Can a lateral wall myocardial infarction (MI) occur with a dissecting aortic aneurysm?

Can Lateral Wall MI Occur with Aortic Dissection?

Yes, lateral wall myocardial infarction can occur with aortic dissection, though it is less common than inferior wall involvement—any coronary ostium can be compromised by the dissection flap, and the left main or circumflex arteries supplying the lateral wall are anatomically vulnerable in proximal (Type A) dissections. 1, 2

Mechanism of Coronary Involvement in Aortic Dissection

Anatomic Considerations

• Type A (Stanford) dissections involving the ascending aorta can extend into any coronary ostium, creating acute coronary malperfusion 1, 2
• The right coronary artery (RCA) is most frequently involved when dissection extends into coronary ostia, producing inferior wall MI as you correctly noted 2, 3
• However, the left main coronary artery and its branches (including the circumflex artery supplying the lateral wall) can also be compromised by the dissection flap, particularly when the dissection originates near the aortic root 2, 3
• The dissection can obstruct coronary flow through several mechanisms: direct extension into the ostium, compression of the true lumen by the false lumen, or creation of an intimal flap that occludes the coronary opening 1, 2

Clinical Presentation

• Myocardial infarction occurs in approximately 5% of Type A aortic dissections, and this can involve any coronary territory depending on which vessel is affected 4
• Patients may present with concomitant features of both acute MI and aortic dissection, creating diagnostic confusion 2, 3
• The presence of eccentric aortic regurgitation on transthoracic echocardiography is a critical clue that should raise suspicion for aortic dissection in any patient presenting with apparent acute MI 4

Critical Diagnostic Pitfalls

The South African Flag Sign

• Your patient's ECG showing the "South African Flag Sign" is highly suggestive of Type A aortic dissection with coronary involvement 4
• This ECG pattern, combined with the classic presentation (tearing chest pain radiating to back, blood pressure differential between arms, hypertension), makes aortic dissection the primary diagnosis 1, 5

Why This Matters for Management

• Coronary angiography in the setting of unrecognized Type A aortic dissection can be catastrophic, potentially causing catheter-induced propagation of the dissection or rupture 4
• In one series, all six patients with ST-elevation who underwent coronary angiography without awareness of Type A dissection had a mortality rate of 36% 4
• Three patients in that series had eccentric aortic regurgitation detected on TTE before angiography, but the diagnosis of Type A dissection was missed, leading to inappropriate catheterization 4

Recommended Diagnostic Approach

Immediate Imaging

• CT angiography or transesophageal echocardiography should be performed immediately before any consideration of coronary angiography in patients with this presentation 1, 5
• CT imaging has 100% sensitivity for diagnosing acute aortic syndrome, while transesophageal echocardiography is 86-100% sensitive 5
• Magnetic resonance imaging has 95-100% sensitivity but is less practical in the acute setting 5

Key Clinical Clues

• Blood pressure differential between arms (as in your patient) is highly specific for aortic dissection and should immediately redirect diagnostic thinking away from isolated acute coronary syndrome 1, 5
• Elevated D-dimer (sensitivity 51.7-100%, though specificity is limited at 32.8-89.2%) can provide additional supportive evidence 5, 4
• Any patient with apparent acute MI who has eccentric aortic regurgitation on TTE should be assumed to have Type A aortic dissection until proven otherwise 4

Management Implications

Surgical Emergency

• Type A aortic dissection requires immediate open surgical repair regardless of which coronary territory is involved, with mortality rates of 26-58% even with surgery 1, 5
• Medical management alone carries mortality rates of nearly 20% by 24 hours, 30% by 48 hours, and 40-70% by day 7 1
• The major cause of early death is aortic rupture, occurring at a rate of 1-2% per hour in untreated patients 1, 6

Preoperative Medical Stabilization

• Beta-blockade should be initiated immediately to reduce heart rate to <60 bpm and systolic blood pressure to 100-120 mmHg, using intravenous esmolol, labetalol, metoprolol, or propranolol 1
• This reduces shear stress on the aortic wall and prevents propagation of the dissection 1

Answer to Your Specific Question

Your assumption that inferior wall infarction is more likely is statistically correct, but lateral wall MI is absolutely possible and has been documented in cases where the dissection involves the left main or circumflex arteries 2, 3. The key point is that any coronary territory can be affected depending on the anatomic extent of the dissection, and the presence of MI in any territory does not exclude aortic dissection—in fact, it should heighten suspicion when combined with other features like blood pressure differential and tearing back pain 2, 3, 4.