Spontaneous Coronary Artery Dissection: Making strides, long journey ahead!

Although the first case of spontaneous coronary dissection (SCAD) was documented at autopsy in 1931,¹ most of the evidence currently available has been generated within the last 5 years. Despite the increasing scientific efforts on this topic, the disease is still poorly understood. Most of the data available stem from retrospective observational studies or case reports. SCAD is defined as an epicardial coronary artery dissection that is not associated with atherosclerosis, trauma or iatrogenic cause. Coronary artery obstruction results from either formation of intramural hematoma or intimal disruption and can lead to acute coronary syndrome (ACS), myocardial infarction (MI) and sudden death. The American Heart Association scientific statement “Spontaneous Coronary Artery Dissection: Current State of the Science on SCAD” represents a comprehensive summary of available data but also the many persistent knowledge gaps on this topic.

Although it has been considered a very rare event in the past, most recent reports suggest that SCAD is more prevalent than previously assumed.^2,3 SCAD occurs most frequently in young women and patients without risk factors for atherosclerotic disease. In this patient population suspicion of ACS is low, which might lead to under- or misdiagnosis. Not only advances in intravascular imaging techniques and development of a SCAD-specific angiographic classification, but especially the increased awareness about this condition has contributed to an improvement in diagnostic capabilities and a change in the understanding of the true prevalence of the disease.

The cause of SCAD is hypothesized to be multifactorial with most important factors including underlying arteriopathies, genetic factors, hormonal influences and systemic inflammatory diseases. Fibromuscular dysplasia (FMD) is an arteriopathy that is strongly associated with SCAD, as documented in several case studies as well as in an analysis of the US Registry for FMD.^4,5 Female sex and pregnancy are other important factors associated with SCAD and widely discussed in the statement.^2,3,6-8 With respect to the latter, hormonal changes are assumed to contribute to alterations in the architecture of the arterial wall and make SCAD the most common cause of MI among patients who are pregnant or postpartum.⁹ Eventually, it is most likely a complex interplay between pre-existent conditions and certain precipitants and triggers including physical or emotional stress that leads to SCAD.

Patients with SCAD most likely present with ACS and increased levels of cardiac enzymes, respectively. Although clinical characteristics and risk factors differ a lot from those found in patients experiencing ACS due to atherosclerosis, presenting symptoms are very similar between both populations. Coronary angiography should be performed immediately once SCAD is suspected. Although angiography is still the first-line imaging method for the diagnosis of SCAD, owing to its 2-dimensional nature it is not the optimal tool to image the arterial wall. The scientific statement by Hayes et al. elaborates not only on the recently proposed and commonly adopted SCAD angiographic classification,¹⁰ but also on new developments in other diagnostic techniques including intracoronary imaging.^11,12

While PCI is the mainstay of treatment in patients with atherosclerotic coronary disease, the results in SCAD patients do not support a routine invasive approach. Observational studies have shown that PCI for treatment of SCAD is associated with increased risk of complications and suboptimal results.^2,13-16 According to analyses of observational data a spontaneous healing of SCAD lesions occurs in the majority of patients.^2,15 Although a primarily conservative approach should be preferred in SCAD, the writing committee points out that it might not be the optimal strategy in patients at high risk including those with ongoing ischemia, left main artery dissection, or hemodynamic instability. A helpful algorithm is provided as part of the scientific statement to guide conservative versus invasive management in patients with SCAD. In addition, important questions regarding the optimal antiplatelet/anticoagulant treatment, other medication and supportive therapy as well as cardiac rehabilitation and psychosocial considerations are addressed. Moreover, special attention is devoted to the post-SCAD phase and its challenges with chest pain syndrome, re-evaluation of coronary anatomy, pregnancy and hormone use. This is particularly important given the fact that the risk of recurrent SCAD is estimated to be up to 30% at 4 to 10 year of follow-up in different series.^2,13,14,16

Overall, the scientific statement on SCAD provides a highly comprehensive and detailed summary on current evidence. At the same time, however, it underlines the fact that there are still many questions left unanswered. Larger-scale prospective studies are urgently needed to improve accuracy in diagnosis and optimize treatment and outcomes. Large gaps in knowledge need to be addressed to decrease morbidity and mortality in this mostly young and predominantly female patient population. This statement is a crucial step to further increase awareness about SCAD, but it also is a strong call to action: Acknowledging recent efforts of the scientific community and SCAD-survivor led initiatives, the writing committee proposes specific research priorities regarding the epidemiology, etiology, diagnosis and treatment of SCAD. This statement will help to drive progress and promote collaboration in order to better understand the natural history of the disease and improve outcomes in patients with SCAD. While it will get us one step closer, there is still a long way to go.