolated angiography as a diagnostic strategy in suspected dissections.^4,19 Cases have been reported where SCAD was diagnosed by cardiac computed tomography or magnetic resonance imaging.⁴ Although these are not practical for an entity that frequently presents as ACS, once coronary angiography has been performed, if IVUS is not available or repeat angiographic is unfavorable, these modalities can be considered.

The DISCOVERY registry, which is currently underway in Italy, will be the first prospective attempt at gathering information on this uncommon condition.² Using a case-control design, they will assess the role of SCAD in patients with ACS. This registry will be a large step toward understanding this condition, but it is not likely to solve all diagnostic and management dilemmas. Whether their defined focus on this entity will result in an observed frequency that is higher than prior reports remains to be seen. Continuation of case reporting must remain a fundamental part of our knowledge base for the foreseeable future.

Conclusions. SCAD is considered rare in the literature.  Limited information is available with regard to the etiology, risk factors, and clinical progression of this disease. Certain aspects of this disorder that have been theorized or reported in the literature suggest potential diagnostic challenges. Limited diagnostic accuracy implies that the true incidence of this disorder may be underestimated.  

Awareness of this disorder and the diagnostic complexity that it presents should continue to be emphasized in the literature. Continued reporting of SCAD is vital to our further understanding of its risk factors and pathophysiology, as well as the optimal diagnostic and therapeutic approaches.

Acknowledgment. We greatly appreciate and thank Tyler Fulgate, DO, for his collaboration in providing the angiographic films.

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From the Penn State Heart and Vascular Institute, Department of Cardiology, Penn State College of Medicine, Hershey, Pennsylvania.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted January 28, 2013, final version accepted March 14, 2013.

Address for correspondence: Giselle Baquero, MD, Department of Cardiology, Mail Code H047, 500 University Drive, P.O. Box 850, Hershey, PA 17033-0850. Email: gbaquero@hmc.psu.edu