Treatment strategy for spontaneous coronary artery dissection based on anatomical characteristics

Spontaneous coronary artery dissection (SCAD) has emerged as an important etiology of acute coronary syndrome (ACS) and sudden cardiac death, especially in the younger patient population, with female predominance [1]. Due to the rarity of the disease, SCAD is often underdiagnosed or misdiagnosed. The accurate definition of SCAD is an epicardial coronary artery dissection, with exclusion of atherosclerotic, iatrogenic, or traumatic causes. The main mechanism of SCAD is coronary artery obstruction caused by formation of an intramural hematoma (IMH) or intimal disruption rather than atherosclerotic plaque rupture or intraluminal thrombosis [2, 3]. However, the true etiology of SCAD may be multifactorial, including gender, hormone secretion, genetic predisposition, environmental, emotional triggers, or underlying vascular pathology, such as fibromuscular dysplasia [4, 5].

In view of the low diagnostic rate, the true prevalence of SCAD remains unclear. Unseasoned clinicians may be unfamiliar with the coronary angiographic (CAG) presentation of SCAD and can often be misdiagnosed as atherosclerosis-related dissection in patients with ACS. Aside from iatrogenic, traumatic and atherosclerotic dissection, about 1–4% of ACS are caused by SCAD [6, 7]. Recent studies have shown that the left anterior descending (LAD) artery is the most commonly affected coronary artery in SCAD, in which the middle and distal segments are the most common lesion site [8, 9].

In contrast to atherosclerotic ACS, the indication of percutaneous coronary intervention (PCI) in patients with SCAD remains elusive. Previous studies have shown that PCI in SCAD is associated with a higher risk of procedural complications, including iatrogenic dissection, acute vascular occlusion, hematoma extension or unplanned stents implantation. Therefore, the American Heart Association (AHA) and European Society of Cardiology (ESC) Statements on SCAD both recommend conservative management over PCI in most SCAD cases [10, 11]. However, in SCAD patients presenting with high-risk coronary anatomy or compelling clinical scenario, the revascularization strategy, including coronary artery bypass grafting (CABG) or PCI should be considered [11]. However, the definition of high-risk anatomical characteristics and the relevant treatment strategy remain debatable.

The present study retrospectively analyzed the clinical and angiographic data of SCAD patients to investigate whether specific high-risk anatomical clusters can be identified, which may help the individually tailored treatment strategies in patients who experienced SCAD.

The present study is the first to compare the clinical characteristics and treatment efficacy of high-risk and low-risk SCAD based on lesion anatomy. High-risk SCAD is defined as dissection involving the LM and the proximal segment of any main coronary artery with a slight modification from previous definition [11]. Conservative management remains the recommended treatment strategy for the low-risk SCAD patients with a high rate of spontaneous vessel healing. PCI in the high-risk SCAD patients could achieve the favorable clinical outcomes and relatively similar vessel healing with the conservative treatment.

Although SCAD belongs to the broad spectrum of coronary heart disease, its treatment strategy is different from traditional CAD [2, 3]. Based on current recommendations, most of the clinically stable patients should consider the conservative management. Only those with ongoing ischemia or hemodynamic instability should consider urgent PCI or CABG [11]. However, emergency CABG is only feasible in certain medical facilities, while emergency PCI has a more widespread coverage. About 5–10% of patients who receive conservative treatment experience early recurrence of MI, which is often related to extension of dissection within the first 7 days after an acute ACS episode [12]. Previous study [13] showed that most SCAD patients undergoing PCI were high risk at presentation, including STEMI, cardiac arrest, TIMI 0/1 flow or proximal dissections. Conservative management in these patients may not be appropriate and can incur greater risks. Several studies have proven the value of PCI in SCAD, especially in high-risk coronary lesions, with promising outcome. Patients with STEMI–SCAD had more favorable prognoses in revascularization management modalities than those who with atherosclerosis-related STEMI [13‐16]. In the present study, the high-risk and low-risk patients had the similar clinical characteristics, including ACS presentation and female predominance. The incidence of 1 year MACE was comparable between the two groups. Due to the retrospective nature of the present study, the appropriate treatment method was determined by the operator. Interestingly, PCI was employed in majority of the high-risk cases, while most of the low-risk cases received conservative management. High-risk patients in the present study underwent PCI treatment for SCAD with low complication rates and similar outcome with the low-risk patients. Several important technical factors, including careful manipulation of guiding catheter and wire, direct stenting without balloon predilation, long stents to cover the proximal and distal ends of the hematoma by 5–10 mm, and guidance with intravascular ultrasound (IVUS), could limit the hematoma propagation-related complications during PCI management of SCAD.

A small portion of the low-risk SCAD patients received PCI in the present study. In SCAD patients who received PCI, cTnT (ng/ml) values were higher in the low-risk group than the high-risk group, which was associated with a higher rate of baseline TIMI 0/1 flow and urgent decision of PCI. This may be associated with a more severe clinical feature, which prompted the clinical decision of PCI. In comparison with the conservative treatment group, cTnT (ng/ml) and CK-MB (U/L) values were higher in the high-risk group (n = 9). Regardless, all 9 patients had a TIMI 3 flow and, therefore, received conservative management and close follow-up. Previous studies have indicated angiographic “healing” of SCAD lesions is plausible in majority of patients after a conservatively managed index episode [8, 9]. According to the follow-up CAG results in our study, majority of the patients in the high-risk group receiving PCI achieved vessel healing. Conservative management was also associated with a significantly higher rate of spontaneous vessel healing in low-risk patients. Therefore, we propose that conservative management is the acceptable treatment approach but should be carefully selected for patients with low-risk SCAD anatomy and stable clinical features. In patients presenting with high-risk SCAD anatomy or compelling clinical scenario, emergency revascularization can be achieved with PCI.

Compared with low-risk lesions, patients with proximal lesions cover a larger myocardial blood supply area. Recent study suggested SCAD involving the proximal coronary arteries was associated with a reduction in post-infarct ejection fraction [17]. This may be associated with a more severe clinical feature, which prompted the clinical decision of PCI. In the present study, no significant difference in Saw classification was noted between high-risk and low-risk groups. Although Saw classification has a high diagnostic value, it cannot provide the reference for treatment decisions in patients with SCAD [18‐21].

There are several limitations in the present study. First, this present study summarizes the experience of a single center, with a rather small sample size. Second, the retrospective nature of the study may incur selection bias especially in treatment methods. Third, this study lacks long-term follow-up data for SCAD patients with different interventions. Future prospective randomized control trial including multi-center data is warranted to validate the present study results.

The present study proposed a new classification method based on lesion segment and anatomical characteristics of SCAD, providing a simple and convenient alternative for interventional cardiologists to quickly formulate a suitable treatment strategy for patients in emergency situations. PCI may be chosen in patients with SCAD involvement of the LM or proximal segment of any main coronary artery. While conservative treatment should be reserved for low-risk SCAD patients with the involvement of the side branch or the middle and distal segments of the main coronary artery.

This study provides insight to the treatment strategy of SCAD patient based on lesion anatomy and affected segment. Conservative management remains the recommended treatment strategy for the low-risk SCAD patients. PCI could be considered in high-risk SCAD patients with favorable clinical outcomes and vessel healing.