Spontaneous Coronary Artery Dissection: The Heart Attack That Is Not Atherosclerosis

Dr. Job Mogire, MD, FACP, FACC Board-Certified Cardiologist | Carle Foundation Hospital, Champaign, IL

The standard mental model of a heart attack is a cholesterol plaque rupturing in a coronary artery. Spontaneous coronary artery dissection breaks that model entirely. In SCAD, the artery wall tears and separates without atherosclerosis, creating a false channel that compresses the true lumen and blocks flow. It is a heart attack in a vessel that was never plaque-laden, it strikes women far more than men, and treating it like ordinary atherosclerotic MI can cause harm.

A different mechanism

In SCAD, a hematoma forms within the layers of the coronary artery wall, or an intimal tear admits blood into the wall, compressing the true lumen. 4 / Promising The result is myocardial ischemia or infarction, but the cause is a structural arterial event, not plaque rupture. The AHA scientific statement on SCAD established it as an important and underrecognized cause of acute coronary syndrome, particularly in younger women and in the peripartum period (Hayes et al, Circulation 2018).

SCAD is a leading cause of heart attack in young women and of pregnancy-associated myocardial infarction, populations in whom atherosclerotic MI is otherwise uncommon. The demographic mismatch, a heart attack in a woman without typical risk factors, is itself a clue.

The FMD and hormonal associations

SCAD is strongly associated with fibromuscular dysplasia, a non-atherosclerotic arterial disease, and patients diagnosed with SCAD warrant screening of other arterial beds for FMD. 4 / Promising It is also associated with pregnancy and the postpartum period and shows a marked female predominance, implicating hormonal and arterial-wall factors rather than the conventional atherosclerotic risk profile. The precise mechanisms remain under study, but the associations are well documented.

Why management differs

This is the most consequential point. 4 / Promising Many SCAD lesions heal spontaneously, and reflexive stenting, the default for atherosclerotic MI, can extend the dissection and worsen outcomes. Guidance therefore favors a conservative, expectant approach in stable patients, reserving intervention for high-risk features such as ongoing ischemia or hemodynamic instability. The treatment algorithm built for plaque rupture does not transfer to SCAD, and applying it blindly is the harm to avoid.

What this means

SCAD is a non-atherosclerotic heart attack that predominantly affects women, associates with FMD and pregnancy, and demands a management approach distinct from typical MI. Recognizing it prevents the harm of inappropriate intervention and directs the right follow-up, including FMD screening and counseling on future pregnancy and recurrence risk. The first step is simply to hold SCAD in mind when a heart attack does not fit the atherosclerotic story, which, in young and peripartum women, it often does not.

How SCAD appears on angiography versus intracoronary imaging

Standard coronary angiography is the first imaging tool used in acute SCAD, but it has real limitations in characterizing the dissection. Angiography images the lumen of the vessel as defined by contrast opacification. It cannot directly visualize the arterial wall layers or the intramural hematoma. This matters because some SCAD presentations, particularly the most common angiographic type, can appear subtle and be misread.

The three angiographic types of SCAD, classified by the Saw classification system developed from the Canadian SCAD registry and subsequent international data, describe what angiography actually shows.

Type 1 SCAD is the most visually obvious: it shows the classic double lumen and radiolucent intimal flap, the split between the true and false channels is visible as a filling defect with contrast in both spaces. Type 1 accounts for a minority of SCAD cases, roughly 25 to 30 percent, but it is the presentation cardiologists are most trained to recognize. When it is present, there is usually less diagnostic uncertainty.

Type 2 SCAD is the most common, accounting for approximately 60 to 75 percent of cases. It appears as a long segment of diffuse smooth stenosis, typically extending several centimeters, in a distribution that does not follow the focal plaque pattern of atherosclerotic disease. The artery is narrowed over a long stretch without a discrete culprit lesion, because the stenosis is caused by external compression from the intramural hematoma rather than a plaque. Type 2 SCAD is the presentation most likely to be misdiagnosed or mismanaged, because the angiographic appearance can resemble either a diffuse atherosclerotic segment or, in some cases, be underappreciated as a near-normal variant. Type 2 is further subdivided into 2A, where the stenosis transitions back to a normal lumen at both ends, and 2B, where the hematoma extends to the distal arterial tip.

Type 3 SCAD is the most subtle and the most often missed on angiography alone. It mimics atherosclerosis, producing a focal irregular stenosis that could be plausibly attributed to plaque. Intracoronary imaging is frequently required to make the diagnosis in Type 3 presentations.

Because angiography has these limitations, intracoronary imaging with optical coherence tomography (OCT) or intravascular ultrasound (IVUS) adds diagnostic clarity when SCAD is suspected but the angiographic picture is ambiguous. OCT provides near-histologic resolution of the arterial wall and can directly visualize the intimal flap, the false lumen, and the intramural hematoma with remarkable clarity. IVUS provides lower resolution than OCT but better penetration into the vessel wall and can image the hematoma extent in vessels where OCT signal is limited by blood attenuation.

The practical caveat with intracoronary imaging in SCAD is that wire passage for OCT or IVUS carries a risk of extending the dissection, and the decision to use intravascular imaging in an acute SCAD presentation requires operator judgment about whether the diagnostic gain outweighs the procedural risk. In stable patients where the clinical picture is consistent with SCAD and the angiographic type is reasonably clear, many experienced operators elect conservative management without intravascular imaging. In ambiguous cases, particularly suspected Type 3 where the distinction from atherosclerosis changes management, the imaging is warranted.

Spontaneous healing: what the evidence shows

One of the most important biological facts about SCAD is that the intramural hematoma resolves on its own in the majority of patients, and the artery returns to near-normal appearance on repeat angiography. This is not speculation; it is documented by serial angiography and intracoronary imaging in registry cohorts.

Data from the Canadian SCAD registry and the Mayo Clinic SCAD cohort document angiographic healing rates of approximately 70 to 90 percent of dissections when repeat imaging is performed at 30 days. 4 / Promising The healing timeline is relatively predictable: most hematomas begin to reabsorb within the first two weeks, and angiographic normalization is typically documented by four to six weeks in uncomplicated cases. This healing occurs because the false lumen is contained within the arterial wall, the hematoma undergoes fibrinolysis and reabsorption, and the compressed true lumen reopens as the pressure from the hematoma dissipates.

This healing biology is the direct argument against reflexive stenting. A stent placed in a SCAD segment prevents the natural reabsorption of the hematoma, creates a permanent metallic implant in a vessel that would have healed to normal, and may cause technical complications during deployment when the wire traverses an abnormal arterial wall. Stent expansion can extend the dissection distally, creating a longer area of involvement than was present before intervention. Serial angiography rather than repeat revascularization is the appropriate follow-up tool in patients managed conservatively.

The minority of SCAD patients who do not show complete angiographic healing at 30 days include those with the most extensive Type 2B dissections and those who developed complications during the acute phase. These patients warrant closer follow-up, but even incomplete healing on imaging does not necessarily indicate clinical deterioration if the patient is symptomatically stable.

Recurrence rates and the evidence

SCAD recurs. This is the finding that patients are most often not told, and the omission sets up future events as surprises rather than anticipated possibilities within a managed risk framework.

Registry data from the Canadian SCAD study group and the Mayo Clinic cohort document recurrence rates of approximately 10 to 15 percent over three to five years of follow-up. 4 / Promising Some analyses show rates as high as 20 percent at five years when follow-up is sufficiently long and recurrence is systematically ascertained (Saw et al, JACC 2019). Recurrences tend to involve different coronary arteries than the initial event, which is consistent with the underlying arterial wall vulnerability being diffuse rather than site-specific.

The predictors of recurrence in published data include fibromuscular dysplasia, which suggests that systemic arterial wall abnormality rather than a localized injury drives both initial and recurrent events. Psychological stress and intense physical exertion appear in registry-based trigger analyses as precipitants of both first events and recurrences, though the evidence for these associations is observational and should be interpreted accordingly.

There is no validated pharmacologic prevention strategy for SCAD recurrence. Beta-blockers have been advocated on the basis of reducing adrenergic and hemodynamic stress on the arterial wall, and registry data associate beta-blocker use with lower recurrence rates in some cohorts, but this is confounded by indication and does not constitute evidence from a randomized trial. Antiplatelet therapy, which is standard after atherosclerotic MI, does not have a clear evidence base in SCAD, because the mechanism of SCAD does not involve platelet-mediated thrombosis in the same way that plaque rupture does. Many SCAD patients are prescribed antiplatelet agents, but the practice is based on expert opinion and extrapolation rather than trial evidence.

Physical and emotional triggers: what registry data shows

The SCAD registry literature has collected systematic data on the circumstances immediately preceding SCAD events, and the findings challenge the assumption that heart attacks happen during physical exertion.

Intense physical exertion, including isometric exercise, straining, and strenuous aerobic activity, appears in a meaningful proportion of trigger reports in multiple registries. The pathophysiology is plausible: intense exertion raises shear stress on the coronary arterial wall and increases intracoronary pressure, both of which could precipitate intimal tear or hematoma formation in a susceptible arterial wall. The implication for women with known SCAD or FMD is that the exercise prescription matters: moderate, consistent aerobic activity is preferred over high-intensity or isometric exercise, and return to exercise after a SCAD event should be gradual and monitored.

Emotional stress triggers appear in registry reports at rates that exceed what would be expected by chance, with some series documenting intense emotional stress preceding the event in 20 to 30 percent of cases. The mechanism may involve adrenergic surging, which raises blood pressure and coronary arterial wall stress transiently. This does not mean emotional stress management is the primary treatment for SCAD, but it is a factor in patient education and in the counseling discussion about daily life after a SCAD event.

Hormonal triggers are documented most clearly in pregnancy and the postpartum period, which represent the highest-risk SCAD scenario. Peripartum SCAD accounts for a disproportionate share of SCAD cases in some registries, with the immediate postpartum period carrying the highest acute risk. The proposed mechanisms include progesterone-mediated arterial wall weakening, hemodynamic stress of labor and delivery, and the vascular changes of pregnancy that predispose to arterial wall vulnerability.

Long-term follow-up: what the evidence says about future cardiac events

Beyond recurrence of SCAD specifically, women who have had a SCAD event carry ongoing cardiovascular risk and long-term quality-of-life burden that the evidence is beginning to characterize.

Major adverse cardiovascular event rates beyond recurrence include heart failure from the index MI and, in some patients, ongoing angina or exercise intolerance. The index event causes real myocardial injury in most cases, with troponin elevation and often echocardiographic wall-motion abnormality. The degree of recovery depends on the artery involved, the territory at risk, and the time to presentation. Left anterior descending artery SCAD, which is one of the more common sites, can produce anterior wall MI with meaningful functional consequences if the presentation is delayed.

Psychological outcomes after SCAD are substantially worse than after atherosclerotic MI in some published series. Women who have had SCAD report high rates of post-traumatic stress symptoms, anxiety, and depression in follow-up studies, partly because the event is unexpected, partly because the recurrence risk creates ongoing uncertainty, and partly because they often report having been dismissed or mismanaged at the time of presentation. A systematic review of quality-of-life data after SCAD found that psychological morbidity was among the most significant ongoing burdens at one to three years of follow-up.

FMD surveillance is an ongoing component of long-term follow-up. Because SCAD is associated with FMD in renal and mesenteric arteries, as well as in carotid and vertebral arteries, one-time screening with computed tomography angiography or duplex ultrasound of the relevant vascular beds is recommended at the time of the SCAD diagnosis. FMD in other beds does not change the SCAD management directly but identifies a patient with systemic arterial wall vulnerability who may benefit from closer monitoring and from recognition that future vascular events, in any arterial territory, warrant prompt evaluation. 3 / Early

Pregnancy counseling after SCAD: what is known and what is not

Pregnancy after SCAD is one of the most clinically difficult conversations in this condition. The evidence base is thin, the stakes are high on both sides, and the right answer depends on individual circumstances that no registry can fully capture.

What is documented: the peripartum period is itself a trigger for SCAD, and women who have had SCAD have experienced recurrence during subsequent pregnancies. Registry data from the Canadian SCAD study and international collaborating centers have documented cases of recurrent SCAD in subsequent pregnancies, though the absolute number of documented recurrences is small because the registry populations are not large and not all cases of subsequent pregnancy are systematically tracked.

What is not documented: a reliable estimate of the absolute risk of recurrent SCAD in a subsequent pregnancy, because the denominator, the number of women with prior SCAD who have become pregnant, is not well established in prospective registry data. The risk cannot be quantified with confidence.

Current guidance from the AHA scientific statement and SCAD registry consensus groups advises against subsequent pregnancy in most women with prior SCAD, but acknowledges that this is a recommendation rather than a contraindication with a precisely quantified risk-benefit calculation behind it (Hayes et al, Circulation 2018). For women who strongly desire pregnancy after SCAD, the conversation should occur with a multidisciplinary team including a cardiologist experienced in SCAD, a high-risk obstetrician, and ideally a genetic counselor given the FMD association. The decision involves the woman’s coronary anatomy as recovered after the index event, the presence of FMD, the artery involved in the SCAD and the degree of functional recovery, and the woman’s own values.

The timing of any future pregnancy is also relevant. Most experts recommend waiting at least six to twelve months after SCAD before any pregnancy attempt, to allow arterial healing and functional recovery from the index event. Women with significant left ventricular dysfunction from the index MI face additional risk from the hemodynamic demands of pregnancy independent of SCAD recurrence.

Questions to ask the cardiologist after a SCAD diagnosis

The gap between what patients need after a SCAD diagnosis and what they typically receive is large enough that a specific list of questions is warranted. These are not optional; they define whether the clinical follow-up is adequate.

What type of SCAD did I have, and which artery was involved? Do I have fibromuscular dysplasia, and have my other arteries been screened? What is my understanding of the recurrence risk, and what symptoms should prompt me to return immediately? What exercise is safe for me now, and when can that be reassessed? What medications am I on and why, specifically for SCAD rather than for atherosclerosis? If I want to consider another pregnancy, who should I speak with and when? Should I be referred to a SCAD specialist or to a center with a dedicated SCAD program? Is there a patient registry or research cohort I could participate in?

That last question is not incidental. SCAD research is still substantially dependent on registry enrollment for outcome data, and women with SCAD who participate in registries contribute directly to the evidence base that will improve counseling for the next patient. The Canadian SCAD registry and the SCAD Alliance have provided the foundational data cited throughout this paper. Contributing to that data is a meaningful option for a patient who wants to understand and act on her diagnosis.