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PubMed This is a summary of 24 peer-reviewed journal articles Updated
Cardiology · Spontaneous Coronary Artery Dissection

The Anatomy of SCAD: Tears, Bruises, and Angiograms

At a Glance

SCAD is a sudden tear or blood collection within a coronary artery wall that can restrict blood flow. Angiograms classify its pattern, while OCT or IVUS may clarify uncertain cases; the cath report records the vessel, type, flow, and management.

Understanding what happened inside your heart requires looking at the architecture of your arteries. While most heart attacks are caused by a slow buildup of plaque (fat and cholesterol), Spontaneous Coronary Artery Dissection (SCAD) is a sudden, structural failure of the artery wall itself [1][2].

The Biological Mechanism: Bruise vs. Plaque

In a traditional heart attack, a “pimple” of plaque ruptures, causing a blood clot to form and block the vessel. SCAD is entirely different. It starts inside the layers of the artery wall [2].

Think of your artery like a three-layered garden hose. In SCAD, blood forced into the middle layer creates a intramural hematoma (a localized bruise or collection of blood) [3]. This bruise is thought to happen in two ways, though mechanistic models cannot always prove which occurred in a specific patient:

  1. Inside-Out: A tiny tear (an intimal tear) develops in the inner lining, allowing blood to push into the wall and peel the layers apart [4].
  2. Outside-In: A tiny vessel within the wall itself (the vasa vasorum) bleeds, creating a bruise that grows and squashes the “true” channel where blood is supposed to flow [5][3].

Regardless of how it starts, the result is a “false” channel that narrows or blocks the “true” channel, starving the heart muscle of oxygen [1].

Why It Happens: Associations and Risks

SCAD is multifactorial, and an identifiable arteriopathy is not found in everyone. However, several important factors are associated with or may contribute to the condition [6].

  • Fibromuscular Dysplasia (FMD): This is the most common association. FMD is a nonatherosclerotic, noninflammatory arterial disease involving abnormal arterial structure, making arteries more likely to dissect [7][8]. Because FMD can affect other arteries, doctors usually recommend evaluating your major vessels (from head to pelvis) using a CTA or MRA scan [9][10].
  • Pregnancy and Hormones: Pregnancy-associated SCAD is a recognized context, most common in the late stages of pregnancy or the first month postpartum [11]. Hormonal and hemodynamic variations have been proposed as contributors [12].
  • Stress and Genetics: Extreme emotional or physical exertion are frequently reported preceding events, though this does not mean you caused your SCAD. In a small number of cases, a genetic disorder affecting connective tissue may be found [13][14].

The Angiographic Types

When you have a coronary angiogram (a procedure where dye is injected into your heart arteries), doctors look for specific patterns to classify the SCAD. The widely used Saw classification system includes Types 1, 2, and 3 (with Type 2 sometimes subdivided), and occasionally Type 4 is used to denote a complete occlusion [15][16].

  • Type 1 (The Classic Tear): The dye clearly enters a tear, showing multiple “channels” or visible contrast staining in the artery lining [17].
  • Type 2 (The Long Narrowing): The most common type. The artery looks long and diffusely narrowed because a long intramural hematoma is compressing it from the inside [15].
  • Type 3 (The Plaque Mimic): This looks like a focal tubular stenosis that could easily be mistaken for traditional plaque, making it the hardest to diagnose [15].
  • Type 4 (Complete Occlusion): The artery is completely shut off [16].

Note: Angiographic type terminology varies by region and does not by itself determine your prognosis or dictate exactly how your artery will heal. Your treating cardiologist interprets the entire angiogram.

Advanced Imaging: OCT and IVUS

If your angiogram is unclear (common in Types 2 and 3), doctors may use “inside-the-vessel” imaging [17]:

  • OCT (Optical Coherence Tomography): Uses light waves to take high-resolution cross-sectional pictures. It can clearly show the hematoma and the tear [18].
  • IVUS (Intravascular Ultrasound): Uses sound waves to see through the artery wall.

The Risk: While these tools are powerful, they are used cautiously. Because the artery wall is already fragile, inserting the imaging probe or injecting the dye required can sometimes extend the dissection or cause a new tear [19][20]. The clinical team weighs the diagnostic benefit against these procedural risks.

Your Cath Lab Report Checklist

Your “Cath Report” is the official record of your diagnosis. A complete report should ideally document the following terms. You should request the actual angiographic images (on a CD or drive) as well as the written report.

  • [ ] Vessel(s) Involved: Which artery was affected? (e.g., LAD for Left Anterior Descending, RCA for Right Coronary Artery) [21]
  • [ ] Angiographic Type: Was it Type 1, 2, 3, or 4? [17]
  • [ ] Lesion Location: Was the tear at the beginning (proximal) or end (distal) of the vessel? [22]
  • [ ] Blood Flow (TIMI Grade): How well was blood moving past the injury? (TIMI 3 indicates normal blood flow) [17]
  • [ ] Imaging Used: If OCT or IVUS was used, what did it show? [23]
  • [ ] Management Choice: Why did the team choose “conservative management” vs. a stent or bypass? [24]

Common questions in this guide

What is SCAD, and how is it different from a typical heart attack?
SCAD happens when a tear or bleeding within the wall of a coronary artery creates a bruise that narrows or blocks the channel carrying blood. A typical heart attack is usually caused by plaque buildup that ruptures and triggers a clot, whereas SCAD is a structural problem in the artery wall.
What does an intramural hematoma mean in SCAD?
An intramural hematoma is a collection of blood inside the layers of the artery wall. It can expand and compress the normal channel, reducing oxygen-rich blood reaching the heart muscle. It may form after a small inner-wall tear or bleeding from tiny vessels within the artery wall.
What do the different SCAD angiogram types show?
Type 1 shows a visible tear or more than one channel, Type 2 shows a long area of narrowing, and Type 3 is a short narrowing that can resemble plaque. Type 4 describes a complete blockage and is used in some classification systems; the type alone does not determine how the artery will heal or what treatment is needed.
Why might doctors use OCT or IVUS during a SCAD evaluation?
OCT uses light and IVUS uses sound waves to create images from inside the artery. They can help show a wall bruise or tear when an angiogram is unclear. Because SCAD arteries can be fragile, placing a probe or injecting dye can extend the dissection or cause a new tear, so the clinical team weighs the benefits against these risks.
Why might someone with SCAD be checked for fibromuscular dysplasia?
Fibromuscular dysplasia, or FMD, is the most common condition associated with SCAD and can affect arteries outside the heart. Clinicians often consider imaging arteries from the head to the pelvis with CTA or MRA, although the appropriate screening plan depends on the person's medical history.
What information should be included in a SCAD cath report?
The report should identify the affected artery, SCAD angiographic type, lesion location, blood flow grade, and whether OCT or IVUS was used. It should also document why conservative management, a stent, or bypass surgery was selected; keeping the written report and angiographic images can help future clinicians.
Can pregnancy or stress be linked to SCAD?
Pregnancy-associated SCAD is a recognized context, particularly during the later stages of pregnancy or the first month after delivery. Extreme physical or emotional exertion is often reported before SCAD, but this does not prove it caused the event and does not mean the patient is to blame.

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References

References (24)
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This page is for informational purposes only and does not constitute medical advice. Your cardiologist should interpret your SCAD angiogram, imaging, and cath report in the context of your individual care.

Guide contents Idiopathic spontaneous coronary artery dissection
Research & Literature
02 Recognizing Red Flags and Managing Symptoms 04 Treatment Approaches