Spontaneous Coronary Artery Dissection

Definition and pathophysiology

Spontaneous coronary artery dissection (SCAD) is an acute coronary disorder caused by separation within the coronary arterial wall, usually through formation of an intramural haematoma that compresses the true lumen. The resulting reduction in coronary blood flow may produce myocardial ischaemia, acute coronary syndrome (ACS), myocardial infarction (MI), or, rarely, sudden cardiac death.

SCAD differs pathogenetically from atherosclerotic type 1 MI. It is an infrequent cause of ACS overall but represents a substantial proportion of ACS presentations in young and middle-aged women. The condition is often under-recognized or misdiagnosed, making accurate angiographic diagnosis particularly important.

The precise initiating mechanism is incompletely defined. Several associations have been described:

• Female sex, particularly in patients aged approximately 40–50 years.

• Hormonal influences, including oestrogen and progesterone-related structural changes in the coronary media.

• The early postpartum period, when marked hormonal changes occur.

• Hypertension and oestrogen exposure.

• Emotional or chronic mental stress.

• Fibromuscular dysplasia (FMD), which may produce arterial-wall abnormalities and intramural haematomas.

• Inherited connective-tissue disorders, including Marfan syndrome and Ehlers–Danlos syndrome.

FMD may be clinically occult and can affect multiple vascular territories, including the renal, carotid, vertebral and coronary arteries. In one study cited in the source material, FMD was identified in 86% of patients with SCAD. SCAD should therefore prompt consideration of systemic arteriopathy rather than being regarded solely as an isolated coronary event.

SCAD predominantly affects the left-sided coronary circulation and may involve multiple vessels. Pregnancy-associated SCAD can occur at any stage of pregnancy or after delivery, although more than 70% of cases occur early postpartum, most frequently during the first week. It is the most frequent cause of ACS during pregnancy and the postpartum period in the cited data.

Angiographic classification

SCAD is conventionally divided into three angiographic patterns:

Type 1 is reported in fewer than one-third of cases in the pregnancy-related source material. Types 2 and 3 are diagnostically more challenging because they may not display the classic double-lumen appearance.

Clinical presentation and symptoms

SCAD generally presents as ACS. Symptoms may therefore include acute chest pain or chest discomfort, with associated manifestations of myocardial ischaemia. In pregnancy, the clinical presentation of ACS is generally similar to that in non-pregnant patients, although symptoms may be atypical. Pregnant patients with SCAD may have a more severe presentation than those with non-SCAD ACS.

SCAD may present with:

• ST-elevation myocardial infarction (STEMI).

• Non-ST-elevation myocardial infarction (NSTEMI).

• Unstable myocardial ischaemia.

• Ventricular arrhythmia or sudden cardiac arrest.

• Chronic coronary dissection presenting as heart failure, although this is described as uncommon.

In pregnancy-associated ACS, STEMI is more frequent than NSTEMI, and up to two-thirds of infarctions are anterior. The risk of ACS is greatest during the third trimester and postpartum period, although SCAD may occur at any time during pregnancy or after delivery.

The clinical context is particularly important. SCAD should be considered in a young or middle-aged woman with ACS and few conventional cardiovascular risk factors, especially when the event occurs during pregnancy or within the early postpartum period. Emotional stress and chronic mental stress are reported triggers, and rehabilitation should address stress management, work–life balance and other identifiable stressors.

Evaluation and physical examination

The initial evaluation follows the standard assessment for ACS. In pregnant patients with acute chest pain, the diagnostic approach includes:

• Clinical examination.

• Twelve-lead ECG.

• Cardiac biomarkers.

• Echocardiography.

The presentation should be interpreted in the context of pregnancy, postpartum status, hypertension, pre-eclampsia, thrombophilia, infection, haemorrhage and other pregnancy-associated prothrombotic or inflammatory conditions.

Physical examination should assess:

• Haemodynamic stability.

• Evidence of ongoing myocardial ischaemia.

• Signs of heart failure.

• Arrhythmia or cardiovascular collapse.

• Blood pressure, particularly because hypertension may contribute to recurrence risk.

• Clinical clues to FMD or associated vascular disease, such as hypertension, epigastric bruit, cervical bruit, pulsatile tinnitus, severe or recurrent headaches, transient ischaemic attack or stroke.

• Features suggesting an inherited connective-tissue disorder or other systemic arteriopathy.

Assessment of the renal, cervical and cerebral arterial beds is relevant when FMD is suspected. The presence of SCAD itself is listed among the clinical circumstances that should prompt consideration of FMD.

Diagnostics

Electrocardiography

The ECG is part of the initial ACS evaluation. The source material does not define a specific ECG pattern diagnostic of SCAD. ECG findings should therefore be interpreted as evidence of the associated acute coronary syndrome rather than as a means of independently confirming the arterial diagnosis.

Echocardiography

Echocardiography forms part of the diagnostic evaluation of acute chest pain in pregnancy. The source material does not specify particular echocardiographic findings or criteria for SCAD. It may nevertheless contribute to assessment of myocardial consequences and haemodynamic status within the broader ACS evaluation.

Coronary angiography

Urgent coronary angiography is recommended for suspected SCAD presenting with STEMI and is an important diagnostic investigation in suspected SCAD generally. Angiography may demonstrate:

• Contrast staining of the arterial wall.

• Multiple lumens or radiolucent channels.

• Long, smooth and diffuse narrowing.

• Focal or tubular stenosis mimicking atherosclerosis.

In patients with NSTEMI or ACS during pregnancy, coronary angiography is considered reasonable, although it need not necessarily be performed emergently in every case. Catheterization and coronary intervention in pregnancy should be undertaken by experienced operators at a cardio-obstetric centre.

A negative coronary CT angiogram does not exclude SCAD. The source material does not provide a role for coronary CT angiography as a definitive test for SCAD.

Intravascular imaging

Optical coherence tomography (OCT) or intravascular ultrasound (IVUS) may help establish the diagnosis when angiography is inconclusive, particularly in type 3 SCAD and some type 2 lesions. Imaging can demonstrate an intramural haematoma or double lumen.

The decision to use intravascular imaging must be cautious. There are no randomized controlled trials guiding this strategy, and coronary instrumentation carries risks, including extension of dissection. Vessel tortuosity, small vessel diameter and distal lesion location may increase procedural risk. If imaging is undertaken, the guidewire must first be confirmed to be within the true lumen before advancing the imaging catheter.

When angiography has established SCAD and conservative treatment is planned, additional coronary instrumentation or intravascular imaging is not recommended because of safety concerns.

Screening for associated arteriopathy

Because SCAD may be associated with FMD, screening of other vascular territories is recommended in the source material. Renal arteries may be assessed with angiography or CT angiography. More broadly, FMD evaluation may include:

• CT angiography or magnetic resonance angiography of the abdomen, pelvis and neck.

• At least one CT or MR angiographic assessment of the head to evaluate for intracranial aneurysm.

• Renal and carotid/vertebral duplex ultrasound in centres with relevant expertise.

• Catheter angiography when clinical suspicion remains high and non-invasive imaging is nondiagnostic, or before catheter-based intervention.

Biomarkers and laboratory findings

Cardiac biomarkers are included in the standard evaluation of acute chest pain and ACS during pregnancy. The source material does not specify characteristic biomarker concentrations or a distinctive laboratory profile for SCAD.

The diagnostic interpretation of biomarkers must account for the clinical setting. The material notes that troponin elevation may also occur after cardiac arrest because of transient ischaemia or loss of myocardial perfusion during the arrest; therefore, a raised troponin level alone does not establish the mechanism of coronary injury.

When FMD is being considered, inflammatory testing may help distinguish it from vasculitis. FMD is characterized by the absence of clinical signs, symptoms or laboratory findings suggesting inflammation, such as elevated erythrocyte sedimentation rate or C-reactive protein.

Treatment and management

General principles

Until evidence from ongoing prospective studies becomes available, patients with SCAD should receive the same pharmacological treatment as other patients with ACS. However, revascularization strategy differs substantially from that used for typical atherosclerotic ACS because PCI carries a high risk of procedural complications and spontaneous healing may restore coronary flow.

Management should be individualized according to:

• Haemodynamic stability.

• Presence or absence of ongoing ischaemia.

• Coronary anatomy and the amount of myocardium at risk.

• Antegrade coronary flow.

• Involvement of the left main stem or proximal vessels.

• Pregnancy or postpartum status.

• Feasibility of PCI or CABG.

• Local expertise and multidisciplinary assessment.

Conservative management

Conservative medical management is generally preferred, particularly in clinically stable patients without active or ongoing ischaemia. The rationale is that SCAD may heal spontaneously and that PCI can extend the intramural haematoma or cause iatrogenic dissection.

In pregnancy-associated SCAD, a conservative approach is specifically advised for clinically stable women without active or ongoing ischaemia. Inpatient monitoring should be prolonged because extension of the dissection may occur during the first seven days; the source material reports this in up to 10% of conservatively managed patients.

Repeat angiography has demonstrated angiographic healing in at least 70% of patients in one pregnancy-related source, while another cited study reported healing in 95% of patients undergoing repeat angiography more than 30 days after SCAD. These observations support conservative management when clinical circumstances permit, although the cited data are not based on consecutive or exclusively pregnant populations.

Percutaneous coronary intervention

PCI is not routinely recommended for SCAD. It is reserved for patients with:

• Symptoms and signs of ongoing myocardial ischaemia.

• A large area of myocardium at risk.

• Reduced antegrade coronary flow.

• Haemodynamic instability.

• Selected left main or severe proximal disease when revascularization is required.

PCI has been associated with coronary complications in more than 30% of patients in an international case series. In a pooled analysis of SCAD-PCI cohorts, complications occurred in approximately 40% of cases, including serious complications in 13%.

Potential procedural strategies include:

• Minimal plain balloon angioplasty to restore flow, followed by conservative management.

• Targeted stenting to seal the proximal and distal ends of the dissection.

• Longer stent coverage when required to limit propagation of the intramural haematoma.

In pregnancy, the risk of catheter-induced coronary dissection is increased, reported at approximately 3% in the source material. The radial approach was associated with a higher risk of iatrogenic dissection in the cited pregnancy-related discussion, and the femoral approach may therefore be preferred. PCI should be performed by experienced operators in a cardio-obstetric centre.

Coronary artery bypass grafting

CABG is recommended or should be considered when:

• The dissection involves the left main coronary artery.

• Two proximal coronary vessels are affected.

• PCI is not feasible or has failed.

• Ongoing myocardial ischaemia persists.

• There is haemodynamic instability.

• Severe proximal disease places a large myocardial territory at risk.

For pregnancy-associated SCAD involving the left main or proximal vessels, a multidisciplinary team should determine whether PCI or CABG is appropriate.

CABG may have favourable early clinical outcomes, but long-term graft occlusion is a significant concern. The source material reports a 68% graft-occlusion rate at five years in one observational study. This may reflect technically difficult anastomosis to dissected vessels and spontaneous healing of the native artery, creating competitive flow. Vein grafts should therefore be considered in order to preserve arterial conduits for potential future use.

CABG does not protect against recurrent SCAD, and graft occlusion may occur as the native coronary arteries heal.

Pharmacological treatment

The optimal pharmacological regimen after SCAD remains uncertain and is being investigated. Until more definitive evidence is available, treatment generally follows ACS practice, with important distinctions between conservatively managed patients, those undergoing PCI and those who are pregnant.

Antiplatelet therapy

For conservatively managed SCAD, the role of antiplatelet treatment remains controversial. Limited evidence favours aspirin monotherapy.

Patients undergoing PCI should receive dual antiplatelet therapy. In pregnancy, clopidogrel is regarded in the source material as the only P2Y12 inhibitor considered safe. The indication for clopidogrel in patients who have not undergone PCI is less certain because of a potential increase in bleeding risk.

Clopidogrel should be discontinued seven days before regional anaesthesia.

Beta-blockers

Beta-blockers may be associated with a lower risk of recurrent SCAD in observational data. Labetalol is given as an example, particularly in the pregnancy-associated setting. Patients with MI should receive beta-blockers unless there is a clinical reason not to do so.

Avoidance of hypertension is emphasized as part of long-term management.

Nitrates and calcium-channel blockers

Nitrates and calcium-channel blockers may be used for angina treatment. During pregnancy, nitrate doses should be titrated carefully because excessive maternal hypotension may compromise placental perfusion; the placenta cannot autoregulate blood pressure.

Anticoagulants

Low-molecular-weight heparin, such as enoxaparin, or unfractionated heparin can be used for acute MI during pregnancy. Fondaparinux is an option when heparin-induced thrombocytopenia or heparin allergy is present.

Direct oral anticoagulants are contraindicated during pregnancy.

Renin–angiotensin system inhibitors

ACE inhibitors and angiotensin receptor blockers are contraindicated during pregnancy. ACE inhibitors may be restarted postpartum, and some are compatible with lactation.

Lipid-lowering therapy

Statins are described as no longer universally contraindicated during pregnancy and may be considered in patients at the highest risk with established coronary artery disease. The source material does not provide a specific statin, dose or pregnancy-specific treatment threshold.

Management of associated fibromuscular dysplasia

Patients with SCAD and associated FMD require assessment for disease in other arterial beds. Aspirin is recommended for FMD, although no studies cited in the source material demonstrate a reduction in major adverse cardiovascular events.

ACE inhibitors or angiotensin receptor blockers are recommended for renovascular hypertension caused by FMD. Smoking cessation is important because smoking is associated with worse outcomes.

Patients with cervical FMD, particularly those with cervical artery dissection or aneurysm, should avoid activities that may precipitate further vascular injury, including:

• Heavy weightlifting.

• Skydiving.

• Scuba diving.

• Roller-coaster rides.

• Chiropractic manipulation of the neck.

• Deep-tissue neck massage.

Pregnancy and postpartum management

Pregnancy-associated SCAD should be managed by a multidisciplinary maternal heart team. Pregnancy and delivery should occur at a referral centre able to provide coronary revascularization and advanced cardiac therapies when required.

The source material describes vaginal delivery with epidural anaesthesia and minimization of maternal effort during vaginal delivery as the current recommendation in patients with MI during pregnancy. Decisions must remain individualized according to cardiovascular status and obstetric circumstances.

Future pregnancy requires careful counselling. Pregnancy is itself a risk factor for SCAD, and subsequent pregnancies should be discouraged in the source material because the three-year risk of major cardiac events after SCAD may reach 30%. Women with a history of SCAD should be explicitly counselled about recurrent-event risk before considering another pregnancy.

Guideline recommendations

The principal recommendations supported by the source material are summarized below.

Prognosis and follow-up

SCAD may heal spontaneously, and angiographic healing is common on follow-up. The source material reports healing in at least 70% of patients in one pregnancy-related series and in 95% of patients undergoing repeat angiography more than 30 days after SCAD in another study.

Despite this potential for healing, SCAD is associated with clinically important early and late risks:

• Extension of the dissection, particularly during the first seven days after conservative treatment.

• Recurrent SCAD.

• Recurrent ACS or MI.

• Heart failure when chronic dissection has produced persistent myocardial injury.

• Arrhythmia and sudden cardiac death in severe presentations.

• Graft occlusion after CABG.

• Procedural complications when PCI is undertaken.

In survivors of SCAD, the cited long-term data report approximately 20% subsequent mortality over three years and recurrent dissection in 10–15% of patients. Another source reports a three-year risk of major cardiac events of up to 30% in patients with SCAD generally.

Follow-up should therefore include:

• Clinical surveillance for recurrent chest pain or ischaemia.

• Blood-pressure assessment and control.

• Review of medication tolerance and adherence.

• Assessment for recurrent dissection or associated vascular disease.

• Screening and serial evaluation for FMD when indicated.

• Psychological assessment and stress-management support.

• Counselling regarding future pregnancy.

• Consideration of follow-up coronary imaging when clinically appropriate, recognizing that routine invasive imaging is not recommended solely when the diagnosis is established and the patient is being treated medically.

Cardiac rehabilitation should incorporate management of emotional and chronic mental stress, attention to work–life balance and psychological counselling when needed. The long-term approach should balance the favourable possibility of spontaneous coronary healing against the persistent risks of recurrence, vascular comorbidity and major cardiac events.