What are the causes and management of ST-Elevation Myocardial Infarction (STEMI) in young patients?

Causes of STEMI in Young Patients

In young patients presenting with STEMI, spontaneous coronary artery dissection (SCAD) is the most important non-atherosclerotic cause to consider, particularly in women, while traditional atherosclerotic disease with thrombotic occlusion remains the predominant etiology overall. 1, 2

Primary Etiologies

Spontaneous Coronary Artery Dissection (SCAD)

• SCAD is an infrequent but critical cause of MI in younger patients, affecting predominantly women (82-90% female), with mean age around 42-52 years 1, 2, 3
• Presents as STEMI in 24-49% of cases, with the remainder presenting as NSTEMI 1, 2
• Multivessel SCAD occurs in 23% of cases, which is an important diagnostic consideration 2
• Associated with extreme physical exertion more frequently in men (44% vs 3% in women) 2
• Peripartum state accounts for 18% of SCAD cases in women, making this a critical consideration in young female STEMI patients 2
• Fibromuscular dysplasia is present in 43-56% of SCAD patients when complete screening is performed, representing a novel causative association 2, 3

Atherosclerotic Coronary Artery Disease

• Complete thrombotic occlusion from atherosclerotic plaque rupture in an epicardial coronary vessel remains the most common cause of STEMI overall, even in younger patients 4
• Traditional risk factors (smoking, diabetes, hypertension, dyslipidemia, family history) drive atherosclerotic disease in young patients 5

Other Non-Atherosclerotic Causes

• Coronary vasculitis should be considered in young patients with systemic inflammatory conditions 6
• Coronary artery anomalies 6
• Hypercoagulable states 5
• Cocaine or amphetamine use causing coronary vasospasm 5
• Takotsubo cardiomyopathy (apical ballooning syndrome), though this mimics rather than causes true STEMI 5

Clinical Presentation Patterns

SCAD-Specific Features

• Chest discomfort is the most frequent presenting symptom (96%), followed by arm pain (50%), neck pain (22%), nausea/vomiting (23%), and diaphoresis (21%) 1
• Ventricular tachycardia/fibrillation occurs in 8.1% of SCAD patients, with 1% experiencing cardiac arrest 1
• Emotional stressor precipitates SCAD in 50% of cases, while physical stressor accounts for 29% 3
• Time from symptom onset to hospital presentation averages 1.1 days, with NSTEMI patients having longer delays to angiography compared to STEMI (2.0 vs 0.8 days) 1

General STEMI Presentation

• Approximately 30% of STEMI patients are women, who present later after symptom onset and have longer door-to-balloon times compared to men 5
• Women are characterized by higher bleeding risk with antithrombotic therapy even after adjustment for confounders 5

Diagnostic Approach

Immediate ECG Evaluation

• Twelve-lead ECG should be obtained within 10 minutes of first medical contact to confirm STEMI diagnosis 5, 7
• ST-segment elevation ≥1 mm in two or more contiguous leads confirms STEMI 5
• New or presumed new left bundle branch block should be considered STEMI-equivalent 7
• Isolated ST depression in anterior leads with ST elevation in aVR suggests left main or multivessel disease 5, 7

Angiographic Recognition of SCAD

• Coronary angiography during primary PCI provides definitive diagnosis of SCAD based on characteristic vessel appearance 6, 2
• SCAD angiographic features require expert adjudication as they can be subtle 3
• Do not delay reperfusion therapy to confirm SCAD diagnosis—proceed immediately to restore coronary blood flow 6

Screening for Associated Conditions

• In confirmed SCAD cases, screen for fibromuscular dysplasia in iliac and carotid arteries, as it is present in 50-56% of patients 2, 3
• Evaluate for genetic disorders (present in 1.6% of SCAD patients) and peripartum state in women 3

Management Considerations Specific to Young STEMI

Reperfusion Strategy

• Primary PCI is the preferred reperfusion strategy regardless of underlying etiology (atherosclerotic vs SCAD), with goal first medical contact-to-device time ≤90 minutes 5, 7, 6
• In SCAD patients, conservative management (84%) is associated with uncomplicated in-hospital course, while PCI has high technical failure rates (35%) and complications 2, 3
• Target only the culprit vessel during index PCI—multivessel PCI at time of primary PCI is associated with higher mortality 6

Antithrombotic Therapy

• Initiate dual antiplatelet therapy immediately: aspirin 162-325 mg plus P2Y12 inhibitor (prasugrel 60 mg or ticagrelor 180 mg loading dose) 7, 6
• Unfractionated heparin 100 U/kg IV bolus for anticoagulation during PCI 5, 7
• Continue DAPT for minimum 12 months post-PCI 7, 6

Long-Term Outcomes and Follow-Up

• In SCAD patients, 3-year mortality is low (0.8%), but recurrent MI occurs in 9.9% (de novo recurrent SCAD 2.4%, extension of previous SCAD 3.5%, iatrogenic dissection 1.9%) 3
• All SCAD recurrences occur in females, emphasizing need for close long-term follow-up in young women 2
• Estimated 10-year rate of major adverse cardiac events in SCAD is 47% 2
• Genetic disorders, extracoronary fibromuscular dysplasia, and peripartum SCAD are independent predictors of long-term MACE 3
• Beta-blockers (73.5%) and aspirin (80%) are maintained long-term in contemporary SCAD cohorts 3

Critical Pitfalls to Avoid

• Do not assume atherosclerotic disease in all young STEMI patients—actively consider SCAD, especially in women without traditional risk factors 1, 2
• Do not routinely perform PCI in SCAD patients unless there are unstable features—conservative management has better outcomes 2, 3
• Do not miss peripartum SCAD—it accounts for nearly 1 in 5 SCAD cases in women and predicts worse long-term outcomes 2, 3
• Do not forget to screen for fibromuscular dysplasia in confirmed SCAD cases, as it is present in the majority and affects prognosis 2, 3