What is the relationship between acute myocardial infarction (AMI) and aortic stenosis (AS)?

Why Acute Myocardial Infarction Occurs in Aortic Stenosis

Acute myocardial infarction is NOT particularly common in aortic stenosis—the actual incidence is relatively low at approximately 2.5% over 5 years, and AS severity itself does not independently increase MI risk. 1 However, when MI does occur in AS patients, it carries a significantly worse prognosis with mortality rates exceeding 50% following the event. 1

Mechanisms Linking Aortic Stenosis to Myocardial Ischemia

Supply-Demand Mismatch (Primary Mechanism)

The fundamental problem in AS is an imbalance between myocardial oxygen supply and demand, not coronary artery occlusion:

• Increased oxygen demand occurs due to left ventricular hypertrophy and elevated wall stress from pressure overload 2
• Decreased oxygen supply results from reduced coronary perfusion pressure, as elevated LV end-diastolic pressure approaches diastolic aortic pressure, diminishing subendocardial perfusion 2
• Tachycardia further compromises coronary perfusion by shortening diastolic filling time when coronary blood flow occurs 2

This represents Type 2 MI by the Universal Definition—myocardial necrosis from supply-demand mismatch rather than acute coronary thrombosis. 2

Coexisting Coronary Artery Disease

• Coronary disease prevalence in AS patients is substantial: 37% in those aged 40-59 years and 68% in those aged 60-82 years 3
• Shared risk factors between AS and atherosclerosis explain this overlap, but AS severity itself does not predict MI occurrence 1
• When angina occurs with exertion without dyspnea, or with emotional stress/rest symptoms, coronary disease is present in 80% of cases 3

Rare Mechanical Complications

In acute aortic dissection (Type A), MI can occur through:

• Direct coronary ostial involvement when the dissection flap extends into the coronary artery ostium 2
• Compression of proximal coronary arteries by an expanding false lumen 2
• This occurs in approximately 7% of acute aortic dissections and carries extremely high mortality 2

Clinical Presentation Patterns

Distinguishing Features

• Angina in AS without CAD typically occurs only with exertion accompanied by dyspnea (45% have coronary disease) 3
• Angina suggesting CAD occurs at rest, with emotional stress, after meals, or during sleep (80% have coronary disease) 3
• Atypical or absent chest pain is more common in men over 60 with heart failure as the predominant symptom 3

ECG Patterns

• Transmural infarction patterns (inferior or anterolateral) nearly always indicate true coronary disease 3
• QS patterns in V1-V2 frequently occur with normal coronary arteries in AS patients and should not be interpreted as prior MI 3

Prognostic Implications

Short-Term Outcomes

• In-hospital mortality is not significantly different between AS patients with and without moderate stenosis during acute MI 4
• Heart failure occurs more frequently during hospitalization in moderate AS patients (8.2% vs 4.4%) 4

Long-Term Outcomes

• One-year mortality is dramatically higher in AS patients after MI: 23.9% with moderate AS vs 8.1% without AS 4
• Post-MI mortality reaches 52.8% during follow-up (median 648 days after MI) in AS patients 1
• Moderate AS independently predicts mortality at one year (OR 2.4,95% CI 1.4-4.1) 4

Clinical Decision-Making Algorithm

When Evaluating Chest Pain in AS Patients

1. Assess angina characteristics:

   • Exertional angina with dyspnea → likely AS-related supply-demand mismatch 3
   • Rest angina, nocturnal angina, or post-prandial angina → 80% probability of CAD 3

2. Interpret ECG cautiously:

   • QS patterns in V1-V2 alone do not indicate CAD 3
   • Transmural infarction patterns (Q waves in inferior/lateral leads) strongly suggest CAD 3

3. Consider coronary angiography based on:

   • Age >60 years (68% CAD prevalence) 3
   • Angina pattern suggesting CAD 3
   • Moderate AS with symptoms despite only moderate stenosis 3

When Acute MI Occurs in AS

• Expect worse outcomes with aggressive monitoring and early intervention planning 4, 1
• Operative mortality for valve replacement is 9.6% with CAD vs 1.4% without CAD 3
• Consider urgent valve replacement in appropriate candidates given the high post-MI mortality 4

Critical Pitfalls to Avoid

• Do not assume angina in AS is always from the valve—64% of AS patients with angina have significant CAD 3
• Do not delay coronary angiography in AS patients over 60 with angina, as CAD prevalence is 68% 3
• Do not misinterpret QS patterns in V1-V2 as prior MI in AS patients—these are frequently present with normal coronaries 3
• Do not underestimate risk when MI occurs in AS—subsequent mortality exceeds 50% 1