Spontaneous Coronary Artery Dissection (SCAD) is an uncommon yet serious cause of a heart attack, unrelated to the typical buildup of plaque in the arteries. SCAD occurs when a tear forms in a coronary artery wall, allowing blood to enter and separate the layers. This separation creates a false channel, or hematoma, that compresses the artery’s true lumen, restricting or blocking blood flow to the heart muscle. Increased awareness and improved diagnostic techniques have clarified its true prevalence, which is significantly higher than once believed.
Quantifying the Rarity of SCAD
SCAD remains a small contributor in the general population of patients experiencing an acute coronary syndrome (ACS), accounting for only 1% to 4% of all cases. When looking at all individuals undergoing coronary angiography, SCAD is found in a narrow range, typically between 0.1% and 1.0%. These figures demonstrate that SCAD is a rare event on a population-wide scale.
The perspective shifts dramatically when focusing on younger patients who experience a heart attack. SCAD is responsible for up to 35% to 40% of heart attacks in women aged 50 or younger. The estimated rate of new SCAD diagnoses has shown a notable increase in recent years, with incidence nearly tripling between 2010 and 2017. This rise is thought to reflect better recognition and diagnosis rather than an actual spike in the number of cases.
The Typical SCAD Patient Profile
The condition overwhelmingly affects women, who make up over 90% of SCAD patients in major registries. The typical age range for a SCAD event is younger than for a typical atherosclerotic heart attack, with the average patient presenting in their 40s or early 50s. These women often lack the traditional cardiovascular risk factors, such as high cholesterol, diabetes, or severe smoking history, common in other heart attack patients.
A strong association exists between SCAD and Fibromuscular Dysplasia (FMD), a non-atherosclerotic disease affecting the arteries. FMD causes abnormal cell growth in the artery walls, which can weaken them and predispose them to dissection. FMD is identified in 45% to 86% of SCAD patients when screening is systematically performed. Hormonal fluctuations also play a role, as SCAD is the most common cause of heart attack associated with pregnancy, accounting for up to 43% of these events. The highest risk for these pregnancy-associated cases occurs in the first week after childbirth.
Factors Masking SCAD Rarity
The true prevalence of SCAD is difficult to determine because the condition is frequently missed or misdiagnosed, leading to an underestimation of its actual occurrence. Since SCAD patients are often young and otherwise healthy, their symptoms are sometimes initially attributed to less serious issues like anxiety or acid reflux, causing a significant delay in diagnosis. Even when a heart attack is diagnosed, the dissection is often mistaken for the more common plaque-rupture type because standard imaging may not clearly show the tear.
In cases of sudden cardiac death outside the hospital, SCAD is a possible cause, often only confirmed during an autopsy. This lack of routine diagnostic follow-up contributes to lower overall reported incidence rates. However, the increasing use of advanced imaging technologies, such as intravascular ultrasound and optical coherence tomography, allows clinicians to visualize the dissection more accurately. This improved diagnostic capability is the likely reason for the reported increases in SCAD incidence over the past decade.
Long-Term Risk and Recurrence Rates
For those who survive the initial event, the long-term outlook is generally favorable, but the risk of recurrence is a significant factor in ongoing management. The primary concern for SCAD survivors is the possibility of a new dissection occurring in the same or a different coronary artery. Recurrent SCAD is observed in approximately 10% to 20% of patients over an extended follow-up period.
The annual rate of recurrence is estimated to be around 2% to 3%. Certain characteristics significantly increase the risk of a subsequent event, most notably a diagnosis of Fibromuscular Dysplasia or a history of migraine headaches. Because of this persistent risk, SCAD survivors require continuous monitoring and specialized care to manage their condition.